illiililiPiiiiiiiiiiiiiliiiiiiliiiiiiiifS ^jfc»i»iTl»litli/. ■!•.•.•., i? ^^ILIBRARY^ ^' University Research Library — I — n «~ > r* -J r- J ► r— z H c -^ £ Jl f CD i— m 1 — 3J I — ' 1— r- r~r to m r~ rr < c- o r- err 1 c- ■D H cr L, o ir o r rr: c_": r^v cr c— CT" r 1 1 > C- C c . I tr' o [Z IT" Cl' C " c t .: c: r 1 This book is DUE on the last date stamped below ' J. MAY 1 3 1929 AR ^ 7 1930 2, '23 LESSONS^ IN THE New Geography FOR STUDENT AND TEACHER BY SPENCER TROTTER, M.D. Professor of Biology in Swarthmore College, Pennsylvania BOSTON. U.S.A. D. C. HEATH & CO., PUBLISHERS 1895 . NOV 1906 Copyright, 1894, By spencer TROTTER. Typography by J. S. Cushing & Co. Presswork by S. J. Parkhill & Co. GfF33 PREFACE. We live in a world of ideas. The real things of life impress themselves upon our brains, through our senses, and are grouped as so many mental pictures in the various complex relations which they hold to one another. In studying Geography the child very early gains ideas or mental pictures of different scenes and places, and it is of the utmost importance that these pictures be not only true, but /iving- ideas of the things themselves. It should be impressed upon every child thal[Geography is a part of his every- day life, not a mere learning of the names of places, but a living reality .J The imagination — that quality of the brain which enters so largely into child life, peopling its wonderland with fairies and creations of fancy — is the one element needful in gaining the ideas of real things. In proportion as a study stimulates the imaginative faculty does it near the end in view of all study — that of creating a fulness of interest in life and in the lives of every man and woman. The purpose of this book is to- bring this conception of Geog- raphy to the teacher's mind. LThe map is a means of gaining clear ideas of the positions of places on the earth's surface in relation to one another. \ We all carry mental maps in our brains. Our sense of right direction is often determined by the early use or misuse of maps. Use the map to call out the perception of iii iv ' PREFACE. the relations of a place to other places. Try to make every part of the map a picture alive with the men, the animals, the vegeta- tion, rivers, mountains, cities, and all that goes to make up the real scenes, on any part of the earth's surface. Good illustrations are as useful as maps, and lantern slides are very helpful in the study of Geography, Modeling surface features in sand and clay, as outlined by Redway in his litde book on " Geographical Forms," is both interesting and instructive, but outdoor lessons are more important than schoolroom exercises. Geography is a universal study, a band that binds many other studies into a living whole.' It is the central study to which the other studies must necessarily gravitate, because it is the study of the earth, and the earth is the theater of all human thought and action. For example, the expression of the mind of a people as embodied in its literature is largely the result of geographical influences. Who can doubt that the poetry and the art of Greece were the expression of that inspiration which is peculiarly the effect of bright blue skies and sparkling seas; of genial, buoyant air, and softly blended landscapes, or that the brave Sagas of the Norse were born out of the gray mists and tempestuous waves of the northern ocean ? On every literature Geography has left its stamp. So with all study, the purely scientific and economical, as well as the more essentially human studies of history and art, all find a basis, a common groundwork in Geography. In writing this book I have been reminded of those early voy- agers who made the study of Geography possible only by sailing around the earth. We all sail around the earth in the sea of our imagination. There are many who can never do it in reality, and if this little book will help them to sail and to see in fancy 1 See article by Dr. Charles De Garnio in " Educational Review " for May, 1893. PREFACE. V the real scenes, the moving and feeling life of the earth, the object for which it was written will be accomplished. In connection with the chapters and lessons I have given Usts of books that both the student and teacher will take pleasure in reading, and lind useful in helping them to gain clear conceptions of the various scenes in different parts of the world. I have freely drawn material from several valuable works. I am espe- cially indebted to Dr. D. G. Brinton's "Races and Peoples," Alphonse De Candolle's " Origin of Cultivated Plants," and articles on various subjects in the Encyclopaedia Britannica. S. T. SWARTHMORE COLLEGE, 1894. CONTENTS. INTRODUCTORY CHAPTER. Geography in its Relations to Life PAGE I CHAPTER I. Some Past and Present Aspects of the Earth : Lesson L Land and Water ..... IL Life and the Earth ..... IIL Conditions affecting the Development of Man lO 21 29 CHAPTER H. Climate : Lesson I. The Elements of Climate IL Climatic Zones ..... in. Winds, Ocean Currents, and Rainfall . IV. Influence of Climate on Man 33 40 43 54 CHAPTER III. Plants which have Affected Man : Lesson I. Tea and Coffee . II. Sugar and Spice . III. The Grains, or Cereals IV. Some Vegetables and Fruits V. Cotton and Flax . . vii 60 64 66 69 CONTENTS. CHAPTER IV. Animals which have Affected Man : Lesson I. Animals of the Chase . II. The Domestication of Animals III. Some Special Animal Products 75 78 85 Man CHAPTER V. Lesson I. Types or Races of Man .... II. Geographical Distribution of the White Race III. Geographical Distribution of the Black Race IV. Geographical Distribution of the Yellow Race V. Man in America ..... VI. Islanders and Coast Peoples 89 92 100 106 "5 125 CHAPTER VI. Commerce : Lesson I. The Beginnings of Commerce II. The Era of Discovery III. Present Features of Commerce and Civilization 129 134 137 APPENDIX. I. The Principal States and Cities of the World II. Population of the Earth III. Forms of Government ....■••■ IV. E.xtract from the First Report of the United States Board on Geo- graphic Names . . . . • • V. Geographical Distribution of Animals ; a Synopsis of Study . VI. How to read a Weather Map ....... 147 157 158 158 160 169 LESSONS IN THE NEW GEOGRAPHY INTRODUCTORY CHAPTER. GEOGRAPHY IN ITS RELATIONS TO LIFE.^ The varied features of the earth's surface in any piece of land- scape is a thing that rarely fails to strike the eye even of the most casual observer. He may take no mental note of this element of variety in itself, seeing only the stretches of field, the masses of woodland, the broken lines of hills, the winding course of streams that lie within his horizon. These are the broad features of almost every familiar landscape. From any given standpoint commanding such a view of the surrounding country the ground is seen to slope gently down to the lowlands, or fall more or less abruptly into a valley. Water from the rills of hillside springs gathers in the hollows, and wet, marshy land often forms a con- spicuous feature in the near view. This diversified surface — river, marsh, field, forest, hill, and valley — is the home of an infinite variety of living beings. Little observation is needed to note that this diversity of life corresponds, in a broad way, with the diversity of surroundings. Aquatic animals, like fishes, crayfish, and many insects, inhabit the waters of ponds, lakes, and streams. Frogs and other am- phibious creatures are denizens of bogs and shallow pools. Some snakes and turtles are aquatic, while others are wholly lovers of the dry land. Birds are found in every situation, — ducks and divers on the lakes and rivers ; herons and bitterns in marshy fens ; gulls and petrels on the open sea ; sandpipers along the shores ; eagles on lofty mountain peaks ; while a host of 1 An address read before The College Association of the Middle States and Maryland at the meeting held at Swarthmore College, Pa., November, 1892. B I 2 INTRODUCTORY CHAPTER. species enliven the woods and fields. The haunts of mammals are no less diversified. The tree-loving squirrels, the burrowing ground hog, the mole digging out its long, subterranean galleries, the water-loving beaver and otter, are each and all associated in the mind with their favorite surroundings. This idea of the animal and its particular home is by no means new. In that wonderful poem, the one hundred and fourth Psalm, the story is told in a language peculiarly its own : " The cedars of Lebanon, which he hath planted ; where the birds make their nests : as for the stork, the fir trees are her house. The high hills are a refuge for the wild goats ; and the rocks for the conies." If this diversity of life is so apparent in a limited area, it is far more so when we come to journey over an extended portion of the earth's surface. As the horizon widens, newer and more sig- nificant features rise into view. Lofty mountain ranges, broad seas, trackless deserts, treeless plains, and vast forests successively present themselves as the traveler girdles the earth, north and south, east and west. Climate and vegetation change from one region to another, and it is not a matter of surprise to find corre- sponding changes in animal life. Many kinds of animals are limited to particular regions, while others range through wide areas of country under a variety of physical changes. A traveler starting on the Atlantic seaboard of the United States and journeying westward along the fortieth parallel will pass successively through a number of distinct regions, each characterized by certain conditions of climate, vege- tation, and peculiar animals. Quite a number of familiar forms will, however, be found throughout the entire extent of his journey across the continent. In bird life alone, the absence of some species, the appearance of others in new regions, and the presence of some throughout a wide area of country, is a marked feature in such a journey. Many familiar eastern species, wrens, thrushes, titmice, wood- warblers, larks, jays, finches, and the like, give place to new, GEOGRAPllV IN ITS RELATIONS TO LIFE. 3 though, in some instances, closely related, forms on the prairies and Great Plains. In the Rocky Mountain region the change becomes still more marked. So in the Great Basin and on the Pacific slope new and strange forms appear, characterizing the several regions over which the traveler passes. He will find, however, that some old friends have accompanied him all the way to the shores of the Pacific. The robin greets him in California with the same loud, cheerful call that he heard in the woods of Pennsylvania. The familiar twitter of the barn swallow is heard about the habitations of men from shore to shore of the continent. Other well-known birds appear in every region throughout the land. If our traveler cross the Pacific .to Japan, he will find larks, wrens, finches, wagtails, titmice, thrushes, and a host of familiar forms, which he recognizes broadly as belonging to such types, though the species are all entirely different from those he knew in America. Should he sail westward by the shortest route to Eng- land, he would pass the shores of countries widely different from those he left and from one another. The bare hills of China, the wooded mountains of Formosa, the volcanic peaks of the Phil- ippines, the hot, tropical jungles of the Malay Islands, the spice groves of Ceylon, the burning, barren deserts of the Red Sea, pass successively before him. Each is tenanted by strange forms of life — beasts, birds, reptiles, insects, and vegetation totally differ- ent from any he has ever beheld in his journey over half the earth. On reaching England he will again find himself surrounded by many familiar features. He will be surprised to see many species of birds almost, if not quite, identical with those he saw in Japan, separated as they are by the immense land mass of Eurasia, with its vast plains, deserts, and 'mountain-rimmed plateaus. None of the familiar, species of North American birds, however, will greet him in his rambles about Britain. We have seen that in an area covered by almost any farm of a few acres there exists a variety of physical conditions each of which is the home of living beings peculiar to it and different from 4 ■ INTRODUCTORY CHAPTER. those in other stations. We have followed in imagination the traveler journeying westward over the earth, and have seen with him the varied features of the lands he visited. In the one case the conditions are local, in the other geographical, yet no line of distinction can be drawn between them, for geographical condi- tions are only the more exaggerated and broader features of what we see in any local area. We learn from a survey of these conditions how intimately related an animal is to the earth, and how each species is fitted to the special conditions of the region it inhabits. Physical Geography, therefore, forms the basis of a study of distribution. The position of mountain ranges and valleys in relation to each other and to the surrounding country ; the presence of rivers, lakes, prairies, steppes, deserts, and forests ; the relative height of land above the sea level ; the position of an ocean and the direc- tion of its currents ; climate in its broadest sense, including rain- fall, humidity, the prevalence and direction of winds, — all these must be considered in relation to the distribution of