A. I. the se HARPER 8c BROT WORLD PL. I - Dramxbf A.Vvullenm NEW YORK A DESCRIPTIVE HISTORY OF THE PHENOMENA OF THE LIFE OF THE GLOBE. BY ELISEE RECLUS. TRANSLATED BY THE LATE B. B. WOODWARD, M.A., AND EDITED BY HENRY WOODWARD, BRITISH MUSEUM. ILL US TR A TED BY TWO HUNDRED AND THIRTY MAPS INSERTED IN THE TEXT, AND TWENTY-THREE PAGE MAPS PRINTED IN COLORS. NEW YORK: HARPER & BROTHERS, PUBLISHERS, FRANKLIN SQUARE. 1871. PUBLISHER'S ADVERTISEMENT. THIS work translated by the late B. B. Woodward, Esq., B.A. Lend., F.S.A., the Queen's Librarian at Windsor Castle, in his leisure hours, and edited, since his death, by his brother is the result of more than fifteen years' careful study, travel, and research, by one of the most able living French authors, ELISEE KECLUS. It has already passed through two French editions, and the pages of the present volume have, from time to time, received the benefit of the Author's attention. There is no work, either French or English, in which so great a task has been attempted, and achieved with such wonderful success.. The illustrations, both in number and excellence, surpass those of any similar work upon Physical Geography. * 9 The careful and laborious research displayed in the elaboration and completion of each portion of the book, and the harmonious manner in which the several parts are united, must insure for M. Reclus an hon- orable place in popular scientific literature. CONTENTS. PART I. THE EAKTH AS A PLANET. Page CHAPTER I. Smallness of the Earth as compared with the Sun and Fixed Stars ; Grand- eur* of its Phenomena. Form of the Terrestrial Globe ; its Dimensions 13 CHAPTEK II. Motion of the Planet. Diurnal Rotation and Annual Revolution. Si- dereal and Solar Day. Succession of Days and Seasons. Difference of Duration of the Seasons in the Two Hemispheres. Precession of the Equinoxes. Nutation. Planetary Perturbations. Movement of the Earth towards the Constellation Her- cules 16 CHAPTEH III. Various Opinions as to the Formation of the Earth. Laplace's Hypoth- esis ; grave Objections raised to it. Theory of a Central Fire ; Objections to it. 2-t CHAPTER IV. Geological Strata. Conglomerates. Sandstones. Clays. Limestones. Fossiliferous Beds. Sequence of Organic Beings. General Classification of Strata. Duration of Geological Periods .*. 32 CHAPTER V. Incessant Modification in the Shape of Continents. Attempts made to learn the former Distribution of Soils and Climates. Object of Geology. Province of Physical Geography 39 PART II. THE LAND. CHAPTER VI. Regular Distribution of Continents. Ideas of Ancient Nations on this Point. Hindoo Legends. Atlas and the Giant Chibchacum. Homer's Shield. Strabo 46 CHAPTER VII. Inequality of Land and Water. The Oceanic Hemisphere. The Sem- icircle of Land. Distribution of the highest Plateaux and loftiest Mountain Chains round the Indian and Southern Oceans. Polar Circle. Circle of Lakes and Deserts. Coasts arranged in Arcs of a Circle. 50 CHAPTER VIII. Division of the Land into the Old and Ne^l^Worlds. Double American Continent. Double Continent of Europe and Africa. Double Continent of Asia and Australia 59 CHAPTER IX. Principal Analogies between Continents. Pyramid Form of Portions of the World. Slopes and Declivities. Closed Basins of each Continent. Southern Peninsulas in each Group of Continents. Hypothesis of Periodical Deluges. Rhyth- mical Arrangements of Peninsulas 0-t <'ii\i'TKH X. Numerous Indentations of the Northern Continent. Heaviness of Form in the Southern Continents. Inequality of Size in the Continents of the Old World. Extent of Coast-line in Inverse Ratio to the Area of Land. Contrasts between the Old World and the New. The Transverse Position of the Axes of America and the Old World. Contrasts of Climate in the various Continents; North and South, East and Wot ... 69 v CONTENTS. Page CHAPTER XI. Harmony of Shape in Oceans. The two Basins of the Pacific. The two Bans of the Atlantic. The Arctic Frozen Ocean and the Antarctic Continent. Con- trasts, an Essential Condition of Planetary Vitality 76 CHAPTER XII. General Aspect of Plains. Alluvial Plains. Cultivated Plains. Uni- formity in Uncultivated Plains. Varieties in Appearance produced by Climates and different Physical Conditions 78 CHAPTER XIII. The French Landes The Brandes and the Alios. The Campine. The Heaths of Holland and Northern Germany. The Puszta of Hungary. The Grassy Steppes of Russia. The Salt Steppes of the Caspian and the Aral. The Tun- dras 81 CHAPTER XTV. Semicircle of Deserts parallel to the Semicircle of Landes and Steppes. The Sahara. Sands, Rocks, Oases. The Deserts of Arabia. The Nefoud. Deserts of Iran and the Indus. The Desert of Cobi 00 CHAPTER XV. Plains and Deserts of the New World. Humidity of the American Continents. Distribution of Savannahs and sterile Tracts. The Prairies of North America. The Llanos and Pampas 97 CHAPTER XVI. American Deserts. The Great Basin of Utah. The Desert of Colo- rado. The Atacama and the Pampa of Tamarugal. Deposits of Salt, Saltpetre, and Guano 102 CHAPTER XVII. Difference between Plateaux and Plains. Material Importance of Plateaux in the Economy of the Globe. Distribution of elevated Regions on the Sur- face of Continents * . . 107 CHAPTER XVIII. The Great Plateaux of Central Asia and the Gate of the Hindoo Kutch. Plateaux of Europe. Their symmetrical Arrangement. Plateaux of the two Americas. Similarity between the closed Basin of Bolivia and the District of Utah. Plateaux of Africa Ill CHAPTER XIX. Isolated Mountains. Mountains in Groups. Chains and Systems of Mountains. The Beauty of Mountain Peaks. Sacred Mountains. Pleasures of Mountain Climbers 117 CHAPTER XX. Various Forms of Mountains. Poverty of polished Languages in de- scribing their Appearance. Richness in this respect of the Spanish Language and the Alpine and Pyrenean Patois. The numerous Provincial Terms employed for va- rious Shapes of Hills and Mountains ., 122 CHAPTER XXI. Inequalities and Depressions in the Vertical Outline of Mountains. Origin of Valleys, Gorges, and other Depressions. Longitudinal Valleys. Transverse Valleys. Winding Valleys with Parallel Sides. Valleys with Defiles and Gradations of Levels. Cluses and Canons. General Arrangement of Valleys. Amphitheatres. The Oules of the Pyrenees.. j> 129 CHAPTER XXH. Depressions in Mountain Ridges. Diversity in the Form of Passes (Cols). Relation between the respective Altitudes of Summits and Passes. Law of Debouchments. Real and Ideal Slopes of Mountains. Estimated Solid Contents of Mountain Groups 135 CHAPTER XXIII. Hypotheses as to the General Laws of Mountain Chains. M. Elie de.Beaumont's Theory of Parallel Upheavals. Chain of the Pyrenees taken as a Type of the Cordilleras or Longitudinal Chain. Various Irregularities in the Chain. The Pyrenees as an Ethnological Barrier 139 CHAPTER XXTV. Mountains of Central Europe. Contrast between the Alps and the Jura. The Jura as a Type of a System of Mountains with Parallel Chains. Appar- ent Chaos of the Alps. Central Group of St. Gothard. Groups of Monte Rosa and Mont Blanc. The Alps considered as a Frontier. 144 CONTENTS. vii CHAPTER XXV. Mountain Chains of Central Asia. The Kouen-Lun, the Karakorum, the Himalaya. The South American Andes, a Type of the Bifurcated Chain 151 CHAPTER XXVI. Gradual Cooling of the Air on Mountain Sides. Difficulty of Ascents. Limits of Man's Habitation. Illness felt by Mountain Travelers 156 CHAPTER XXVII. Gradual Subsidence of Mountains during the Lapse of Ages. Sad- den Downfalls and Chaos. The Fall at Felsberg. Slow Action of Meteoric Agencies 159 PART IIL THE CIRCULATION OF WATER CHAPTER XXVIII. Snow-fall on Mountains. Lower Limit of Snow. Zone of Per- petual or Permanent Snow 162 CHAPTER XXIX. Influence of the Sun and Meteoric Agents on the Snow. Avalanches. Protecting Forests. Defensive Works against Downfalls of Avalanches 168 CHAPTER XXX. Gradual Transformation of Snow into Ice. Neve's, or Glacier-reser- voirs. Phenomenon of Regelation. Crystals of Ice. Glaciers of the First and Second Order 173 CHAFFER XXXI. Movement of Glaciers. Experiments and Theories. Convexity of the Central Part of a Glacier. Its successive Windings. Friction of the Ice against the Bottom and Sides of the Bed. The Glacier Gauge. Inclination of the Glacier Bed 177 CHAPTER XXXII. Marginal, Transversal, and Longitudinal Crevasses. Seracs. Monlins. Bridges of Snow. Veins of fresh Ice. Surface-streams on Glaciers. Gouilles. Lakes and Inundations. Discharging Channels 183 CHAPTER XXXIII. Debris lying on the Surface of the Glacier. Holes in the Surface. Glacial Tables. Moraines; Lateral, Medial, and Frontal. Ribbons of Mud. Measurement of the Speed of Glaciers. Ablation. Sub-glaciary Streams. Terminal Arches. Contrast between the Glacier Ice and the surrounding Vegetation 192 CHAPTER XXXIV. Progress and Retirement of Glaciers. Appearance of the Bed when abandoned by the Ice. Roches Moutonne*es. Parallel Furrows 201 CHAPTER XXXV. Distribution of Glaciers over the Surface of the Earth 206 CHAPTER XXXVI. The Glacial Period. Ancient Glaciers of Europe. Dispersion of Rocks and Boulders from Scandinavia and in North America. Ancient Glaciers in Tropical Regions 216 CHAPTER XXXVII. Secondary Part taken by Glaciers in the Circulation of Water. , Mountain Flood-waters. Absorption of Rain and melted Snow by the Earth, Peat- mosses, and Rocks. Springs and their Nymphs 222 CHAPTER XXXVIII. Variation in the Discharge of Springs. Estavelles. Equaliza- tion of the Supply in Springs with deep Sources. Intermittent Springs 227 CHAPTER XXXIX. Ascending Springs. Artesian Wells. Temperature of Jetting Springs 231 CHAPTER XL. Cold and Thermal Springs 234 CHAPTER XLI. Mineral Springs. Incrusting Springs. Metallic Veins. Salt Springs 238 CHAPTER XLII. Subterranean Rivers. The Spring of Vaucluse, the Touvre. Sub- marine Affluents. The Rios of Yucatan. The "Mud-lumps" of the Mississippi 245 CHAPTER XLIII. System of Subterranean Streams. Joints and Fissures of Rocks. Stalactites. The Inhabitants of Caves. The Mammoth Cave. Caverns of Camiola and Istriii . 251 viii CONTENTS. Page CHAPTER XLIV. Eivers. Various Denominations of Water-courses. Determination of the principal Branch among the Affluents of a River. River Basins and Water- sheds. Forks of certain Rivers 261 CHAPTER XLV. The Hydrographical Systems of various Parts of the World 271 CHAPTER XL VI. The River of the Amazons. Diversity in the Character of Water- courses. Unity of the Law which governs them. Equalization of their Slopes. Upper, Middle, and Lower Courses of Rivers 279 CHAPTER XLVII. Mountain Torrents. Inequalities of their Beds and of their Dis- charge of Water. Temporary Streams. Filling up of Lakes. Erosions, Gorges, and Slopes. Torrents of the French Alps 284 CHAPTER XL VIII. Erosion of Lacustrine Dikes. Cataracts and Rapids 296 CHAPTER XLIX. Formation of Islands. Reciprocity of Curves. Windings and Cut-' tings. Shifting of the Courses of Affluents 306 CHAPTER L. Periodical Rising of Streams. "Embarras" of Floating Trees. Ice- floods in the Northern Rivers. Inundations 317 CHAPTER LI. Means of Preventing Floods. Natural and Artificial Reservoirs. Irri- gation Channels Embankments, and Cracks in them . 325 CHAPTER LII. The Mouths of Rivers. Estuaries. Long Banks of Sand. Deltas. Net- work of Branches of Rivers in Alluvial Plains 339 CHAPTER LIII. The Channels of the Mississippi. "Working Rivers." Shifting of the Point of Bifurcation. Raising of the River-bed above the Delta. Alteration in the Situation of the Mouths of Rivers 349 CHAPTER LIV. Bars of Rivers. Operations undertaken for Deepening the Mouths of Rivers 363 CHAPTER LV. Alteration in the Position of Water-courses in Consequence of the Ro- tation of the Earth. Masses of Water brought down to the Sea by Rivers. General Considerations 372 CHAPTER LVI. Lakes. Formation of Lakes. Their Increase and Diminution. Their Form and their Depth. Lakes lying in Successive Gradation of Elevation 383 CHAPTER LVII. Various Phenomena in Lakes. Color of their Waters. Seiches. Currents and Tides. Formation of Ice in Lakes 394 CHAPTER LVIII. Lakes acting as Regulators of the Rivers which pass through them. Fresh-water and Salt-water Lakes. The Caspian Sea 399 CHAPTER LIX. The Dead Sea. The Salt Lakes of Asia Minor and the Russian Steppes. The Great Salt Lake. The Melr'ir 407 ^CHAPTER LX. Marshes. Swamps of North America. Peat-bogs. Unhealthiness of Marshes... .. 413 PART IV. SUBTERRANEAN FORCES. CHAPTER LXL Eruptions of Etna in the Year 1865. Mutual Dependence of all Ter- restrial Phenomena 419 CHAPTER LXII. Sea-coast Line of Volcanoes. The Pacific "Circle of Fire." Vol- canoes of the Indian Ocean ; of the Atlantic ; of the Mediterranean ; of the Caspian ; of Central Asia 426 CHAPTER LXIII. Torrents of Steam escaping from Craters. Gases produced by the Decomposition of Sea-water. Hypotheses as to the Origin of Eruptions. Independ- ence of the several Volcanic Outlets 433 x F*. CHAPTER LXIV. Growth of Volcanoes. Theories of Humboldt and Leopold von Buch as to the Upheaval of Craters. Disagreement of these Theories with the Pacts observed 440 CHAPTER LXV. Number and Arrangement of Volcanic Outlets. Form of Volcanic Cones and Craters 445 CHAPTER LXVT. Composition of Lavas ; Trachytes: Pumice-stone; Obsidian; Ba- salts ; Basaltic Colonnades 453 CHAPTER LXVII. Sources of Lava ; Stromboli ; Masaya ; Isalco ; Kilauea. Lateral Crevices in Volcanoes. Eruption and Motion of Lava 458 CHAPTER LXVIII. Volcanic Projectiles. Explosions of Ashes. Subordinate Volca- noes. Mountains reduced to Dust. Flashes and Flames proceeding from Volcanoes 468 CHAPTER LXIX. Streams of Mud ejected by Craters. Mud Volcanoes 475 CHAPTER LXX. Volcanic Thermal Springs. Geysers. Spring in New Zealand. Kuinerolles. Solfataras. Craters of Carbonic Acid 480 CHAPTER LXXI. Submarine Volcanoes 48!) CHAPTER LXXII. Periodicity of Eruptions. Influence of Temperature on Volcanic Phenomena. Extinction of Furnaces of Lava 497 CHAPTER LXXIII. Earthquakes. Vibrations of the Ground. Various Hypotheses . . 500 CHAPTER LXXIV. Earthquakes of Volcanic Origin. Subterranean Downfalls. Ex- plosions of Mines and Powder-mills 503 CHAPTER LXXV. Great Catastrophes. Earthquake at Lisbon. Area of Disturb- ance. Earthquakes at Sea 507 CHAPTER LXXVI. Movement of Terrestrial Waves. Variations caused by the In- equality of Vertical Outline and the Diversity of Rocks. Areas of Disturbance. Noise of Earthquakes. Fright of Men and Animals 511 CHAPTER LXXVII. Secondary Effects of Shocks. Springs. Jets of Gas. Fissures. Depressions and Elevations of the Ground 519 CHAPTER LXXVIII. Periodicity of Earthquakes. The Maximum in Winter. The Maximum at Night. Coincidence with Hurricanes. Influence of the Heavenly Bodies 523 CHAPTER LXXIX. Slow Oscillations of the Ground. Difficulties presented in the Observation of these Phenomena. Causes of Error : Erosion of Shores, Swelling and Sinking of Peaty Soils. Influence of Temperature. Local Upheavals 527 CHAPTER LXXX. Upheaval of the Scandinavian Peninsula; of Spitzbergen ; of the Coasts of Siberia ; of Scotland ; of Wales 531 CHAPTER LXXXL Upheaval of the Mediterranean Regions. Former Libyan Strait. Coasts of Tunis, Sardinia, Corsica, Italy, and Western France 538 CHAPTER LXXXII. Coasts of Asia Minor. Ancient Ocean of Hyrcania. Coasts of Palestine and Egypt. The Adriatic Gulf. 542 CHAPTER LXXXIII. Subsidence of the Shore of the Channel, of Holland, of Schleswig, of Prussia 54(5 CHAPTER LXXXIV. Upheaval of the Coasts of Chili and Peru. Probable Depression of the Coasts of La Plata and Brazil. Coasjs of North America and Greenland 550 CHAPTER LXXXV. Reefs of the South Sea. Darwin's Theory as to Upheavals and Depressions 556 CHAPTER LXXX VI. The Great Areas of Upheaval and Depression. Mobility of the so-called Rigid Crust of the Earth 562 LIST OF COLORED ILLUSTRATIONS. I. MAP or THE WORLD : . . . Frontispiece. II. GEOLOGICAL CHART OP THE WORLD To face paye 13 III. GEOLOGICAL MAP OP ENGLAND 37 IV. NORTH AMERICA 52 V. SOUTH AMERICA 58 VI. EUROPE 63-64 VII. AFRICA 66-67 VIII. ASIA 70-71 IX. AUSTRALIA AND THE ADJACENT ARCHIPELAGO , 72-73 X. THE ALPS 148-149 XI. THE MER E GLACE AND ITS AFFLUENTS 178 XII. GLACIERS OF GEISBERG AND ROTHMOOS 194 XIII. GLACIERS OF LANGTHAL AND GURGL 201 XIV. GLACIER OF VERNAGT 204 XV. FORMER GLACIERS OF THE VALLEY OF THE ADIGE 211 XVI. MIDDLE COURSE OF THE MISSISSIPPI 311 XVII. DELTA OF THE GANGES 353 XVIII. LAKE GARDA 388 XIX. THE BUGORS OF THE CASPIAN SEA '. 405 XX. ERUPTIONS OF ETNA 425 XXI. VOLCANOES 432 XXII. UPHEAVALS AND DEPRESSIONS 527 XXIII. ATOLL AM... .. 560 GEOLOGICAL CH/ Di-awn by A.ViriUeinin HARPER &. EROT OF THE WORLD PI.. II. THE EARTH. PAKT I. THE EARTH AS A PLANET. CHAPTER I. SMALLNESS OP THE EARTH AS COMPARED WITH THE SUN AND FIXED STARS ; GRANDEUR OF ITS PHENOMENA. FORM OF THE TERRESTRIAL GLOBE ; ITS DIMENSIONS. THE earth on which we dwell is one of the lowest in rank among the heavenly bodies. If an astronomer in some other planet were exploring the immensity of space, our earth, owing to its small size, might readily elude his intelligent view. A mere satellite of the sun, the volume of which is 1,255,000 times greater, the earth is but a point as compared with thejmmense tract of ether traversed by the planets in their courses round their central globe. The sun itself is only a spark, which seems lost amid the eighteen millions of stars which Herschel's telescope dis- cerned in the Milky Way ; the latter, an immense agglomeration of suns and planets, which looks to us like a broad streak of light round the whole universe, is in reality nothing but a nebula ; that is, a cloud of stars re- sembling a mist, which would be as nothing in infinite space. Beyond our own sky, other skies stretch far away into infinity, and others beyond these, so that light, notwithstanding its prodigious rapidity, takes eterni- ties to cross them. How small the earth seems in this fathomless abyss of stars ! Individually, it may seem immense to us ; all too vast for our littleness, we have not yet succeeded in investigating the whole of its sur- face ; but, as compared with the whole sidereal cosmos, it is less than a grain of sand by the side of a mass of mountains, or an atmospheric par- ticle compared with aerial space. True enough that the earth is nothing but an almost impalpable grain of dust to the vision of the astronomer scanning the nebulae in the field of his telescope, but it is, nevertheless, quite as much worthy of study as any other of the heavenly bodies. If it does not possess magnitude of di- mensions, it presents an infinite variety in all its details. Whole genera- tions, living one after the other upon its face, might pass their lives in 14 THE EARTH AS A PLANET. studying its phenomena without comprehending all their full beauty. There is not even any special science, having for its aim some portion of the terrestrial surface or some particular series of its products, which does not present to our savants an inexhaustible field of inquiry. Moreover, is not our little globe, as well as the sky, a real cosmos, both by the admira- ble arrangement of its parts, and by its supreme harmony as a whole ? In a certain point of view, is not our almost imperceptible planet as great as the universe, in that it is the expression of the same laws ? In the form of its orbit, in its movements round the sun and on its own axis, in the succession of days and seasons, and in all the phenomena governed by the great law of attraction, the earth becomes the representative of all the other planets ; in studying it, we study all the heavenly bodies. Our planet is a spheroid ; that is, a sphere flattened at the two poles and enlarged at the equator, so that all the circles passing through the extremity of the polar axis form ellipses. The presumed depression of each pole is about thirteen miles, nearly a three-hundredth part of the ra- dius of the earth ;* but it is not altogether certain that the two poles are equally flattened. Perhaps a contrast exists between the two hemispheres, not only in the features of their continents and the distribution of seas, but also in their geometrical shape. Be this as it may, it appears to be proved that the curvature is not exactly the same at all points of the earth at an equal distance from the poles ; the meridians appear without exception to be irregular ellipses. The recent measurement of degrees carried out by astronomers, and especially the great trigonometrical sur- vey made between 1816 and 1852, under the direction of Struve, from the coasts of the Frozen Ocean to the banks of the Danube, have*disclosed some singular deviations in the form of the earth, caused either by the geological nature of the crust or by the vicinity of considerable mountain chains. Thus, among the countries of Europe, the surfaces of England and Italy are sensibly depressed in comparison with adjacent countries. These inequalities of curvation, which are doubtless variable, and cor- respond to the changes in the position of the earth's centre of gravity, are cognizable only by the astronomer, and nowhere interrupt the apparent horizontal character of the surface of plains and seas. As far as man is concerned, the roughness and hollows forming our plains, mountains, and valleys, are more important than any inequalities in the roundness of the globe. According to Von Schubert, the academician, an enlargement, perpendicular to the equator, and therefore parallel to the meridian, bulges out all round the globe, passing through Europe and Africa ; this hypoth- esis is not, however, made good by the measurements of an arc of the me- ridian recently made in India. The dimensions of the earth, as we have already seen, are almost as nothing compared with the larger celestial bodies, and especially with the extent of space which can be explored by the telescope. If light, the * According to Bessel, the astronomer, 299' 1528. All possible errors are embraced be- tween 302-301 and 296 '005. THE EARTH AS A PLACET. 15 speed of which has been adopted in astronomy as a terra of comparison, could be diffused in a curved line, it^would travel seven times round the globe in a second of time; this standard of measurement, therefore, the only one suited to the stellary field, is completely inapplicable to the sur- face of our globe. Man, small as he is in comparison with the planet on which he lives, in the first instance chose out for the measurement of his domain either parts of his own body, such as the foot, cubit, or fathom, or the distance traveled during a certain period of time, as the parasany, stadium, mile, or league. It was not until the end of the last century that the savants who then adorned France conceived the idea of dividing the circumference of the earth into equal parts, which for the future should serve as a standard of measure for all terrestrial distances. This measure, or metre, which, with the aid of its multiples and divisions, enables us to estimate, with equal ease, the circumference of the globe or that of an al- most invisible molecule, is the ten-millionth part of the arc described from the equator to one of the poles. Owing to errors which the difficulties of actual measurements rendered inevitable, the ideal metre exceeds the customary one by nearly the eleventh part of a millimetre; but this very trifling difference, which is imperceptible to the naked eye, may be. disre- garded in practice without any inconvenience. A line, therefore, going round the earth, and passing through the two poles, would be of the length of about 40 millions of metres, or 40,000 kilometres. Thus, as Schubert* remarks, it is about the distance which the usual pace of a man would travel over in a year that is, if hetlid not stop for a single instant. The superficies of the globe, as calculated by Wolfers, according to the most recent measurements which astronomers have made of the arcs of the lon- gitude and latitude in various countries, is 197,124,000 square miles. Ac- cording to Encke, the astronomer, it amounts to 197,108,580 square miles, and the planetary mass would attain to a bulk of 256,000 millions of cubic miles. * Geschichte der Seek. X/ THE EARTH. CHAPTER H. MOTION OF THE PLANET. DIURNAi ROTATION AND ANNUAL REVOLUTION. SIDEREAL AND SOLAR DAY. SUCCESSION OF DAYS AND SEASONS. DIF- FERENCE OF DURATION OF THE SEASONS IN THE TWO HEMISPHERES. PRECESSION OF THE EQUINOXES. NUTATION. PLANETARY PERTURBA- TIONS. MOVEMENT OF THE EARTH TOWARD THE CONSTELLATION HER- CULES. THE isolated globule in the immensity of space which we call the earth is not motionless, as the ancients necessarily supposed, looking upon it, as they did, as the immovable base of the firmament of heaven. Hurried on in the vortex of universal vitality, our globe is ever actuated by ceaseless motion, describing in ether a series of elliptic spirals so complicated that astronomers have not yet been able to calculate their various curves. Be- sides rotating on its own axis, the earth describes an ellipse round the sun, and, under the influence of this body, is drawn along from one heaven to another toward distant constellations. It also oscillates and rocks on its axis, and deviates more or less from its path, to salute, as it were, every heavenly body which meets it. It is probable that it never passes a sec- ond time through the same regions of the air; yet, if it has again to trav- erse the spiral line of ellipses it has already described, it would be after a cycle of so many thousands of millions of years, that the earth itself, com- pletely transformed, would be no longer the same planet. Nature, immu- table in its laws, but forever variable in its phenomena, never repeats itself. The motion of the earth, the immediate effects of which are the most obvious to the notice of men, is the daily rotation which takes place round an ideal axis passing through the two poles. The globe turns from right to left, or from west to east that is, in a contrary direction to the appa- rent motion of the sun and stars, which seem to rise in the east and to set in the west. As the earth's axis terminates at each pole, there is least surface-motion at those points, and the motion is .the more rapid in any part of the surface of the globe the farther it is from the central axis. At St. Petersburg, in 60 latitude, the speed of rotation is about nine miles a minute ; in Paris, it exceeds eleven and a half miles during the same brief time ; on the equatorial line, which may be looked upon as the ring of an immense wheel, the speed of the earth is twice as great as it is at 60 of latitude that is, about eighteen miles a minute, or 528 yards a second a rapidity equal to the flight of a 26-pound cannon-ball impelled by thir- teen pounds of powder. By means of this rotatory motion, the earth pre- sents toward the sun each of its faces alternately, and each also in turn toward the comparatively darker regions of space; the succession of day MOTION OF THE PLANET. 17 and night is thus constituted. In addition to this, the rotation of the rurth is an important fact which must always be taken into account in determining the direction of fluids in motion on the surface of the globe, Mich as streams and rivers, also marine and atmospheric currents.* The annual revolution which the earth performs round the sun follows the line of an ellipse, one of the foci of which is occupied by the central star ; the eccentricity of the ellipse is nearly equal to TJJIJTJ of the great axis. The distance between, the sun and the earth always varies accord- ing to the particular point of its orbit which the latter is traveling over. At its aphelion, that is, at its greatest remoteness, this distance is about 93^ millions of miles; at the period of its perihelion, when the two heav- enly bodies are nearest to each other, it is approximately 90,259,000 miles. The mean distance, as estimated by astronomers since the corrections of Knckr, Hansen, Foucault, and Hind, is 91,839,000 miles. This extent of space is traversed by the solar rays in 8 minutes 16 seconds; sound would take fifteen years in passing through the same distance. As Kepler has laid down in his celebrated laws, our planet moves with an increased rapidity as it approaches nearer to the sun, and travels more slowly in proportion to its distance from that luminary; but its mean speed may be estimated at nearly 19 miles a second, or sixty times the rapidity of a ball from the cannon's mouth. This speed, which makes one dizzy to think of, is. to be added, as regards each point in the surface of the earth, to the rotatory motion which impels it round the polar axis. Modified by this latter motion, the line described by any one point on the terrestrial superficies becomes a spiral. After having turned round 366 times on its axis, our planet has termi- nated its orbicular course, and is in the same position relatively to the sun as at its starting-point ; it has then accomplished its year. During this period of time, composed of 366 terrestrial rotations, the sun has only il- lumined each hemisphere in turn 365 times. How does this apparent anomaly arise ? How does it happen that a complete movement of rota- tion performed by the globe round its own axis does not exactly coincide with the solar day ? The cause is this that the earth in its rotation, car- ried on as it is in its immense orbit, k constantly changing its position in respect to the sun. As regards the fixed stars, situate at an almost infi- nite distance from our planet, the earth remains, so to speak, always in the same position ; consequently, the sidereal day, that is, the interval which separates two transits of the same star over the same terrestrial meridian, has the precise duration of one rotation of our globe. After each of its diurnal rotations, our earth presents to these far-remote stars the same part of its surface, and if the light of the sun became suddenly i-xtinct, and if a star, such as Sirius or Aldebaran, became our great focus of illumination, our days would have the exact duration of a terrestrial rotation, that is, about 23 hours 56 minutes. But the sun, although a star, is comparatively near to the earth. While the lattrr is^u-rform- * Vitlr the chapters as to "Rivers," "Currents," "The Atmosphere, and Winds." B 18 THE EARTH. Fig. 1. Inequality of the Solar and Sidereal Day. ing a movement of rotation, it alters its position 1,604,300 miles along the course of its orbit ; consequently, the sun, in its apparent progress, seems to retrograde this distance, and in order that the earth should present to it exactly the same portion of its surface as at the commencement of its rotation, it would be necessary for it to turn round four minutes more. The next day, a fresh change in the position of the earth again adds four minutes to the duration of the day, and so on till the end of the year. These daily additions of four minutes to the length of the day form, during a whole year, a period equal to the duration of one of the diurnal rotations ; the result is that the sidereal days in the year exceed the solar by one.* Thus the daily rotation of the earth 1'ound its axis produces the succes- sion of days and nights, and, in the same way, its annual revolution round the sun causes the alternations of the seasons. If the axis of the earth, that is, the ideal line which passes through its two poles, were perpendic- ular to the plane of its annual orbit, it is evident that the portion of the globe lighted by the sun would invariably extend from one pole to the other, and that in both hemispheres the days and nights would always consist of twelve hours each. But this is not the case. The earth per- forms its revolutionary movements in an inclined position ; its ideal polar axis is sloped about 23 28' from a perpendicular to its plane, and this po- sition is so far maintained that as regards the comparatively rapid suc- cession of days and seasons it may be looked upon as invariable. This * For a more complete explanation of all the astronomical phenomena relating to the earth, we must refer to the excellent work of M. Ame'de'e Guillemen, Le del. From this work we have borrowed the above plate. ORBIT OF THE EARTH. 