life. Humboldt laid the present basis of Physical Geography. Carl Ritter enlarged the thought of Geography as the all-important factor in life and human affairs. The multitude of facts collected by Darwin on the cruise of the Beagle, and Wallace in the Malay Archipelago, opened out a broad and suggestive field of thought. Obscure problems became clear in the new light shed upon them. The work of Lyell and other geologists bridged the gulf between the great Present and the infinitely greater Past, showing that the life of to-day in all its varied and obscure forms is the effect of physiographic causes working throughout the earth's history. Time and Place became the fulcra on which thought was levered in turn- ing the great questions of life. Evolution was the word and the light of science. Distribution was the key that unlocked many of the mysteries. A new conception of the importance of Geography was at hand. Geography acted upon Biology and History, and they in turn reacted upon Geography. The Geography of our childhood is GEOGRAPHY IN ITS RELATIONS TO LIFE. 5 remembered by most of us for its dry-as-dust detail and its enter- taining pictures. Among these pictures none were more attrac- tive than the zones of animal life. Seals, polar bears, and Eskimo struggled with one another in the frigid zone, with a precarious footing on cakes of ice under the conventional arch of an aurora borealis. Horses, cattle, herds of bison, wolves, deer, and bears were seen in all conditions of activity in the landscape of the temperate zone. The real menagerie feeling came out in the picture of the torrid zone. In one corner a dense jungle screens a tiger ever ready to spring upon the approaching antelope. Near by a herd of elephants are browsing. Hippopotami, rhinoceroses, and other creatures appear in the scene, while a herd of zebra or giraffe are invariably scampering off toward the other corner, where a secretary bird is finishing its serpent. We learned, too, that the land was divided into continents — Europe, Asia, Africa, Australia, North and South America — islands, peninsulas, seaports, capes, and so forth ; that Canton was noted for tea and china, Yokohama for Japanese, Philadelphia for Independence Hall, Rome and Greece for antiquity, and Buenos Ayres for hides and tallow. But we never knew why they were noted for these things, or what part their geographical position played in their history and exports. In 1857 P. L. Sclater of the London Zoological Society first gave a definite outline of Zoological Geography. There are powers of dispersal and barriers to dispersal. Animals increase rapidly in any given area unless checked by the presence of enemies or the scarcity of food. In a restricted area the food supply is sure to diminish from the increasing number of individuals. The animal must needs wander in search of new pastures and wider hunting grounds, and in so doing meets with barriers of a various nature which tend to check its advance. Of these barriers high mountain ranges, seas and wide rivers, deserts, deep forests, climate, the ocean, the presence of certain enemies and competi- tors for the same kind of food, are conspicuous. Certain species have greater facilities for overcoming barriers than others, some 6 INTRODUCTORY CHAPTER. by their ready adaptation to changed conditions, their more varied diet and powers of resistance, others by superior means of loco- motion, as with birds and many mammals. In the lapse of time these two factors, dispersive power and barrier, tend to map out a definite territory or habitat for the animal to the physical con- ditions of which it is more or less adapted. Changes of a geological nature now enter into our consideration as factors of the greatest importance in determining the ranges of various animals. Slight changes of level have, at no very remote geological period, caused sea and land to change places with each other, thus raising a barrier in a once continuous area. Climate and vegetation undergo change. The animal, cut off from the old , land mass, diverges more and more from the parent stock, and in time appears as a distinct species. The camels of the Old World and the llamas of South America illustrate this fact. Naturalists find abundant fossil remains of a cameloid animal in the Tertiary strata of Western North America. It was long a standing puzzle how two such closely aUied forms as the camels and llamas should exist in so widely separated areas. Here was the solution : The common ancestor of the two species arose in the area of country now forming the western portion of our continent. In the ages that followed, the descendants of this animal wandered in search of food, reaching the south and northwest. What is now the shallow Aleutian bank of the North Pacific was in the middle and later Tertiary a land area continuous with the northwestern and northeastern shores of America and Asia. The climate, too, was decidedly mild and supported a luxuriant vegetation as compared with these latitudes to-day. Sinking of the sea floor is still going on over a wide area in the Pacific, and it was this same subsidence which carried a contin- uous shore line beneath the sea, leaving only the highest points of land, as the Aleutian, Fox, and Kurile chain of islands. Extraor- dinary changes of climate followed, and extinction of animal life occurred over wide areas. The descendants of the camel-like beast that penetrated farthest into the Asiatic continent became, GEOGKAPIIY IN ITS RELATIONS TO LIFE. 7 in the long course of time, adapted to a desert life, appearing in the present age as the camels of Bactria, Arabia, and North Africa. Those that wandered south became isolated on the high Andes and, conforming to a mountain life, are to-day the llamas of South America. This is only one of many such suggestive problems that Geography has solved. In accordance with the facts of distribution and the presence of certain barriers Sclater mapped out the earth into six great zoolog- ical regions. The great land mass of Europe and Asia north of the Sahara Desert and Himalaya Mountain range is regarded as constituting one natural primary region, Palaearctic or Eurasiatic. Africa south of the desert with Madagascar constitutes a second well-defined region containing numerous highly characteristic species of animals. Tropical Asia south of the great mountain barrier with the Malay Islands as far east as Borneo and Bali forms a third great region. The Australian, a highly peculiar and isolated region, includes the land mass of that name, Poly- nesia, and the islands of the Indian Archipelago to the narrow strip of water separating Lombok from Bali and to the Macassar Straits between Celebes and Borneo. North America to the Mexican highlands is the fifth or Nearctic ; while Central and South America together comprise the Neotropical. The broad features of plant distribution conform quite closely to the faunal regions. Here, then, is a natural geography based on the distribution of life. As the animal world has been so largely influenced by Geog- raphy, so man has been shaped, and his destiny hewn out mainly through geographical influences. Biology has pointed the way toward a new conception of Geog- raphy and its importance as a point of view for all study — -history, political science, linguistics, archaeology, ethnography, even mathe- matics, and last but not least, commerce. What is more essen- tially geographical than "reciprocity"? The New Geography is before us with a new significance, clothed with a perennial interest, for by it we are to see things in their 8 INTRODUCTORY CHAPTER. proper relations. The Old Geography is dead, a fossil buried in the drift of a past educational epoch. We shall always speak of Europe as distinct from Asia, for it has long borne, in the light of history, a different geographical stamp. In the light of present knowledge, however, Flurope can no longer remain a thing apart from the " land of the rising sun," for the Ural system forms no barrier between them. Even political boundaries are breaking down. Our children will learn about Eurasia, its climate and rainfall, its mountains, tablelands, and deserts, its great plains and river valleys, its widespread animal and plant life, and the influence of all these factors on the destiny of man. As we linger over the teacups, let us be reminded that the plant which gives us so many pleasant hours is part of a long and won- derful story. When it grew wild, which was so long ago no one can remember, it must have looked very different from what it does now. Ages' before this plant ever left its native shores it was cultivated by a curious people in the fertile valleys of the Yang- tse-kiang and Hoang-Ho, doubtless making them happier by its genial influence. The climate of these valleys and their ranges of hills must have been peculiarly favorable to the growth of the tea plant, for it will not grow everywhere. The life of this curious race of people is full of interest ; their civilization extends back for centuries and is lost in the dawn of history. What shut them out from the world so long? Great mountain ranges have always barred them off from the desert plateau of Asia. The warm, vapor-laden currents of the Pacific have ever borne in clouds that dropped their rains on the eastern mountain slopes, coursing back to the sea through fertile jiver valleys. Populous cities have stood for centuries on these river banks. Strange fish inhabit the waters ; many birds and be-asts roam through its forests. The land was sufficient in itself — its people stayed at home. At last the outer world, with its fleet of restless navigators, penetrated the shores of this strange country, and China, the Chinese, and the tea trade became factors in the world at large. So Geography has linked Biology with History and Commerce, GEOGRAPHY IN ITS RELATIONS TO LIEE. 9 since Biology first pointed out the New Geography, and Biology conies to mean more than merely what the microscope has to show. Geographies and text books on biological subjects are useful as repositories of facts and for reference, but not as a means of reci- tation in the usual acceptance of the term. Too often they lack the spirit essential to the development of broad thinking and the clear conception of things. Nothing can take the place of direct contact with the real object and of the personality of teacher and student. The true spirit of culture and education is not in the amount of knowledge acquired, but in the attitude of thought toward a subject. Cultivate this attitude of thought. Learn to look for the significance of facts. Never lose sight of the cause and the effect. Facts are the raw material of thought, to be trans- formed within the man and reappear glowing with his personality. When you read, read widely. History, travel, poetry, romance, biography, as well as Biology and Geography. Each in some way will light up the mind and help to clear the mists of ignorance. Lastly, as far as lies in your power, come in contact with the liv- ing life of the world. Touch it on every side. Books and study will soon wither the intellect unless the man or woman be alive to all the impressions that come to them from the great world of humanity and nature. I have laid down no hard and fast methods of teaching. Indi- vidual experience is the best indicator of method. Let me say one thing, however. The value of Geography as a study lies in its relations with other studies. Political Geography, so called, hinges directly on Physical Geography, and the two should be brought before the youthful mind as essential elements of one great study. This aspect of the subject is History in its widest sense. It is also Natural History. Every shower of rain, every breath of air, every flower, every living thing, holds a lesson for us — in Geography. The education of every child is the history of the entire race. The same world, stirring with life, still surrounds us ; we are to feel it, to know it, to grasp its meaning if possible with a living sense of the eternal fitness of things. CHAPTER I. SOME PAST AXD PRESENT ASPECTS OF THE EARTH. Readinc in Connection with the Lessons of this Chapter. Works »iarked * are especially icseful. *Physiography. — Huxley. Elements of Geology. — Le Conte. *Comparative Geography. — Ritter. *Dar\vinism (Chap. XII.). — Wallace. * Humboldt's Cosmos. LESSON L — LAND AND WATER. Coast Lines. — The coast or shore Une — that Hne which marks the boundary between the great bodies of land or continents and the great bodies of water or oceans — is, and ahvays has been, a scene of wonderful activity in the play of those forces which are so potent in the long process of building up and tearing down the surface features of the earth. We stand u])on sandy beaches beholding the labor of ages, the long and slow piling up of grains of quartz into beds of immense thickness. On bold and rocky coasts we see the results of a grinding and wearing action in cleft and cove and overhanging cliff. The granite rock is mainly a mass of quartz, and the obvious conclusion as to the relations between the rocky headland and the low, sandy beach is that of cause and effect. Ever since the first land appeared the waves of the ocean have ceaselessly battered against ID LAND AND WATER. 