19 obliquity of axis causes continued changes in the phase presented to the sun. The portion of the earth illumined by the rays of the sun varies every day ; for, although the planetary axis may appear to maintain its extremity in a fixed position as regards some point in infinite space, in re- spect to the sun it presents a constantly varying degree of inclination, in consequence of the continual motion of the earth. Twice during the course of the year it so happens that the solar rays fall perpendicularly upon the equator of the earth ; at every other period in the annual revolution, some- times the northern and sometimes the southern hemisphere receives the greatest amount of light. The astronomical year commences on the 20th of March, at the exact momiMit when the sun illumines the equator in a vertical direction, and the line of separation between light and shade passes through the two poles. The period of darkness is then equal to that of light, and admits ^ of exactly twelve hours at all points of the earth. Hence the name of ^ "equinox" (equality*of nights). But after this day, which in the northern hemisphere serves as the starting-point of spring, the earth continues its translatory movement. In consequence of the inclination of its axis, tile northern hemisphere, being turned toward the sun, receives a greater quan- tity of light, while the southern half of the globe is less vividly lighted. The vertical rays of the sun now fall more and more to the north of the equator, and the circle of light, far from arresting its progress at the poles, whore the day of six months' duration is commencing to dawn, extends far beyond it over the regions of the north. On the 21st of June, the day of the first solstice,* the axis of the earth being deeply inclined toward the sun, this luminary shines on the zenith of the tropic of Cancer at 23^ north of the equator, and its light illumines the whole of the arctic zone, that is, the portion of the earth's surface extending to 23^ round the north pole. Then spring ceases and summer begins as regards the northern hemisphere. In the southern hemisphere, on the contrary, autumn is giv- ing place to winter. Above the equator long days are prevailing, inter- rupted by short nights; while in the south it is the nights which last the longest. In the arctic zone the sun performs its apparent course of diurnal rotation entirely above the horizon. The six-months' day, which spring inaugurated at the north pole, attains its high noon on the first day of summer. At the same moment midnight arrives in the darkness which is oppressing its antipodes. Immediately after the 21st of June all the phenomena which took place during the preceding season are directly reversed. The sun appears to retrograde toward the southern horizon ; its vertical rays cease to fall on the line of the northern tropic, and constantly approach the equator. The /one of light in the northern pole and of shade in the southern equally di- * The usual term "summer solstice" is altogether improper, as it is suitable only to coun- tries in the northern hemisphere. The summer solstice of London is the winter solstice at the Cape of Good Hope. The designations of vernal and autumnal equinox ought equally to be abandoned. 20 THE EARTH. .1'i'fiti'tnbt'i I'.ifiilrii'.i- ]' at last counterbalanced by the centrifugal force; and although the larger portion of the gaseous mass continued to condense around the cen- tral nucleus, the outer zone, acted upon at the same time by two opposite forces, ceased to modify its distance in respect to the axis of the spheroid, and assumed the form of a circular revolving ring. Other rings were in succession separated from the diminished mass in the same way, and continued to describe their rotatory movement round the nucleus or sun. According to the hypothesis, these rings were the future planets of the solar system. The lightest were necessarily those which were the most remote from the sun, on account of the greater tenu- ity of the incandescent atmosphere of which they were formed. The heav- iest were those which were subsequently constituted out of the denser gaseous layers which were situated nearer to the centre of the sun. It is, we may remark, a matter of fact that the planets farthest removed from the central focus, such as Uranus and Neptune, have the specific gravity of cork, and that the density of the globes increases (although not follow- ing any absolutely regular law) as they are in closer propinquity to the sun, until we come to the small and heavy planets in the interior of the system. Besides, the planes of the planetary orbits which are slightly in- clined toward one another would point out the position of the sun's equa- tor at each of the epochs when one of the great disruptions took place, which gave rise to a fresh planet. Although constantly getting more compressed, owing to the gradual loss of their caloric, these annular bodies retained their shape through a more or less prolonged series of ages ; but, as soon as one of these seg- ments became denser than the rest (in consequence of some astronomical perturbation), it exercised an ever-increasing force of attraction, and at last, breaking up the zone of gaseous matter, gathered the matter round itself in a concentric atmosphere. Under the influence of the laws of ro- tation, the new planet soon assumed a spheroidal shape, analogous to that of the body from which it had sprung. In consequence of the first im- pulsive force communicated to its molecules, its motion became twofold ; it continued its revolution round the sun, and began to turn round on its own axis. The forjnation of satellites is similarly explained by the gradual shrink- ing of the gaseous mass of the elementary planets. The rings separated 26 THE EARTH. from the equatorial zone of these -bodies would be likewise condensed, and, contracting in consequence of the abstraction of their caloric, would be- come so many moons. The pale rings of Saturn are the only objects in the heavens which would recall the ancient shape of the spheres which the condensation of the sun, and, afterward, that of the planets themselves, have thrown off successively into space. Once upon a time, according to the hypothesis, they were nothing but an equatorial enlargement of the mother planet ; some day they will become spherical satellites, like the eight moons which now illumine the short nights of Saturn. Thus, according to Laplace's ideas, the whole planetary system formed, in long past ages, a portion of the sun. This luminary, composed solely of gaseous particles much lighter than hydrogen, pervaded with its enor- mous rotundity the whole of the space in which the planets, including Neptune, are now describing their immense orbits. The diameter of the solar spheroid must then have been GSOO^times greater than it now is, and its bulk must have surpassed its present volume by more than 860,000 mil- lions of times. In the same way, the earth, before it began to get cool and solidify, would have embraced the moon within its limits, and its di- ameter would have been nearly six times greater than that of the planet Jupiter. "But, unsubstantial and aerial as it was, our earth had then noth- ing but a cosmical life which could hardly be called material ; it was not until it became more solid and its outer crust was hardened that it actu- ally commenced its real existence. This is, no doubt, a brilliant hypothesis, and certainly the most beauti- ful and simple that any astronomer has yet put forth. It accounts better than any other for the uniform translatory motion of the planets in the direction of west to east ; it also apparently agrees in a remarkable way with certain facts in the subsequent history of the earth, as disclosed to us by geology ; finally, the marvelous rings which surround the planet Saturn seem to proclaim the truth of the theory devised by Laplace. There have been some experiments on a small scale which appeared to re- produce in miniature the magnificent spectacle presented in the primitive ages by the origin of the planets. M. Plateau, a Belgian savant, managed to make a globe of oil revolve in a mixture of water and spirits of wine, which was of exactly the same specific gravity as the oil. When the rev- olution of the little globe was sufficiently rapid, it was noticed to flatten at the poles and to swell at the equator; after a time it threw off rings which suddenly assumed the shape of globules actuated by a rotatory mo- tion of their own, and turning round the central globe. Although these planets in miniature owed their existence solely to the expansion of the drop of oil and not to its shrinking, any one looking at it might well fancy it was an exact representation of the solar system. But Laplace himself, in putting forth this hypothesis, says that he does so " with diffidence,"* and no one has a right to be more confident than the great geometrician. In fact, his conjectures do not account for the * Exposition du Systeme du Monde, p. 450. FORMA TION OF PL A NETS. 27 presence of comets which gravitate round the sun in determinate orbits, although, according to his hypothesis, they are " strangers in the solar system;"* they also fail to explain the elliptical form of the planetary or- bits and the inclination of their axes ; finally, they appear to be contra- dicted by the retrograde motion of the satellites of Uranus. Some of the li>tant nebulw, which were taken by astronomers to be masses of uncon- densed cosmical matter, possess the most fantastic forms, which would be very difficult to explain by means of the new hypothesis; some of the nebulfje, too, are variable, and the telescope discloses them to us under very different aspects in succession. Finally, the discovery of the spectral analysis an eternal glory to MM. Kirchhoff and Bunsen warrants us in believing that the chemical composition of the sun differs very decidedly from that of the planets forming its system ; for the solar body, at least in its external layers, does not contain either silex, tin, lead, mercury, sil- ver, or gold. We must therefore confess that Laplace's celebrated and seductive hypothesis is inadequate to account for all the phenomena which have been observed. The human intellect ever thirsts for certainty, and readily allows itself to be led away to look upon mere conjectures as ab- solute truths ; the ability of fearlessly doubting is not the meanest attri- bute of genuine philosophy. When the investigator is unable to discover th- truth, let him dare to avow his ignorance, and rest courageously on the threshold of the unknown world. Another hypothesis connected with Laplace's brilliant astronomical the- ory mirst be added, in order to describe the formation of the planetary crust. When the gaseous ring became condensed into a globe, it would not cease to contract, owing to the continued radiation of its caloric. The whole mass, having become liquid through the gradual cooling of its molecules, -y^ould be changed into a sea of lava whirling round in space; but this state was only one of transition. After an indefinite term of cen- turies, the loss of heat was sufficient to cause the formation of a light sco- ria like a thin sheet of ice over the surface of the fiery sea, perhaps just at one of the poles where nowadays the extreme cold produces icebergs and a frost-bound sea. This first scoria was succeeded by a second, and then by others ; next they would unit* into continents floating on the sur- face of the lava, and, finally, would cover the whole circumference of the planet with a continuous layer. A thin but solid crust would then have imprisoned with in it an immense burning sea. This crust was frequently broken through by the lava boiling beneath it, and then, by means of the solidification of the scorice, was again united ; the cooling process would tend also to slowly thicken it. After a lapse of time, which must have been immensely protracted, since the interval luring which the temperature of the territorial crust would be lowered from 2000 to 200 has been estimated, at the very least, at three and a half millions of centuries,! the pellicle at last became firm, and the erup- tions of the liquid mass within ceased to be a general phenomenon, local- * Esjivsition du Systeiue du Monde, p. 475. t llehnliolz. 28 THE EARTH. izing themselves at those points where the firm crust was the thinnest. The surrounding atmosphere, replete with vapors and various substances maintained by the extreme heat in a gaseous state, would gradually get rid of its burden ; all kinds of matter, one after the other, would become disengaged from the luminous and burning aerial mass, and precipitate themselves on the solid crust of the planet. When the temperature was lowered sufficiently to enable them to pass from a gaseous to a liquid state, metals and other substances would fall down in a fiery rain on the terrestrial lava. Next, the steam, confined entirely to higher regions of the gaseous mass, would be condensed 'into an immense layer of clouds, incessantly furrowed by lightning. Drops of water, the commencement of the atmospheric ocean, would begin to fall down toward the ground, but only to volatilize on their way and again ascend. Finally these little drops reached the surface of the terrestrial scoria, the temperature of the water much exceeding 100, owing to the enormous pressure exercised by the heavy air of these ages; and the first pool, the rudiment of a great sea, was collected in some fissure of the lava. This pool was constantly increased by fresh falls of water, and ultimately surrounded nearly the whole of the terrestrial crust with a liquid covering; but, at the same time, it brought with it fresh elements for the constitution of future con- tinents. The numerous substances which the water held in solution formed various combinations with the metals and soils of its bed ; the cur- rents and tempests which agitated it destroyed its shores only to form new ones ; the sediment deposited at the bottom of the water commenced the series of rocks and strata which follow one another above the primi- tive crust. Henceforward the igneous planet was externally clothed with a triple covering, solid, liquid, and gaseous ; it might therefore beconje the theatre of life.* Vegetables and lowly forms of animals were called into exist- ence in the water, and on the land which had emerged from it ; and, final- ly, when the temperature of the surface of the globe had become less than 50, allowing albumen to liquefy and blood to flow in the veins, the Fauna and the Flora would be developed, the remains of which are found in the earliest foss.il strata. The era of chaos was succeeded by that of vital harmony ; but in the immense series of ages we are dealing with, the life which appeared on the refrigerated planet was little else than the " mould- iness formed in a day."f According to the theory generally propounded, the solid crust was not very completely formed ; it is, indeed, much thinner than the layer of air surrounding the globe; for, following the common estimate, which, how- ever, is purely hypothetical, at 22 to 25, or, at most, 50 miles below the surface of the earth, the terrestrial heat would be sufficient to melt gran- ite. J Compared to the diameter of the earth, which is about 250 times greater, this crust is nothing more than a thin skin, a just idea of which * De Jouvcncel, Lcs Commencements du Monde, p. 37 seq. t Daubree. } Ilumboldt's Cosmos ; Studer's Physikalische Geographic, vol. ii., p. 37, etc. MUTABILITY OF ITS SURFACE. 29 may be given by a sheet of thin cardboard surrounding a liquid sphere a yard in diameter. In the case of the earth, this liquid is a sea of lava and molten rocks, having, like the ocean above it, its currents, its tides, and perhaps its storms. The geological revolutions of the globe are only the reaction of the subterranean undulations of this hidden hell, and the moun- tains of porphyry, greenstone, and ophite are but the congealed ripples of a fiery ocean. Those giants on the sea-shore, Etna, the Peak of Tene- riffe, and the Mauna Roa, bear witness by their eruptions and their lava- streams to the tempests which are raging below the earth's solid crust. It is, in fact, very probable that a great part of the rocks which form the outer portion of our planet, especially the most ancient formations, existed in former times in a state effusion like that of volcanic lava. As most geologists are of opinion, granite and other similar rocks, forming the principal building-blocks in the architecture of continents, existed once in a soft or semi-soft state ; but even if this were placed beyond a ques- tion, it could not confirm the hypothesis relative to the origin of our plan- et, the tenuity of its crust, and the existence of a vast central fire. The flattening of the earth at the two poles and the enlargement at the .equator have been alleged as unexceptional evidence that the globe once existed in a state of liquid incandescence ; in fact, any liquid sphere turn- ing round on its axis would necessarily assume this shape on account of the unequal speed of certain points of its bulk. But it may also be asked, with Playfair, whether even a solid globe would not equally tend to en- largement at its equator if it unceasingly rotated for an indefinite series of centuries? For no existing matter is altogether inflexible, and under the powerful pressures exercised in our laboratories, certainly very inferior to the influence of planetary forces, all kinds of solid bodies, as iron and steel, become almost as yielding as liquids.* Besides, the observations and cal- culations of astronomers and geometricians have led them to the belief that the flattening of the earth at the two poles is not a constant quanti- ty, and that, therefore, there are other laws different from those of the mo- tions of rotation and revolution, which assist in modifying the form of our planet. Less probably at the northern than at the southern pole, the ir- regularity of the sphere appears to be subject to periodical changes dur- ing the course of ages, and is also complicated with several other inequal- ities, elevations, or depressions which the oscillations of the pendulum and the measurement of terrestrial arcs disclose to science. One of the grav- est subjects of study presented by physical geography is precisely this mutability of the surface of the earth, which, at various points of the globe, rises or sinks with extreme slowness. Although we are still ignorant of the certain cause of these risings and depressions, there is at least no rea- son to believe that they are due to the centrifugal force developed by the rotation of the earth. f Neither must it be forgotten that, under the hypothesis admitted by * Experiences du Conservatoire des Arts et Metiers, 1804. t Vide the chapter as to " Upheavals and Depressions." 30 THE EARTH. those who assume the existence of a central fire, our planet is to be con- sidered as actually a liquid mass, as the external orust is in comparison but a thin skin. Under these conditions, it would be difficult to believe that this great ocean of lava is not, like the watery ocean, agitated by the alternating motion of tides, and that it does not move twice every day the raft, as it were, which is floating on its surface. It is difficult to un- derstand how it is that the earth is not much more depressed at the poles than it now is, and has not been transformed into a real disk. This flat- tening of the poles is not more considerable than the mere superficial in- equalities in the equatorial zone between the summits of the Himalayas and the abysses of the Indian Ocean. M. Liais attributes the slight flat- tening of the two poles to the erosion which the water and ice in those parts, irresistibly drawn as they are toward the equator, incessantly cause, year after year and century after century, by the enormous quantity of debris torn away from the surface of the soil, which they bear with them. j Lastly, M. Bischoff, having ascertained from the principal soundings that 7 have been taken that the sea increases in depth from the poles in the di- ' rection of the equator, goes so far as .to deny the ellipsoidal form as re- I gards the bed of the sea, that is, over the greater portion of the planetary surface. The principal argument of those-who look upon the existence of a cen- tral fire as a demonstrated fact is that, in the external strata of the earth, so far as they have been explored by miners, the heat keeps on increasing in proportion to the depth of the excavation. In descending the shaft of a mine we invariably pass through zones of increasing temperature; only the rate of increase varies in different parts of the earth, and according to the strata through which the shaft is sunk. The heat increases more rap- idly in schist than in granite, and in metallic veins more even than in .schist; in lodes of copper more than in those of tin, and in beds of coal I more than in metallic veins.* In the Artesian well at Neuffen, in Wtir- I temberg, the temperature increases one degree Fahrenheit for every 19 feet. In the mines of Monte Masi, in Tuscany, near the boracic springs, the increase of heat is one degree for every 24 feet. Near Jakutzk, in Si- beria, the heat of the earth increases one degree for every 29 feet of depth. f Almost every where, however, the progression is less rapid ; and the mean depth which in this great stratiform thermometer corresponds to a degree of heat is from 45 to 54 feet.J In the mines of Saxe, the increase of heat, according to Reich, is one degree for every 76 feet. Still, the earth has not yet been explored to any very great depth. The most remarkable excavations which have yet been made are those of Kut- tenberg, in Bohemia, and one of the mines of Guanajuato, in Mexico ; even these have scarcely attained a depth of 1100 yards, not more than a six or * Foxe, Gilbert, Reich von Dechen, quoted by Bischoff in his Wdrmelehre, p. 169-171. t Collegno, Geoloyia, p. 26. * Bischoff, Warmel ehre, p. 2;">4. The learned German professor endeavors even to trace out in various countries c/tlhonisotheriites, or curves of equal subterranean heat. ITS INTERNAL CONDITION. 31 seven thousandth part of the earth's radius. It would, therefore, be some- thing more than imprudence were we to attempt to form a judgment as to the whole interior of the globe by the temperature of the external strata, and to affirm that the heat, increasing according to some constant propor- tion from the surface of the soil to the centre of the earth, would attain to a temperature of 200,000 a heat far beyond the power of man's im- agination to conceive. In the same way we should have to conclude, from the gradual cooling of the high aerial layers, that the decrease of heat would continue up to the midst of celestial space, and that at miles above tlu- earth the cold is equal to 5000 below zero. The superficial portion of the globe is traversed incessantly by magnetic currents, taking their course from pole to pole, and in this portion all those phenomena of plan- etary vitality take place which are constantly modifying the elevation and form of continents; this surface, therefore, must doubtless exist under altogether special conditions as regards the development of heat. The thinness of the earth's crust is therefore any thing but proved by the grad- ual increase of temperature in the shafts of mines and other excavations. M. Cordier, being struck by all the objections which presented them- selves to his mind as to the thinness of the terrestrial crust, has admitted that this covering could not be stable without having at least from 75 to o o 175 miles of thickness. Quite lately, Mr. Hopkins having subjected to the calculations of the higher mathematics all the elements furnished by the phenomena of the terrestrial precession and nutation, has arrived at the following result. He has proved that, either with or without a central fire, our planet would be actuated by periodical movements of a totally different character, if the solid portion of its crust had not a thickness of 800 to 1000 miles that is to say, about a quarter or a fifth of ^e earth's radius.* MM. Thomson, Emmanuel Liais, and other savants, taking up and discussing all these investigations, have endeavored to prove that, looking at the va- rious astronomical phenomena, the interior solidity of our planet is an in- controvertible fact.f Nevertheless, the recent experiments of M.Delaunay on srlass globes filled with water render it very probable that even if the earth contained a mass of molten matter, this mass would rotate, together with the crust, as if it were a solid body, and would adopt a similar course as regards the attractiofis of the sun and moon. We are not, therefore, warranted as yet in pronouncing any decisive opinion. The hypothesis which seems, both to Mr. Hopkins and also to Sartorius von Waltcrshau- st n. tin historian of Etna, to harmonize best with the volcanic phenome- na, J is, that there is no actual central fire, but only internal seas of red- hot molten matter scattered about in various pails of the inside of our planet, situated not far from the surface of the earth, and separated from one another by masses of solid strata. * Philosophical Transactions, 1839, 1840, 1842. t L'Espace Celeste ct la Nature Tro/ricale. J Vide the chapter on ' ' Volcanoes. " THE EAMTM. CHAPTER IV. GEOLOGICAL STRATA. CONGLOMERATES. SANDSTONES. CLAYS. LIME- STONES. FOSSILIFEROUS BEDS. SEQUENCE OF ORGANIC BEINGS. GEN- ERAL CLASSIFICATION OF STRATA. DURATION OF GEOLOGICAL PERIODS. THE most ancient positive evidence relative to the geological history of the earth is afforded by the first sedimentary layers which can be cer- tainly recognized as having been deposited by water 'on some primitive ocean-bed. Below the superficial strata of more modern origin we find others belonging to a remoter epoch, and then others of a still antecedent formation ; thus we proceed from stratum to stratum down to the naked skeleton of the earth, or, at all events, to those rocks which the pressure of the masses above and the planetary heat have gradually transformed during the long duration of ages, so as to render their stratification uncer- tain. These superimposed beds, which have often been compared to the pages of a book, furnish the date of their seniority by the order of their succession ; certainly we can not say how many hundreds or thousands of centuries have elapsed during the formation of each sedimentary bed, but we may at least learn the relative ages of the series of rocks. Wherever these strata have not been disturbed since their first origin, they still lie in parallel and almost horizontal layers as at the bottom of the sea which deposited them ; in this case nothing is more easy than to class them in their orde^of seniority. The geologist who descends the shaft of a mine sunk vertically into the earth may, as it were, traverse tl.e whole series of periods down to the primitive ages ; in a few minutes he may see a kind of abstract of the geological history of the earth. In the same way, in places where the agency of various meteoric phenomena and the forces at work in the interior of the earth have cut through any por- tion of the upper strata, causing steep escarpments, which show, as on an immense wall, the superimposed beds, the order of succession of the differ- ent rocks can not be the subject of doubt.* On" the other hand, in coun- tries where the strata have been upheaved at various angles, being either distorted, displaced, or sometimes even completely turned upside down where rocks springing from the earth in a liquid state, such as porphyry and lava, have forced their way between the beds, the investigations of the geologist become very difficult, and much patience and sagacity are required to attain any result. Finally, the greatest and most difficult problem is to establish the harmony in age and formation between various * The opposite profile of the "Pyramid Mountain," taken from vol. iii. of the Pacific Rail- road Report, has been revised by M. Marcou, the geologist, who was the first to bring under notice the existence of this remarkable mountain (Fig. 3). THE CRUST OF THE EARTU. 33 rocks separated by valleys, large plains, or even by the ocean. Thus doubt still exists as to a great number of details, and variance on these points often arises among geologists. Nevertheless, whether deciphered or not, these strata, with the various indications which are presented by their minerals and fossils, are the only authentic annals of our planet. They are the hieroglyphics, still in part mysterious, which relate to us in their magnificent characters the history of the world itself. Fig. 3. The Pyramid Mountain. These innumerable strata, so diverse in their position, inclination, and thickness, are analogous to the beds of the same nature that we notice in- cessantly in the course of formation. Mountains furrowed out by torrents and cliffs, sapped by the wave^, supply either to rivers or direct to the sea masses of debris, which, spread out into shingle-strands or beds of pebbles, are gradually changed into solid conglomerates. The crystalline rocks, pulverized by atmospheric agencies and the friction of river and sea-water, become submarine sand-banks, which sooner or later are converted, under the pressure of the superincumbent masses, into rocks of sandstone. The tranquil waters of slow-flowing streams and rivers, which neither carry pebbles along with them in their course, nor are charged with sandy mat- ter, are still loaded with small particles of ooze and earth, which they de- posit on their banks and in the bed of the sea, forming those beds of clay which also ultimately constitute important geological formations. On the banks of the Mississippi there are enormous argillaceous beds which the water of the river has left behind it; these are apparently no less firm than (he rocks which have for centuries met the assaults of the waves and C 34 THE EARTH. storms. In certain lakes in Mexico, and especially round the reefs of Florida, oolites like those of the Jura are daily being formed before our eyes. Finally, in the shallows of the sea, fresh beds are being formed, as of limestone at Guadaloupe, or of drift brought by the sea, as upon the great bank of Newfoundland. In the same way, coral insects, madrepores, and other marine animals are incessantly at work in building up new beds similar to those of the ancient geological periods. The formations caused in days of yore by the movement of the water, and the perpetual activity of teeming marine life, all are still in progress, and disclose to us in what way the earth's surface was modified during a long series, of ages. Although all strata may be classed in a general way in one of the five great series conglomerates, sandstone, clays, gravels, and limestone nevertheless, in their various shades of distinction, their relative positions, and the minerals which they contain, they present indications which allow of their being classed according to their respective ages. But the organic remains, animal or vegetable, which are contained in the greater part of these various formations, are the means which afford us the principal data for ascertaining, often with certainty, the order of succession of the vari- ous layers. Natural history alone enables us to decipher clearly these pages in the earth's history. That organic remains are preserved in the ground in an altogether ex- ceptional way is a fact which naturalists have innumerable opportunities of satisfying themselves of, in the study of the plants and animals of our own time. Dead animals are soon devoured by beasts of prey and in- sects ; water, wind, and sun ere long dissolve all that remains of flesh or ligaments ; the skeleton itself is finally reduced to dust. The infinite le- gions of inferior creatures which have no solid bones disappear in myriads without leaving the slightest trace behind them, and the piled-up masses of their remains are soon changed into humus and gas. Forest trees and herbaceous plants disappear like animals, and furnish nutriment to other existences. Scarcely have they perished ere the former organisms aid in forming new ones death is the constant food of life. The remains of ex- tinct vitality can only be preserved for futuje ages by being suddenly re- moved from the tooth of the animal and the action of the elements. Thus organic remains which are clothed by petrifying springs with a covering of lime, and the trunks of trees which are surrounded by sheets of lava, become as indestructible as stone itself. Animals caught in the ice, over- whelmed by falling earth, or which have died in some deep and inaccessi- ble cave, may be kept for centuries in a condition of perfect preservation, and may pass into a fossil state. But although it is comparatively very rare that a terrestrial being is preserved for future ages either whole or only in fragments, the case is not the same as regards marine creatures, which are ingulfed immediately after death or even during their life in the sand or mud which is brought by the waves. Thus, in the sediments of former marine beds and deltas, we find multitudes of fossil animals of which even the most delicate parts are wonderfully preserved; we see RARITY OF ORGANIC REMAINS. 