11 its rocky shores, some portions of which, more readily yielding to the disintegrating effect, have gradually worn away. The vast quantity of sand thus formed has been slowly shifted along the coast and spread over the marginal sea bottom. The further action of the waves heaps up this sediment into beaches. Wave action is not the only source of sedimentation along the coast line. Rivers draining the land wash immense quantities of mud and sand out into the ocean, which form vast deposits at their mouths. In this way great deltas are formed when the river empties into a bay or gulf but little affected by the tides, such as the Mississippi, the Nile, and the Po. This enormous deposit of earthy matter — sand and mud — occurring along the shore line has largely aided in producing the most important relief forms of the continents ; namely, mountain ranges. Height and Depth ; Mountains and Sea Bottoms. — From the coast line, as the boundary between land and sea, the surface of the earth gradually rises on the one hand above the sea level, and on the other hand passes below the surface of the water to form the sea bottom. The land may rise more or less abruptly into a succession of hills, finally culminating in lofty mountain ranges, or broad and low plains may extend inland for many miles, gradually rising into some ' height of land.' The sea bottom may slope gently, extending many miles from shore as shoals and shallows. Sooner or later, however, it falls off more or less steeply into great depths, forming in this way a sub- marine bank. The bottom of the ocean, like the surface of the land, is traversed by mountain-like ridges, the highest tops of which appear above the surface of the sea as islands. Many islands occur in groups lying off the shores of the continents, like the British Isles, Japan, the Philippines, etc., and have once formed a part of the mainland. Mountain ranges stand in a certain relation to the oceans. The great ranges of the earth, as the Himalayas, Rocky Mountain 12 PAST AND PRESENT ASPECTS OF THE EARTH. system, Andes, and the mountains of East Africa, rise from the lands bordering on the largest body of water, the Pacific and Indian considered as one ocean. The Atlantic appears as a narrow trough toward which the lands on either side slope gently as long plains, broken, in some instances, by smaller, secondary mountain ranges. This is seen in the Appalachian system of North America, the mountains of Brazil, the Ural range of Eurasia, the Kameroons and low elevations of Western Africa. The North Polar Area is a basin-like depression toward which the land gently slopes as long plains. The great plains of Russia and Siberia and the Barren Grounds of British America, stretching to the shores of the Arctic Ocean, are instances of this. The great rivers of the world taking their rise in the higher mountain ranges traverse these plains and empty into the Atlantic and Arctic oceans. Note the Missouri and Mississippi in North America, the Amazon, La Plata, and Orinoco in South America, some of the larger rivers of Europe, and the Nile, Niger, and Congo in Africa. The Mackenzie, Yukon, and Nelson rivers in British America, and the Dwina, Obi, Yenisei, and Lena in Eurasia, are some of the great rivers emptying into the Arctic Ocean. Comparatively few large streams find their way to the Pacific, because that ocean is nowhere surrounded by extensive plains. Permanence of Main Geographical Features. — The large features of the earth's surface — the sites of the present continents and oceans — have always been much the same. Land and sea on a large scale have nowhere and at no time in the history of the earth exchanged places. The great depressions in the crust have from the very beginning been occupied by the oceans as the result of physical laws. Land first appeared above the surface of an ancient ocean, world wide in its extent, by an uplifting process which resulted from the very nature of the earth's genesis and history as a part of the solar system. The earth was at one time much hotter than it is now, and its substance much softer and more yielding. Indeed, it is highly LAND AND WATER. 13 probable that it started as a cloud of glowing vapors which gradu- ally lost their intense heat and became liquid or molten in char- acter. In this state it must have presented the appearance of a great ball of fused matter like the flux from an iron furnace. Still losing heat, its outer portion slowly hardened until a solid crust was formed of some thirty miles thickness. This crust cooled very unevenly, especially in its under layers, and as a result it shrank more in some places than in others, producing an uneven or wrinkled surface. As cooling went on, the dense atmos- phere of vapor surrounding the earth was condensed into liquid or water, and this water filled up the hollows of the uneven sur- face. In this way the ocean was formed. It is altogether prob- able that this primitive sea spread around the entire earth, not only filling the great depressions of the crust, but even covering the tops of the highest ridges or wrinkles. The surface of the crust was now a sea bottom, and the cooling and shrinking pro- cess still going on in its deep layers, the great wrinkles were finally pushed or lifted above the surface of the ocean and appeared as the first laud. In this way the present broad feat- ures of the earth were, at a very early period, roughly mapped out. This shrinking process took place at a very slow rate, and is still going on in many places, unnodced, however, on account of the extreme slowness of its movement. In some parts the crust is sinking, in others risitig, the one often complementary to the other. This change of level was without doubt true of the Mediterranean region in a past period of the earth's history. It was anciently a land area which slowly sank, letting in the waters of the Adantic Ocean, at the same time leaving scattered rem- nants of the old land mass above the surface in the form of numerous islands and peninsulas. These islands and peninsulas were the highest parts of ancient mountain ranges which were not entirely carried under by the sinking process. To this fact is due the present peculiar features of this remarkable inland sea and their effect on the development and destiny of various nations. As this portion of the crust sank, the present area of 14 PAST AND PRESENT ASPECTS OF THE EARTH. the Sahara desert, then a sea bottom, probably arose, and its vast deposits of salt help to confirm this fact. So in the Pacific Ocean the entire sea floor has been sinking for thousands of years, while the western part of North America has slowly risen to form the plateau region. Off-shore islands separated from the main- land by shallow straits and seas offer evidence of a submerged shore hne. The coast of Norway is said to be rising, that of Greenland sinking, and this last fact is so well recognized by the natives that they never build their dwellings near the shore. Huts previously built on the edge of the sea now stand partially submerged. The Thousand-fathom Line and what it teaches. — Though the continents and oceans have undoubtedly occupied their present positions from the beginning, yet changes in the relations of land and sea have frequently occurred. These changes have been alons the shore line. In his work on " Darwinism " Alfred Russel Wallace devotes some space to the subject of the thousand- fathom line about the continents and its probable significance. In his map he shows by a contrast of color the former much wider extent of the shore lines of the continents as marked by the depth of a thousand fathoms off shore. All within this line to the existing shores of the continents represents, in all proba- bility, iosf land — land that has sunk beneath the waves. The significance of this becomes apparent when we study the Mediter- ranean region in all its past and present relations ; the northern regions of Eurasia and America in relation to the North Atlantic and Pacific areas ; the groups of islands lying off the shores of the continents ; the shores of the Indian Ocean, Australia, and the islands of the Malay Archipelago in connection with their past and present life features. It is not within the scope of this book to enter at length into these inviting problems. Bear in mind, however, that it is along the coast lines of the continents that the changes of level have occurred, which, in the course of time, have so greatly modified the surface features of the earth. LAND AXD WATER. 15 "I drive my wedges home, And carve the coastwise mountain into caves. I with my hammer pounding evermore The rocky coast, smite Andes into dust, Strewing my bed, and, in anotlier age, Relsuild a continent of better men. Then I unbar the doors : my paths lead out The exodus of nations : I disperse Men to all shores that front the hoary main." Origin of Mountain Ranges. — The situation of mountain ranges in relation to the oceans is explained in the following way. The shore line, as already stated, is the seat of a vast accumulation of sediment, often many thousand feet in thickness. In past time these enormous beds of sand and clay become hardened or con- solidated throughout their underlying portions from the pressure exerted by the increasing weight of the top layers, and strata of sandstone, shales, and slates were thus formed. The immense weight and pressure of these rock beds induced a greater degree of heat in that portion of the crust included in the area of mar- ginal sea bottoms, and this heat tended to soften the rock mass. As a result of unequal shrinkage a certain amount of lateral pres- sure took place from time to time, causing the crust to bulge at its most pliable point, namely, the marginal sea bottoms, and this bulge finally appeared above the surface of the ocean as new land added along the beaches of the old. Increased pressure upon the edges of these great beds of softened rock, from move- ments in the surrounding portions of the crust, would continue to push the new land higher and higher until it appeared as a mountain range flanking the shores of the ocean. The experi- ment of taking layers of clay in a suitable vessel of water and pressing on the sides of the clay with the. hands gives a similar result. Indeed, 'it is highly probable that mountains originated in this way, as is shown by the following proofs, i. The flanks or sides of mountain ranges consist of immense beds of stratified rocks, and stratified rocks are the consolidated sediments formed 16 PAST AND PRESENT ASPECTS OF THE EARTH. by water. 2. These stratified rocks contain the fossil remains of marine animals in abundance, showing that at one time they must have formed a part of the sea bottom. 3. The interior or cen- tral core of a mountain range consists of granite-like rocks, mas- sive and dome-shaped, over which the stratified rocks lie like a saddle. Granite, gneiss, and various other crystalline and glassy rocks form the great bulk of the crust underlying the sedimentary or stratified rocks, outcropping here and there upon the surface. They are igneous or fire rocks, having cooled and crystallized from an original highly heated, molten mass. Mountain ranges thus appear as upheaved marginal sea bottoms. The Heat of the Earth ; its Cause and Effects. — Geologists now incline to the theory that the earth consists of a densely solid nucleus or central portion between which and the outer crust is a layer of semi-fluid material in a state known as hydmthennal fusion, or fusion in the combined presence of heat and water. This heated, semi-fluid layer is manifested on the surface in various places as the outpouring of lava or melted rock from volcanoes, and the presence of geysers and hot springs. The cause of the internal heat and fusion is not thoroughly known, but is thought to be due largely to the crushing and grinding action of immense masses of rock and in part to a chemical action. The effect of the earth's internal heat over large areas is con- spicuous. In Western North America vast fields of lava occur from the overflows of ancient volcanoes. The Pacific Ocean is surrounded by volcanoes both active and extinct, and this in con- nection with the sinking of the sea bottom and the near presence of high mountain ranges, among which many of the volcanoes are situated, throws considerable light on the fact that interior heat is probably the. primary cause of many surface features. Outside of this region the Mediterranean volcanoes, in an area of subsidence, are also remarkable. This earth energy finds its primary cause in the attractive power of the sun. The earth has passed, in its long history, from LAND AND WATER. 