35 this in the beautiful specimens in our museums brought from the beds of Solenhofen, Monte Bolca, Grignon, and Montmartre. Besides all this, on those shores where the tides are considerable in the Severn, St. Michael, and the Bay of Fundy the ooze brought by the waves has frequently covered the footmarks of vertebrate animals, the tracks traced out by Crustacea?, worms, and molluscs, and also the marks made by the rain-drops, and by strong squalls of wind. This mud, grad- ually hardening, may at last become beds of schist, sandstone, and clay ; and thus, after millions of years, similar imprints of an instant are found graven on the rocks, deeper and more legible to the eye of the geologist than the ambitious inscriptions of the kings of the world. But these magnificent evidences of the past are only common as regards marine beings ; there is very little chance of fossilization for any thing which lives on the emerged strata, in the air, or in fresh water. As the preservation of organic forms, or of impressions made by them, depends on exceptional conditions, a great number of strata are partly destitute of fossils, whilst immediately above and below them geologists are able to discover multitudes of the remains of the ancient inhabitants of the globe. Thus the deficiency of evidence in a stratum absolutely de- cides nothing against the existence of life in any particular period of the planetary history. The negative conclusions as to life which many savants have desired to deduce from the absence of fossils in certain beds are not based on any sure ground. Besides, the exploration of the globe is scarce- ly commenced, and a number of beds in which no relics had previously been discovered have since presented to science plenty of geological treas- ures ; in addition to which, we must not forget that there are great unex- plored tracts at the bottom of the sea, as well as on terra-firma. The appearance and disappearance of fossil species are not in perfect harmony with the succession of rocks, and consequently the idea is not warranted which connects some kind of cataclysm, with the end of each geographical period. A continuity of life has linked together all the for- mations, from the first organized beings w.hich made their appearance on the earth down to the countless multitudes which now inhabit it. One species would perhaps live but for a very short period of the planetary history ; another species would make its appearance in a certain bed ; at first it would be rare, and as if trying to force its way into life ; then it would multiply from stratum to stratum, and afterward would either gradually become extinct, getting less and less through a whole series of ages, or suddenly disappear. Other generic forms appear to have passed through every epoch, and representations of them exist after millions of centuries. The duration of a species does not depend either on the various revolutions which have modified the bed, or on any other external cause, but on its own special vitality. In a general way, the duration of the existence of any series of beings is in proportion to the more or less rudi- mentary character of its organization. The inferior vertebrate creatures have all pervaded a more extended geological cycle than that in which 36 THE EAETH. superior vertebrate animals are found ; Foraminifera have run through a much longer series of ages than molluscs ; the latter, as well as fishes and reptiles, have a much longer existence as species than Mammalia. Finally, the great mammals of the Tertiary epoch enjoyed but a comparatively short term of existence ; they were unable to resist the variable influences of climate so well as the inferior animals. The higher an organism is raised in the scale of being, the narrower are the limits between which it is confined ; all that it gains in rank, it loses, if not in number, at least in duration of existence as a species.* In what order did the various species of animated beings follow one another on the earth ? Not long ago, geologists put forward a very sim- ple system on this point. According to their preconceived ideas, the infe- rior animals, including the class of Crustacea, were the exclusive inhab- itants of the surface of the planet during the formation of the most ancient geological beds. Fishes made their first appearance during the period of the Old Red Sandstone ; reptiles came into existence in those hollows and marshy shallows where the vegetable remains were accumulating, which subsequently became transformed into coal. Birds, properly so called, first took flight at the Cretaceous epoch ; next came quadrupeds in reg- ular order, from the inferior species to the very highest. The ape did not form one of their number until immediately before the appearance of man, and the latter was created after all the other animals, as if to sum up in his person all the long catalogue of anterior life. The discoveries made during the last few years by indefatigable inves- tigators, such as Lyell, Forbes, Barrande, Owen, Leidy,Emmons, and Wag- ner, have singularly disturbed the serial order of species which had been previously established. Ferns, Lycopodiacece, and Calamitece, which were thought to be the only families represented in the Coal Measures, have been added to by many other species, belonging to other families, and even to the Dicotyledonous order. More than thirty species of reptiles have been discovered in those very strata in which, according to the views of many geologists, not one ought to have been found. Mammals of the marsupial order have been discovered in the Rha?tic beds of Somerset, and even in the Trias, at the termination of rocks of Palasozoic formation. Apes, at least as highly organized as those of our day, lived during the period of the Upper Miocene, and man was the contemporary of the. cave- bear, of the mammoth, the woolly rhinoceros, and other great animals now extinct. No year passes in which geologists fail to discover in the terres- trial strata new animal and vegetable forms, which transfer our geological horizon to periods still more and more remote. The facts which prove the existence of organisms of a superior class in the more ancient terres- trial beds have become so numerous that certain paleontologists have ventured to doubt the progressive development of the animal and vege- table series during the various geological periods. In their view, it is in * Collomb, Bibl. de Geneve, Archives Scientifiques, Aug., 1866. Wallich, North Atlantic Sea-bed, p. 95. Lyell, Darwin, Gaudry, Carpenter, etc. GEOLOGICAL MAP OF ENGLAND PL.m. Lkawii byAVmHenun after HARPER 6c BROTHERS. NEW YORK EARLIEST LIVING BEINGS. 37 each group of species, and not among animated beings as a body, that we must seek for the order of development.* If, however, we embrace in one glance the whole body of beings, instead of considering only the earliest and the latest ones, we are bound to recognize that there has certainly been a progress in the organic series. In its period of greatest exuberance vegetable life preceded animal life ; in the primitive ages plants destitute of flowers were much more numerous than the flowering species ; Crusta- cece, molluscs, and other lower animals had their golden age before fishes and reptiles, and the latter appear to have been the lords of the earth be- fore mammals appeared on the scene. Even, among the latter it seems very probable that progress was the rule, for most of the animals in the Oolitic beds are marsupials, and it was not until the Tertiary age that the larger mammals attained their more complete development.! Agassiz thinks that the types of the ancient epochs represent the embryos of now existing beings, so that paheontology teaches us of the infancy of all those forms of existence which are now found in a fully developed state. Be this as it may, the fossiliferous geological beds, from the most an- cient to the most recent, are all linked one to another by species common to two or more of their number. Thanks to the succession of their differ- ent species, and in spite of the numerous variations in the names used by them, geologists are now pretty well agreed as to the general classifica- tion of the rocks over the whole surface of the earth. The most ancient formations, or the Palaeozoic, resting on the granite or other rocks of a similar nature, and comprising the Taconic, the Cambrian, the Silurian, and the Old Red Sandstone groups, are the earliest strata in which we find any remains of organic beings ; in them, " in the dawn of vitality," sprang into life Eozoon Canadense (if, indeed, it exists at all, except in the imag- ination of certain geologists) and the Braintree trilobite (Paradoxides Pig. 4. Paradoxides Ua.rla.ni. Ifarlani), which disputes with the Eozoon the honor of having been the " Adam" of the terrestrial Fauna. This period of the earth's history, itself the successor of periods all unknown, was followed by the age of Carbon- * Lyell, Supplement to Manual, p. 35. [Sir Charles Lyell has since (in the tenth edition of his " Principles of Geology," 1808) fully accepted the Darwinian Theory.] t Bronn, Albert Gaudry, Owen, Hermann von Meyer, Lartet. 38 THE EARTH iferous beds, including the Mountain limestone rocks and the various lay- ers of the Coal formations. Above lie the beds of the New Red Sand- stone. Next in the geological series come the numerous Jurassic and Cretaceous stages, known as a whole under the name of Secondary rocks. The last period preceding the present epoch witnessed the deposit of the Eocene, Miocene, and Pliocene rocks, and is connected by the Quaternary strata to the formations which are now being constituted before our eyes. Finally, the incandescent lavas, trachytes, dolerites, and basalts which have made their way from below and have traversed the stratigraphical series, constitute a sixth class of rocks. Although the general groups are the same in the two hemispheres, the numerous geological strata in the various countries of the world differ singularly in their fossils and other characteristics. Nowhere do they present absolute harmony, and it is therefore very difficult to class them certainly in their respective order of succession. In former times, as now, animals and plants differed according to climates, and therefore the strata which received all these debris, received each of them its own special geo- logical character. In the varieties which the fossil Fauna and Flora pre- sent to us, how much is owing to a difference of epoch, and how much to a diversity of climate? The solution of this problem is one of the great tasks of science ?* * Marcou, Roches du Jura, p. 240. MODIFICATION OF THE EAMTH'S SURFACE. 39 CHAPTER V. INCESSANT MODIFICATION IN THE SHAPE OF CONTINENTS. ATTEMPTS MADE TO LEARN THE FORMER DISTRIBUTION OF SOILS AND CLIMATES. OBJECT OF GEOLOGY. PROVINCE OF PHYSICAL GEOGRAPHY. WITH regard to the ages necessary for the accomplishment of the im- mense geological processes, the history of which are disclosed to us in the earth's strata, they certainly must have been of prodigious duration ; for all the annals of humanity are but as a passing moment compared with the cycles of the globe ; the cosmogonical chronology of the Hindoos can alone give an idea of the periods of the earth's history. All the calcula- tions which astronomers have made as to the duration of the great planet- ary evolutions result in very formidable series of years, and it is in mill- ions or thousands of millions of centuries that estimations are made as to the duration of these ages. Professor Haughton, a mathematician, has en- deavored to establish, according to the formula of Dulong and Petit, that the mere fall in the temperature of 25, occurring previously to the pres- ent epoch of our planet, would require about i6 millions of years. In the same way, the formation of each of the strata which constitute the sum- total of the geological records of the earth's surface must have taken up a long series of centuries, before which the mind recoils in perplexity. The unceasing transformations of all the rocks which compose the outer layers of the globe could not have taken place without at the same time modifying the elevation and outline of the land ; thus the general con- figuration of the emerged portions of the surface has never ceased to vary since the first ages of the^globe. The old mountain chains have crumbled down, stone by stone, and particle by particle, and have been distributed, in the form of sand and clay, over plains and seas ; on the other hand, ocean-beds have gradually been elevated, and have changed into dry land, which has here and there been upraised into hills and ranges of peaks. Strata, when scarcely formed, were soon invaded, and made to assist in forming other strata. Every particle, as if caught in an eternal eddy, never ceased to wander from rock to rock ; and consequently, con- tinental masses, which are, indeed, nothing but vast agglomerations of (articles, must have incessantly shifted their positions on the circumfer- ence of the globe. It would be of the highest scientific interest if we could follow, from age to age, all these shillings of the outward features of the earth's sur- face, and the oscillations of their elevation from century to century. The harmony of the continental structure, even now so beautiful to contem- plate, notwithstanding the apparent immobility of its outline, would as- sume a different kind of grandeur if one could see with the mind's eye the 40 THE EARTH. infinite succession of undulations which have rippled the surface of our planet. Unfortunately, although the direct investigations of geologists can point out to us those portions of our present continents which emerged at any particular epoch, they can not disclose any thing to us as to those regions which, although now buried by the sea, were once elevated above its surface. Therefore the charts which are prepared of any geological period can only be partial ; but still, these charts, incomplete though they may be, are none the less an admirable result of ingenious and patient in- vestigation. It is beautiful, after an unknown lapse of centuries, to be ena- bled to recognize, among all the various continental regions, those which were raised above the sea at the same epoch, and thus dimly to trace out some of the features of the ancient architecture of the globe. The fault of many geologists, in their too great hurry to fix the com- mencement of the present period, has been that they have looked upon these first beds of our continents as being the only land which existed at this epoch of our planet. It is quite possible that there was a time when the whole surface of the globe was covered with water, and that the first land was nothing but a mere shoal ; then, perhaps, that islets, and then islands made their appearance, and, grouping themselves into archipela- gos, ultimately united into continents. But nothing warrants the idea that during the formation of the strata examined by geologists, the pro- portion between land and water has sensibly changed. Fresh land may have risen up at points where an examination of the strata proves that the ocean once flowed ; but to make up for this, there are numbers of facts which bear witness to the disappearance under the water of vast tracts of country. Age after age, the general plan of continents has been con- tinually modified ; our plains, and even our very mountains, have been covered with the waters of the sea; while chains of hills and plateaux rose high up in latitudes of th globe where^he waves of the ocean are now rolling. In order to ascertain approximately the former extension of con- tinents across our present seas, geologists have one means at their com- mand that of establishing the perfect harmony of the various strata of a formation broken through and disconnected by the waves. For instance, between France and England, the correspondent character of the strata on the two shores of the Straits of Dover is plainly evident. The fossil remains which are found accumulated at certain spots in the earth whither the currents have borne them, likewise prove the ancient extent of some countries which are now reduced to very small dimen- sions. Thus Attica, which in the present epoch is a mere rocky promon- tory of the Greek peninsula, must certainly, in the Miocene period, have formed a part of a continent presenting vast plains, wide-spreading, grassy prairies, and thick forests, which must have extended across the space now occupied by the Archipelago and a portion of the Mediterranean Sea, stretching away far enough to unite itself to Africa. This is the tale told, in a way evident enough to geologists, by the remains of gigantic animals found in the Pikermi deposits. The droves of hipparions, like those of EVIDENCE OF FOSSILS. !] Mhariiun/. sJ^Meo Cretaceous &+d# . Fig. 5. The Weald of Kent and the opposite French Coast Juitistie-Bedr . the wild horses of South America, the flocks of antelopes of various spe- cies, the tall giraffes, the mastodons, the rhinoceros, the powerful Dinothe- rium, the formidable Machairodus, stronger than the lion of the Atlas, and so many animals of large size, the fossil bones of which are kneaded into the soil, could not have existed on mountains either entirely bare or thin- ly sprinkled with scanty shrubs, and in the narrow valleys which form the Attica of our day. No, they required a vast continent like that of Africa, where we still see, in the portions not yet invaded by the white man, such prodigious multitudes of hippopotami, elephants, antelopes, ze- bras, and buffaloes.* The fossils of the two series, animal and vegetable, serve to prove still more directly the former existence of lands which have now disappeared. In fact, if we find the same fossil species in the corresponding geological strata of islands and continents which are at present separated by arms of the sea, and subject to different conditions of climate, we may natural- ly conclude that the regions in which these species existed were once united. A harmony of this sort between the Fauna and Flora have ena- bled geologists to establish the fact of the former existence of Jand joining England and Ireland,! Ireland and Spain,J and even Europe and America. In exploring the lignite beds of the Tertiary formation in Europe, geol- ogists have, in fact, found fossil tulip-trees, the remains of the Louisiana cypress (Taxodium distichiari), seeds of the Robinanuts of a United States species, leaves of the maple, oak, poplar, pine, magnolia, sassafras, ana tax- us ; also of the sequoia those giants of the California!! forests, and other * Altart Gaudry, Animaux fossiles de Pikertni. t Murchison, Anniversary Address, 18G3. } Edward Forbes. 42 TEE EARTH. North American trees, which do not now exist in European forests. Half way between the two continents, the lignites of Iceland present an analo- gous fossil vegetation. Unless a continent, or at least a series of adjacent islands, had served as a bridge across the wide Atlantic, how was it possi- ble for these American trees to have invaded the land of Europe ? In the same way, in the Miocene strata of Nebraska, remains have been found of the rhinoceros, the machairodus, and the palaeotherium that is, exactly the same animal fossils as in the corresponding beds in Europe. The for- mer existence of an identical system of organic life in two continents, now so entirely distinct in their Fauna and Flora, gives us the right to assume that, at the epoch of the Tertiary lignite, the scattered lands and the few clumps of mountains which formed, as it were, the rudiments of our Eu- rope, were connected with the American coast by an isthmus, separating the waters of the Atlantic from those of the Frozen Ocean. This isthmus was the Atlantis, and the traditions which Plato speaks of about this van- ished land were perhaps based upon authentic testimony. It is possible that man may have witnessed the submergence of this ancient continent, and that the Guanches of the Canary Islands were the direct descendants of the earliest inhabitants of this primeval land.* At a still more ancient epoch, when the fossils which are now found in the beds of the Jura formation were still being deposited at the bottom of the sea, the Atlantic was in existence, but of very different dimensions. It would appear that during these ages of the earth's history a vast con- tinent, including the two Americas, Africa, the Indies, and New Zealand, extended in an oblique direction as regarded the equator between the two great oceans of the north and south. This continent, which, like the land at the present time, covered scarcely a third of the surface of our plan- et, separated by its enormous mass many of those gulfs in which the re- mains of organized beings were being deposited ; this is proved by the fact that the Jura formations of Texas,- in the same latitude as those of Southern Europe, do not present, among the few fossils they contain, the remains of those numerous species of the Old World which, like their con- geners of the present epoch, travel to very considerable distances. If there had been no obstacles between the two basins, this absolute contrast between the two Faunas would have been impossible. In the same way, the species of the Jurassic formations of South Africa are completely dif- ferent from those of the Himalaya, Persia, and Europe ; this must lead to the admission of the former existence of an intervening continent which prevented the migration of living creatures. Finally, the Australia of our own day presents, both in its Flora and Fauna, the very greatest similari- ty to the animals and plants which lived in the Jurassic seas of Europe and on their shores. In looking at the kangaroos of Australia, which re- mina us of the marsupials of the Jurassic formations of England, and the strange ornithorhynchus, scarcely less fantastic in its shape than the an- cient pterodactyle, half bird, half batrachian, or than the problematical * linger, Die versunkene Insel Atlantis. Oswald Heer, Klee, Gaudry, etc. OLD CONTINENTS. 43 Archceopterix of Solenhofen, one can hardly refrain from the belief that Australia once formed a part of the ancient Jurassic continent. Besides, the coast of New Holland is the place where we now find the only living representatives of Trigonia which once inhabited the Jurassic seas.* Round the inland sea which has now become our present Europe, the great continental mass threw out a large, crescent-shaped peninsula, at the origin of which was the mouth of a considerable river, the delta of which may still be traced out from the coast of the English Channel as far as Westphalia. On the sheet of water which this peninsula protected from the freezing winds of the polar zone, warmed, too, as it was, by the heat of the equatorial lands, the mean temperature must have been much high- er than it now is in the corresponding portion of the earth; it was, with- out doubt, more than 68 Fahr., if we may judge by the presence of the ichthyosaurus and plesiosaurus.f It must, however, be understood that the outlines and various conditions of these long-vanished regions are still o o very far from being known with any degree of certainty, and it will per- haps require centuries of investigation before a chart of the Jurassic con- tinent could be satisfactorily drawn up. Circumstances very similar to those which have enabled us to form some approximate idea as to the temperature of Europe in the Jurassic period have also permitted savants to venture on some general indica- tions relative to the fluctuations of climate which are presented by the other great periods in the earth's history. Thus the mean temperature of Europe was first mild ; then, during the Silui'ian ages, it became gradu- ally raised ; in the period of the Carboniferous formations the climate was very warm and very damp, because the greater part of the land, then mostly situate in the torrid zone, consisted of an uninterrupted series of archipelagos. The epoch of the Trias was comparatively cold, on account of the great extension of the continent toward the poles. After the ages of the Jura formations, which were very warm and very dry, came in suc- cession a temperate period, that of the Chalk ; then an epoch of heat, the Eocene ; and then times of cold, gradually increasing up to the Glacial period ; after which the temperature again increased. This is a very brief abstract of the succession of climates in the region which is now Eu- rope, following the inferences which Lyell,J Marcou, Oswald Hcer,| and other savants have drawn from the facts which they have observed and carefully classified. We thus see what grandeur there is associated with the labor of the geologist. Starting from the increasingly profound study of the present strata, the science of geology has adopted as its task to reconstitute the varying forms of continents and seas in each of the successive periods of the history of the globe; it follows out, in the various epochs, the courses of the winds and the currents, which also have shifted with the continents * Marcon, Roches du Jura, p. 331. t Roches du Jura, p. 326 seq. t Manual of Geology. Roches du Jura, p. 335 seq. II Tertidr-Flora der Schwciz. 44 THE EARTH. themselves; it endeavors to measure, as if with the thermometer, the tem- peratures which have prevailed in different ages in the various countries of the earth ; finally, it seeks, by all the connecting links which the scat- tered debris can afford, to trace out the marvelous filiation of animal and vegetable species from the earliest fossils of which all that has been dis- covered is but a faintly-marked impress down to the innumerable beings which now stock our earth. Still dissatisfied with the ideal she has aspired to, science entertains the hope that she will one day be able to point out the exact conditions under which every organism was developed in the periods gone by, and that she will be able even to specify, as regards fish- es, shells, and sea-weeds, the depth of the water in which these beings once lived. The astronomer explores the boundless infinities of space ; the geologist penetrates into the abyss of time. The investigation of various rocks testifies more and more to the pro- digious activity of the forces which are ever remodeling the earth. Just as our planet, like all its sister orbs and all the stars of heaven, is borne on in eternal motion, so all the particles composing the mass of the globe are incessantly changing their place, and are circulating without repose in a cycle no less harmonious than that of the heavens. In the first en- velope of the earth, the atmospheric ocean which sustains the life both of animals and plants, continual eddies of winds, blowing from the pole to the equator toward all points of the horizon, are continually circulating. In the great ocean, too, of waters, every drop also rolls on from sea to sea, and from the wave is borne up to the cloud, and from the cloud de- scends to the river. The so-called solid portion of the planet is not less mobile than the atmosphere and the water, though the shifting action of its particles is slower ; sometimes, perhaps, when, in a short interval of days, years, or centuries, man has failed to see any vast, modifications ac- complished, he is tempted to say that the earth is immutable. Was there not a time when he also designated as faced stars those distant luminaries which nevertheless move through ether with so prodigious a rapidity ? Rocks, mountains, and continents are all in a perpetual state of change, and their particles move round and round the globe like the water and the air. By the action of torrents and atmospheric agencies, mountains are crumbled down and carried away into the ocean ; new regions are up- heaved out of the water, while others slowly sink and are finally sub- merged ; the earth itself is rent open, and gas and the molten matter of vast strata make their escape. Finally, in consequence of the incessant chemical reactions going on within the bowels of the earth, the composi- tion of the rocks themselves is changed, and growths of crystals follow one another in the metamorphosed stone, just as the Fauna and Flora on the soil above.* An exchange of matter is likewise going on between the earth and the celestial spaces, as is proved by the trains of burning stones which become detached from meteoric bodies rushing through the atmos- phere, and the tails of comets, through the invisible waves of which the * Otto Volger, Erdbeben der Schweiz, vol. ii., p. 20. GENESIS OF THE EARTH. 45 earth occasionally passes. Planetary vitality, like every other vitality, is a continual genesis, an incessant eddy of particles, at one time fixed, at an- other free, which pass from one organism to another. Nevertheless, in whatever aspect of its infinite modifications the earth is contemplated, it is ever beautiful in its form, and its consecutive phenomena take place with a marvelous harmony. Physical geography, in confining itself to the present epoch, merely de- scribes the earth as it is existing before our eyes. Its aim is not so am- bitious as that of geology, which tries to recount the history of our planet during the long succession of ages; but still, it is geography which col- lects and classes the facts ; she it is that discovers the laws both of the formation and the destruction of strata. She opens out a path for geol- ogy to travel over, and each of her advances in the knowledge of existing phenomena helps to render easier some victory of the human intellect over the past history of the globe. Without her aid it would have been impossible even to have ventured the initiative step into the labyrinth of vanished acres. PAKT II THE LAND. CHAPTER VI. REGULAR DISTRIBUTION OF CONTINENTS. IDEAS OF ANCIENT NATIONS ON THIS POINT. HINDOO LEGENDS. ATLAS AND THE GIANT CHIBCHACUM. HOMER'S SHIELD. STRABO. THE globe of our earth is in evident conformity to all the laws of har- mony, both in the spherical uniformity of its shape, and also in its con- stant and regular course through space. It would, therefore, be incom- prehensible if, on a planet so rhythmical in all its methods, the distribu- tion of continents and seas had been accomplished, as it were, at random. It is true enough that the outlines of coasts and mountain ridges do not constitute a system of geometrical regularity; but this very variety is a proof of a higher vitality, and bears witness to the multiplicity of motions which have co-operated in the adornment of the earth's surface. The uneven and yet harmonious configuration of the continents is, as it were, the visible representation of the laws which, for a long series of cen- turies, have ruled in the external modeling of our planet. " There is not a fundamental line in the outline of the earth which is not a line of ge- ometry."* ^ So long as the greater part of the surface of the globe was unknown to geographers, and they were ignorant of the true form of the earth, it may be easily understood that man, embracing in his feeble glance but a lim- ited horizon, should have recognized nothing but chaos in the intricate net-work of geographical lines. It was impossible for them to take* into account the laws which had influenced the distribution of continents, be- cause they were ignorant of their very outlines; as the analysis of the va- rious terrestrial forms was not yet completed, they were, of course, una- ble to accomplish the synthesis of them except by making unproved as- sertions, or by speculations in miraculous cosmogonies. At all events, nations, in their infancy, being well assured beforehand of tke vitality of the bountiful earth which supported them, have, without exception, looked upon nature as an immense organism endowed with su- preme beauty. For some, nature was an animal ; for others, she was a plant ; for all, she was an incorporated god. The ideas which they formed on this point are in general the most precious matter which is handed * Jean Keynaud, Terre et del, p. 26. HARMON? OF THE CONTINENTS. 47 down in their traditions, either oral or written ; for in these legends, in which they display the loftiest manifestations of their poetical genius, they sum up their persuasions as to the origin both of the earth and also of their own race. For the comparative study of the history, manners, and ideal of every nation, no book could be more useful than one which would contain all the cosmogonical conceptions which have been devised down to our own times. But, as may easily be understood, these legends are more simple and rudimentary in their nature, jtist in proportion as the cosmical features among which they were conceived, and of which they are in a great part the reflection, were more subdued in their manifesta- tions and phenomena. The people of the extreme north, who are in the habit of digging out subterranean habitations in order to avoid the cold, their country being for a great part of the year covered with ice and snow, can not have their ideas as to the harmony of the globe inspired by the same conceptions as the men of the south, who dwell at the foot of the highest mountains in the world, and constantly contemplate all the great phenomena of planetary life monsoons, hurricanes, the sudden overflows of rivers, and the rapid increase of immense tropical forests. To the Hin- doos, every thing in nature is motion, never-ceasing creation, and startling activity. According to one of their books, Brahma, the %ternal laborer, created the earth while surveying his own reflection in the ocean of sweat that had fallen from his brow. The Hindoo legends as to the formation of the earth and the distribu- tion of continents are very numerous ; besides, most of these hypothetical cosmogonies are remarkable for their boldness and for the deep convic- tion they manifest of the vitality which animates the earth, and all that it contains. However strange some of these grandly poetical theories may seem to us, they are not on this account any less true than the dry systems of mere nomenclature in which certain unhappy scholars have considered the whole scheme of geography. According to an ancient Hindoo belief- 1 very similar to that of several of the American nations the earth is nothing but a burden placed on a gigantic elephant, the sym- bol of intelligence and wisdom ; while an immense tortoise, representing the still rude forces of nature, bears the enormous animal over a shoreless sea of milk, boundless as infinity. Subsequently, the ideas which the Hindoos formed as to the origin of the globe were singularly diversified, according to the various epochs and sects. The Brahmins fancied that the earth was a full-blown lotus, float- ing on the surface of the waters. The two peninsulas of the Ganges and the other Asiatic countries are the expanded flower, the isles scattered over the ocean are the half-opened buds, distant lands are the softly spread- ing leaves. The Ghauts and the Neilgherries are the stamens of the im- mense flower, while in the midst culminates the lofty Himalaya, the sacred pistil, in which are organized the seeds of the world. Man, like the tiny insect which sees infinity in a rose, builds his imperceptible cities near the honey-cups of the flower, and sometimes spreads his wings to glide over 4-8 THE EARTH. the sea from the corolla of the Indies to that of Ormuz or Socotora. The stalk of the plant disappears in the depths of the ocean, and, descending from abyss to abyss, at last buries itself in the very heart of Brahma. This fantastic, but yet somewhat grand conception, which at least at- tributed to the earth some degree of motion and life, is very superior to all the dogmatic theories of the Syrian priests and the Hebrew Talmudists ; the latter, in their terror of change, looked upon the terrestrial mass as an immovable block solidly based on immense columns of stone or metal, which were themselves lost in primitive chaos. These ancient and coarse hypotheses are met with again in the more noble myth of the Greeks, ac- cording to which the globe was placed upon the shoulders of a kneeling giant. This was an idea which was in full harmony with the plastic ge- nius of Greece, which ever sought to recognize in every thing the propor- tions of the human form, deified, as it was, by strength and beauty. The idea, in the main, had remained much the same, but it had assumed a shape which was more poetic, and consequently more in conformity to the genius of an infant nation. Imbued with similar ideas, the aborigines of the plateau of Bogota tell how, in punishment for some crime, the good goddess Bochica condemned the giant Chibchacum to bear upon his shoul- ders the burden* of the earth, which previously rested upon pillars of the lig- num-vitce wood. Earthquakes, therefore, were derived from no other cause than the wearied or impatient movements of this Atlas of the New World.* With regard to the ideas in respect to the distribution of continents and seas over the surface of the globe, they could hardly fail to be erroneous, inasmuch as they took their rise among nations who endeavored to form a judgment as to the whole of the earth by means only of the few coun- tries which were known to them. According to the poems of Homer, which are imbued with the ideas of the ancient Greeks as to nature, and also mankind and their ways, the earth is a great disk, elevated at the edges by a lofty girdle of mountains, round which the river Ocean rolled its swelling waves. In the centre of the disk Olympus towered up with its three rounded summits, on which stood the mansions of the ever-happy gods, and Jupiter, throned on its loftiest crest, looked down through the clouds and saw the restless crowd busy at his feet. The land, divided into two halves by the blue sheet of the Mediterranean, stretched far away to the very verge of the disk, like the raised figures which ornament the front of a shield. Down from the heights of Olympus the immortals contemplated in one glance all the pen- insula of Greece, the white isles of the Archipelago, the coasts of Asia Mi- nor, the plains of Egypt, the mountains of Sicily, inhabited by the Cy- clops, and the Pillars of Hercules the boundary-stones of the ancient world. All round, above the tract inhabited by man, stretched the crys- tal dome of the firmament, borne up by the two columns of Atlas and Caucasus. But the discoveries of travelers and the calculations of the Greek as- * Bollaert, Antiquarian Researches, p. 12. EARL T IDEAS OF THE EARTH. 4.9 tronomers must have gradually modified this primitive theory. Strabo, who was, however, one of the greatest travelers of antiquity, having trav- ersed the earth from the mountains of Armenia to the shores of the Tyr- rhenian Sea and the Euxine, and to the frontiers of Ethiopia, had already formed a very just idea of the real distribution of the continents of the ancient world, and discussed with wonderful sagacity their mutual rela- tions. Overstepping the limits of the regions already known, he went so far as to hazard the assertion that, between western Europe and eastern Fig. 6. The World after the poetic accounts of Homer. Asia, there existed an inhabited land forming an equipoise to the Old World. In all his scientific audacity, he conjectured that which modern geography has since discovered that " not only mere masses of rock and islands, large or small, but also whole continents, may be upheaved from the bed of the sea." As the great Ritter has stated, with a feeling which may al- most be called filial, Strabo is the real founder of geographical science, and modern savants have only resumed his work, after so many centuries smit- ten with sterility, first by the Roman Caesarism, and subsequently by the barbarism of the Middle Ages. D 50 THE EARTH. CHAPTER VII. INEQUALITY OF LAND AND WATER. THE OCEANIC HEMISPHERE. THE CON- TINENTAL HEMISPHERE. THE SEMICIRCLE OF LAND. DISTRIBUTION OF THE HIGHEST PLATEAUX AND LOFTIEST MOUNTAIN - CHAINS ROUND THE INDIAN AND SOUTHERN OCEANS. POLAR CIRCLE. CIRCLE OF LAKES AND DESERTS. COASTS ARRANGED IN ARCS OF A CIRCLE. THE most prominent fact which strikes an observer in an examination of the superficies of the earth is the unequal extent of the ocean and of the land which has emerged from it. Although at the two polar regions there are still vast unexplored tracts forming about a sixteenth of the ter- restrial surface, still it may be approximately stated that three quarters of the surface of the globe is covered by sea. The plate gives an idea of Fig. 7. Relative proportions of land and water in different latitudes. the distribution of land and sea in the explored regions of the globe from 75 north latitude to 70 south.* An equilibrium between the two ele- ments exists only on two parallels of the terrestrial circle, one of which is in 45 of north latitude, half way between the equator and the pole. In this part of the earth's circumference, the land occupies exactly one half of the surface of the globe. The principal accumulation of water is in the southern hemisphere, and * Dove, Zeitschrift Jur aflgemeine Erdkunde. Jan., 1862. LASD AND WATER. 51 the continental masses, on the other hand, are grouped in the northern half of the earth's surface. This contrast between the two divisions of the globe becomes much more striking if, instead of taking the two poles as the centres of our hemispheres, two points are chosen which are situated, one in the midst of the most extensive tracts of ocean, and the other about the centre of the group of continents. If we describe a great circle round London, which at the present time is, in fact, the great focus of attraction for the commerce of the whole world, almost all the continental surface Fig. 8. Oceanic Hemisphere. surrounding the basin of the Atlantic, rendering it almost an inland sea, will fall within this hemisphere. . The other half of the terrestrial surface, the centre of which would be situated somewhere near New Zealand, the antipodes of Great Britain, is almost entirely filled up with the immensity of water. The antarctic countries Australia, Patagonia, and the adja- cent archipelagos form the only land which breaks the uniformity of this oceanic hemisphere. According to a very plausible hypothesis, this ex- uberance in the development of continents on one side of the globe, and the afflux of the waters of the ocean towards the opposite hemisphere, are 52 THE EARTH. caused by the unequal weight of the materials which constitute the mass of the globe and the consequent non-coincidence between the actual cen- tre and the centre of gravity.* The coast outline of the continents which surround the great ocean tends to a form which is perceptibly circular ; it is a kind of ring, broken in two at the south near the frigid zone of the antarctic circle. From the southern point of Africa to Kaintschatka, and from the Aleutian Isles to Cape Horn, the land is arranged in an immense amphitheatre, the circum- No. 9. Continental Hemisphere. ference of which is equal to the circumference of the globe, and can not be less than 25,000 miles. They are not merely low shores which spread in this hemicycle round the oceanic hemisphere ; the highest plateaux, the loftiest mountains of the world, are drawn out in a vast semicircle in those countries which are adjacent to the Pacific, and tend to incline toward that ocean the centre of gravity of the whole of the continental bulk. Thus it is along the side of the Indian Ocean, an appendage as it is to the great Southern Ocean, that Africa presents its loftiest ridges ; there, * Herschel, Physical Geography, p. 15. NORTH AMERICA PL. IV -v ErhuM. ~l r Duguay -"frouin DnmBibf AVinllemm HAP-PEH & BROTHERS. NEW YORK CONTOUR OF THE LAND. 53 . Fig. 10. Basin of the Pacific. too, are found the snowy mountains of Kenia and of Kilimandjaro and the plateau of Ethiopia, like a great fortress surrounded by bastions. East- ward of the narrow entrance to the Red Sea stands another plateau, that of the Yemen, whose steepest slopes are likewise turned toward the shores of the ocean. Farther on, this rampart of lofty ridges, which might well be called the " vertebral column" of the body of continents, is interrupted by the de- pression of the Euphrates and the Persian Gulf; but it again commences at the north of Persia. The Caucasus, the Elburz, the Hindu-Kutch, the Karakorum, and the proud Himalaya, the summits of which rise more than 5 miles above the plains of Hindostan, all are, on an average, three or four times nearer to the Indian than to the Arctic Ocean. This difference would be still more increased if we did not take into account, as portions of the great Asiatic body, the southern peninsulas which stretch away so far into the sea. Taken as a whole, the continental mass may be divided into two gradients, one of which descends rapidly toward the plains next the Indian Ocean, whilst the other side, ribbed with divergent mountain chains, inclines more gradually toward the immense marshy tundras which border the Frozen Ocean. The great plateaux of Central Asia, bounded on the north and south by the mountain chains which radiate in a fan-like shape from the knot of the Hindu-Kutch, form, in the direction of the northeast, the highest portion of the continental amphitheatre ; then, in the north of the valley of the Amoor, they are prolonged up to a short distance of the coast-line by ranges of peaks, which tower over the Sea of Ochotzk and Behring's Straits. Beyond this the waters of the Pacific have opened out a passage to join the tides of the Frozen Ocean ; but yet the line of mountains is still prolonged. Arranged as they are, in the form of a broken isthmus, on the south of the Straits, the Aleutian Isles unite the two continents of Asia and North America ; one might almost fancy them the shore-line of some ancient and submerged land. 54 THE EARTH. The lofty peninsula of Aliaska, which follows on to the Aleutian range, is the starting-point of the series of highlands which border the coasts of the Pacific along the whole length of the two American continents. Par- allel chains, abutting in some places on large groups of mountains, bend round the shores of Sitka, British Columbia, and California, gradually merging into the plateau of Anahuac. The latter is prolonged on the southeast by a volcanic chain, here and there interrupted ; but on the coasts of the Gulf ofDarien the great chain begins again, and, plunging the rocks which form its base deep into the waves of the Pacific, extends Fig. 11. Circnmpolar Circle. its double or triple snowy ridges down to the Straits of Magellan. The other elevations of the surface of the ground lie to the east of this back- bone, as it were, of the South American continent, and attain a very much less considerable altitude ; they are, indeed, intersected and even crossed by some of the rivers which take their rise in the perpetual snows of the Andes. Added to this, the steepest slope of the principal chain is uni- formly turned toward the coast of the Pacific, and the distance from the mouths of the Amazon to the summits of the Andes is on the average, at POLAR CIRCLE. 55 least, fifteen times longer than the short span from the ridges of the latter to the shore of the ocean. The immense semicircle of high land forming the inner coast-line of the mass of continents which extended from the Cape of Good Hope round to Cape Horn is not, however, the only evidence of the forces which are al- ways in action, tending to elevate the salient portions of the terrestrial sphere, and operating in great circular lines. Thus in the chain of the Andes is commenced a series of volcanic mountains and islands which forms a vast circle round the Southern Ocean. This is the great ring of Fig. 12. Circle of Inland Lakes and Seas. active volcanoes which was for the first time described by Leopold von Buch, and designated by Carl Ritter as the " Circle of Fire."* Thus, also, the continental and insular shores which are turned toward the Arctic Ocean assume a circular curve. As far as it is possible to judge from the present state of our knowledge as to this part of the world, it appears as if a polar circle inclined about five degrees toward Beh ring's Straits would have for its almost regular circumference the northern o * Vide the chapter on "Volcanoes." 56 THE EARTH. coasts of Siberia, of Parry's archipelago, Greenland, Spitzbergen, and Nova Zembla. Another circle, inclined about ten degrees to the pole in the direction of the meridian of Paris, would pass through the greater part of the inland seas of the Old and New Worlds. This curve would enter the Mediter- ranean through the Straits of Gibraltar, and, crossing this sea, as well as the Euxine, would unite the Caspian and the Sea of Aral, both of which, during a recent geological epoch, formed but one sheet of water; it would then be prolonged toward the Pacific through the chain of the chief Sibe- rian lakes, including the Baikal. On the American continent the curve Fig. 13. Semicircle of Deserts. passes through the Winnipeg Lake, the Mediterranean of the great lakes of the St. Lawrence, then the Champlain Lake, and the Bay of Fundy. Thus terminates this great series of continental depressions, which cer- tainly was not formed at random. On the north of the Mediterranean, the most important of all the inland seas, the loftiest mountains in Europe form a rampart similar to that which bounds the South American shore of the Pacific. In fact, the Pyrenees, the Alps, and the Balkans form a sort of wall, broken through with numerous gaps, which is much nearer to the Mediterranean than to the northern seas, and presents also its steepest slopes toward the south. DESERTS AND SEA-COASTS. 57 Jean Reynaud has also thought that he could point out* the existence of another terrestrial ring, which must likewise have been formed in obe- dience to some great geological law. This third circle, inclined 15 (or rather 20) to the pole, passes through the Isthmus of Panama, which is the deepest depression of the land of America, and crosses almost all the great deserts in the Old World, many of which were covered with water during the later terrestrial periods. These sandy or rocky tracts are ar- ranged obliquely across the continents of Africa and Asia, and consists of the Sahara, the sandy districts of Egypt, the Nefoud of Arabia, the salt plateaux of Persia, and the Gobi, or Chamo, the latter inferior in extent only to the African solitudes. It is a remarkable thing that this series of dried-up seas is commanded on the north by various mountain chains, the Fig. 14. Western Shores of the Mediterranean. Alps, the Taurus, the Caucasus, and the Altai ; like the Pacific and the Mediterranean, these now vanished waters were bordered on the north by a rampart of high lands. Oscar Peschel has, however, proved that the phenomena of climate constitute the real cause of the supposed " Equator of Contraction," and that this semicircle of deserts is to be attributed to the general direction of the winds and the scarcity of rain. Not only those various regions which are distinguished by some strik- ing analogy in elevation and aspect are circularly arranged on the surface of the planet, but the mere outlines of the continents themselves seem to be obedient to some rhythmical law, in conformity to which they present * Terre et del, Eclairtissements scientijiques. 58 THE EARTH. a series of arcs of a circle, assuming a regularity which is sometimes al- most perfect. The coasts of the three southern continents, South Amer- ica, Africa, and Australia, afford remarkable instances of this rule. The coast-lines of all the peninsulas of the northern continent may likewise be cut up into arcs of a circle, and multitudes of islands, of which Sicily can perhaps be taken as a type, may be compared to actual curving-sided tri- angles. This circular arrangement of the coasts is so frequently re- marked that many geologists have gone so far as to endeavor to class va- rious countries according to the degree of the curvature of their gulfs and bays. SOUTH AMERICA PLY. Ej^ 4 V Erird u r.Dufcuay-Ttuum Drum }y A VuilWnm - '- 3 P.O T H R P S . N E r A" V Q RK DIVISION OF THE LAND. 59 CHAPTER VIIL DIVISION OF THE LAND INTO THE OLD AND NEW WORLDS. DOUBLE AMERI- CAN CONTINENT. DOUBLE CONTINENT OF EUROPE AND AFRICA. DOUBLE CONTINENT OF ASIA AND AUSTRALIA. ALTHOUGH we may consider the continental masses as arranged in cer- tain great circles traced round the sphere, we must also recognize the ef- fect of another law in virtue of which the various groups of land are ar- ranged in three double continents, forming respectively three parallel series. At first sight, it would seem as if the portions of the earth which have have emerged from the waters, form, in fact, but two groups those of the Old and New Worlds : and that the shapes of these groups appear to bear little or no resemblance to one another. Yet a careful examination can not fail to reveal a striking unity of plan, where at first sight all seems disorder and chaos. The fact is, in consequence of the crossing of the different upheaved portions of the earth some in a circular direc- tion rund the seas, others parallel to the meridian there is produced among the continental groups a series of contrasts which so interfere with the resemblances, as to cause that, in the general distribution of the land, opposite forms should successively predominate. Neverthiless, this med- ley, by its infinite variety, is the very thing which gives so great a har- mony to the ensemble of the terrestrial outline. In the comparative study of the configuration of continents, we must choose America as our type, because in this portion of the world the line of upheaval, tending from north to south, forms a tangent to the curve which is described by the disposition of the land round the Pacific, and is even coincident with it along a certain portion of its extent. In con- sequence of this coincidence of the axis, the New World exhibits a very great regularity of shape. It is composed of two triangles, each pointing its apex toward the south, and linked together by a very narrow isthmus. These two halves of America, one of which belongs entirely to the north- ern hemisphere, the other being tropico-meridional, form two perfectly distinct continents, and yet they show so great a similarity of structure that they are evidently the counterparts of one another. Nevertheless, as the natural effect of the increasing divergence in North America be- tween the continental axis and the circle of mountains which spread round the Pacific, this continent is much larger than its companion, and its coast-line is much more indented. The more typical form, therefore, is that of the southern continent. . In the Old World, Africa evidently follows the same model as South gO THE EARTH. America. As regards their general structure, the two continents are alike in their great triangular mass, with coasts slightly inflected ; and the similarity extends even to the details of their gulfs and promonto- ries. The contrasts, are, it is true, very numerous ; but they exhibit so much regularity and rhythm, so to speak, that even in these we can not fail to see a new proof of unity of formation in the two continental masses. As far as Europe is concerned, we should, at first sight, be tempted to say that there was no degree of correspondence between this part of the world and the North American continent. In fact, this collection of pe- ninsulas, which even in our days is still the most important region of the whole world, on account of the high civilization of the nations inhabiting it, might be looked upon as nothing but a geographical appendix a mere prolongation of Asia ; in fact, we almost hesitate to compare it with North America, the bulk of which occupies a superficies twice as large. Yet a geological study of the conformation of Europe proves that in re- ality it forms a distinct continent. At some previous epoch it was sepa- rated from Asia by a sheet of water, which stretched from the Mediterra- nean to the Gulf of Obi, through the present Euxine, Caspian, and Aral seas. At the foot of the mountain chains of Oural and Altai extend those immense steppes which, like most deserts, still retain much of their former oceanic appearance, and form the eastern boundary of Europe quite as effectually as would a second Atlantic. The arm of the sea whic^i once divided these two divisions of the world is, indeed, dried up; but, al- though now united, the two lands none the less retain their distinctly de- fined charactqjs. Thus, geology bears its testimony in establishing the continental form of Europe and its similarity to North America. The resemblance be- tween the two quarters of the globe is kept up on the southern as well as on the eastern side. It is very true that on the southern side the land of Europe is no longer connected with that of Africa by an isthmus similar to that which joins the two Americas ; but, as even Strabo well knew, an upheaving of scarcely a hundred yards would suffice to form a tongue of land from Sicily to Tunis, dividing the Mediterranean into two halves. A submarine bank separates this sea into two deep basins, and, owing to its steep elevation, may be considered as an actual isthmus. Added to this, the northern part of Africa that is, the region of the Atlas, com- prised between the former sea of the Sahara and the present coasts of Morocco, Algiers, and Tunis is certainly an ancient dependency of Eu- rope. Modern science has established the fact that, as regards both its Fauna and its Flora, as well as its geological constitution, the whole of the eastern sea-coast of the Mediterranean the north as well as the south forms an inseparable whole. Thus, M. Bourguignat has clearly estab- lished, by his examination of living molluscs, that Northern Africa does not possess one single species which is peculiar to it, and that all the types of the animals which are found on the slopes of the Atlas proceed DOUBLE CONTINENTS. Ql from the Iberian peninsula. The western Sahara and Tripoli being equal- ly devoid of any species specially belonging to them, it becomes evident that these latter regions, at the commencement of the present epoch, had not yet emerged from the bed of the ocean, and that Mauritania formed the southern continuation of the Spanish peninsula ;* the headlands of Ceuta and Gibraltar then formed portions of one and the same chain of mountains. The ancients were not ignorant that the western entrance to the Mediterranean had once been closed, since they attributed to Hercules the honor of having opened the gate between the two seas. Many au- thors even regarded it as a vexatious innovation that the geographers had made Europe and Libya two distinct parts of the world ; for although separated by the sea, the two regions appeared to them to belong to the same geographical whole. f The external outlines of Europe remind one forcibly of those of North- ern America. In both continents, the coasts which border on the Atlan- tic are deeply indented, and not only allow the sea to penetrate a long way into the interior of the land in various places, but also throw out pe- ninsulas far into the ocean. Tn Europe, the Mediterranean and the Baltic Sea correspond with the Gulf of Mexico and all those seas which extend between Greenland and British America. But it must be remarked that in Europe, the arrangement of which is finer and more delicate than that of any other part of the world, the peninsulas are more slender in form, and the inland seas more surrounded with land. In Europe, the penin- sulas have become islands, and the seas have become lakes. Neverthe- less, Europe corresponds in its structure with North America to a great extent, and forms, with Africa, a second pair of twin continents, parallel to those of the New World. qitadrtfiaa. Asia and Australia constitute the third pair of continents, although their form only very imperfectly reproduces the primitive type. There is an interruption of equilibrium to the great advantage of the northern portion ; but in the general configuration of these great masses we can still discern the principal features which distinguish the other double continents. Like North America and Europe, Asia is geologically iso- lated ; like these two parts of the world, she throws out numerous penin- * Bourguignat, La Malacologie de VAlgerie. t Sallust, Bell. Jug., c. 17; Von Hoff, Veranderungen der Erdoberfliiche. 62 THE EARTH. sulas into the seas which surround her; and although she is not directly united to Australia by a continuous isthmus, yet the Sunda Isles, " like the piles of a demolished bridge," stretch across the sea between the two continents. As regards Australia, both by its regular and almost geo- metrical form, and also by its entire absence of peninsulas, it evidently reminds us of the two other parts of the world which push their way far into the Southern Ocean. Fig. 1C. Mundus tripartitus. Finally, if we consider separately the Old World, or eastern group of continents, we may recognize a quadripartite division, or the separation of the land into four parts arranged two by two on the north and south of the equator. This is the idea that was taught by most of the ancients, whic% also induced them to give to the world then known the name of Terra quadrifida* Others, no less following certain systematic concep- tions, fancied that the land that had emerged from the deep was shaped like an egg, and composed of three portions, surrounding the sacred tem- ple of Delphi, " the umbilicus of the world." Thus, in the external form of continents, we find two quite distinct laws in action ; one, according to which they arc arranged in circles ob- liquely to the equator, the other which distributes them in three lines par- allel to the meridian. To this complication is due the apparent irregular- ity of the double continents in the Old World, for there the two axes of formation cross, and consequently there, too, is produced a great diversity in the relief of the land. The mutual resemblances and contrast exhibited by the two halves of the world can, however, be perfectly well explained if we connect them with one or the other of these two orders of facts. If we look upon the land as forming three parallel double continents, we must then be struck with the similarity which they mutually present both as a whole and in details ; if, on the contrary, we admit the usual division of the continental masses into two worlds, we discern the reason of the contrasts, which are only another kind of resemblance. In this way we may explain the variety in the forms of the continent of Europe, by looking upon it either as the half of two twin continents parallel to the two Americas, or as a great Asiatic peninsula, forming a portion of the immense ring of land which extends round the ocean. Just as in a * Joachim Lelewel, Pytheas de Marseille. EUP aS *o 15 jo S o J K> Drawn by A.. Vuillenom PI VI CHAD'S OF THE HDfDU-KUTCH. 53 woven fabric, we can discern both the warp and the woof in the marvel- ous texture of the earth's surface. The principal feature in the relief of the Old World is the enormous elevation of the land near the centre of Asia, at the intersection of the lofty chains of the Hindu-Kutch, in that region*of grandeur to which the epithet " the roof of the world " has been justly given. This elevated spot, round which radiate the Himalaya, the Karakorum, the Kuenlun, the Thian-Chan, the Soliman-Dagh, and other chains of mountains, is, in fact, the point of the earth at which the two continental axes cross one anoth- er, one tending from the north to the south, the other from the southwest to the northeast, parallel to the outline of the Pacific. At their meet- ing-point the two terrestrial waves overlap one another, just as two bil- lows coming together in the open sea from two different points of the horizon. There, at the intersection of the axes, stands the real apex of the earth, the orographical centre of continents ; there, too, we find, was the centre of dispersion of the Aryan nations. By a remarkable contrast, at the exact antipodes of this region of elevated plains and lofty mount- ains, we find those broad tracts of the Pacific which are most destitute of islands; and there, too, are probably situated the deepest profundities of the ocean. THE EARTH. CHAPTER IX. PRINCIPAL ANALOGIES BETWEEN CONTINENTS. PYRAMID FORM OF POR- TIONS OF THE WORLD. SLOPES AND DECLIVITIES. CLOSED BASINS OF EACH CONTINENT. SOUTHERN PENINSULAS IN EACH GROUP OF CONTI- NENTS. HYPOTHESIS OF PERIODICAL DELUGES. RHYTHMICAL ARRANGE- MENT OF PENINSULAS. EVERY continent, considered by itself, may be compared to a pyramidal mass having an enormous base and a summit placed far from the centre of its figure. Thus Mont Blanc, the loftiest summit of the Alps, is sit- uated at a comparatively short distance from the west and south coasts of Europe. The latter, therefore, taken as a whole, may be looked upon as a pyramid, the height of which is not more than a thousandth part of its base ; the faces turned toward Asia and the Frozen Ocean being four times as long, on the average, as the sides which tend toward the Atlan- tic and the Mediterranean. The Asiatic continent has for its apex the lofty mountains of the Himalaya, and from these elevated points the face of the country inclines in very different gradients toward the two op- posite oceans : on one side the fall is rapid down to the plains and gulfs of Hindostan; on the other side the descent is very considerably longer. The general outline of the relief of the continent of Africa is less known ; it is, however, probable that the mountains Kenia and Kilimand- jaro are the culminating points of the continental polyhedron. These mountains, which rise very far from the centre of Africa, also exhibit on one side a comparatively steep incline, and on the other a very gradual descent. In Australia we see the same phenomena, for the most elevated points of this continent are probably to be found in New South Wales at a short distance from the edge of the Pacific ; from these mountains to the Indian Ocean the distance is at least six times as great. The two Americas, also, may likewise be considered as two solid bod- ies having their culminating points far distant from the centre of the figure one at Orizaba, or Popocatepetl, the other in the group of the Bolivian mountains. In spite of the varied outlines of relief which* con- tinents exhibit, in spite, too, of the basins and depressions in their surface, there are but few localities where the ground shows any hollows lower than the level of the sea ; and these hollows, such as the neighborhood of the Caspian and the valley of the Dead Sea, are situated precisely on the respective confines of two continents, Europe and Asia, and Asia and Africa. Even the depressions of the Algerian Sahara, the surface of which is in many places lower than the Mediterranean, are the bed of the PYRAMID FORMS. 