17 a sphere of cloudy vapor through a Ucjuid, into an increasingly contracting solid state. Through all this it has steadily lost heat, and its present activities are only the ghosts of its past giant forces. Like its satellite the moon, it is destined to pass from old age into a cold, dead planet destitute alike of air, water, and life. The Action of Water. — The elevating force, converting portions of the primitive sea bottom into a land surface by lifting it above the surface of the ocean, has always had a counteracting agent in the destructive force of water. No sooner was any considerable land surface presented above the sea level than the vapor of the ocean, condensing into clouds, poured as torrents of rain upon the face of the dry earth. Rain soaks through soil, finding under- ground channels which bring the water to the surface again as springs, or, when in excess, runs off the surface in muddy rills. All this water is ultimately gathered into streams flowing from higher to lower levels, and through the large rivers it finally reaches the ocean whence it started. This circulation of meteoric water is attended by a slow but impressive wearing down of land surface. The action of the atmosphere in disintegrating rock into soil still furthei- prepares the way for the destructive action of water. Water itself is not the eroding agent ; the sediment or grains of sand which it carries in suspension is the graving tool sculpturing the face of the earth throughout all ages of time. At a distance we behold the mountains in mass and outline standing against the sky, seeing, as a geologist somewhere expresses it, only the evidence of the uplifting forces of nature. Once among the mountains, we lose -sight of this, seeing only the mighty effects of water, — gorges, chasms and ravines ; bare, jagged cliffs ; torrents and cascades cutting their way still more deeply into the solid rock. Everywhere, dn lowland and highland, by the seacoast and on the tops of mountains, we see the marvelous results of the action of water. The varied features of scenery are largely the result of the cut- ting and carrying power of water. Narrow valleys, flumes, caiions, c 18 PAST AND PRESENT ASPECTS OF THE EARTH. and cataracts are prominent features of the cutting or erosive action of water in all parts of the earth. In the lower reaches of rivers, broad flood plains are formed by the checking of a sedi- ment-laden current as it meets the incoming tide of the ocean. The river spreading out in times of flood, drops its burden of mud over a wide area, leaving broad, marshy flats when it recedes into its main channel. Plains thus grow by the accumulations of mud carried down by rivers as a result of erosion in their upper or tor- rential courses. Deltas are similarly formed by the velocity of the rivers' flow, carrying mud out into a comparatively tideless body of water. These low, marshy regions are peculiarly liable to overflow, as in the case of the Nile, the Mississippi, the Ganges, the Po, the rivers of China, etc. In the form of ice, as glaciers, water has sculptured the surface, making a characteristic landscape in many countries. In a past age of the earth, glaciers spread widely over many northern lands, leaving a ' drift ' of bowlders and moraines, billowy hills, river terraces, antl wide mountain valleys as characteristic features of scenery. The effect of the glacial period upon climate and the distribution of life and its probable relations to early man are subjects of extreme interest. Action of the Atmosphere. — The chemical action of rain water gradually dissolves the cementing material of rocks, allowing them to fall away as loose masses of sand and earthy matter. In this way soil is formed by the so-called 'weathering' of rock. The effects of frost in breaking up masses of rock are conspicuous in temperate and cool countries. Water penetrating into rock fis- sures expands in freezing, and in this way plays an important part as a disintegrating agent. On low, sandy beaches the wind piles up the sand into immense dunes which flank the shore for miles and gradually work inland, frequently encroaching upon, and in some places entirelv obliter- ating forests and fertile lands. The same is true of tlie desert sands, the winds blowing them from deserts over neighboring countries. In this way they gradually encroach upon fertile lands LAND AND WATER. 19 and in time completely overwhelm them. This is seen in some parts of Egypt and along the borders of the Sahara, where the desert sands are piled about the bases of the Pyramids and over the vegetation of the Nile Valley. Living Matter and its Effects. — The soil of a forest is the accu- mulation of the fallen leaves and rotting tree trunks of centuries. It is known as vegetable mould, and in most places, wherever plant life abounds, forms an important element of the soil. In the presence of water, as on the shores of a lake or in a marsh, and where the climate is sufficiently cool and moist, this vegetable matter is slowly converted into thick beds of a black, mud-like material known as peat. Still further compression and solidifica- tion by overflows of silt and clay bring about a hardening, and this fact throws light on the probable origin of the coal measures in various parts of the world. Peat bogs often form in a com- paratively short period, in some instances entirely hiding impor- tant landmarks. Thus in Europe, old Roman roads have been lost under peat formations. Bog iron ore, the workable form of the metal, results from the presence of organic matter which takes an excess of oxygen, and thus reduces the iron from its higher state of oxidation. It is in this higher, but unworkable state, that iron exists widely diffused through the crust, imparting a charac- teristic red color tp many soils. Limestone and accumulations of lime result from the immense deposits of the shells of various marine animals, notably the Foram- inifera and coral polyps. The chalk of France and England is a hardened material almost identical with the lime ooze of the Atlantic sea bottom, and undoubtedly represents an upheaval of this deposit in past ages. The growth of coral polyps has re- claimed lost land over a considerable area in the Pacific, growth taking place at a slightly faster rate than the subsidence of the sea floor. In this way numerous reefs have been formed, on the tops of which islands are gradually built up by wave action. Birds, winds, and ocean currents carry the seeds of plants and disperse them over wide areas. By this means vegetation has sprung up 20 PAST AND PRESENT ASPECTS OF THE EARTH. and covered many of these islands.' Extensive caves often occur in limestone districts from the dissolving action of underground waters containing carbonic acid. In many places these caves have played an important part as slielters in the early history of mankind. Soil and Forests. — The character of the soil often influences the vegetation over wide areas. This results largely from the nature of the combined elements of soil, giving rise to certain mechanical conditions. Thus a soil made up largely of sand is loose, allowing water to percolate freely through its beds, while a clay soil is stiff and lumpy and more or less completely impervious to water. A mixing of these two elements, sand and clay, is un- doubtedly the best soil for plant growth. The stiff loam of our middle prairie lands may possibly have been a factor operating against the growth of a forest. The roots of plants penetrate the soil, thus forming channels along which water finds its way. Earth- worms Hkevvise perform an important part in plowing the soil by bringing the deeper layers to the surface and thus exposing them to the influence of air and sunlight. The roots of plants tend to hold soil together and prevent its too rapid washing by rain and rivers. Marshes are formed in this way, the sod of mud and grass roots being often two and three feet in thickness.^ The veg- etable mould or humus from the decay of plants forms an impor- tant element of soil, and a source of food supply to the seedlings and young undergrowth. 1 In tropical seas the completion of an island is often due to the growth of the mangrove and cocoanut. The mangrove is a tree of low, marshy seacoasts, and grows out of the water, spreading itself by the formation of adventitious roots, or long branches that strike downward from its limbs and take root in the mud to form new tiees. The conditions of shallow water on the top of a coral reef or a submarine bank are entirely favorable to the growth of this tree, and its form of reproduction is curiously fashioned for dispersal over shallow seas. Mud accumu- lates rapidly about the mangrove roots, and forms a resting place for the cocoanuts that drift about in their tough, buoyant husks. Dry land gradually appears from the growth of mud, and this is soon covered with the tall palms and low mangrove swamps which are so characteristic a feature of tropical shores and islands. - See article by J. Gifford on "Salt Tide Marshes of South Jersey;" Science, Vol. xxii. 556, /,//'■/'; AA'D THE EARTH. , 21 Forests have an imijortant inlluence on the cHmate and rain- fall of a country. Their canopy of foliage acts as a shelter from the heat of the sun and the washing effects of rain. The immense area of leafage exposed acts as a vast evaporating surface and also radiates heat into the surrounding air, thus equahzing the con- ditions of moisture and temperature. Wy this means prolonged periods of drought followed by heavy downfalls of rain are averted and the perennial flow of springs is maintained. The forest has exerted an important influence on mankind throughout history. It has formed a natural hiding place and shelter, a harbor for the wild animals of the chase, a source of timber supply and of many varieties of food. By no means the least has been its widespread influence upon climate. In the advance of civilization the cutting off of the forests is a menace to the welfare of a country. LESSON II. — LIFE AND THE EARTH. Life a Part of the Earth's Surface. — The greatest feature of the earth's surface is the life that dwells upon it, and of which man himself forms a part. The multitude of living beings that find a home in the waters of ocean, lake, and river, or on the surface of the land, are, each and all, a part of this wonderful sphere, in every way dependent upon it for their existence. The simplest speck of jelly endowed with this living or vital prin- ciple ; the highest creature, man ; the grass and flowers that make beautiful the face of the land ; the rock masses and minerals of the crust, were all breathed into existence as a part of the earth. The infinite variety of the living beings that people the earth is the result of life having slowly unfolded from the simplest be- ginnings, like a plant from its seed. Life is the earth itself. Without hfe the earth would be a dead sphere ; a world without a history. Animal Life. — Two kinds of living beings inhabit the earth, — animals and plants. Some kind of animal is found in evefy part of the earth, from pole to pole, and from the highest mountain 22 PAST AND PRESENT ASPECTS OF THE EARTH. summits to the deepest depths of the ocean. The wonderful variety of forms is a striking feature of animal life. The animal is fitted to all conditions of existence — the fishes and creatures of the sea to a life in the water ; the land-living or air-breathing forms to the varied states which such a life offers. The higher animals, like the backboned creatures, — beasts, birds, etc., — are distributed over the earth in relation to climate and other causes which led in past time to their present geo- graphical distribution. First among these causes was the search for food, brought about by the cutting down of the food supply in the places where they lived, on account of the increasing number of individuals. Wandering over the earth, they met with various checks or barriers in the shape of mountains, deserts, oceans, cUmate, etc., which tended to stop their wanderings .in certain directions, producing in time the present features of animal dis- tribution. Vegetation. — Plant life is widely spread over the face of the earth, giving rise to prominent features of various regions. Some regions are covered with vast forests ; others are treeless pasture lands ; others, again, are barren deserts, with little, if any, vegeta- tion. All this is largely the result of climatic conditions, rainfall, etc., as well as topographical features, lay of the land, mountain tops, lowlands, etc. The character of the vegetation differs in various regions. The virgin forests of the tropical zone abound with the most wonderful forms and varieties of plant life. The vegetation of the temperate zone is a strong contrast to this, forests of entirely different trees characterizing the landscape. The Arctic regions are, for the most part, barren wastes, covered here and there with a few stunted alpine shrubs and wild flowers. The Air or Atmosphere. — The atmosphere is the gaseous envelope surrounding the solid earth, and extending to the height of many miles. It is literally an ocean of air in which we and all other land animals live, containing a principle without which life could not exist. This principle is a gaseous element called oxygen. LIFE AND THE EARTH. 