65 ancient sea which once separated the real Africa from the districts of the Atlas. Another great feature of resemblance between the various continental masses is that each of them contains one or more closed basins, where a receptacle is found for the water-courses which can not flow to the outer side of the continent ; these concavities having their own peculiar system of lakes and rivers, are, as it were, so many worlds by themselves. The Asiatic continent, the largest of all, and that in which the supposed cen- tre is most distant from the sea, is the continent in which the inland hy- drographical basins are of the greatest extent. They comprehend nearly the whole area of the high plateaux of Tartary and Mongolia, namely, the basins of Lob-Xor, Tengri-Xor, Koko-Xor, and Oubsa-Xor ; and on the wi->t of the great mountain chains of Central Asia they also embrace the plateau of Iran, the basin of Balkach, and also the basins of the sea of Aral and the lakes of Van and Ourmiah. By the depression of the Cas- pian, the Asiatic series of lakes without outlet is connected with the Eu- ropean system, which extends to the very centre of Russia, to the sources of the Kama and the Volga. The whole of this region, the waters of which, from the hills of the Russian Valdai to the plateaux of Mongolia, tind no outlet in the direction of the sea, embraces an area at least as ex- tensive as that of Europe. The two continents of America likewise have their isolated systems of lakes and rivers occupying a corresponding posi- tion one in the "Great Basin," between the Rocky Mountains and the Sierra Nevada of California, the other on the plateau of Titicaca, between the chain of the Andes and the Cordi^ras properly so called. Africa, too, has several basins without outlet, tne principal one being that of the Lake Tchad, situated in the centre of the continent. Finally, even Aus- tralia, in spite of its comparatively small extent, has its lakes, Torrens, Gairdner, and others, which do not communicate with the sea.* As Bacon formerly remarked, the three groups of continents exhibit also a singular resemblance to one another in the pyramidal form of their terminal points in the direction of the Antarctic Ocean. These three southern peninsulas do not advance to an equal distance into the sea, as they reach respectively to 36, 44, and 56 degrees of south latitude, but they may be connected by an ideal circle, inclined 10 degrees to the South Pole.f The distances between the extremities of the three conti- nents are not very far from equal on the terrestrial periphery, as the tracts of ocean between the Cape of Good Hope and Cape Horn, Cape Horn and Tasmania, Tasmania and the South of Africa are nearly in the ratio of the numbers 7, 8, and 9. Each of these promontories, pushed forward, as they are, from the rest of the land, appears to have been partly demolished by the waves. Thus the extremity of South America presents the appearance of an immense ruin ; the tortuous Straits of Magellan separate it from the Tierra del Fnego, which is itself divided into numerous islets by a labyrinth of * Vide the Map of the World, PI. I. f Jean Reynaud, Terre et Ciel. E THE EARTH. Fig. 17. Circle of Jun^on of the Continental Points. channels, and is guarded on the south, as by a couching lion, by the for- midable headland of Cape Horn. At the southern point of Africa stands another " Cape of Stoi-ms," to which a feeling of confidence in the ap- proaching discovery of India gave the name of the Cape of Good Hope. To the east of this promontory, which is connected with the main body of the continent by a system of plateaux and mountains, a great bank or shelf pushes out far into the sea ; this bank is doubtless the remains of some vanished land, and the force of the marine currents still breaks over it.* The Australian continent, too, has for its southern projection the steep shore of Van Diemen's Land ; for, by its geographical position, this island evidently belongs to Australia ; the error, therefore, of Cook, who looked upon Tasmania as nothing but a promontory of New Holland, was more apparent than real. There is another fact which completes the re- semblance between the terminal points of the three continents of the antarc- tic hemisphere, namely, that each of the seas which extend to the east of these countries washes some island or considerable archipelago. On the east of Australia there is New Zealand ; at the east of the South American continent we find the Falkland archipelago ; east of Africa, the large island of Madagascar. * Houzeau, De la Symetrie des Formes des Continents. AF Drawn by A Vuillemin PI. Ml PENINSULAS. 67 These remarks of Bacon, since developed by Buffon, Forster, the com- panion of Cook, and in modern times by Steffens, Carl Ritter, Arnold Guyot, and others geographers, have given rise to the hypothesis that a terrible deluge, coming from the southwest, once rushed over the conti- nents of the southern hemisphere, crumbling them up, dismembering them, and carrying their debris over the northern continents, thus forming the long slopes which incline toward the Arctic Ocean. The land in the north would thus be disproportionately augmented at the expense of the south, of which nothing would be left, so to speak, but the skeleton. To this great inundation, which carved out afresh the great continental masses, Pallas, the Russian traveler, attributes the transport of the innu- merable remains of mammoths which are found buried in the soil of the Siberian tundras. This hypothesis has been, as we know, adopted since by Adhemar and his disciples. In the opinion of these geologists, who recognize the great agents of terrestrial renovation in a series of periodi- cal deluges proceeding alternately from the north and south every 10,500 years, the bones found in Siberia were brought there by the last deluge but one, which resulted from the breaking up of the ice at the south pole. According to one of these hypotheses, the last dissolution of the ice came from the south ; according to the other, from the north. It is, therefore, prudent to set aside these contradictory ideas which attribute to some cataclysm the peninsular form of the southern continents. Besides, at the present day, there is no longer any doubt that both the mammoth and rhinoceros were once natives of Siberia the very country where their remains are now found.* Almost all the great peninsulas of the earth as Greenland, Kamt- schatka, and Corea, including even those which would suggest a sudden change in the sea-level extend in a southerly direction. Added to this, each of the three northern continents, in their southern articulations, seem to adopt as a type the three southern continents taken as a whole ; thus, each puts out three peninsulas into the seas which bathe its southern shores. In Europe, Asia, and North America respectively, three groups of secondary peninsulas correspond to the three great promontories of the southern world. In the Old World especially, these peninsular articulations are formed with a considerable degree of regularity, and, so to speak, of rhythm and measure ; in the different continents, they exhibit the most striking anal- ogies. Arabia, in the proud and simple beauty of its outline, recalls to mind the elegant and yet majestic form of -Spain ; Hindostan, in the gen- tle undulations of its banks and the roundness of its bays, corresponds to Italy ; India beyond the Ganges, by its numerous indentations and the enormous development of its coasts, seems the counterpart of Greece that beautiful country, the outline of which has been so justly compared to that of a mulberry-leaf. In both continents, the peninsulas become more and more articulated, and more and more, as it were, endowed with * Die nevtsten Arbeiten uber das Mammuth, Mitthfilungen von Petermann, ix., 18GG. 65 THE EARTH. vitality as we proceed from west to east. The Mediterranean peninsulas particularly present the remarkable phenomenon that the variety of out- line is greater in proportion to their nearness to the rising sun. The nu- merous bays which hollow out the coast of Spain all along the Mediterra- nean shore are developed in regular arcs of a circle equal on the average to a quarter of its circumference. The Italian gulfs those of Genoa, Na- ples, and Salerno are spread out in perfect semicircles round the coast of the peninsula ; while the gulfs of Greece form very deep indentations into the land, and, like the Gulf of Lepanto, might be called Mediterra- neans in miniature. It must also be remarked that on the east of the somewhat severely- designed coasts of the analogous peninsulas of Spain and Arabia, the isl- ands are but few and of small importance. Italy and India, on the con- trary, the forms of which are richer, have each their large island, and, with their southern extremities, almost touch Sicily and Ceylon respect- ively. With regard to Greece and the Transgangetic peninsula, the seas which bathe their eastern coasts are dotted over with innumerable islands and islets, like a brood of young birds nestling under the wing of their mother. The two other eastern peninsulas, which are also thrown off by the great Asiatic continent, are each of them likewise accompanied by an archipelago. The three southern peninsulas of North America do not exhibit the same regularity in their aspect as those of Europe and Asia. In conform- ity with the somewhat narrow and elongated form of the continent itself, two of these peninsulas Florida and Lower California seem attenuated in comparison with the analogous portions of the Old World. The other peninsular appendage, which, being placed in the very axis of the New World, is much more developed, is none other than the isthmus of Cen- tral America, now modified and distorted. In fact, a simple depression of the ground of about one hundred feet is all that is needed in order that the Pacific and the Caribbean Sea should unite their waters between the two American continents ; besides, it appears that, at a recent geological epoch, a channel, at least thirty-seven miles wide, connected the two seas across the plain which is now filled with a lava deposit, and is command- ed on one side by the Sierra de Maria Enrico, and on the other by the Sierra Trinidad.* A single feature of the earth's relief may at the same time fulfill several functions : thus, exactly at the antipodes of Central America, the Sunda Islands are also an isthmus between the two conti- nents of Asia and New Holland. There are numerous other analogies between the different parts of the world which we might also mention ; but most of them may be referred to those we have named, or else they belong more to the province of ge- ology properly so called. * Moritz Wagner, Mittheilungen von Petermann, 1861. CONTRASTS IN AREA AND FORM. CHAPTER X. NUMEROUS INDENTATIONS OF THE NORTHERN CONTINENT. HEAVINESS OF FORM IN THE SOUTHERN CONTINENTS. INEQUALITY OF SIZE IN THE CON- TINENTS OF THE OLD WORLD. EXTENT OF COAST-LINE IN INVERSE RATIO TO THE AREA OF LAND. CONTRASTS BETWEEN THE OLD WORLD AND THE NEW. THE TRANSVERSE POSITION OF THE AXES OF AMERICA AND THE OLD WORLD. CONTRASTS OF CLIMATE IN THE VARIOUS CONTINENTS: NORTH AND SOUTH, EAST AND WEST. THE contrast between the shapes of the various continental shores is one which is very easily verified. North America, Europe, and Asia have a very considerable extent of coast-line in comparison with their bulk. They are penetrated for long distances by deep gulfs and inland seas, and their outline is rugged with promontories ; it might be said that the organization of these continental masses bears some resemblance to an articulated body and its limbs. South America, Africa, and Aus- tralia seem, on the other hand, to enjoy but a rudimentary conformation ; their contour is almost geometrically regular and simple, and their bays and gulfs are so slightly indented into the land, that the regular line of the coast is scarcely altered ; there is, too, an almost complete deficiency in promontories of a peninsular form. In the great scale of terrestrial or- ganization, these continents present an inferior phase of life. Neverthe- less, this heaviness of contour and deficiency of peninsulas are in great part compensated for by the more oceanic position of the southern conti- nents and the prevalence in them of a tropical climate. In fact, under the tropics, the air, being much warmer, is saturated by a larger quantity of moisture ; and the atmospheric currents, being more rapid and regular, carry the sea-breezes across much wider areas. Thanks to the tropical rains, trade-winds, and hurricanes, the enormous masses of South America and even Africa are as much exposed to oceanic influences as other parts of the world which are more deeply indented by gulfs and bays. The three northern continents, on thetcontrary, the shores of which are so cut into and pierced in every direction, owe to their inland seas the ability (as re- gards a considerable portion of their surface) of imbibing those aqueous vapors without which they would be nothing but immense deserts. The area of the continents is a fact no less important than their form, and the contrasts afforded in this respect are also not a little striking. While the two halves of America are almost equal in extent, the four continents of the Old World differ much in the size of their respective areas. Asia, by herself, includes a larger surface of land than the two Americas together. Europe, pushed out into the ocean as a mere Asiatic 70 THE EARTH. peninsula, is foin % or five times smaller than the enormous mass with which she is connected. In the south, the surface of Africa is three times as great as that of Europe, while Australia, compared with its northern neighbor, the area of which is six times bigger, scarcely deserves more than the name of a great island. It must, however, be remarked that, by a very curious phenomenon of compensation, the two halves of each con- tinental pair are arranged so as to balance on the terrestrial sphere. In the western pair, Africa, which is the preponderant portion, lies to the south, and the smaller Europe extends to the north. In the eastern pair, it is just the reverse: on the north is the great continent of Asia, and on the south the region of New Holland, which would correspond with Eu- rope. AREA OF CONTINENTS. FIRST PAIR. North America 7,953,315 square miles. South America 6,949,674 " " SECOND PAIR. Europe 3,822,320 " " Africa 11,244,958 " ' THIRD PAIR. Asia 16,771,879 " Australia 2,972,916 " " The continents may also be compared by pointing out the respective distances of their ideal centres from the nearest point on the shore of the ocean. CONTINENTAL RADII. FIRST PAIR. North America 1087 miles. South America... . 931 " I SECOND PAIR. Europe 478 miles. Africa 1118 " THIRD PAIR. Asia 1491 " Australia 615 " This great inequality in the size of the continents might furnish cause for surprise, were we not well aware that, according to the beautiful law pro- pounded by Geoffroy Saint-Hilaire, no function can be unduly developed except at the expense of some other function. Europe is small, it is true ; but what an opulence of coast-line does she enjoy ! What profusion of gulfs and peninsulas diversify her outline, how many islands and islets there are in her seas ! In Europe, land and water are arranged in alter- nate layers as if to form an immense electrical battery, where the acid, sheets of metal, and conducting wires are replaced by seas, land, and aeri- al currents. Europe is so variously articulated that she enjoys a more considerable extent of coast-line than either South America or Africa it- HARFEP &. r : PL .V III ' y&* 7-7^ 'P.K EXTENT OF SEA.-COAST. 71 self, both of which fill so much greater an area. Australia at first sight appears, from its solid form, to constitute a modification of the law ac- cording to which the smallest continental masses are the most highly organized. But Australia must not be looked upon as an isolated body; we are bound to take into account the elongated isthmus of islands and islets which connects it with Ind^lhiua. Along this former isthmus are scattered numerous archipelagos, presenting an almost incalculable devel- opment of coast-line, and consequently possessing all the advantages of climate, richness, and fertility which are afforded by a maritime position ; there, too, more than in any other part of the world, the magnificence of terrestrial vitality is displayed in the splendor and variety of its pro- ductions. The following tables, which give in miles the absolute and relative length of the sea-coast of each continent, are therefore necessarily incom- plete. How shall we separate from Europe England, Ireland, Sicily, and the Isles of Greece all of them countries which have played so important a part in the history of civilization? How can we neglect, in the New World, the West India Islands, and the islands lying to the east of the continent of Asia the Moluccas, the Sunda Archipelago, and Japan ? EXTENT OF SEA-COAST. FIRST PAIR. North America 29,969 miles. South America 16,012 " SECOND PAIR. Europe 19,825 " Africa 12,561 " THIRD PAIR. Asia 35,886 " Australia 8,947 " PROPORTION OF SEA-COAST TO SURFACE. FIRST PAIR. North America 1 mile to 265 square miles. South America 1 " "434 " " SECOND PAIR. Europe 1 " " l<)2 " " Africa 1 " " 895 " " THIRD PAIR. Asia 1 " " 469 " " Australia 1 " " 332 " " By taking account of the principal islands Great Britain, Ireland, Sar- dinia, Sicily, and several others the total extent of the European coast- line may be estimated at 26,716 miles, which will give one mile for 143 square miles of surface. In the two continents of the New World, the plateaux and the plains show a surface nearly equal in extent, and, in this respect, present a har- 72 THE EARTH. mony which does not exist in the Old World. All the western countries of North America, as well as a great part of its eastern regions, consist of plateaux, some level and others commanded by mountain chains. The plains which extend between these two systems of elevated ground, and embrace the fluviatile basins of British America and of the Mississippi and Missouri, are equal in surface to fp higher regions along the edges of the two coasts. In South America the plains are comparatively more extensive. Nevertheless, if to the chain of the Andes and their subsidi- aries, we add all the Colombian plateaux, those of Peru and Bolivia, the groups of Famatina, Aconquija, and Cordova, the sierras of the Guianas, the chains of the Brazilian coast and of Minas Geraes, the gigantic steppes of Patagonia between the ridges of the Andes and the Atlantic coast, we shall find that the balance is kept pretty equal between the high and the low lands of this part of the world. According to Humboldt, whose fig- ures, however, should be carefully criticised with all the means afforded us by our increasingly exact acquaintance with the outline of the terres- trial relief, the mean elevation of North America is 747 feet, and that of South America would 'attain to 1149 feet. The continents of the Old World do not afford an equal harmony in the general configuration of their elevation. Asia, taken as a whole, is a vast system of plateaux, extending from the headlands of Asia Minor to those of the Corea, and from the shores of Beloochistan to those of the province of Ochotsk. The central region of Asia, surrounded by the highest mountains in the world, is the most elevated district existing in any of the continents, and in some places attains the mean height of 9000, 12,000, and 15,000 feet. The total area of the Asiatic plateaux is esti- mated by Humboldt at five-sevenths of this part of the world ; Mesopo- tamia, the plains of the Ganges and of the Indus, China proper, and the Siberian tundras make up the other two-sevenths of the continent. As if to make up for this, Australia is comparatively very deficient in pla- teaux and mountain chains ; of all the divisions of the earth this is the one which exhibits the least amount of prominence above the ocean level. The mean elevation can as yet be given but very hypothetically, as a great part of the regions of the interior is still unknown ; but this conti- nent must present about a third of the elevation of Asia the latter be- ing approximately estimated by Humboldt at 1162 feet. Europe being situated, in the Old- World group, in a diagonal line as regards Australia, affords, like the latter continent, a great preponderance of plains and plateaux. Almost the whole of Eastern Europe is a level country ; and this district a great part of which is cultivated, although here and there covered with turf and heath extends through Poland and Prussia as far as the frontiers of France and Belgium. Over this im- mense area, the level of the ground is so uniform that from Nijni-Novo- gorod to Cologne, a distance of 2454 miles, there is not a single railway tunnel. In Western Europe, which, in a historical point of view, is the real Europe, the more elevated regions are, it is true, very numerous : AUSTRALIA AND 'brawn by A Vuiiiemir. . RARPER v ADJACENT ARCHIPELAGO PL. IX. Erhard. NEV. r YORK PLATEAUX. 73 but most of them amount to mere mountain chains, on each side of which extend considerable tracts of level country. The only plateaux of any notable importance in the general configuration of the continent are those of the Iberian peninsula, Suabia, and Turkey ; all three, with a kind of rhythm, abut on mountain chains, the other faces of which command hor- izontal flats of alluvium. On the north of the Pyrenees and the Spanish plateau lie the plains of the Garonne and Languedoc ; on the south of the Bavarian plateau and the rampart of the Alps stretch the plains of Lombardy and Piedmont, forming a continuation of the level surface of the Adriatic Sea; finally, the low-lying lands of the Danube are separated from the plateaux of Turkey by the Balkan chain, which extends in a line almost parallel to that of the Pyrenees.* On account of the plateaux existing in Europe being so few, the mean elevation of this continent JS not much more than half that of Asia ; ac- cording to Humboldt it is about 672 feet. With regard to Africa, we need hardly say that it is impossible to fix the mean elevation with any certainty ; but modern travelers who have penetrated into the interior of this division of the world have seen enough of it*to warrant them in stating that Africa is very similar to Asia in respect to the elevation of the land. With the exception of Egypt, the plains of the Niger, some por- tions of the sea-coast, and districts of the Sahara, which were once covered by the sea, the continent is entirely composed of plateaux, most of which abut on lofty mountain chains. The laic of diagonals, which is followed in the respective dimensions of the four continents of the Old World, is found also to hold good as regards their general configuration. Asia and Africa, the two continents in which the plateaux predominate, are placed diagon- ally to Europe and Australia, in which the plains are the most extensive.f Another great contrast between the Old and New Worlds is one that is exhibited in the central portions of these groups. Between the two Americas stretches a sea of an almost circular shape, surrounded on all sides by a belt of islands and continental shore. The centre of the Old World, on the contrary, is occupied by the plains of Mesopotamia, and high ground toward which tend several seas in an oblique direction. The Persian Gulf, the Red Sea, the Mediterranean, the Euxine, and the Caspian surround this central spot of the Eastern continents, and approach the pentagonal mass obliquely at almost symmetrical intervals. Looking at the form and direction of these seas, it seems as if the region which they circumscribe had experienced a kind of wrench, as if it had been drawn into some vast eddy. Another very remarkable phenomenon of equilibration is exhibited in the fact that the highest mountains of each of the two halves of the world arc situated in opposite hemispheres, but at an equal distance from the- equator. Near one of the tropics rise the lofty Himalaya and the other great mountain groups of Asia ; close to the other tropic stand the Boli- vian and Chilian Andes. * Carl Ritter. Eurnpa. f Guyot, Enrth and Man. 74 THE EARTH. There is another difference between the various divisions of the world which we must call attention to. In pursuance of the annular distribu- tion of the continents round the great ocean, the western coasts of Europe and Africa correspond with the eastern coast of the New World, and not with the western, as analogy would seem to dictate. On the north, Scan- dinavia forms a counterpoise to Greenland. More to the south, the two shores which front each other across the North Atlantic bear a strikino- O resemblance to each other in their numerous indentations, their deeply- penetrating gulfs, their peninsulas, and their islands, while between the coasts of Europe and those of California and British Columbia there is no symmetry whatever. With regard to Africa, several geographers, includ- ing Humboldt himself, have thought that this continent and South Amer- ica had their corresponding coasts set in the same direction. But this is not the case ; these two divisions of the wor^d present the same mutual contrast as the two hands of a man. There is symmetry, but not equal- ity. In fact, the highest plateaux and the loftiest mountains in Africa rise at the east side of this continent, while the chain of the Andes com- mands the western "Shores of South America. The most important Afri- can rivers the Orange River, the Congo, the Niger, and even the Nile empty their waters, either directly or indirectly, into the basin of the At- lantic, into which are also discharged the immense rivers of the Colombian continent the La Plata, the Amazon, the Orinoco, and the Magdalena. In the same way, the Saharan deserts, which tend toward the Atlantic Ocean, answer to the llanos of Venezuela and the pampas of La Plata ; the latter being likewise inclined toward the same oceanic basin. Finally, the two isthmuses of Suez and Panama, each at the angle of their respect- ive continents, occupy a corresponding though opposite position. Sim- ilarly, Cape Verd must be considered as the corresponding point to the Brazilian promontory of St. Roch, and the Gulf of Guinea is represented on the other side of the ocean by the wide semicircle of coast which opens out on the south of Brazil. Even in the bed of the sea the symmetry still prevails, since an upheaval of 4500 yards would have the effect of calling forth in the midst of the Atlantic a long strip of land separated from Europe and the New World by two parallel channels. In each of the two groups of continents, the steep and gentle inclines are distributed respectively in contrary directions. In Europe, Africa, and Asia, the most elongated incline of the land tends in a northerly and westerly direction toward the Atlantic Ocean and the Frozen Sea. In the New World the more gradual slopes of the continent likewise de- scend toward the Atlantic coast that is, in an eastward direction. We thus have a contrast which is also a harmony : it is as if the faces of the two worlds were turned one to the other, thus rendering more easy of ac- cess their coasts, their plains, their rivers, and all the regions suitable for the abode of man. Another contrast, which is perhaps the most important of all in the his- tory of mankind, is that exhibited by the transverse position of the two CONTRASTS OF CLIMATE. 75 groups of continents in reference to each other. The countries of the Old World, which show the richest luxuriance and the most exuberant vital- ity, lie between the Straits of Gibraltar and the Archipelago of Japan, and extend from west to east in a line parallel to the equator; the New World, on the other hand, stretches from north to south, in the direction of the meridian. Thus, the double continent is set right athwart the course followed by the winds and the currents, and across the path taken by the human race in making their way from the other group of coun- tries ; it, therefore, receives and develops the germs of life, the elabora- tion of which had commenced on the other side of the sea. This trans- verse position of America in respect to the Old World is one of the prin- cipal features of the planetary relief, and one also which exercises a de- cisive influence on the future of the whole human race. Finally, it must not be forgotten that the principal contrasts of the con- tinental masses proceed naturally from all the modifications produced by the difference of longitude and latitude. These contrasts are those of climate, and their real cause is to be found in the form of the earth and its movements round the sun. Thus, the astronomical % contrast between the north and the south divides distinctly the different parts of the world into two separate groups. Almost the whole extent of "the three northern continents be- long to the temperate zone, and it is only their most advanced peninsulas which are pushed forward on one side into the frigid, and on the other into the torrid, zone. With regard to the three southern continents, they present their chief development between the tropics or in the south tem- perate zone. They receive the greatest amount of annual heat, and con- sequently become the theatre of the most remarkable phenomena of plan- etary vitality. There the cross action of the winds and rains between the two hemispheres takes place, and hurricanes take their rise ; there, immense deserts extend over vast areas; there, too, vegetation manifests all its productive energy, and the terrestrial Fauna attains its greatest force and its highest beauty. The contrast between the east and the west is also of the highest im- portance in each group of continents ; for all the train of climatic phe- nomena which accompanies the sun in its apparent course round the earth does not uniformly follow the latitude in a parallel line to the equa- tor. In consequence of the unequal division of land and sea, there is a modification in the direction of the currents and winds, and also a trans- position of the climates themselves sometimes toward the north, and sometimes toward the south ; the most distinct contrariety in this respect is thus produced, in some cases, between the western side of one conti- nent and the eastern side of the continent opposite to it. It is principal- ly between the Old and New Worlds that this contrast is most striking ; at equal latitudes, the western shores of Europe, and those which face them on the other side of the Atlantic, have very different climates a fact which is caused by the changes produced by marine currents, the winds, and all the other atmospheric phenomena. 76 THE EARTH. CHAPTER XL HARMONY OF SHAPE IN OCEANS. THE TWO BASINS OF THE PACIFIC. THE TWO BASINS OF THE ATLANTIC. THE ARCTIC FROZEN OCEAN AND THE AN- TARCTIC CONTINENT. CONTRASTS, AN ESSENTIAL CONDITION OF PLANET- ARY VITALITY. THE harmony of the continental forms is fully paralleled by that of the oceanic configuration. The Southern Ocean alone that mighty breadth of waters, in comparison with which all the other oceans seem but mere arms of the sea extends over nearly an entire hemisphere of our planet. Notwithstanding its enoi*mous dimensions, it none the less exhibits a most harmonious ensemble, caused partly by the amphitheatre of shore spread all round the Pacific, from Van Diemen's Land to Tierra del Fuego ; partly also by the marvelous belt of the Polynesian archipelago. These numerous and lovely islands, which Hitter calls the " Milky Way of the ocean," are dotted obliquely over the whole breadth of the south seas, from the Philippines to Easter Island, dividing the immense basin of the Pacific into two sheets of water, distinct from each other both by their winds, the course of their currents, and the undulations of their waves. Thus the great hemisphere of waters constitutes a kind of oceanic pair, in accordance with the same law which distributed the land in three con- tinental pairs. The tortuous, valley of the Atlantic, which separates the Old World from the New, is also decisively divided into two basins, differing in the shape of their outline, their climates, winds and currents. An ideal line, traced from the Cape Verd Islands to the nearest of the Antilles, marks the limit of separation between the two halves of the great oceanic valley. On one side, the South Atlantic spreads out in a vast semicircle between the scarcely undulated shores of the more massively formed continents; on the other, the North Atlantic gradually contracts toward the polar regions, throwing out, both to right and left, gulfs, channels, and inland seas. On the east, the Mediterranean, the British and the Irish Channels, the North Sea, and the Baltic ; on the west, the Caribbean Sea, the Gulf of Mexico, the isle-dotted estuary of the St. Lawrence, Baffin's Bay, and Hudson's Channel and Bay all these appear to correspond on either side of the ocean, and, by the resemblance of their outlines, add to the harmony of the continents themselves. Thus the general form of the two Atlantic basins recalls to. mind the two continental pairs, the shores of which they bathe. The northern basin, bordered as it is by variously articulated lands, is, from this very cause, the richest of the two oceans in THE POLAR REGIONS. 77 indentations of every kind, and is also that which was destined by nature to become the high-road of the commerce of nations. The Indian Ocean, shut up, as it is, in the immense hollow formed by the coasts of Africa, Arabia, the Gangetic peninsula, the Sunda Isles, and Australia, can not exhibit the same characteristic of duality as the two other oceans the Southern Ocean and the Atlantic. If, however, we take into account the ancient geological conditions of Asia, we may, per- haps, be warranted in looking upon the Caspian, the Sea of Aral, and the other lakes of Western Asia, as the remains of the former ocean which, in the northern hemisphere, formed the equipoise to the Indian seas. There would then have been three double oceans, just as there are three conti- nental pairs. Added to this, it is probable that the northern and southern polar regions likewise afford an instance of an equilibrium existing between land and water. We are at present but very imperfectly acquainted Avith the regions either of the north or south poles ; but the explorations of navigators and the investigations of meteorologists more and more tend to confirm the old hypothesis, which supposed that open sea extend- ed round the Arctic pole, and that the circle of the south pole was occu- pied by a covering of dry land. If this be really the case, the harmony of the continental masses, and the sheets of water which are interspersed among them over the surface of the planet, is admirably completed by the contrast between the two poles of land and water which occupy the two extremities. The general similarities and the great contrasts which we have now pointed out constitute but a small number of the features of this kind Avhich the surface of the globe, presents, and it would be an easy thing thus to follow out our parallels from sea to sea, from river to river, and from mountain to mountain. But the purely external symmetry pre- sented by the continental configurations is a trifling matter compared Avith the profound harmony resulting from the alternation of winds, cur- rents, climate, and all the geological phenomena ; it is not in the various portions of the globe but in their working action that we must seek for the real beauty of the earth. Planetary vitality is composed of perpet- ual contrasts in a perpetual harmony, and these very contrasts are inces- santly being modified. Continents, seas, and atmosphere and, in a more special way, every mountain, every peninsula, every river, every marine current, every wind that blows may be considered as the organs of the globe on which we live; it is therefore by watching these organs at Avork, and by studjjing deeply and thoroughly their action and reaction, that we can best arrive at an acquaintance with the physiology of the planetary body. Physical geography is nothing else but the study of all these terres- trial harmonies. An inquiry into the superior harmonies which emanate from the relations of mankind to the planet which is the scene of human life must be left to history, the task of which is to describe them. 78 THE EARTH. CHAPTER XII. GENERAL ASPECT OF PLAINS. ALLUVIAL PLAINS. CULTIVATED PLAINS. UNIFORMITY IN UNCULTIVATED PLAINS. VARIETIES IN APPEARANCE PRO- DUCED BY CLIMATES AND DIFFERENT PHYSICAL CONDITIONS. THE portions of the terrestrial surface on which the vitality of the globe shows itself with the least intensity and variety are those countries which present the slightest diversities of level. In these regions, the flat- ness or slight declivity of the surface of the earth prevents the waters from flowing rapidly ; the country exhibits the same amount of vegeta- tion, or the same sterility, over vast extents, and its general aspect is often most monotonous. Nevertheless, in spite of the uniformity of a flat dis- trict, the phenomena of nature are all the more easily observed there, be- cause they are developed in a more simple and regular manner. Nearly half of the continental regions is composed of low and compara- tively level lands, the even or gently inclined surface of which still testi- fies to the action of the waters of the ocean, or of the inland seas by which it was formerly covered. These are former sea-beds, which have emerged, from the deep; and, from the uniformity of their appearance often much resembling a tract of ocean contrast sharply with the high lands or mountains surrounding them. Some of these plains, which are watered by streams and rivers, have been greatly modified by the courses which the latter have taken ; and by means of the fertile alluvium that has been brought to them, and the moisture which penetrates them, have spontaneously given birth to immense forests. They then lose their re- semblance to the surface of the sea, except when looked at from the top of some lofty bluff, around which the thick trees seem to crowd like bil- lows. At length, when man comes to take possession of the plains, to erect his towns, and to cultivate the soil, he introduces a great variety into these uniform tracts, and never ceases to modify their primitive as- pect. These low-lying regions, which, by reason of the flatness of the ground, are destined to be the scene of but slight activity in the planet- ary life, have become the principal seat of mankind, and it is there that civilization makes its most remarkable progress. * The plains which best retain their appearance of times gone by are those which, owing either to the want of rain, or the almost complete ab- sence of slope either in one direction or another, are watered by only a small number of streams, or sometimes, throughout vast tracts of country, are utterly without them. For this reason, in many parts of the globe, a plain and a desert are almost synonymous. Setting aside the low lands which have been brought under cultivation, the plateaux and the inter- ASPECT OF PLAINS. 79 vening mountain chains, we find that there is a coincidence between most o * of the large level plains and the continental deserts. Thus the western and eastern regions of the Sahara, the Nefoud of Arabia, the steppes of the Caspian, the Aral, the Balkash, and the tundras of Siberia, are at the same time the most extensive plains and the most widely-spreading des- erts on the face of the globe. The general axis of the principal plains in the Old World, as well as that of the deserts, mountains, and continents themselves, is set in a direction from southwest to northeast; while in the New World the axis of the low-lying lands tends from north to south in a parallel line to the chains of the Rocky Mountains and the Andes. All lands which are bare plains, destitute of large trees, resemble one another, on account of their uniformity. On the surface of these plains, as on the sea, it is only necessary to scan the horizon round in order to perceive clear proofs of the rotundity of the globe. Although the sight readies without difficulty over the bare ground, or its green carpet of plants, yet the bases of hills and the trunks of trees which appear at the limits of the plain are hidden by the convexity of the earth. At first we only perceive the summits of the hills and the branches of the trees; then, in proportion as we draw nearer, the lower declivities and the trunks of the trees begin to make their appearance, in the same way as, in the open sea, the hull of a ship is not seen until long after the sails and masts have come into view. Lastly, as on the ocean, the variable aspect of the sky, to which, in hilly countries, we are in the habit of paying only a second- ary attention, here regains all its importance, and becomes the principal feature in the landscape. The uniform and motionless surface of the plain slopes down toward the horizon, like the back of a gigantic shield, and its whole extent offers no object which can arrest the attention ; but above, on all sides, stretches the enormous dome of the atmosphere, with its fit- ful play of light and shade, the successive gradation of its colors, from deep blue to fiery purple its clouds, which, chasing one another across the sky, first disperse and then cluster together ; drawing themselves out into long transparent lines, or accumulating in massel of a sombre gray. Occasionally, when the air which hangs over the plain is unequally heat- ed by the rays of the sun, distant objects assume a distorted shape, seem- ing nearer than they really are, or, perhaps, inverted, producing that fan- tastic illusion called a mirage, which was formerly believed to be th* work of mocking j;enii. . o o * Although all the bare plains on the various continents resemble one an- other in the curvature of the ground, the circularity of the horizon, ami the play of the atmosphere, yet their aspect sometimes varies much in different countries, according to the geological nature of the soil, the mean temperature, the changes of the seasons, the direction of the winds, the quantity of rain-fall, and all the other physical conditions of the region . generally. Thus, a clayey plain is hard and compact, like the ground of a threshing-floor which has constantly been beaten with the flail ; another, 30 2'2/A' EARTH. the rocks of which are of a calcareous nature, is intersected here and there by ravines with perpendicular sides ; another is sandy, and, under the influence of the wind, is rippled with waves like the surface of the sea. Some, but these are rare, present vast extents completely destitute of vegetation ; others offer, here and there, a solitary green plant ; but every one of them is a plant of the same species ; and one may travel whole days in these deserts without seeing any other representatives of the vegetable world. The greater number of plains have, it is true, a Flora, composed of a tolerably large number of species ; but two or three plants, which are commoner than the others, appearing uniformly on hundreds and thousands of acres, have appropriated to themselves the whole dis- trict, and thus give it a special character. Lastly, some solitudes are temporarily, during the rainy season, or even during the whole year, mag- nificent and verdant prairies enameled with flowers. These are the tracts which man can most easily turn to account by breaking them up with the ploughshare. THE FRENCH LANDES. 81 CHAPTER XIII. THE FRENCH LANDES. THE BRAXDES AND THE ALIO8. THE CAMPINE. THE HEATHS OF HOLLAND AND NORTHERN GERMANY. THE PUSZTA OF HUNGARY. THE GRASSY STEPPES OF RUSSIA. THE SALT STEPPES OF THE CASPIAN AND THE ARAL. THE TUNDRAS. THANKS to the rains blown up by the sea-breezes, the comparatively small deserts of Western Europe do not assume the formidable character of the Sahara, or the Nefoud of Arabia. Those best known are the landes of Gascony. The old tracts of French landes embrace not only the department which takes its name from them, but also include half of La Gironde, as well as the extreme corner of Lot-et-Garonne, extending over nearly 2,500,000 acres. This region, which was once covered by the waters of the Atlantic, is a plateau averaging 160 to 190 feet in height, and sinking in a gentle decline on the northeast toward the Gironde and the Garonne, on the west toward the lakes on the sea-shore, and on the south toward the River Adour. The uniformity of the great plateau of the landes is so great that, for a distance of twenty-eight miles between Lamothe and Labouheyre, the railroad from Bordeaux to Bayonne is perfectly rectilin- ear; one might call it a " visible meridian." For some years past, the labor of man has done much in turning to ac- count this vast domain, once so neglected ; private individuals and com- munities have, with equal ardor, sought to enrich themselves by replacing the heath with pines and other trees, and there can be no doubt that, at an early future, the whole extent of the landes will be covered with for- ests and cultivated grounds. There are now but few places where we can still see what the whole plateau once was, stretching from the edge of the vineyards of Bordeaux to the country at the foot of the first Pyrenean hills. In these uninhabited tracts the landscape is certainly deficient in vari- ety, but it always possesses a certain grandeur and a singular charm for those who love nature in all her freedom. All round, within the limited circle which is surrounded by the level line of the horizon, nothing is to be seen but a thick underwood of bmndes and various other kinds of heath, springing up to the height of a yard or two above the ground. During their flowering-time these plants mingle a light shade of pink with their delicate green, but they are always roughened with a number of heath- branches, stripped of leaves, and black as if charred in a fire. In other spots tall ferns have taken* possession of the ground and fill the air with their penetrating odor. Farther on we come upon large patches of furze F 82 THE EARTH. and broom, which flower together in the spring and cover the plain with an immense veil of gold. Mosses, grasses, and briers grow together along the edges of the paths ; water-lilies, and other aquatic plants, repose qui- etly on the surface of the muddy pools ; bunches of rushes and sedge Fig. 18. The " Landes" of Gascony. spring up in the spongy earth around the water. And this is all. Per- haps, on the extreme horizon, a bluish line, pointing out the edge of a pine forest, may be faintly visible. Over a vast extent of the landes the superficial soil is composed of a white and almost unmixed sand ; but in general it is very much mingled THE LANDES OF OASCONT. 83 with vegetable remains, which give it a gray or blackish color, like char- coal ashes. Below this upper layer extends a stratum of agglutinated sand, generally of a rusty color, and bearing a great similarity in appear- ance to ferruginous sandstone; the hardened dust known in the landes of -Medoc under the denomination of "olios" owes its color and its firm- ness to the continual infiltration of rain-water, which carries down into the ground various organic substances in a state of solution, and blends them intimately with the arenaceous particles. In a general way olios, notwithstanding its ferruginous appearance, contains the oxide of iron only in an almost imperceptible proportion. When it is thrown into the fire it is noticed to carbonize slowly, and is then reduced to ashes ; yet, in certain localities, especially in marshy districts where the argillaceous iron is naturally formed, the subjacent layer is gradually changed into an actual mineral. Generally, the bed of olios, which is hardest where it is least thick, is completely impervious to water, like a stratum of rock. Rain-water, being thus checked by the continuous layer of olios, must necessarily remain in the upper soil, and, during the wet season, the sur- face of the landes would be changed into one great marsh if care were not taken to cut trenches or drains, which receive the overflow of the scattered pools, and carry it either to the different rivulets, or to the lakes on the sea-shore. In order to cross more easily the sheets of water which sometimes extend farther than the eye can reach between the patches of heath, the shepherds of the landes have adopted the custom of walk- ing and watching over their flocks on stilts more than a yard high. In this respect the Lanusquets, or Landescots, are without parallel all over the world, and, if I am not mistaken, in the history of mankind. Nearly all the regions of Western Europe, which were in early ages covered by the sea, and have since retained the uniformity of surface of the former sea-beds, have long since come under cultivation ; such as, for instance, the low ground of the ancient Gulf of Poitou, the filled-up estua- ry of Flanders, the largest part of Holland, and German and Danish Fries- land. But, farther inland, there are here and there tracts of landes like those of Bordeaux. In France one may mention those of Sologne and Brenne, which were formerly a vast forest of about 1,234,000 acres in ex- tent, and are now being transformed anew by patches of pines, drainage, canals, and other improvements. In Belgium the sandy landes of the Campine, which, since the establishment of the Germans and Batavi in the neighboring countries, have always been a flat surface of heaths dot- ted over with pools, extended in 1849 over a surface of 345,000 ncres; but the brave Belgian husbandmen who laid siege to these landes continue to reduce their dimensions at the rate of 3950 acres a year.* In Holland and the north of Germany the belt of heaths assumes its greatest width, and extends over a much more considerable surface than that of the landes of Gascony. In Holland alone an extent of about 4,196,875 acres, more than half the territory, consists of a sandy soil, * Emile de Laveleye, Revue des Deux Afondes, June, 1861. 84 THE EARTH. which was once nothing but a vast solitude, the uncultivated parts of which still contrast most strikingly with the rich polders of the coast. A great part of this sandy region, which is elevated, upon an average, 48 feet above the sea, is covered with spongy peat-mosses, which will readily burn after having previously been dried by means of drainage-canals, and cut into pieces of a proper size. One fine day in the summer time the peasants set light to these masses of dry turf, and soon the conflagration spreads over wide extents, and thousands of acres are burning at the same time. When t^e north wind passes over these immense fires it car- ries with it smoking particles of the smouldering turf hundreds of leagues away from Holland, and sometimes even to the centre of France, Switzer- Fig. 19. Extent of the Heath-smoke in 1857. land, Bavaria, and Austria. This is the origin of those dry fogs, or north- ern fogs, which give a yellowish tint to the atmosphere, and sometimes half hide the face of the sun.* However, when the wind is favorable, a comparatively slack fire transmits its smoke to very great distances; thus, in 1865, at the time of the fire in a part of the city of Limoges, the cloud of smoke, which stretched aAvay in long eddies toward the west, was perfectly visible as far as Marennes, a distance of about 125 miles in a straight line. * Emile de Laveleye, Revue des Deux Mondes, Jan., 18fi4. M. de Laveleye thinks that the name of " brandes," given in Gascony to the high-growing species of heath, is derived from the habit they have of burning them. In German, brand signifies burning. PLAINS OF HUNGARY AND RUSSIA. 5 The landes of the north of Europe enjoy a colder climate than those of Gascony, therefore their vegetation is less developed and not so diver- sified ; but it seems that in both belts of heath the composition of the soil is nearly the same. In Germany and in Jutland, as well as in France, the yellow color of the sand is due to the gradual infiltration of the juices of the plants, which are loaded with tannin ; and the ferruginous-looking tufa, which is found at a certain depth in the substratum, through which the roots of trees can not penetrate, is no doubt nothing else than a bed of hardened sand of the same nature as the olios of the French landes. In Jutland, where this bed is on an average from two to four inches in depth, they give it the name ofjern-al, or iron-sand. In England, Scot- land, and Ireland a thin bed of " iron-pan," of the same appearance, is found under the large barren heath-covered moors. Very different, indeed, in their vegetation are the large grassy plains of Hungary and Central Russia ; they are, in fact, immense prairies, not less uniform than the landes, but presenting a much more lovely and pleasing aspect, especially in the season of flowers. The Magyar Pttszta, *> celebrated by Petoefi, was formerly a lake of more than 310 miles in circumference, bounded on one side by the large bend of the Danube, from Pesth to Belgrade, and on the other by the semicircle of the Carpa- thians and the western mountains of Transylvania. -The soil, which is nourished by the fertile alluvium that the Tisza, the Maros, and other rivers bjing down from the surrounding mountains, is very fertile, and in the cultivated districts yields abundant crops. Vast extents, which art- left as natural meadows, look like perfect seas of waving grasses, over which roam in unrestrained freedom herds of half-wild oxen and those uncouth horses which are ridden by the rude Czikos troopers. The beauty of these green and flowering plains, dotted over with low, mud- built houses, often hidden almost to the roofs in the tall herbage, is heightened by the contrast afforded by the wide semicircle of blue mountains forming the distant horizon. The grassy steppes of Central Russia do not possess, like the Hunga- rian puszta, this beautiful framework of lofty mountains, but they offer a charm no less peculiar in the beauty of their flowers and the gracefulness of the ears of corn gently waving in the breeze. The vast region of the Tchornosjom (black earth), thus named on account of the color of its soil, is still in great part a sea of grasses, varied only here and there by vil- lages, cultivated fields, and rivers flowing slowly between steep banks. The Tchornosjom, which extends over the valleys of the Don, the Dnie- per, and the Volga, comprehends an area of more than 197,500,000 acres, nearly twice the size of France, and throughout this immense district the vegetable soil is of a depth varying from three to fifteen, and sometimes even reaching to thirty and sixty feet. Thus the geological nature of the soil proves that this plain is not of oceanic origin ; marine. debris is not found in any part of it, nor any of those irregular boulders brought down from the mountain glaciers of Scandinavia. The " black lands" gg THE EARTH. were formerly an irregularly shaped continent, surrounded on all sides by water. Though they are incessantly fertilized by the remains of de- cayed turf, yet they seem unable to nourish the roots of trees ; forests, therefore, are entirely wanting in these regions ; thanks, also, to the nat- ural drainage, there are no stagnant swamps. These lands, prepared for culture by a grassy vegetation for many thousands of centuries, are among the best in the world for the production of cereals, and sooner or later they will become one vast field of corn.* To the south of the Tchornosjom there are, here and there, some oases of the same nature which are equally remarkable for the richness of their Fig. 20. The "Black Lands" of Russia. vegetation ; but the greater part of the steppes are former sea-beds, which have emerged at a recent epoch, and exhibit no traces of verdure except in the spring. The heat of summer soon scorches up the grass, and the flocks which graze on these vast plains are obliged to take ref- uge by the banks of the rivers in order to obtain their food. The only oases of the steppes of the Don and the Dnieper are those districts in * liuprecht, Bulletin de F Academic de Petersbourg, vol. vii., No. 5. THE RUSSIAN STEPPES. 37 which the inhabitants have been able to renew and purify the soil by the use of spring water. Some villages, which were founded in the last cen- tury by German colonists, are perfect little nests of verdure, the beauty of which contrasts most strikingly with the formidable aspect of the sur- rounding solitudes. Nearly all the countries of Russia and Tartary, which are situated be- low the level of the sea in the great Caspian depression, are steppes of a still more arid and desolate character than those even of southern Russia. They are interminable tracts of loose sand, interspersed with banks of hard clay, like a threshing-floor beaten solid by the flail, and beds of rock here and there intersected by clefts in which a little vegetable soil some- times accumulates. These steppes of sand or clay comprehend the prin- cipal part of the western basin of the Caspian ; the rocky steppes extend to the east toward Tartary ; lastly, the salt plains, which, by their efflores- cence, bear witness to the fact of the former extension of the sea, occupy a considerable tract between the course of the Volga and that of the Yak. There, too, is situated the desert of Narin, the clayey and barren surface of which is scattered over with sandy plateaux covered with ver- dure, and crossed from north to south by a chain of downs sheltering the pastures which lie half hidden in the hollows.* With the exception of these scanty green patches, which are frequented by some few wandering tribes, nearly the whole of the Caspian depression is the very picture of aridity. No natural meadows reach the eye, like those in tfc steppes of the Dnieper, the Don, and the Irtysh ; and the pastures occupy only a very limited breadth at some considerable distance to the north of the present sea-shore. When the locusts settle down there, which is fre- quently the case, not a blade of grass is left, and the very reeds in the marshes are eaten down to the level of the water. It is well known what an inauspicious aspect the surface of the steppes present in the middle of winter, when all is hidden under the snow, and the freezing wind stirs up this silvery sea iijto waves and eddies. But even in the most joyous season of the year the immense extent of- white sand and reddish clay, varied here and there with scanty shrubs of worm- wood and euphorbia, with their, sombre-colored leaves, likewise presents a most, forbidding aspect. The vast tracts of ground, which are crossed by travelers in cars drawn by horses at full gallop, appears like a fiery- colored sheet striped with long gray lines. Here and there ravines, hol- lowed in the soil by the torrents of rain-storms, have to be crossed with great labor; then some mai-sh, with its thick whitish waters seen in glimpses through a forest of reeds, has to be avoided. In the distance a border of blood-red saltwort betrays the presence of a salt pool, and quite in the extreme horizon, heavy hanging clouds, in long rows, one above the other, point out the vicinity of the sea-shore. The soil reflects an in- tolerable amount of heat. At the same time the breeze, drawn as by a centre of attraction to the burning surface of the steppes, raises before it * Pallas. EARTH. columns of dust ; at the side of the car the debits of withered plants may be seen strangely bounding along by thousands and by millions ; these racers of the steppes, which are rolled into balls by the wind, seem to be having a contest of speed, and, keeping close to the earth, pursue each other furiously, sometimes making leaps of several yards ; one might al- most fancy that they were human beings hurried along in some demo- niacal race. At the end of each stage the traveler stops an instant before a miserable cabin, half buried in the sand. He catches a glimpse of a hu- man face with haggard eyes and disordered hair, and then off he goes again like a dart, to plunge anew into the desert. It is seldom that he can distinguish in the distance the kibitkas of the Calmucks or the Kir- ghizes, or the tombs formerly raised over the bones of warriors. Fre- quently hundreds of miles are accomplished without seeing any other trace of man having passed over the same route, except the ruts left by the wheels in the hardened clay.* In these solitudes trees are almost completely unknown, and the few that are found there are looked upon with a kind of adoration, as if they were the miraculous gifts of some divin- ity. Between the Sea of Aral and the confluence of the Tchoni and the Yatchi, that is to say a distance of 310 miles in a straight line, only one tree is to be found, and this is a species of poplar, with drooping boughs, the roots of which creep far into the arid soil. The Kirghizes have such a veneration for this solitary tree that they often go several miles out of their way iiArder to- pay it a visit, and each time they hang an article of their clothing upon its branches. From this custom the name of sindc- richagatch, or " rag-tree," has been given to the desert poplar.f The plains of southern Siberia, which extend eastward as far as the Al- tai Mountains and the lake of Dsa'i-Sang, present a very diversified aspect compared with the steppes of the Caspian, and even with the landes of France and the heaths of Germany. These plains are intersected in vari- ous directions by chains of rounded hills, and by woods of coniferous trees, which here and there bound the horizon and give a little life to the whole- landscape. Besides the meadow grasses, hundreds of plants and shrubs also embellish the surface of the ground. In the spring rosaceous plants, thorny plum-trees, cytisi, tulips, and other plants, with white, pink, yellow, and variegated flowers, glitter on the greensward of the undula- ting valleys of the steppe.J In the north of Russia and Siberia the long plains which descend in an imperceptible slope toward the Arctic Ocean are not less solitary than the Caspian steppes, and have an equally formidable aspect. During a great part of the year the circular space bounded by the horizon presents nothing but an immense winding-sheet of snow rippled by the wind. When this bed of snow melts under the summer sun, the lowest districts in the plain, or tundra, appear dotted over here and there with plots of * Von Baer, Kaspische Studien. Pallas. t Zaleski, La Vie des Steppes Kirghizes. I Humboldt, Asie Centrale and Tableaux de la Nature. PLAIXS OF SIBERIA. 89 Sphagnum and various other green plants, which grow and swell almost like sponges by means of the half-hidden pools of water. Nearly the whole extent of the soil is covered with reindeer moss and other whitish lichens ; and one might readily fancy that the interminable carpet of winter snow was still spread before one's eyes. In these regions, how- ever, the earth is always frozen to a great depth, in spite of the rudiment* ary vegetables which grow on its surface and the lagoons of w.ater which sparkle during several months in tho marshy depressions of the soil.* * Wrangell. 90 THE EARTH. CHAPTER XIV. SEMICIRCLE OF DESERTS PARALLEL TO THE SEMICIRCLE OF LANDES AND STEPPES. THE SAHARA. SANDS, ROCKS, OASES. THE DESERTS OF ARA- BIA. THE NEFOUD. DESERTS OF IRAN AND THE INDUS. THE DESERT OF COBI. AT a great distance to the south of this zone of landes, prairie^ steppes, and tundras, which extends in an irregular semicircle from Prance to Siberia, there is another zone of plains, deserts, and plateaux which curves round in a parallel direction to the former, and exhibits a still more formidable and monotonous aspect. This zone, which is crossed by an imaginary line called by John Reynaud the "equator of contrac- tion,"* comprehends the great Sahara of Africa and the deserts of Ara- bia, Persia, Gobi, and Chinese Mongolia. This zone is in a great measure destitute of water and vegetation, and, on the whole, is much less accessi- ble to man than the northern solitudes. Not only is it more intensely heated by the solar rays, but it also enjoys a much less amount of moist- ure on account of the chains of mountains which, at several points, im- pede the passage of the rain-clouds, and especially on account of the po- sition it occupies as extending diagonally across the most massive por- tion of the two largest continents, Africa and Asia. The most important group of deserts in the world is that of the Sahara, which extends across the African continent from the shores of the Atlan- tic to the valley of the Nile. This immense area is more than 3100 miles from east to west, and is, on an average, more than 600 miles in breadth ; it is, in fact, equal in size to two thirds of Europe. This is the part of the earth in which the heat is most intense ; although it is to the north of the equator, yet, as regards most of the world, it is the reaksowA,f and the principal focus of attraction for the atmospheric currents. In this region there is only one season, viz., summer, burning and merciless. It is but rarely that rain comes to refresh these regions, on which the solar rays dart vertically down. The mean altitude of the Sahara is estimated at 2000 feet ; but the lev- el of the soil varies singularly in the different districts. To the south of Algeria, the surface of the Chott Mel-R'ir, the remains of an ancient sea, which communicated with the Mediterranean, is at the present time more than 165 feet below the Gulf of Cabes; while to the south and east, the ground rises into plateaux and mountains of sandstone or granite to a height varying from 3300 to 6600 feet. In the centre of the Sahara stands the Djebel-Hoggar, the sides of which are covered with snow dur- * Vide above, p. 56, Fig. 13. t Carl Hitter. DESERT OF THE SAHARA. 91 ing three months in the year ; from December to March* its picturesque defiles are traversed by streams which flow some distance and lose them- selves beneath the surrounding plains. This group of lofty mountains is the great landmark which forms the boundary between the eastern deserts, or the Sahara proper, and the group of western deserts, desig- nated under the general name of Sahel. Farther to the east, the oases of Asben, R'at, and Fezzan, which extend obliquely toward the shores of the Gulf of Sidra, might likewise be considered as the frontier between the two regions. The Sahel is very sandy. Throughout the greater part of its extent, the soil is composed of gravel and large-grained sand, which does not give way even under the foot of the camel. Some of the ranges of sand- hills which rise in this desert are chains of small hills, composed of heavy sand which resists the influence of the wind.f But in many districts of the Sahel, the arenaceous particles of the soil are fine and small. The trade-winds which pass over the desert distribute these sandy masses into long waves similar to those of the ocean, and here and there raise them into movable sand-hills, which overwhelm all the oases which lie across their path. Traveling toward the southwest, in which direction they are driven by the wind,J the sands reach the northern shores of the Niger and Senegal at many points of their course, and by their incessant deposits gradually drive the waters of these rivers toward the south. To the west, the sand of the desert encroaches also upon the ocean. OS the coast which stretches between Cape'Bojador and Cape Blanco pointed out from afar by the highest dunes in the world a line of sand-banks ex- tends far out into the sea. These banks are constantly renewed by the. desert-wind ; and the Arabs, who go to collect the waifs and strays from shipwrecked vessels, can safely venture out several miles from the shore. A current of sand is, therefore, constantly passing across the desert from northeast to southwest. The debris of rocks in a state of decomposition, and the particles brought to the coast of the Gulf of Cabes by the tide, which is very powerful at this point, are driven before the wind into the plains of the Sahel, and thence, after a journey lasting hundreds and per- haps thousands of years, they at last reach the sea-shore of the Atlantic, in order to recommence in the oceanic currents another eventful odyssey. Some parts of the eastern Sahara are equally sandy ; but the principal parts of the surface of this desert are occupied by plateaux of rock or clay, and by groups of grayish or yellowish mountains. The chains of sand-hills are numerous, and, like those of the west, they travel incessant- ly under the impulse of the wind in a south or southwest direction.]