23 Its Relation to the Surface. — The air is the great reservoir into which a large portion of the surface water of the earth passes as vapor to be circulated over the land in the form of clouds. These clouds are carried by currents of air or winds, their vapor falling as rain, to be again returned to the ocean through the rivers. It is also the great distributer and equalizer of the sun's heat, receiving the heat radiated from the earth's surface and modifying the direct rays of the sun passing through its cloudy vapors. The water of the ocean is salt, from the various min- eral matters that are leached out of the rocks by rain water, and carried into it through the rivers ; but by evaporation into the air it becomes fresh, the salt being left behind. Hence rain water and the water of springs, rivers, and many lakes is fresh. Its Relations to Life. — Without this atmosphere or air life were not possible. It is the great medium from which animals and plants draw the materials for their existence, and through which the interchange of material between the plant and the animal takes place. The animal breathes in the oxygen of the air to carry on its vital activities. This act of living in the animal pro- duces a waste material called carbonic acid, which the animal throws out in its breath as a gas. This goes into the atmosphere, and is the substance upon which the plant feeds. Its leaves absorb carbonic acid gas, and this is converted into starch, which forms a large part of the plant's substance. The animal, in turn, feeds on the plant, thus getting back material to make good the loss to its body caused by the wasting action of oxygen. The plant also at times gives out oxygen from its leaves into the air. Both plants and animals absorb a great deal of moisture from the atmosphere and throw it off again from their bodies. Animals living in the water get their oxygen from the air, though indirectly, as water always absorbs a certain amount of air, especially when it foams and breaks on the surface. We thus see how animals and plants are dependent for their very existence, upon one another and upon the atmosphere. Distribution ; Primary Life Areas of the Earth. — The ques- 24 PAST AND PRESENT ASPECTS OF THE EARTH. tion of the distribution of animals and plants over the earth's surface under the conditions of climate, topography, etc., resolves itself into the consideration of seven primary areas characterized by the number of peculiar forms, of both animals and plants, in each. Dr. J. A. Allen has recently summed up his views upon this subject in an exceedingly interesting and valuable paper.^ In our Introductory Chapter the divisions as outlined by Sclater in 1857 were briefly alluded to. In the lapse of more than thirty years many facts have been ascertained in both Biology and Geography which shed new hght upon the subject. These are embodied in Dr. Allen's classification of the Ufe areas as follows : — " (i) An Arctic Realm, occupying the region northward from about the limit of forest vegetation, or from about the isotherm of 32° F. It is characterized by its paucity of life and its homo- geneousness, nearly all its forms of both animal and vegetable life ranging throughout its whole extent. " (2) A North Temperate Realm, extending from the northern limit of forest vegetation to the northern border of the palm belt, or between the annual isotherms of 32° and 70° F. " (3) An American Tropical Realm, consisting, as the name implies, of tropical America. " (4) An Judo- Africa 11 Realm, consisting of Africa (except the northern border), and tropical Asia and its outlying islands. "(5) A South American Temperate Realm, embracing extra- tropical South America. " (6) An Australian Realm, including not only Australia, but New Guinea, New Zealand, and the various groups of islands to the northward and eastward. " (7) A Lemurian Realm, consisting of Madagascar." From this it will be seen how closely the life areas conform to climate as well as to the general distribution of the land masses. 1 "Tlie Geograpliical Origin and Distribution of North American Birds, consid- ered in Relation to Faunal Areas of North America," The Auk, April, 1893. LIFE AND THE EARTH. 25 The North Temperate Reahii embraces two regions: (i) the North American Region, consisting of temperate North America; and (2) tlie Eurasia tic Region, consisting of temperate Eurasia. The Hfe forms of these two regions are very similar in many instances. Thus a species of bear, lynx, and wolf are essentially the same in both. The red deer of Europe has its counterpart in the so-called ' elk,' or wapiti, of North America. So with the bison and auroch and several other closely allied forms of animal life. A general similaritv characterizes the broad features of vegetation in the two regions. A zone of deciduous trees, oaks, willows, beeches, birches, etc., with a belt of pines, larches, and other conifers to the north, and a vast assemblage of herbaceous forms, give character to both the North American and Europaeo- Siberian forests. The American tropical and Indo-African realms, though under very similar conditions of climate, are strongly contrasted in their life forms on account of their wide separation by the ocean. The South American tropical forest, with its gigantic cinchonas, green hearts, cow trees, and other remarkable forms \ its curious sloths and anteaters ; its hosts of peculiar birds (among them the hum- ming birds), and its general scarcity of large mammals, is strik- ingly opposed to the tropical life of the Old World with its peculiar baobabs, banyans, giant grasses like the bamboo, and other no less remarkable forms of vegetation, and the wonderful development of large mammalia, — elephants, rhinoceroses, buffa- loes, antelopes, zebras, the giraffe, hippopotamus, the man-like apes, leopards, lions, tigers, hyenas, etc. Australia and its adjacent islands are especially remarkable for the development of marsupials or pouch-bearing mammals, like the kangaroo, wombat, etc., numerous peculiar birds, and charac- teristic forms of vegetation. Madagascar is the home of most of the existing species of lemur, a group of monkey-like mammals which was once widely spread over the earth. The South Ameri- can Temperate Realm has a life largely derived from the tropical region to the north modified by temperate conditions. These 26 PAST AND PRESENT ASPECTS OF THE EARTH. last three realms, the Australian, Lemurian, and Temperate South American, have derived their special life features from their pecu- liarly isolated position in relation to the rest of the great land mass reaching back to a very remote period of time. Madagascar, Australia, and the adjacent islands are the result of subsidence which surrounded them by an ocean barrier, while temperate South America is isolated by climate, being cut off from the North Temperate Realm (save along the higher ranges of the Andes) by the tropical zone. In a general view of the distribution of vegetation over the earth, we see the effect of climate as a primary cause, giving rise to a series of vegetable zones or belts characterized by the pre- dominance of certain forms. These correspond to the annual isotherms, the great forest regions being the result of the special conditions producing an abundant rainfall. Mountain ranges trending north and south carry temperate conditions far into the tropics, thus aiding the wide dispersal of temperate forms of both animals and plants. We thus recognize an Arctic belt of stunted vegetation extending to 32° F., a temperate forest belt from 32° to 70° F., and beyond this a palm belt of tropical vegetation in general. (See Climate, Isotherms.) The North American Region is divided into two Subregions : (i) a Cold Temperate Sub region, and (2) a Warm Temperate Subregion. The Cold Temperate Subregion extends across the continent, reaching from the northern limit of forests southward to about the mean latitude of 43° N. Its southern border is extremely irregular, owing to topographical conditions. The Appalachian Mountain range carries cold temperate features southward along its crest, appearing as a narrow belt penetrating the Warm Temperate Subregion. The influence of the great plains of the Saskatchewan, on the other hand, pushes its south- ern boundary line far to the north. The Warm Temperate Sub- region extends southward from this line to the palm belt or the northern limit of the American tropical realm. It is subdivided east and west as a result of physical conditions into two provinces : LIFE AND THE EAR 77/. -27 (i) an eastern or Humid Province, and (2) a western or Arid Province. These subregions and provinces are remarkably well defined by their life forms, both animal and vegetable. Their boundaries are nowhere abrupt, but overlap or pass gradually into one another. Certain broad features of flora characterize the subregions of North America. The Arctic Realm to the north is a region of saxifrages. The Cold Temperate Subregion is especially charac- terized by the abundance and variety of asters and goldenrods besides numerous heath-like forms, as the various species of huckleberries. Among forest trees the great variety of oaks and spruces is characteristic. A striking feature of the Warm Temper- ate Subregion is the abundance of magnolias, while tulip pop- lars, horsechestnuts, and locusts are conspicuous trees in the woodland landscape. These forms are all noted for their magnifi- cent blossoms. This subregion is also the center of rice, cotton, and sugar cane growth in the United States. Wheat and maize are grown over both subregions, though the latter attains its best development and highest degree of cultivation in the Warm Tem- perate. The Humid Province is throughout a fertile region, the greater part of its area being under cultivation. West of the looth meridian the eastern edge of the Great Plains forming the North American Plateau, marks the beginning of the Arid Province, characterized by the agave, yucca, and cactus forms of vegetation. Sequence of Life. — Living beings present a gradually unfolding series in the history of the earth, from simple beginnings to later complex forms. The oldest stratified rocks contain the remains of single-celled organisms in all respects like the lower forms existing to-day, and throughout the immense lapse of time, since life first began, the strata of the crust bear testimony to this unfold- ing plan of development. The older forms of life were aquatic, like the lower forms of to-day, water being the primitive element of existence. It was not until the atmosphere had parted with its excess of carbonic acid, through the action of the wide-spread vegetation of tlie Carboniferous period, that air-breathing animals appeared. 28 PAST AND PRESENT ASPECTS OF THE EARTH. In a universal ' struggle for existence,' which is a law of life, living beings strive to fill unoccupied places in the economy of nature, and in time become adapted to new conditions through a change in function and structure. This gives rise to diversity and subsequent ' origin of species.' Conditions of Life; Environment. —The earth's surface is the home of life — hence, the conditions of the surface are the con- ditions of life — or its environment. Land, air, water, heat, and sunlight are essential conditions of life. The distinctive feature of living matter is energy in the form of motion, growth, and reproduction. This results from the activity of oxygen, or com- bustion — the never-ceasing attack of that element upon living matter in an effort to form combinations with its elements. Waste of the living organism ensues, necessitating a constant renewal by food. This food is obtained from the surrounding elements, and is an important condition of life. , The Unity of Life. — Life, then, is a part of the earth's surface dependent upon its conditions for existence. From the lowest and simplest organism — a mere speck of jelly — up to the highest and most complex, as in man and the higher animals and plants, this unity of life, this dependence upon the same primary condi- tions, forms an essential and conspicuous feature. Furthermore, the most complex animal exhibits in its individual development the same steps as are seen in the long history of life as a whole. Whether we view the individual or the race, each alike begins as a simple germ potent with unseen but marvelous possibilities. Intelligence. — Man, as the crowning work of this wonderful thing called ' life,' reflects that intelligence which seems to per- vade all nature. He only, of the countless living beings, has recognized that ' something,' higher and greater than all life and nature, that — " divinity that shapes our ends, Rough-hew them how we will." The forces of nature have slowly wrought out through the long centuries of time the present aspects of the earth. Not for CONDITIONS AFFECTING THE DEVELOPMENT OF MAN. 29 themselves alone have these forces operated. The intelligence that manifested itself with the development of man as a part of nature grasps the inheritance of time, the opportunities of environment, rising above the mere blind instincts of tlie animal. Climate and physical forces no longer coerce man into complete subjection. A noted geographer once wrote a work entitled, " The Earth and Man." ^ In view of the intelligence that has so far fitted its home to suit its own purpose, might we not as truly say, Man and the Earth ? LESSON III. — CONDITIONS AFFECTING THE DEVELOP- MENT OF MAN. Mountain Walls. — The relative position of mountain ranges, table-lands, plains, and valleys, and the resulting determination of water courses have exerted an important influence in the history and development of man. The preservation of early civilizations, as those of China and India, and in later times that of Rome, though subject to barbarian invasion, was largely due to their position in lowlands flanked by lofty mountain barriers. The Swiss owe their long independence among the nations of Europe mainly to their impregnable position among the ranges of the Alps. So with Greece on her islands and mountainous peninsula. France and Spain have been greatly protected by a mountainous border ; while Austria, lying open to the Black Sea and the plains of Central Europe, has been from time to time the scene of inroads by Asian peoples, as attested by her present relations with Hungary and the Danube countries. The early settlements of North America, as Professor Shaler has shown, owe their pres- ervation in great part to the nearness of the Appalachian ranges, which shielded them from the greater body of savages occupying the region west of these mountains. The Peruvian civilization was developed on the western slopes of tlie Andes under almost temperate conditions of climate, and protected by the snowy 1 Guyot. 