! The rocky plateaux are crossed and recrossed here and there by wide and deep clefts, which are gradually filled by the drifted sand, and into which * Duveyrier, Exploration du Sahara, vol. i., p. 120. + Vide in vol. ii. the chapter on "Dunes." J Duveyrier, Exploration du Sahara, voL i., p. 9. Carl Ritter, Erdkunde. || Georges Pouchet, Dongolah et la Nubie. 92 THE EARTH. the traveler runs the risk of sinking, like the mountaineer into the cre- vasses of a glacier. In the hollows, patches of salt take the place of the lakes which in more rainy countries would be found there. Those districts of the Sahara which are destitute of oases present a truly formidable aspect, and are fearful places to travel over. The path which the feet of the camels have marked out in the immense solitude points in a straight line toward the spot which the caravan wishes to reach. Sometimes these faint foot-marks are again covered with sand, and the travelers are obliged to consult the compass, or examine the hori- zon ; a distant sand-hill, a bush, a heap of camels' bones, or some other indications which the practiced eye of the Touareg alone can understand, are the means by which the road is recognized. Vegetation is rare, de- prived as it is of the moisture which it requires ; the only plants to be seen are the Artemisia, thistles, and thorny Mimosas ; in some sandy dis- tricts there is a complete absence of all kinds of vegetation. The only animals to be found in the desert are scorpions, lizards, vipers, and ants. During the first few days of the journey some indefatigable individuals of the fly-tribe accompany the caravan, but they are soon killed by the heat ;* even the flea itself will not venture into these dreadful regions.f The intense radiation of the enormous white or red surface of the desert dazzles the eyes ; in this blinding light, every object appears to be clothed with a sombre and preternatural tint. Occasionally the traveler, when sitting upon his camel, is seized with the rdgle, a kind of brain-fe- ver, which causes him to see the most fantastical objects in his delirious dreams. Even those who retain the entire possession of their faculties .and clearness of their vision, are beset by distant mirages ; palm-trees, groups of tents, shady mountains, and sparkling cascades, seem to dance before their eyes in misty vapor. When the wind blows hard, the travel- er's body is beaten by grains of sand, which penetrate even through his clothes and prick like needles. Stagnant pools, or wells, dug with great labor in some hollow, from the sides of which oozes out a scanty and brackish moisture, point out, each day, the end of the stage. But often, this unwholesome swamp, where they hoped to be able to recruit their energies, is not to be found, and the people of the caravan must content themselves with the tainted water with which they filled their flasks at the preceding stage. It is said that in times of great need the travelers have been compelled to kill their dromedaries in order to quench their thirst in the nauseous liquid which is contained in the stomach of these animals. Terrible stories are also told by the side of the watch-fires, of caravans being overtaken when amid the sand-hills by a sudden storm of wind, and completely buried under the moving masses ; they also tell of whole com- panies losing their way in the deserts of sand or rocks, and dying of mad- ness after having undergone all the direst tortures of heat and thirst. Happily such adventures are rare, even if the accounts of them are at all * Daniel, Handbuch der Geographic, vol. i., p. 446. f Duveyrier, Exploration du Sahara. OASES ZV THE DESERT. 93 authentic. Caravans, when led by an experienced guide and protected by treaties and tribute against the attacks of plundering Arabs and Ber- bers, nearly always arrive at the end of their journey without having un- dergone any other sufferings than those caused by the intolerable heat, the want of good water, and the coldness of the nights ; for the nights which follow the burning days in the Sahara are in general very cold. In tact, the air of these countries being entirely destitute of aqueous vapor, the heat collected during the day on the surface of the desert is, owing to the nocturnal radiation, again lost in space. The sensation of cold pro- duced by this waste of heat is most acute, and especially so to the* chilly Arab. Not a year passes without ice forming on the ground, and white frosts are frequent.* During his travels in the country of the Touaregs, M. Duveyrier observed a difference of more than 129 F. between the low- est temperatur% (24 F.) and the highest (153 F.) ; but it is probable that the real difference between the extremes of heat and cold amounts to at least 144 degrees, f In all those countries in the Sahara where the water gushes out in springs or descends in streams from some group of mountains, there is an oasisj formed a little green island, the beauty of which contrasts most strikingly with the barrenness of the surrounding sands. These oases, compared by Strabo to the spots 'dotted over the skin of the panther, arc very numerous, and perhaps comprehend altogether an area equal in ex- tent to one third of the whole Sahara. In the greater part of this region, the oases, far from being scattered about irregularly, are, on the contrary, arranged in long lines in the middle of the desert. The cause of this is either the 'higher proportion of moisture contained in the aerial currents which pass in this direction, or, and perhaps principally, the subterranean water which follows this slope, and here and there rises to the surface. Thanks to this distribution of the oases, like beads on a necklace, the car- avans dare to venture into the solitudes of the Sahara, their stages being all marked out beforehand by the patches of A r erdure which in turn rise on the horizon. The oases are, par excellence, the country of date-trees ; in the neighbor- hood of Mourzouk there are no less than thirty-seven varieties. These trees form the riches of the tribe, for their fruit supplies food to man as well as to beast to dromedaries, horses, and dogs^. Below the wide fan of leaves, which quiver in the blue air, are thickly-growing clumps of apricot, peach, pomegranate, and orange-trees, their branches loaded with fruit, and vines intertwining round the trunks ; maize, wheat, and barley ripen under the shade of this forest of fruit-trees, and, lower still, the modest trefoil fills up the very smallest intervals of the soil which is ca- pable of irrigation. In order not to encroach on this precious ground, which is the very life of the whole tribe, the inhabitants construct their on the most unproductive land in the oasis, and even on the very Curette. t Exjtloration du Sahara, vol. i., p. 110. Derived from the ancient Egyptian word ouahe, signifying " habitation." Vogel. 94 THE EAMTH. verge of the desert. Unfortunately, these wonderful gardens which the traveler, just emerged from the ocean of sand, looks upon as a place full of enjoyment, are for the most part unhealthy, on account of the constant evaporation of tepid and bad water which the irrigation-drains bring to the foot of the trees. For this reason the Caesars of the Lower Empire used to send convicts to the oases, in order that they might get rid of Fig. 21. Oueld-E'ir. them the sooner.* But the supply of water, which is so precious to these gardens, is badly regulated ; at the time of heavy rains, which are, how- ever, rare in the desert, the brook, suddenly transformed into a river, sometimes destroys the channels and washes away the trees ; whereas, if retained in vast reservoirs, this water might be the means of extending the limits of the oasis. New tracts of cultivated ground may even be * Humboldt, Tableaux de la Nature. AEABIAN DESERTS. 95 created* by boring artesian wells; this has, indeed, been done in some places, though in a rough manner, by the native tribes. In eight years, from 1856 to 1864, the French engineers dug, in the Hodna and the Sa- hara of the province of Constantineh, eighty-three wells, which yield al- together 11,859 gallons a minute, and nourish more than 125,000 palm- trees ; a few strokes of the boring-rod have thus changed the terrible as- pect of the desert and adorned it with magnificent groves. No doubt, if all the subterranean springs of the Sahara were brought to the surface, they might succeed in bringing a great part of it under cultivation, and, in course of time, in modifying the climate as they have done in Egypt,* by augmenting the quantity of rain and aqueous vapors. Added to this, the examination of the soil and the remains which are contained in it, proves that at a recent geological epoch the Sahara was much less sterile than it now is. The tribes of the Algerian Sahara say that at the time of the Romans the Ouad-Souf was a great river, but some one threw a spell upon it and it disappeared.! To the east of Egypt, which may be considered as a long oasis situated on the banks of the Nile, the desert begins again, and borders the whole extent of the Red Sea. A large part of Arabia presents nothing but sands and rocks, and toward the southeast, in the Dahna, there are soli- tudes which no traveler, either Arab or Frank, seems yet to have crossed. To the north and east stretch the Nefouds, or " daughters of the great desert," which are much smaller than the Dahna, but are nevertheless for- midable tracts to travel over. One of these regions, which was crossed by Palgrave, is that in which the mass of sand, formerly deposited there by the marine currents, affords the greatest depth ; in certain places it is 330, 400, and even 500 feet deep. It can be measured by the eye by de- scending to the bottom of the funnel-shaped cavities, which the springs of water, spouting out of the adjacent granite or calcareous rock, have gradually hollowed out in the bed of sand. This enormous bed of mate- rial, which represents chains of pulverized mountains, does not exhibit an even surface, as one would expect, but, throughout its whole expanse, presents long symmetrical undulations, similar to those waves which roll in the Caribbean Sea under the even influence of the trade-winds. These waves stretch from north to south, parallel to the meridian ; it is probable that they are owing to the movement of the earth round its axis. The solid rocks beneath unresistingly obey the impelling force which carries them toward the east, but the movable sands which are above them do not allow themselves to be carried away with an equal rapidity ; each day an infinitesimal quantity remains behind and seems to glide toward the west, like the waves of the ocean, the atmospheric currents, and ev- ery thing that is movable on the face of the globe. J The parallel furrows ff sand in the Nefoud certainly rise to a greater height than those of the other deserts, and differ much in their aspect from the smaller waves * Vide the chapter on " Labor of Man." * Carettc. J Vide the chapter on "Rivers." 90 THE EARTH. of sand formed by the wind ; but the reason is, that the bed of sand in this region is of a very great bulk, and because at this point the swiftness of the globe nearly attains its maximum/on account of its vicinity to the equator.* To the east of the Arabian peninsula, the chain of deserts is prolonged obliquely across Asia. The principal part of the plateau of Iran, occupv- ing a quadrilateral space, surrounded by mountains which stop the rains in their passage, consists of sterile solitudes, some covered with saline- beds, the remains of dried-up lakes, others spread over with shifting sands, which the wind blows up into eddies, or dotted over with reddish-colored hills, which the mirage renders either nearer or more distant to the eye than they really are, incessantly modifying them according to the undu- lations of the atmosphere. This plateau is only separated from the steppes of Turkestan by the Elburz Mountains, and is continued toward the east by the deserts of Afghanistan and Beloochistan, which are not so large, and much easier to travel over. Even the rich peninsula of In- dia is protected by a belt of sterile tracts situated on the right and left of the Indus. Between each of the five rivers (Punjaub), which, by the union of their waters, form the great river, stretches a line of steppes in which the torrent-waters of the mountains are soon lost. The soil of these steppes is nearly every where barren, except on the edge of the irri- gation canals constructed by the inhabitants at a very heavy outlay. Beyond the mighty central group, whence radiate far and wide the mountain-chains of Asia, the steppes and deserts, mutually alternating according to the topographical conditions, and the abundance or scarcity of water, extend over a space of more than 1850 miles between Siberia and China Proper. The eastern part of this belt is called, according to the languages, Gobi or Chamo, that is to say, the desert par excellence, and, from its enormous dimensions, corresponds with the Sahara of Africa, situated exactly at the opposite extremity of the long chain of solitudes which stretches right across the Old World. The mirage, the moving sand-hills blown up into eddies, and many other phenomena described by African travelers, are found in certain districts of the Gobi, just the same as in all other deserts. But the cold here is exceptionally intense, on ac- count of the great height of the plateaux, which is on an average 4950 feet, and the vicinity of the plains of Siberia, which are crossed by the polar wind. It freezes nearly every night, and often during the day. The dryness of the atmosphere is extreme ; there is hardly any vegeta- tion, and a few grassy hollows are the only oases of these regions. From Kiahkta to Pekin, there are only five trees for a distance of 400 to 500 miles, which ig the width of the desert in this part of Mongolia.f The Gobi, however, like the Sahara, was formerly covered by the waters of the ocean ; even on the elevated plateaux, old cliffs may be noticed, the bases of which are worn away by the waves, and long strands of round shingle stretch around the area which was formerly occupied by a now vanished gulf. * Gifford Palgrave. Journal of the Geographical Society, 1864. t Kns.-ell-Killough, Seize milles lieves, p. 111. PL A IXS OF THE NEW WORLD. 97 CHAPTER XV. PLAINS AND DESERTS OF THE NEW WORLD. COMPARATIVE HUMIDITY OF THE AMERICAN CONTINENTS. DISTRIBUTION OF SAVANNAS AND STERILE TRACTS. THE PRAIRIES OF NORTH AMERICA. THE LLANOS AND PAMPAS. THE American continent, being narrower and more exposed throughout its whole extent to the moist sea-breeze than the larger mass of the Old World, presents, therefore, but a very small number of districts in which the dryness and sterility are to be compared to certain parts of the Sahara and Arabia. It is true that plains occupy a relatively much larger area in the New World than in the continents of Asia and Africa ; but they are for the most part regions which, from the abundance of water and the deposit of fluviatile alluvium, have become very fertile. Thus, the low grounds which extend along the two banks of the Mississippi, and especially the districts lying along the edges of the Amazon and its large tributaries, are covered with immense forests, which are perfect seas of trees and creepers, into which no one would dare to venture without a guide, even if they are not completely impenetrable, except for the native, armed with his machete. The selvas of the Amazon are the regions o where vegetation exhibits its richest exuberance, and over the most ex- tensive area.* Plains which are devoid of trees occupy very considerable tracts of land in the two Americas, and, notwithstanding the absence of all forest vegetation, several of them being formed of fluviatile, or lacustrine alluvi- um, are extremely fertile. In consequence of the composition of the soil, the distribution of the rain-fall and water-courses, and perhaps, also, in obedience to some still unknown law governing the apportionment of plants on the surface of the earth, savannas of the various grasses alter- nate suddenly with virgin forests. This unexpected contrast between the wall of trunks, through which the sight can not penetrate, and the unbounded extent of the grassy plain waving in the breeze, is one of the most striking spectacles imaginable. In the basins of the Mississippi, the Amazon, and the tributaries of the La Plata, these sudden transitions from forest to savanna are frequently found ; next to the great rivers and large sheets of marshy water, they are the most prominent feature of the land- scape in the plains of the New World. Taken as a whole, the grassy expanses of America are all like the landes, the steppes, and the tundras of the Old World regularly ar- ranged in a line parallel to the axis of the continents themselves. In North America, they are contained in the vast central basin formed by * Vide the chapter on " The Earth and its Flora." G 98 THE EARTH. the Alleghanies and the first spurs of the Rocky Mountains. In South America, they likewise occupy a part of the depression in the middle of the continent between the plateaux of the Guianas and Brazil, and the first groups of the Andes. Thanks to the rainy sea-breezes which blow over these plains either from the north or south, vegetation is here kept up, at least, during several months of the year ; and nowhere, even in the less fertile districts, are real deserts to be found. These plains, which, as in Africa and Asia, are likewise arranged in a line parallel to the belt of sa- vannas and to the continental axis of America, are all situated on the western side, on the slopes, or in the inner basins of the Rocky Mount- ains and the Andes. They are, however, comparatively inconsiderable, and intersected by fluviatile valleys, some of which terminate in lakes without an outlet, while others run down to the sea. The savannas or prairies of Illinois and the other Western States of the American Republic resembled, not long since, the Magyar puszta and the grassy steppes of Russia, except as regarded the difference of vegetation attributable to climate. Some of those plains, which, at a former geolog- ical epoch, were covered by the waters of Lake Michigan, have not yet been transformed into cultivated fields, and they have a uniform and placid surface like that of a lake. The flowering grasses growing on them wave and quiver in the wind like the ripple of the waves, and the clumps of trees are dotted about like islands. Here and there these islands are grouped into archipelagos, and the arms of the prairies which surround them fork out and unite again like the arms of a grassy sea ; one single prairie, situated in the centre of the State of Illinois, is so vast, that, as far as the eye can reach, not one of these thick clumps of trees appears in sight. But in consequence of the very rapid colonization of the Western States, these countries are every day changing their aspect. The traveler, therefore, must not delay if he wishes to survey these immense prairies, where the horizon, as on the sea, is only limited by the rotundity of the globe where the grasses are so high that they reach up to, and bend over, the head of the traveler, and the roebuck can dart through them without even being perceived ! Ere long, these prairies will have ceased to exist, save in the narrations of Cooper, the novelist ; the furrows of the unrelenting ploughshare will have converted them all into cultivated fields. The Americans are active in turning them to account and in tak- ing possession of this fertile land. The country, which is strictly surveyed, is divided into townships of about six miles on each side, and subdivided into square miles, which are again separated into four parts. All these quadrilateral spaces are so accurately set as to aspect that each of their sides points to one of the four cardinal points. The purchasers of small or large squares never allow themselves to deviate from the straight line ; as true geometricians, they construct their roads, build their cabins, dig their ponds, and sow their turnips in the direction of the meridian or the equator. Thus the prairies, once so beautiful with their gently undula- ting contour and their misty distances, now bear a strong resemblance THE PAMPAS. 99 to an immense chess-board. Even the railway engineers will hardly make up their minds to cross the degrees of longitude in an oblique direction. In the southern continent, the regions which correspond with the prair- ies of the United States are the pampas of the La Plata and the llanos of Columbia. These latter expanses, so well described by Humboldt,* are probably, of all the plains in the world, those which exhibit in their appearance the most striking contrast, according to the different seasons of the year. After the rainy season, these plains, which extend over the immense zone contained between the course of the Orinoco and the Andes of Caracas, Merida, and Suma-paz, are covered with thick grass, and graminaceous and cyperaceous plants, among which the sensitive and other species of mimosa here and there exhibit their delicate foliage. Horses and oxen wander by millions over these magnificent pastures. But the soil gradually dries up, the water-courses become exhausted, the lakes change into pools and then into sloughs, in the mud of which croco- diles and serpents delight to wallow; the clayey ground shrinks and cracks, the plants wither, and are torn to shreds by the wind ; the cattle, driven by hunger and thirst, take refuge in the neighborhood of the great rivers, and multitudes of their skeletons lie bleaching on the plain. This is the special time when the llanos most resemble the deserts of Africa, which are situated farther from the equator on the other side of the At- lantic all at once, the storms of the rainy season inundate the soil, mul- titudes of plants shoot out from the dust, and the immense yellow ex- panse is transformed into a flowery meadow. The rivers overflow their banks, and the inundations will sometimes extend over a breadth of hun- dreds of miles ; the ancient islands, called " tables" or mesas, form the only land which appears above the troubled sheet of waters. The llanos of Venezuela and New Granada have an area estimated at 154,000 square miles, nearly equal to that of France. The Argentine pampas, which are situated at the other extremity of the continent, have a much more considerable extent, probably exceeding 500,000 square miles. This great central plain, which forms one of the most remarkable features of South America, stretches its immense and nearly horizontal surface over a length of at least 1900 miles, from the burning regions of tropical Brazil to the cold countries of Patagonia. In so vast a territory, the climate and vegetation must necessarily differ very much, and yet a great monotony prevails, on account of the horizontal character of the ground and the want of water. The rivers of the pampas, the Pilcomayo, the Vermejo, and the Salado, which rise in the Andes and the Sierra Aconquija, ultimately reach the great fluviatile artery of the Parana, but not without having lost a large part of their waters on the road, owincr to the evaporation in the lagoons and marshes. Farther south, the Rio Dulce, which also rises in the ravines of Aconquija, is lost in a salt lake at some distance to the west of the Parana. In the same way all the water- courses of the provinces of Catamarca, Rioja, San Juan, Mendoza, and * Tableaux de la Nature and Voyage dans les Regions Equinoxiales. 100 THE EARTH. Fig. 22. The Pampas. Cordova, growing smaller in proportion to their distance from the mount- ains, ultimately spread out into marshes, or break up into pools ; the sand of the desert gradually absorbs them. The Rio-Quinto, which formerly reached the sea, and emptied itself to the south of the estuary of La Plat'a into the bay of San-Borombon, now stops at about the middle of its for- mer course ; but to the east some lagoons connect it with the sources of a small stream, which may be considered as the Lower Quinto. The diminution of rains, and the increase of evaporation during the present geological period, have resulted in severing the river into two parts. THE PAMPAS. 101 The western plains, which partly surround the Cordovan group, are dotted over with prickly plants, brooms, mimosas, and other shrubs of scanty foliage. There is only a short turf growing upon the clayey and compact soil, and here and there vast salt plains, completely devoid of vegetation, glitter in the sun. These are real deserts, which were former- ly crossed by travelers in caravans, just as in the solitudes of Africa and Persia. The carriages which now run regularly between the towns on each side of the plain go across in a straight line, and their drivers do not even take the trouble to trace out a road. Farther to the east, the pampa proper extends from north to south, between the Salado and the regions of Patagonia. Here are situated the immense and celebrated pasture-grounds which form the wealth of the Argentine Republic, on ac- count of the cattle which overrun it by hundreds of thousands, and, in- deed, millions. The grassy surface seems to be completely flat ; no ob- ject interrupts the majestic uniformity of the landscape, except, perhaps, a herd of oxen, the yellow wall of some estancia^Qv a solitary tree spared by the hatchet of the gaucho. Pools, some brackish x>r saline, others filled with fresh water, are scattered over the prairie, and continue the wavy covering of grasses with their tufts of rushes and reeds. To the north of the Salado, the great sea of grass is succeeded by thickets of mimosas, and other prickly shrubs, which surround the small savannas. Lastly, beyond the windings of the Pilcomayo, bunches of palm-trees are seen here and there among the clumps, and the pampa, called in this district the Great CJiaco, ultimately joins on to the large selvas in the basin of the Amazon by swampy grounds and isthmuses of forest. 102 THE EARTH. CHAPTER XVI. AMERICAN DESERTS. THE GREAT BASIN OP UTAH. THE DESERTS OF COLO- RADO. THE ATACAMA AND THE PAMPA OF TAMARUGAL. DEPOSITS OF SALT, SALTPETRE, AND GUANO. IN North, as in South America, the deserts proper lie to the west of the continent, and occupy the basins commanded by the parallel or di- vergent walls of the Rocky Mountains. In both hemispheres it is the want of rain which is the cause of the sterility of these expanses, to which the moist winds can not obtain access, on account of the high mountains by which the plains are surrounded ; but, by a remarkable contrast, the rains in the northern continent, which are stopped en route before reach- ing the deserts, are those brought by the clouds from the Pacific, and in the southern continent those which come from the Atlantic with the trade-winds. In the north, the ridges of the western chains, the coast- range, and the Sierra Nevada are the impediments which detain the moist- ure of the atmospheric currents of the neighboring ocean : in the south it is, on the contrary, the eastern groups of the Cordilleras which, by op- posing the course of the Atlantic trade-winds from the northeast and southeast, are the cause of the barrenness which exists on their opposite declivities.* Besides, in both continents, most of the deserts, whether plains or plateaux, seem to have been, at some former geological epoch, leveled by the waters of some inland sea. The most northerly of these American deserts occupies, to the west of Lake Utah, a part of the space called the " Great Basin," and is comprised between the principal chain of the Rocky Mountains and the Sierra Ne- vada of California. The desert of Utah is an immense surface of clay, dotted over with thin tufts of artemisia ; in certain places, however, it ex- hibits no trace of vegetation, and resembles a causeway of concrete, in- tersected by innumerable clefts, forming nearly regular polygons.. In the midst of these solitudes no rivulet flows, and no water-spring gushes forth ; only after journeying for many a long hour the traveler sometimes comes upon some field of crystallized salt, a white expanse, on which the clouds and blue sky are reflected as on the surface of a lake. On the ex- treme horizon some volcanic rocks may be seen, like great scoria, half veiled by warm atmospheric columns, quivering like the air over the flame of a hot brazier. Across these vast plains, inhabited only by a pro- digious quantity of extraordinarily-shaped lizards, the road employed by the emigrants used to pass, which was so soon destined to be supplanted by the 'Pacific Railway from New York to San Francisco. Since the dis- * Vide the chapters on "Winds" and "Rain." UTAH AND COLORADO. 103 covery of California, thousands of men have perished in this desert, and innumerable horses and oxen have died of thirst ; the right direction of the road is indeed recognized by their bones lying scattered over the ground. The traveler is obliged to stop during the night, for fear of losing his way, when he no longer hears the sound of the skeletons crush- ing under the feet of his steed.* Separated from this desert by chains of mountains, among which are to be found several shady valleys enlivened by brooks, there are some soli- tudes extending southward which are less sterile than those of which we have just spoken. The only vegetation which some of these exhibit is a few scanty brambles here and there creeping over the ground ; others are clothed with a thin foliage of thorny shrubs ; but the greater part of the bare rocks or clay in these desert tracts appears just the same as when it first emerged from the water. Only a few pitahayas, like gigantic wax candles, stand solitarily at considerable distances from each other. Their trunks, which rise to the height of from 48 to 60 feet, are as straight as columns, and from the base to the summit have a nearly uniform thick- ness, equaling sometimes the size of the human body ; the branches, to the number of two or three only, jut out from the trunk at a right angle, and then stand erect, like the branches of. an enormous candelabrum. Owing to the regularity of their shape, their parallel sides covered with thorns, and their grayish-green color, these curious plants seem to be a kind of intermediate substance between the tree and the rock, and give to the landscape an aspect which is both fantastic and repulsive. In some regions hundreds of miles may be traversed across the mountainous val- leys and plains, and during the whole journey no other species of terres- trial vitality can be seen but these immense pitahayas. Even this amount of vegetation is wanting in the most sterile districts of New Mexico and Arizona. Thus the desert of Colorado, situated near the mouth of the river bearing thfe same name in the Gulf of California, is a totally barren expanse of clay and sand. In the evening, when the sun is setting far away behind the ruddy mountains and darting its rays across the dusty atmosphere, the traveler, when encamped in the bed of some dried-up river on the border of this immense plain, which was, indeed, formerly a lake-, might easily fancy that he sees stretching before him the surface of a sea of fire.f The deserts of North America, crossed here and there by fertile valleys, extend eastward toward the basins of the Red River and the Arkansas, where they blend with the savannas, and to the south into the Mexican states of Chihuahua, Sonora, and Sinaloa. But in the tropical zone, which commences beyond these points, the heavy summer rains and the much smaller extent of the Mexican territory between the two oceans, have pre- vented the formation of deserts. Regions destitute of trees and verdure are only again found on the coasts of Peru, to the south of the Gulf of * Pacific Railway Report. Jules Rdmy, Voyage an Pays des Mormons. t Pacific Railway Report. 