30 PAST AND PRESENT ASPECTS OF THE EARTH. crests of the range from the savages of the tropical forests to the east. Hardly anywhere do we find a better example than this of a mountain's influence in developing man ; for even the extreme dryness of the region was overcome under the stimulating effects of altitude. Mountain walls have had other influences than merely pro- tecting man from man. They are one of the most important regulators of rainfall, and hence determine the fertility of a region. China and India, the northern shores of the Mediterranean, the Pacific slope of Western North America, are examples of this influence. The character of mountain ranges themselves has played an important part in more or less completely separating neighboring countries. The Alpine passes have been important factors in his- tory, permitting intercourse among various European peoples. The Himalayas, on the other hand, affected by only a few passes, and those at a great height, have effectually isolated the surround- ing countries from any extended intercourse with one another. " Mountains interposed Make enemies of nations, who had else Like kindred drops been mingled into one." Continental Irregularity. — The outline or contour features of a continent have played a very important part in the development of nations. The deeply dissected coast line of Europe has greatly affected the history of the various peoples inhabiting the con- tinent. A glance at the map of Europe is sufficient to show how vast an extent of seacoast is presented by its irregular shore line in relation to the entire territory. With the exception of Switzer- land there is not an important country in Europe that does not possess a more or less extended seacoast, and that within tem- perate latitudes. Nearly all the important points of Western Europe are thus within easy reach of the sea. This has had an important influence in the destiny of European nations. The fostering influence of a sheltered body of water like the Mediter- CONDITIONS AFFECTING THE DEVELOPMENT OF MAN. 31 ranean was an important factor in the development of the early seagoing nations. Phoenicia, Greece, Rome, Carthage, Venice, were all nurtured under the protecting headlands and sheltered bays of an irregular shore line. Holland has been reclaimed from the sea. Spain has sent fleets from both Mediterranean and Atlantic shores. The Baltic nations have been seafarers from the days of the Vikings to the present time. The British Isles owe their great human interest in history to the sinking process that gave to the shores of Western Europe their present jagged out- line. In like manner Eastern North America was open to the early discoverers through its far- inland-reaching estuaries and navigable rivers. We may thus, for example, trace the history of coloniza- tion along the Great Lakes and the Mississippi Valley. South America and Africa have a comparatively even coast line, no great bays reaching far inland. Many of the rivers of Africa present a series of dangerous rapids for many miles before enter- ing the low coast regions. This is especially the case with the Congo and the Nile. The effect of this upon the inhabitants and the difficulty which civilized man finds in penetrating to the inte- rior is in a large measure the reason why Africa is still a " Dark Continent." River Valleys and Garden Spots. — All the great civilizations of history began in fertile river valleys, — Egypt in the fertile valley of the Nile, surrounded on all sides by the desert ; Babylon and the Assyrian civilization in the valleys of the Tigris and Euphrates. The Hindus on the Ganges and the Indus, the Chinese on the Yang-tse-kiang and Hoang-Ho, are examples of the river's influ- ence in the development of civilizations. In later times the Tiber and the Po nurtured the germs of great civilizing centers. In our own country the river valleys were the garden spots which invited the first settlers. Even in savage countries the densest popula- tion is along the great rivers. The navigability of rivers, as already alluded to, has been of the utmost importance to the peoples of history. 32 PAST AND PRESENT ASPECTS OF THE EARTH. The distribution of minerals, plants, and animals, and the con- ditions of climate have been throughout all time among the most important factors in the development of man. These will be further alluded to in later chapters. The great end in view through the operation of these various physical conditions is the evolution of the social state of man. Man and Man as well as Man and the Earth. CHAPTER II. CLIMATE. Reading in Connection with the Lessons of this Chapter. Works iiiarked * are especially useful. ♦Humboldt's Cosmos. ♦IsLind Life (especially chapters on Climate). — Wallace. Tropical Nature. — Wallace. Climate and Time. — Croll. ♦Articles on "Meteorology" and " Climate." — Encyclopaedia Britannica. ♦Eclectic Physical Geography. — Hinman. The Ocean, Atmosphere, and Life. — Elisee Reclus. LESSON L — THE ELEMENTS OF CLLMATE. Definition. — Climate is the character of the atmosphere dependent upon the condition of two primary factors, tempera- ture and moisture. The condition of these two main elements is influenced by : i, latitude or distance from the equator; 2, alti- tude or height above the sea level ; 3, distance from the sea ; and 4, prevailing winds and ocean currents. From all of these causes arises that diversity of climate which is so marked a feature of the earth's surface. We speak accordingly of a hot or a cold, or of a dry or a moist climate. The word ' climate ' is of ancient origin. It comes from a Greek verb meaning to incline, and was used by the ancients to signify the difference in the length of day and night, resulting from the slanting or inclination of the earth's axis in relation to the plane of its orbit. This fact was recognized 34 CUM A TE. by the ancient geographer Ptolemy (127-15 1 a.d.), who divided the earth's surface, from the equator to the arctic circle, " into chmates or parallel zones, corresponding to the successive increase of a quarter of an hour in the length of midsummer day." Latitude or Distance from the Equator. — On those parts of the earth where the sun's rays fall more or less directly downward, Fui. I. — Diagram illustrating the result of vertical and slanting rays of sunlight on th'e earth's surface. Parallel rays (i) falling vertically are concentrated on a smaller space of surface, A, B, and consequently exert greater power than the same number of rays falling obliquely (2, 3), which being spread over a larger space, C, B, are diffused and exert less power. the temperature of the air is raised. This is the case, as we know, in tropical countries and lands under the equator where the sun's ELEMENTS OE CUM ATE. 35 rays are always more or less vertical. Hence the term torrid or hot zone. As we go north or south from the equator, we pass through regions having a temperate climate, because the sun's rays fall slantingly, and consequently with less power. Here the " change of seasons " occurs as a result of the successive changes of position of the earth in its path around the sun. As the earth in its revolution thus brings the places on its surface under differ- ent degrees of slanting rays, it follows that a certain cycle of heat and moisture must result from this changing of the relative posi- tions of the sun and earth. In the tropics, as the sun appears to move northward or southward from the equator, the cloud belt follows, and the "rainy season" is ushered in. This occurs in lands just north of the equator in F'ebruary, and reaches the tropic of Cancer about September. As the sun and its cloud belt pass south again, a second "rainy season" will occur at certain places north of the equator later in the autumn. The rainy season of tropical lands north of the equator corresponds, therefore, with spring and summer in the north temperate regions and the mid- night sun of the long arctic day. The rainy season lasts, in a general sense, from April until October. In countries south of the equator, it is then the " dry season " of the tropics and winter in the southern realm. The rainy and the summer season south of the equator corresponds to the dry season and the winter of the north, from October to April. On account of the inclination of the axis, the curvature of the earth cuts off the rays of light from the polar regions for many weeks at one time of the year, while at another, the same cause gives these lands continuous daylight, as the sun is vertical north or south of the equator. The failure of light and heat in the polar regions throughout a greater part of the year makes them ice- locked lands of desolation.^ 1 The seasonal changes of temperature in the temperate zones are in great part due to the different relative lengths between the day and night, as a result of the relative change of the sun's position. Thus, the more continuous sunlight in the long day of the Northern summer is a factor quite as important as the highly- inclined rays. The cold of winter is likewise the result of a lessened amount of sunlight, due to the short day and long night. 36 CUM A TE. Altitude, or Height above the Sea Level. — The air of high mountain regions is much colder ihan that of lower levels and sea- board countries. Even at the equator eternal snow lies upon the crests of the higher ranges. A traveler climbing one of the lofty mountains in the tropics passes through the same zones of vegeta- tion that he would meet in going north from the equator to the pole. In the hot, moist lowlands, at the mountain's base, he is surrounded by a dense forest of luxuriant, tropical growth, palms, creepers, and great climbing vines, orchids, rubber plants, gigantic fern-like forms, brilliant-colored flowers, and all the wonderful pro- fusion of plant life that is so characteristic of tropical scenery. Ascending the mountain slope the traveler gradually passes out of the tropical forest into the belt of hard-wood trees, first the evergreen hard woods, as the live oaks and magnolias, and finally the upper deciduous trees of the temperate zone. Still climbing, he reaches the pine belt, — the birches, larches, and pines of the north temperate zone. The cold increases as he goes upward, the trees become stunted, and finally disappear (timber line). He finds himself, at last, in an open, alpine region, like that above the northern limit of trees, the ground covered with mosses, lichens, and short grasses. Above him towers the snowy range, a region of perpetual winter, with only a few arctic wild flowers blossoming along the snow line, 15,000 feet or more above the sea. Altitude, therefore, corresponds with latitude, climate and vegetation pass- ing through the same changes. Though the sun's rays pour straight down upon these high moun- tain redons, the climate is cold because there is so little surface off"ered to retain the heat. In the lower regions, near the sea level, the broad surface of land and sea absorbs an immense quan- tity of the sun's heat, which warms the surrounding air by radia- tion, just as a stove warms the air of a room by radiating the heat from its whole surface. The steep and comparatively narrow mountain ranges reaching far up into the sky allow what litde heat is absorbed by their surface to pass rapidly into the surrounding air, which soon dissipates it in space, and becomes increasingly ELEMENTS OE C/JMA7E.. 37 colder as the mountain mass narrows upward. For this reason, the moisture of the air falls upon the mountain summit as snow, which never melts above a certain limit (the snow line), because the conditions of temperature never change. These snow fields Fig. 2. — Diagram of vegetation zones of latitude and altitude. W, E, equator (also sea level), i, Zone of Palms (tropical) ; 2, Zone of Hardwood Trees, ever- green and deciduous (sub-tropical) ; 3, Zone of Deciduous Trees and Pines (tem- perate) ; 4, Alpine Zone (arctic and antarctic). feed a multitude of torrents that spring from the mountain sides, and go roaring and foaming down to make the great tropical rivers of Asia, Africa, and South America. ' Slope Exposure. — The effects of increased temperature con- ditions on the southern slopes of hills and mountain ranges in the northern hemisphere is conspicuous on the development and dis- tribution of vegetation. This is often marked by an early appear- ance of certain species of plants in the spring, and by the higher 38 CUM A TE. elevation reached by certain trees on the southern exposures. Thus on the San Francisco Mountain, Arizona, a peak nearly 13,000 feet high, a series of timber zones succeed one another, extending much higher on the southwestern than on the north- eastern slope. Rising from the desert of the Little Colorado, there is first the piiion or nut-pine belt followed by the pine, fir, Cv\^\ s. w. Tt. If.B. Fig. 3. — Diagram of a mountain, illustrating Slope Exposure (after Merriam). I, Desert; 2, Piiion Zone; 3, Pine Zone; 4, Fir Zone; 5, Spruce Zone; 6, Timber- line Zone; 7, Alpine Zone. R, relative position of sun's rays. spruce, and timber-line belts, and culminating in an alpine zone at the summit.^ In the southern hemisphere, from the different relative position of the sun, the northern slopes are exposed to greater warmth. Distance from the Sea. — In the temperate zone the climate of lands bordering on the sea is less severe and more uniform in character than in the interior of the continents. This results from the f:ict that a great body of water like the ocean retains the sun's 1 On " Slope Exposure " Dr. C. Hart Merriam, in Bulletin No. 3, United States Department of Agriculture (North American Fauna). ELEMENTS OF CLIMATE. 39 heat much longer than does the land. The surrounding air slowly receives this heat and is more continuously warm than the air over inland regions, so that in winter the climate of a seacoast is comparatively mild. In summer, for the same reason, the air over the ocean is not heated so fest as over the land, remaining cooler for a longer period, so that the climatic contrast between summer and winter is not nearly so marked in lands bordering on the sea as in those farther inland. The interior regions of North America, Europe, and Asia suffer extreme changes of climate, the mean summer and winter differ- ences of temperature amounting often to ninety degrees or more. Prevailing Winds and Ocean Currents. — The direction of winds blowing over regions is an important element in determin- ing climate. A wind blowing off the sea usually brings with it large quantities of vapor, which falls upon the land as rain, and also modifies the temperature. Winds blowing over the land are mostly dry, having been deprived of their moisture in crossing highlands and mountain ranges. This is the case with the west- erly winds of the Atlantic seaboard states, blowing, as they do, over an immense area of land and high mountain ranges. Ocean currents are even more powerful influencers of climate. The Japan current reaches far into the North Pacific, tempering the climate of the coast of Alaska and British America. Back of the mountain ranges of Alaska, a rigorous northern climate prevails, while its seaward slopes are evergreen, and its harbors always open. The Gulf Stream of the Atlandc produces similar effects. Sweeping along the shores of the United States, it spreads north- eastwardly, warming the air over the British Isles, and far up the coast of Norway, quite to the arctic circle. On the western side of the Adantic, the icy arctic current flowing out of Baffin's Bay and the Polar Sea makes Labrador, in the same latitude with Ireland, a land of desolation. Two types of cHmate are found, therefore, according to the situation of a place in reference to the above relations of land and sea, — Oceanic and Continental. 40 CLIMATE. From these general considerations of climate we may proceed to examine into the nature of the elements themselves, and, by so doing, gain a clearer view of the question of climate in its relations to man. LESSON II. — CLIMATIC ZONES. Cause of Climatic Zones. — The unequal distribution of heat and light upon the surface of the earth, as a result of the earth's form, motion, and the inclination of its axis, determines the so-called astronomical zones. The tropical, or torrid zone, 232° north and south from the equator, is the region over some part of which the sun is always shining vertically. The temperate zones lie north and south of this central torrid girdle, while 23!^° from either pole mark the arctic and antarctic circles, enclosing the north and south frigid zones. Isothermal Lines. — The astronomical zones, though of theo- retical value to the geographer, are of little practical use to mankind in general, when compared with the isothermal zones. The isotherm is a line drawn through all places having the same mean annual temperature, north or south of the equator. The irregularity of the isothermal line results from the configuration of the land, its altitude, relations to the sea and to ocean currents, to prevailing winds, moisture, rainfall, etc., in fact, to all the conditions that go to make up climate. Follow, for example, the isotherm of 50° F., north, around the earth. Starting in the Pacific Ocean, west of North America, it touches the shores of the continent at Puget Sound, about 50° north latitude, but soon deflects sharply to the south, bending around the high ranges of the Rocky Mountains, and thence across the United States, passing out on the Atlantic Ocean in the neighborhood of New York. Here it meets with the Gulf Stream, and bends north- ward to the British Isles, slowly dropping southward through the continent of Eurasia, cutting the northern shores of the Black, Caspian, and Aral seas. Bending still further south, on the CLIMATIC ZONES. 41 Mongolian Plateau, it passes through Korea and into the Pacific, between the northern and southern islands of Japan. It is not to be imagined that these places, traversed by the isotherm, have identically the same character of climate. Their extremes may be widely different, and yet the mean annual temperature be the same. The Isothermal Zones and their Oscillation. — Temperature zones bounded by isotherms, though approximating to the astro- nomical zones, have a far greater influence upon the destiny of races. The tropical zone lies between the isotherms of 70° F., north, and 70° F., south latitude. The isotherm of 70° north fol- lows an irregular line parallel to and somewhat north of the tropic of Cancer. It bends sharply north around the head of the (iulf of California ; skirts the Gulf Coast of the United States ; bends northward with the Gulf Stream in the Atlantic ; passes through the Canary Islands ; crosses Africa along the northern edge of the Sahara ; continues through Persia, and sweeping southward along the Himalayas touches the tropic of Cancer at the island of Formosa. The isotherm of 70° south crosses the tropic of Capricorn under the influences of the cold Humboldt current off the western coast of South America ; slopes southward across that continent into the Atlantic, where it cuts the tropic twice by a northward curve ; crosses Africa north of the Cape Colony, and bending northward again touches Capricorn in Central Australia. The thermal equator, in the Pacific, lies south of the true or astronom- ical equator, but sweeps northward along the northern shore of South America ; dips southward in the Atlantic, touching the equator, and bending north enters Africa near the mouth of the Niger, and passes into the Indian Ocean at Cape Guardafui. Sweeping south, it cuts the southern end of Hindustan and crosses the Malay Peninsula and Borneo. On either side of the tropical zone are the temperate zones, bounded north and south by the isotherms of 30° F. The northern isotherm of 30° F. bends northward in the Atlantic considerably beyond the arctic circle, owing to the influence of the Gulf Stream, but is otherwise far to the south in the great continental areas. 42 CUM A TE. By far the most interesting and important factor in these isother- mal lines and zones is their annual oscillation with the sun. Thus in July, when the sun has moved over Cancer, the isotherm of 70° north moves northward into British America, the North Atlantic, Central Europe, and Siberia, pushing the conditions of the temper- ate zone into the polar realm, and causing the brief arctic summer with its burst of alpine blossoms, its swarms of insect life, and flights of breeding birds. Tropical conditions are, at the same time, carried north into the temperate lands. The warm sunshine of spring quickens the life in seed and bud, calls " the squirrel and the bee from out their winter home," and urges the migrating bird to seek its nesting place in the northern wildwood. The heat of summer whitens the harvest fields and ripens the kindly fruits of autumn. With the waning sunlight of November the leaves loosen and fall from the trees, the birds move south, and the Frost Giant steals noiselessly into the woods and fields of the temperate zone. As the isotherms thus oscillate north and south with the sun, we see the cause of the increase and decrease of temperature over the earth, bringing with it the varying seasonal changes. Though the greater or less obliquity of the sun's rays is the essential fac- tor, the irregular curves of the isothermal lines show how vastly important are the physical features of land and sea in deter- mining climate.^ 1 An isothermal line is to be regarded, not as ■&. fixed line of mean annual tem- perature, but as one that moves north and south in relation to the increase and decrease of heat over the earth's surface from the greater or less slant of the sun's rays. Thus the coast of Alaska, the Central United States, and Lower Lake Region, Newfoundland, the Scandinavian Peninsula, Central Russia, Mongolia, Korea, and Northern Japan have the mean January temperature of 20-' F., while in July the temperature of these places does not correspond in any way. For instance, in July, the coast of Alaska has the same mean temperature as Northern Siberia, and the July isotherm of the Central United States passes through Northern Africa. The annual isotherm is a line drawn to represent the average sum of the mean monthly temperatures taken from observations covering a period of several years. WINDS, OCEAN CURRENTS, AND RAEXEALL. 43 LESSON III. — WINDS, OCEAN CURRENTS, AND RAIN- FALL. Primary Cause of Winds. — The atmosphere is in a state of unstable equiHbrium, heat and moisture being unequally' distrib- uted. It is losing or gaining heat in different regions, since the surface of the earth is heated unequally by the rays of the sun. A portion of land or sea heated above the temperature of the surrounding territory warms, by radiation, the overlying air, caus- ing it to expand. This warm, expanded air has a greater capacity for holding vapor than when cooler and more dense. In conse- quence, it eagerly takes up vapor by the process of evaporation from the surface of the ocean or from the waters of the land. It thus becomes lighter than the surrounding cooler air, since water vapor is lighter than air itself, and takes the place of a certain proportion of air in any given volume. In the process of expansion, this warm, vapor-laden air pushes the cooler air immediately above it against the whole mass of the E' TS ^ ^;^55j5j:j5 55^^^5^^5v^^^??S^^^^^^^^^^5S^p5^5^;;^ Fig. 4. — Diagram of Winds. A, B, surface of tlie earth ; C, heated portion of air, expanding upward along line a, b ; D, /?i, level of cooler air, compressed by being squeezed between a, b, and E, E^, the upper atmosphere ; C, Ci, C^, calm areas. Arrows indicate direction of winds. overlying atmosphere, causing an increase of pressure in the air thus squeezed which becomes denser and heavier in consequence. If we can imagine this expanded volume of air pushing up in the shape of a mound, then we can see how the dense and heavy air 44 CLIMA TE. above will slide down the slopes of the mound on all sides toward surrounding areas of less pressure, simply because it is heavier air and is under the influence of gravity. This movement of the air is a wind blowing some distance above the surface of the earth. Immediately over the surface, however, where the heated and expanded air is much lighter than the cooler and denser surface air surrounding it, a movement of air takes place on all sides from these surrounding denser areas toward the central heated portion. This movement is felt as a sensible 7i'ind or breeze blowing over the surface of the land or sea. Its direction is opposite to that of the upper currents of air. There is no appreciable movement in the warm, expanded area, as the wind, rushing in on all sides, rises as an up-draught just as in the case of a fireplace and its chimney. It is therefore an area of calm. In the surrounding areas of high pressure there is, likewise, no horizontal movement, as the upper, heavier air is always sinking down and taking the place of the surface wind that flows out toward the center. As the barometer indicates the pressure of the atmosphere under its various conditions, we know that the warm, moist, and expanding air is an a?'ea of low pressure- or low barometer, while the surrounding heavier, drier, and cooler air constitutes an area of high pressure or high baro/ncfer. A law governing the move- ment of the atmosphere can thus be formulated : Wi?ids always blow from high-pressure areas into lozv-pressure areas. Effect of the Earth's Rotation on the Direction of "Winds. — In the northern hemisphere a wind, blowing from latitudes near the equator toward the polar regions, is successively deflected from its original due north direction by the inertia of the earth's rotation, carrying the wind, as it blows, more and more to the east. This imparts a whirling motion to the wind as it sweeps around to enter the polar area. A wind blowing due south on a meridian in high latitudes appears to turn westward as it approaches the equator by being carried eastward on the same meridian. So a wind blowing due west or due east on a given parallel appears to turn toward the north or south, respectively, under the influence WINDS, OCEAN CURRENTS, AND RAINFALL. 45 of rotation. (See Diagram.) Winds in the northern hemisphere are thus deflected from their true course by being carried continu- ally eastward on the meridian at which they started. Thus, from the polar area, as a point of observation, winds are turned or deflected toward the right. An originally south wind thus becomes southwest; a north wind, northeast; a west wind, northwest; and ^^.__ SOUTH ^^••ection Of Tioia\'^on Fig. 5. — Diagram of a section of Northern Hemisphere, ilhistrating the effect of the earth's rotation in deflecting winds. (Observer at north pole.) P^ wind from the south blowing due north on meridian 3, is carried successively eastward by the earth's rotation, and is apparently deflected or turned to the right, as it advances, appearing as a southwest wind on reaching the position of meridian 4 (above parallel C). So a wind blowing due south on meridian 2 is carried east- ward and apparently turned toward the right, thus becoming a northeast wind. A west wind on parallel B, at meridian i, is apparently turned to the right, as the meridian advances eastward along the parallel, owing to the curvature of the earth, and becomes a northwest wind on reaching the position of meridian 2. In like manner an east wind on parallel B, between meridians 3 and 4, is apparently turned to the right, and becomes a southeast wind. an east wind, southeast, in the direction from which each blows. In their effort to reach the low-pressure area, they struggle, as it were, against this deflective movement, and keep curving around in an opposite direction, or toward the left. This produces a 46 CLIMA TR. whirl about the center of low pressure. Any loAv-pressure area in the northern hemisphere will thus have the winds describing arcs about it from right to left, or against the hand movement of a watch. The reverse of this is true in the southern hemisphere, taking the south pole as the center of observation. Thus, the winds will be deflected to the left, and will describe arcs from left to right, or with the hands of a watch, as they advance into the area of low pressure. As a result of this law, first pointed out by Professor Buys Ballot of Utrecht, if an observer in the northern hemisphere stands with his back to the wind, the center of low pressure will always be to his left, while in the southern hemisphere it will be to his right. Constant and Periodic Winds. — The same movement of air that takes place in any local area occurs on a grand scale between the heated equatorial region as an area of low pressure and regions of high pressure on either side. A constant movement of cold and heavy air blows as surface winds from about latitude 30° north and south toward the equatorial belt of low pressure. These are known as the trade winds} Being deflected from their due north and south course by the rotation of the earth, they appear as northeast and southeast winds. The warm, vapor-laden air of the equatorial region, rising as an upward-flowing current, constitutes a belt of calms? In the higher, denser levels, this air becomes cooled, and flows out on each side toward the northeast and southeast as upper, countercurrents of wind, known as the counter- trades. In the tropical belts of high pressure on either side (about 30° north and south) these cooled " counter-trades " 1 It was the steady blowing of these winds that so alarmed the shipmates of Columbus on his first voyage, they believing that the wind would carry them farther and farther away from the shores of Spain, and never allow them to return. 2 The region of the equatorial calms is known to seamen as the doldrums, characterized by cloudy skies, and light, baffling winds. The calms of Cancer, in the North Atlantic, in the neighborhood of the Sargasso Sea, are known as the horse-latitudes, from the fact that vessels carrying deck-loads of horses between New England and the West Indies were sometimes becalmed in this region, and forced to throw some of the horses overboard, as the water supply gave out. (See Maury, " The Physical Geography of the Sea " (8th cd,) , p. 276.) WINDS, OCEAN CURRENTS, AXP RAINFALL. 47 descend to the surface, and take the place of the outflowing "trades" moving toward the equator. Cahn belts are thus formed near the northern and southern limits of the tropics. From these high-pressure calm belts the air likewise flows out in the opposite direction as a surflice wind blowing toward the low-pressure polar area in each hemisphere. The low pressure of the air in the polar regions results from the depressing effects of the whirling motion of the winds, for winds approaching the poles move in ever-narrowing circles, from being turned aside by the rotation of the earth. A countercurrent blows as an upper wind from each pole toward the tropical belts of high pressure. In the northern hemisphere, from the preponderance of the land masses, these winds become much more variable in character, and further disturbances are induced by the unequal heating of land and water. This gives rise to storms, sudden changes of weather, and to periodic winds blowing on or off shore. Of these periodic winds are the sea and land breezes of coasts, as a result of the difference in the day and night temperature of the air over the land and the water. On a larger scale are the monsoons of the Indian Ocean and coasts of South America, which blow steadily for half the year in one direction, and then blow in an opposite direction for the other half. The monsoons are caused by the change of the sun's position in the heavens, bringing vertical rays over part of the great land mass, thus raising the temperature of the air, and causing a strong wind to set in from the ocean. Between April an;l October, when the sun is almost directly over Southern Asia, that region becomes an area of low pressure, and the moisture-laden monsoon blows steadily and with great force from the southwest. Storms. — The rush of the winds around the center of low pressure produces a whirling column of air, somewhat funnel- shaped, its center of lowest pressure being surrounded by belts of increasingly higher pressure toward the circumference from the development of centrifugal force incident to the whirl. These belts of pressure are termed isobars, and the difference between 48 CLIMA TE. them is iht gradient, or slope, from higher to lower pressure levels. On reaching the center the wind rises as an up-going current, which flows out above on all sides. These circling storms of wind are called cyclones, and are usually accompanied by clouds and Fig. 6. — Diagram of Cyclonic Movement in Northern Hemisphere, c, area of low pressure, or storm center. The large arrow, pointing northeast, indicates the track of the cyclone under the impulse of the strongest winds. The small arrows fly with the in-blowing winds from right to left, or against the hands of a watch. rain. The storm center is an area of calm, of low barometer, and small precipitation, surrounded by an area of heavy cloud sheets and copious rainfall. The nimbus, or rain cloud, extends about WINDS, OCEAN CURRENTS, AND RAINFALL. 49 it on all sides, fringed by the lofty streamers of cirrus clouds, "mare's tails" and "mackerel sky," the threatening sky of. approaching foul weather. The storm center has a forward move- ment under the influence of the strongest wind, and travels with varying velocity. The cyclonic storms of the northern hemisphere are frequently generated in the ocean area of the tropical zone, and move at first northwestward within the tropics, but on reach- ing the temperate zone turn to the northeast, thus describing a parabolic curve. The typhoons and hurricanes of the East and West Indies belong to this class of storms. A cyclonic storm may embrace an area of several hundred to a thousand or more miles in diameter. As it advances, it grows in dimensions from the in- crease of low pressure produced by the centrifugal force of the whirl- ing winds. The storm dies away as the result of friction ; more air entering the center than can escape at the top causes the whirl to finally lesseji in velocity, and a higher pressure is thus established. The high-pressure areas on all sides of a cyclone have the air flowing out from them as a whirl of winds in the opposite direction ; i.e. from left to right. These outward-whirling areas are known as a7iti-cyclones. Their winds, at first cold, grow increasingly warmer as they approach the low-pressure area, and are conse- quently dry, and accompanied by clear or fair weather. It has been observed that the most constant areas of low pressure in the northern hemisphere are distributed as follows : To the west-southwest of the Great Lakes in the United States ; the Gulf of St. Lawrence ; the Mid-Atlantic area ; an area southwest of Greenland ; one southwest of Iceland, which is the most important of all ; and one over a portion of Northwestern Europe. In these areas nearly all of the great northern storms are bred, and the direction of their path is governed by the surrounding conditions of pressure. For instance, the high winter pressure over North- western America drives a storm, developing in the Rocky Mountain region, eastward across the United States to the Atlantic seaboard. Easterly winds, bringing increased cloudiness and rain from the ocean, blow at first toward the advancing center of depression, which E 50 CUM A TE. has no sooner passed over a given locality than the wind veers to the west, and clearing weather with a " cold wave " from the area of high-pressure marks the westerly half of the cyclone. The pecul- iar characteristics of the winter and summer climates in Europe and the United States are largely the result of the tracks taken by cyclones under the surrounding conditions of atmospheric pressure. The term tvcaihcr relates to the local conditions of temperature and moisture at any given time and place. We speak of hot or cold, wet or dry, fair or foul weather in any locality at any time. It is the condition of the atmosphere of a place from day to day. Places in the path of an advancing storm have increased temper- ature and humidity as characteristics of weather resulting from the southerly and easterly winds blowing from warmer into colder areas, which causes increased condensation of their moisture, and the consequent liberation of a large amount of latent heat. The westerly half or " wake " of the storm is characterized by clear and cold, or cool weather, with dryness or decrease of liuniidity, because the north and northwest winds blowing from colder into warmer areas evaporate, or take up moisture, in increasing quantity. Thunderstorms, tornadoes and waterspouts are the result of local disturbances of the atmosphere. Tornadoes are supposed to be due to the formation of a narrow and violent whirl of air gen- erated within the larger whirl of a gentle cyclonic movement. Somewhere in this area the air, becoming highly heated, forms a focus of low pressure, which causes the gentle whirling winds about it to rush in with terrific and destructive force. The im- mense amount of vapor formed is condensed into a heavy, black cloud, which is twisted by the wind into its characteristic funnel- shaped form. The waterspout is a similar phenomenon, occurring at sea. In the same way the air over sandy deserts and dusty roads becomes superheated in places, and rises, while the sur- rounding air rushes in sweeping the sand and dust along in a whirling column. These dust whirls sometimes attain enormous proportions, as in the simooms of the Sahara and Arabian deserts. Ocean Currents. — From the unecjual distribution of heat in WINDS, OCEAN CURRENTS, AND RAINFALL. 51 different parts of the earth, a difference in the specific gravity of the water of the ocean takes place, as a result of which it is thrown into a series of currents in an effort to establish the proper equi- librium. At the e(iuat()r, the heated water of the ocean rises to the surface and flows away north and south, being displaced by colder, deeper, and heavier currents of water flowing in from each side. The position of the land masses in relation to the oceans, and the force and direction of the prevailing winds, modifies the direction of these currents and gives to each great body of water its characteristic circulation. A striking feature in oceanic circulation is the northern and southern whirls. In the Atlantic the equatorial current flowing west divides off Cape St. Roque, sending the so-called Gulf Stream northeastward along the American coast, while the Brazil current flows south along the eastern coast of South America. Part of the Gulf Stream flows into the Arctic Ocean, while the other portion flows south along the shores of Europe and Africa to join its par- ent equatorial current. This constitutes a ivJiirl in the North Atlantic, the center of which is comparatively quiet and character- ized by a vast area of seaweed, which has settled there from drift- ing, as a natural result. This is the so-called Sargasso Sea.^ In the South Atlantic there is likewise a whirl with its central Sar- gasso Sea, and so in the North and South Pacific and in the Indian Ocean the same essential features prevail. Rainfall. — The primary cause of a fall of rain is the lowering of the temperature of the air below the dew point. This is effecte