104 THE EARTH. Guayaquil. The trade-winds, after having discharged their moisture on the eastern slopes of the Andes, pass away through the air far above the sea-shore on the western side of the mountains, and then sweep far out to sea over the surface of the Pacific. It is rarely that an atmospheric eddy blows back upon these coasts even the smallest rainy current ; sometimes five, ten, and even twenty years elapse without a single drop of rain hav- ing fallen in Payta and the other sea-coast towns. The greater part of the houses in the rich and commercial city of Iquique were sirnply com- posed of four walls, without the useless luxury of a roof. Nevertheless, the coasts of Peru are not completely destitute of verdure. Some small riv- ers, fed by the snows from the Andes, and tapped throughout their whole length by irrigation-drains, maintain a little vegetation in the valleys, and, during the season which is called winter, particularly in May, June, and July, heavy dews refresh the soil of the mountains on the coast, and cause the cactus and various bulbous plants to shoot forth here and there ; hence is derived the name of tiempo de flares given to this part of the year.* The commercial towns situated on the sea-shore, the gardens in the valleys, the rare grasses on the hills, and, lastly, the cliff-like declivi- ties of the Andes, which rise, ridge after ridge, up to their snowy sum- mits, give to the whole landscape an animated character which is entirely wanting in the deserts of North America. The solitudes of the Andes most resembling the desert regions of the Old World and of the United States are the elongated plateaux which rise one above another between the sea and the principal chain of the An- des, in southern Peru and on the frontiers of Bolivia and Chili ; such as the pampas of Islay and Tamarugal and the desert of Atacama. The pampa of Tamarugal, so called from the Tamarugos, or tamarisks, which grow in the hollows where some moisture oozes out of the soil, has a mean altitude of from 2900 to 3900 feet. It is a plain nearly covered with beds of salt, or salares, which are worked like rock quarries. The strata of salt are so thick, and rain is so rare upon the plateau, that the houses of the village of Noria, which are inhabited by the workmen, are entirely con- structed of blocks of salt. Some deserts, situated to the east of the Tam- arugal, on more elevated plateaux, contain a still larger quantity of salt. The pampa of Sal, which is overlooked by the volcano of Isluga, has a mean altitude of not less than 13,800 feet, and its whole extent, which is 125 miles long and from nine to twenty-four miles wide, is perfectly white. The depth of salt deposited upon this plateau varies from five to sixteen inches, according to the undulations of the ground. Whence do these enormous masses of salt proceed ? Doubtless from the sea or ancient lakes which formerly covered these countries and have been gradually emptied by the rising of the soil. Saline matter saturates even the rocks and clays, for a film of salt again forms by efflorescence on all the ground in the desert from which crops have previously been taken. The district of Santa-Rosa, which was completely cleared of salt * Bollaert, Antiquities. DESERT OF ATACAMA. 105 in 1827, was all white again and fit for working after a lapse of twenty- three years. Sea-salt is not the only production of these immense natural laboratories; but nitrates, sulphates, carbonate of soda, borates of soda and lime, are also found there and increase every year in thickness, thanks to the ephemeral torrents which sometimes descend loaded with debris from the adjacent Cordilleras. Saltpetre is also procured from ihepampa of Tamarugal, and is the article which, during all the wars of Europe and America, gave such great commercial importance to the town of Iquique. About the middle of the eighteenth century, an Indian, named Negre- ros, discovered the existence of saltpetre in the pampa; having lighted a fire of brush-wood upon the soil, he perceived that the ground was melt- ino-, and that a stream issued from the midst of the firebrands and cinders. O' * From this date they began to work these beds; but it is only since the last fifteen years especially that this branch of industry has been carried on to any considerable extent. According to Smith, the engineer, the beds of nitrate occupy in ihepampa of Tamarugal an area of 483 square miles ; in some spots, where the mass is not less than ten feet in depth, a ton of saltpetre may be taken from a square yard of ground ; but reckon- ing only on a product of 110 Ibs. a yard, it is found that the total quantity of saltpetre at present contained in the superficial beds of the pampa is not less than sixty-three millions of tons, or enough to supply the require- ments of trade for 1393 years, if the working does not exceed, on an av- erage, that of the year I860.* The desert of Atacama, the largest of all those in South America, occu- pies a wide belt of plateaux between the shores of the Pacific and the high rampart of the Andes, which separates Bolivia from the Argentine Republic. This expanse of reddish -colored rocks, and crescent -shaped shifting sand-hills, is so repulsively desolate a place that the conquerors of Chili, whether Incas or Spaniards, never made up their minds to ven- ture into it, in going along the sea-coast ; they have been obliged to pass far into the interior, by the plateaux of Bolivia, and to twice cross the Andes before entering the Chilian valleys. Not long since, men of sci- ence were the only travelers who dared to enter the desert of Atacama. Nevertheless this formidable - looking country also possesses, like the pampa of Tamarugal, great natural riches, 'which will not fail to summon the labor of man and all the progress of civilization to these desolate re- gions. Besides salt and saltpetre, this desert produces guanof that is, heaps of the almost exhaustless droppings of all the searbirds which set- tle down in clouds upon the sea-shore. During the course of centuries the ordure has accumulated into perfect rocks which the sun dries up, and the surface of which is but rarely softened by rain. These masses of detritus, which are, to all appearance, useless upon these barren shores, are life itself to the countries of England, France, and Belgium, which have become exhausted by the extent of cultivation ; and, consequently, this substance constitutes a most important element of national com- * Bollaert, Antiquities, pp. 155, 240. t Derived from the word huanu. THE EARTH. raerce. The principal treasure, or national bank, so to speak, of the Pe- ruvian Republic is represented by the heaps of excrement which cover the Chincha Islands, off the coast of Callao. According to the various calculations, from twelve to fifteen millions of tons of excellent guano are to be found there, a quantity which is worth to Peru more than eighty millions of pounds sterling, an amount which, if well laid out, would en- able the happy possessors to construct a magnificent system of railways, and to build a school in each of their villages. But they must be quick about it, for the treasure of guano will probably be exhausted in twenty years; already, since the year 1866, the northern island has been cleared down to the solid rock. PLATEAUS. AND PLAINS. 107 CHAPTER XVIL DIFFERENCE BETWEEN PLATEAUX AND PLAINS. MATERIAL IMPORTANCE OF PLATEAUX IN .THE ECONOMY OF THE GLOBE. DISTRIBUTION OF ELE- VATED REGIONS ON THE SURFACE OF CONTINENTS. NOTWITHSTANDING the variety of aspects and vegetation which is in- troduced by the difference of climate, low-lying lands, among which, it must be remembered, are included so many sterile deserts, play a much less important part in the history of the globe than the more elevated portions of the emerged surface of the earth. Both the organization and the vitality, so to speak, of continents are owing to the external relief of the planet ; these inequalities in the surface are also the cause of the va- ried development and distribution of climates, water-courses, products, and populations over the whole world. All the elevated portions of continents and islands may be naturally divided, according to the height and inclination of the land, ito plateaux and mountain systems. By the word plateau we now usually understand some extent of land raised to a considerable elevation above the level of the sea ; but the surface is not always uniform and level, as the name would seem to indicate. When the surface is very irregular, either fur- rowed by deep ravines, or dotted over with hills and mountains, the ideal plain which would pass through the bases of all the mountains at a height to allow for filling up all the intervening depressions is considered as the superficies of the plateau. There are, however, some plateaux which are almost perfectly level, such as the staked-plains of Texas and some por- tions of the Utah basin. Low-lying lands, also, very often present a surface undulated with hills and valleys, and connected with higher plateaux either by gradual slopes, or by a succession of terraces, which may be looked upon either as the rise of the plain or the descent of the plateau. The difference existing between high and low lands is purely relative ; we can only define them by saying that a plain is a surface comparatively level, and commanded on one or all sides by more elevated tracts, and that plateaux exceed in height the land surrounding them. The ground which would be a plain for the inhabitants of the mountains above it, would be a plateau for those who live on a lower level. Thus, in Louisiana, where the surface is so frequently inundated, undulations of the ground which are almost im- perceptible to the eye go by the name of hills, because they are not in- vaded by the floods of water; also, on the level surface of the sea, the blocks of ice detached from the glaciers of Greenland and Spitzbergen are commonly called mountains of ice, or icebergs. Agassiz, when con- 108 TRE EARTH. templating the heights of Obydos, in the midst of the interminable plains of the Amazon, fancied that he was again looking upon the sublime mountains of his native country.* The absolute height of the several stages of elevation of the land is not, therefore, the chief thing taken into account in the geographical division into plains and plateaux, but the relation which they bear to the conti- nental mass of which they form a part. The country of North Hindostan is more elevated than the plateaux of Suabia and Bavaria, and yet it must nevertheless be considered as a plain, because it belongs to a continent the general features of which are gigantic, in comparison with those of Europe. In both parts of the world the respective proportions are re- tained between the various stages of the continental edifice. The pla- teaux of Asia correspond to those of Southern Germany; the Himalayas remind us of the Alps ; Hindostan, with its plains and mountains, is the counterpart of the Italian peninsula. Although plateaux, precisely on account of their size and the grandeur of their proportions, make less impression on the human mind than a steep and rugged mountain chain, towering up between two countries like an enormous rampart, nevertheless in their importance in the vitality of the globe they are certainly superior to any other features in the con- tinental configuration. If the emerged surface of the planet were perfect- ly level, the most dispiriting uniformity would every where reign. The same phenomena would be produced over the whole extent of the conti- nental surface from one ocean to the other ; the winds, meeting with no obstacle in their course, would sweep round the globe with an ever-equal motion, like the long bands of cloud which the telescope discovers on the planet Jupiter. There would be none of those elevated masses which, by their transverse position to the natural course of the winds, produce an in- terruption of'the equilibrium, and drive back the atmospheric currents in every direction. There would be none of those great refrigerators, as they may be called, which condense the moisture in the clouds, storing it in their reservoirs of ice and snow. Rain would fall every where to nearly an equal extent, and the water, finding no declivity along which it might be carried off to the ocean, would stagnate in putrid marshes. A perfect equilibrium of the forces of nature t would have as its effect uni- versal stagnation and death. Supposing that men could exist on such an earth as this, the uniformity of one great plain would be far from afford- ing them any greater facilities for mutual communication" ; they would, on the contrary, remain scattered round their miserable lagoons in all their primitive barbarism. The migrations of whole nations down the inviting slope of some of the^vast continental plateaux, in quest of a new country, like a great river seeking the sea, could never have taken place. All civilization would have been impossible. Perhaps, as some geologists think, the surface of the globe was uniform and without any prominent relief when the Icthyosaurus swam heavily through the marsh-pools and * Conversayoes sobre o Amazonas. PLATEAUX AND PLAINS. 109 the Pterodactyl spread his sluggish wings over the reed-beds. Jt was then an earth for reptiles, it could not be a world for men. If the great plateaux of the globe had been arranged round the Arctic Frozen Ocean, and their long slopes had gradually sunk toward the In- dian and Pacific oceans, the full development of humanity would have been equally impossible. In the north the altitude of the plateaux would have doubled the cold of the frozen zone ; all organic life, even that of the most rudimentary plants, would have probably ceased to exist, and, doubtless, the freezing winds, sweeping down from this citadel of snows, would have changed into a second region of ice those temperate countries which are now the fields of so many varied products, and where so many powerful nations have taken their rise. The only habitable lands would be the islands of the South Seas and the tropical regions of the continents, if, indeed, man could exist at all in a climate where overwhelming heat would be succeeded by icy winds blowing down from the lofty plateaux of the north. But, even supposing that isolated tribes could have found a footing in these countries, mankind in a general sense could not have ex- isted ; for by the word mankind we must not understand merely a multi- tude of scattered individuals, but the whole human race, having a full self-consciousness and knowledge of its destiny. Whatever may have been the geological causes of the present distribu- tion of plateaux over the various continents, the following remarkable fact must be recognized, that their height increases in proportion to their proximity to the torrid zone, as if the rotation of the globe had caused, not only the equatorial enlargement of the planetary mass, but also the elevation of the continents themselves. In the Tropic of Cancer, the mean altitude of the plateaux is nearly equal to that of the mountains in the temperate zone, while the plateaux of the latter are, on the average, the same height as the mountains of the polar zone.* In consequence of this distribution of the various high lands, it comes to pass tfiat, in every latitude, certain portions of each continent exhibit an epitome of all the climates which succeed one another over the circumference of the planet from this latitude to the poles. Owing to these plateaux and the mount- ains which crown them, the Iberian peninsula, Turkey, and Asia Minor enjoy, at various points of their surface, all the varieties of a temperate climate, and thrust their loftiest peaks into cold regions almost similar to those of the poles. In countries of this sort, the traveler can change both the climate and the features of nature round him by a journey of a few days, or even sometimes of a few hours ; while at sea, he must have made a voyage from the tropics to the icebergs of the poles if he wished to traverse the corresponding stages of climate. The fact of the gradually increasing elevation of plateaux as we go south tends actually to double the number of the zones in the middle latitudes. A polar climate is, as it were, placed above the temperate climate. In Hindostan, three zones of temperature merge into each other on the slopes of the Himalaya, the * Metcalfe. THE EARTH. lofty southern boundary of the Asiatic plateaux. The plains beneath, where vast rivers flow down to the sea and impenetrable forests extend over vast tracts, are inhabited by an almost innumerable population ; higher up, we find mountain torrents, long avenues of firs, and flocks wandering over wide pastures;, higher still, there is little but brushwood, mosses, snow, and masses of ice.* The function of these highlands in the economy of the globe is to bring down the north into the very bosom of the south, and to unite within a limited space all the climates of our planet and all the seasons of the year. All these plateaux are, so to speak, small continents emerging from the midst of the plains, and, like the great continents bounded by the ocean, their phenomena, as a whole, present a kind of epitome of the phenomena of the entire globe ; they may, in fact, be called so many microcosms. Vital centres, as they are, of the planetary organism, they arrest the winds and the cloxids in their courses, and, discharging the rain, modify all the movements which take place on the surface of the globe. Owing to the circulation of elements which is incessantly taking place between all the more prominent por- tions of the continental relief and the two oceans of the atmosphere and the water, the gradations of climate on the sides of the plateaux are di- versely blended, and are constantly bringing into mutual connection both the Flora and Fauna of every country, and also different nations and races of men. * Vide the chapter on "The Earth and its Flora.'' THE GBEA T PL A TEA UX OF CENTRAL ASIA. CHAPTER TIIE GREAT PLATEAUX OF CENTRAL ASIA AND THE GATE OF THE HINDOO- KUTCU. PLATEAUX OF EUROPE ; TIIEIK SYMMETRICAL ARRANGEMENT. PLATEAUX OF THE TWO AMERICAS. SIMILARITY BETWEEN THE CLOSED BASIN OF BOLIVIA AND THE DISTRICT OF UTAH. PLATEAUX OF AFRICA. PLATEAUX, like the continents themselves, exhibit an organization more or less rudimentary, and a shape more or less articulated, and therefore their importance as agents in the vitality of the globe proportionately va- ries. Thus the great plateaux of Central Asia, which may be looked upon as the very skeleton of the continent, exercise, it is true, an influence of the very highest order in the general economy of the earth, but they are almost cut off from all the rest of the world ; their water-courses run into inland basins, without any outlet to the sea, and the nations which inhabit them live in a state of almost perfect isolation from the other peoples of the earth. The principal group of plateaux, which is bounded on the south by the mountains of Karakorum and Kuenlun, on the west by the Bolor, on the north by the Thian-Chan, the Altai, and the Daurian Moun- tains, and on the east by the solitudes of the great Mongolian desert and the variously ramified mountain chains of the interior of China, constitute an immense quadrilateral nearly equal in extent to the whole of Europe. Among these elevated ranges there are some, as the Dapsang and the Boullon, resting upon the Kuenlun, which exceed 16,400 feet in mean height.* Round the greatest part of its extent this enormous fortress of plateaux is rendered almost inaccessible by its formidable girdle of moun- tains, snows, and deserts ; only toward the northwest, between the Thian- Chan and the Altai, several depressions in the surface open out a road through which, some centuries back, the terrible Mogul horsemen poured down to enter upon their course of devastation through Asia Minor and Eastern Europe. At one of its angles, the great quadrilateral plateau of Central Asia borders upon another elevated tract, of smaller dimensions but of nearly similar shape ; this is the territory of Iran, which, although likewise in great part made up of deserts, does not form so much of a prison to the people who inhabit it as the high grounds situated more to the east. On the north it has several outlets toward the plains of Tartary and the Cas- pian Sea, on the west toward the valleys of the Tigris and Euphrates, and also is connected with the mountain-systems of Asia Minor the long- reaching peninsula pushed out between the two European seas. It is a remarkable thing that just in the very vicinity of the central knot of * Schlagintweit. THE EARTH. mountains where the two great plateaux-systems of Mongolia and Iran are united, the principal portal of the Aryan nations is situated the de- file through which passed the flux and reflux of wars, migration, and com- merce. By a singular geographical contrast, this vital knot of the conti- nent of Asia is at the same time both the spot where the two great pla- teaux join one another, and also where the plains of Hindostan communi- cate with those of Tartary and the Caspian. The diagonals both of the high and low-lying lands of Asia cross at right angles on this point of the Hindu-Kutch.* Here too is found, as regards the history of mankind, the most remarkable spot of the whole earth. In Europe, too, the arrangement of the most considerable plateaux also exhibits a singular symmetry. In the same way as in the continent of Asia, all of them, with the exception of the narrow plateau of Southern Norway, are situated in the south of Europe, and bounded on one side by a chain of mountains. On the west there is the plateau of Spain, backed up by the great rampart of the Pyrenees, the mean height of the plateau being about 1980 feet; in Central Europe there is the plateau of Suabia and Bavaria, commanded on the south by the lofty Alps of Switzerland and the Tyrol ; on the east there are the high lands of Turkey, situated all along the southern base of the Balkan range. Thus the central pla- teau of the three extends northward from a system of mountains, whilst, by a kind of polarity, the two others, situated at the two extremities of Europe, are at the south of the range which serves as their base of sup- port.f These elevated districts are, moreover, much more richly organ- ized than those of Asia, and call to mind the form of the continent of which they form a part, indented as it is with its numerous bays and pen- insulas. These plateaux also possess their promontories, which push out far into the plains ; wide valleys, too, break a way into their elevated lev- els, thus providing numerous outlets to the peoples which inhabit the body of the plateau and the country surrounding it. By means of their diver- sified outlines, the elevated countries of Europe are in no way isolated from the rest of the continent ; in no place are the rivers compelled to ac- cumulate in stagnant lakes; every drop of water, every product of the soil, and every man that dwells there, can find an easy pathway to the surrounding plains. As a type of those elevated tracts, the edges of which are very sharply defined by steep ramparts which, however, thanks to the valleys which cut into them, are in no way like inaccessible fortresses, we may mention the Gausses, or the limestone masses of southern France. In the region of the Jura, similar plateaux, especially that of Nantua, have been cut out by the water with so much regularity that one involuntarily thinks of the legendary giants who used to cleave mountains with a blow of their swords. The plateaux of the two Americas are of much greater altitude than those of Europe, and thus correspond to the continents on which they * Carl Hitter, Erdkvnde. t Carl Ritter, Europa. ' PLATEAUX OF THE TWO AMERICAS. 113 stand. With the exception of the secondary plateaux of the Alleghanies, the Guianas, and Brazil, all the elevated tracts of land in America are comprised between the various ramifications of the mountain chains which rise up in the far west in the vicinity of the Pacific. The plateau of Utah, or the " Great Basin," is a vast territory, the outline of which is of a bold character, and guarded by parallel ramparts of rocks ; it is bounded on 1 i.ut Par,:. Fig. 23. The Caussade Department Tarn et Garonne. one side by the foot of the Rocky Mountains, on the other by that of the Sierra Nevada ; it is the principal vertebra of the back-bone of the conti- nent. Farther to the south extend the plateai* of New Mexico, Arizona, Chi- huahua, and La Sonora, all alike surrounded by mountains, and intersected with ravines and valleys. The table-land of Anahuac, the enormous cita- del which towers up between the two seas, is commanded by the peaks of Popocatepetl, Cofre de Perote, and Orizaba. Next, beyond the Isth- H THE EARTH. mus of Tehuantepec, we meet with various smaller plateaux those of Guatemala, Honduras, Salvador, and Costa- Rica which are all based on ranges of mountains partly volcanic. Their respective heights correspond in a general way with the greater or less width of their base, which is bathed on one side by the Pacific, and on the other by the Caribbean Sea. Fig. 24. Indented Plateau of Nantua Department Ain. On the south of the Gulf of Darien we have a series of high plateaux commencing with the enormous chain of the Andes. In every place where this lofty chain divides into two forks, or spreads out its ridges in a fan- like shape, it includes between the mountain spurs a plateau of 4500, 6000, or sometimes even as much as 12,000 feet in altitude. In Columbia we have the plateaux of Paste, Antioquia, Cundinamarca, and Caraccas. Farther south, the two chains of the Andes and the Cor- PL A TEA VX OF AMERICA AND AFRICA. dilleras, which separate and then unite only to divide again, include be- tween their snowy ridges the plateaux of Quito, Cerro de Pasco, Cuzco, and Titicaca, and lean laterally on the high desert tracts of Atacama, be- tween Bolivia and Chili, also on the hilly terraces of Cuyo, westward of the Argentine pampas. Of all the South American plateaux, there is but one which is so completely shut in by the rising ground round it that it is unable to discharge its collection of rain-water into the plains below. This is the plateau of Titicaca; its mean ele.vation is not less than 13,200 feet, and, from its height and extent, forms the most prominent feature in the profile of the Columbian Continent. This Bolivian plateau is the counterpart of the " Great Basin" of North America. These two corre- sponding regions both alike occupy the central portion of their respective continents, each being about 1860 miles from the isthmus of Central America ; they are also both situated between the forked extensions of a great system of mountains, and, in the depressions of their surface, con- tain lakes without any outlet to the sea. Geographically speaking, these countries are as if isolated from the rest of the world. It is with great difficulty that the semi-barbarous inhab- itants of Bolivia are able to enjoy any of the intercourse of commerce or civilization with the other American republics or the countries of Europe. The plateau of Utah is the spot where the Mormons have established their settlement in order to escape the pressure of their fellow-countrymen round them ; a full measure of the North American energy must indeed have been necessary for pursuing the youthful theocratic community into the deserts which protected them. The plateaux which witnessed the de- velopment of the autochthonous civilization of the Aztecs, the Toltecs, the Guatimaltecs, the Muyscas, the Chibchas, and the Incas, have one immense advantage over the closed-up basins of Utah and Bolivia they communi- cate freely with the sea-shore by means of their open valleys and the courses of their rivers. The African plateaux are still more isolated from the rest of the world than the corresponding tracts of land in America; but it is not on account Fig. 2B. Section of Africa from Cape de Verde to Tadjnra. of their great height, or the perpendicular cliffs of the mountains which command them ; the cause is rather to be attributed to the conditions of their climate, and to the situation of the continent itself. The greater part of the elevated regions in Africa are but of comparatively low eleva- tion, and their slopes afford an easy means of access. The plateaux of the THE EARTH. Cape Colony, the mean height of which, on the south, is scarcely 660 feet, gradually rise toward the north up to the desert of Kalahari, at an eleva- tion varying from 2000 to 3000 feet above the level of the sea. All that we at present know of the interior of Africa fully warrants us in thinking that the average height of the plateaux increases but very slightly as we approach the equator. In the very centre of the continent, the region of lakes, whence the Nile derives its source, does not present an elevation of more than 4000 to 4600 feet; also, in the north of Africa, the plateaux of Morocco and Algeria, along almost their whole extent, are below 3000 feet in height. The most remarkable plateau on the continent is that of Ethiopia, over the entire extent of which about 750 miles a mean alti- tude is maintained of 7000 to 8000 feet. The steepest escarpments of this mass of land are turned toward the sea, as if to defend, the Abyssin- ians from any attacks on the part of foreign nations. But the descent on the opposite or northwest side, in the direction of the Nile, is twenty times more gradual ; and at this point Abyssinia would be easily accessible, if it were not that by the desert character of the country, the incessant con- flict of tribe with tribe, and the miseries of the slave-trade, any way of access to its frontiers is sown thickly with perils. Although the African continent is the least known of all the great divisions of the world, and is also inhabited by the most barbarous races of men, yet, taken as a whole, as regards its means of access to the intercourses of trade and civilization, the natural obstacles which it offers are not to be compared with those presented by the mountainous walls of the plateaux of Central Asia and of the Andes. In the disti'ibution of its mountain ranges, its elevated tracts, its plains and its deserts, and also in the general outline of its coasts, Africa reminds one of the peninsula of Hindostan ; it is an India magnified eleven fold, but is much less beautiful and well shaped than the wonderful Asiatic peninsula. ISOLATED MOUNTAINS. CHAPTER XIX. ISOLATED MOUNTAINS. MOUNTAINS IN GROUPS. CHAINS AND SYSTEMS OF MOUNTAINS. THE BEAUTY OF MOUNTAIN PEAKS. SACKED MOUNTAINS. PLEASURES OF MOUNTAIN CLIMBERS. ALTHOUGH mountains do not play nearly so important a part as pla- teaux in the economy of the globe, they are, nevertheless, much better known, on account both of the majesty of their appearance and the sharp contrast which they present to the country round them, and also of the variety of the phenomena of which they are the scene of action. Moun- tains which tower up in solitary greatness either from the bosom of the sea or from some level plain, produce, more than all others, an effect of the highest grandeur, and make the most vivid and durable impression on the mind. The mind's eye can hardly picture scenes superior in beau- ty to those formed by the gracefully undulating slopes and purple sum- mits of solitary mountains like the Ventoux, Etna, the volcano of Tene- riffe, Orizaba, and so many other peaks, at the base of which a whole ho- rizon seems spread out. Some of those heights which in mountainous countries would scarcely deserve to receive a name, and would be hardly looked upon as hills, make pretensions to be formidable peaks when they spring from the midst of a level plain, or on the edge of the sea. This applies to a little hill of about 780 feet in height which stands in the cen- tre of the monotonously level districts of Lower Pomerania; this hill has seemed so prodigious to the inhabitants of the country, on account of the savage wildness of its cliffs, that they have given it the name of the "Mountain of Hell" (Hottenberg). In the same way, a ridge in Denmark, which rises to about 557 feet in height above the level of the sea, has been called the " Mountain of Heaven" (Himmdberg) : it is an Olympus, like that of Greece. With the exception of volcanic cones, there are but very few solitary mountains which rise by themselves in the midst of a level country. In almost all the countries of the world in those at least which possess an at all strongly-defined relief we meet with summits in considerable num- ber, either arranged in groups or in long ranges. Generally those moun- tains which are grouped in the form of a circle surround a more elevated central summit, and are also themselves surrounded by heights of a sec- ondary class, which abut upon lateral buttresses, and gradually sink down to the level of the plain surrounding them. As instances of this sort, we may mention the group of the Hartz Mountains in Germany, Mount Fer- rat in Piedmont, Sinai in the Arabian peninsula, the lofty cluster of the Sierra-Nevada of Santa Marta, which towers up to a height of 19,680 feet THE EARTH. in an insular tract bounded by the sea, the marshes, and the deep valleys of the Rio-Cesar and the Rancheria. The chains, properly so called, which are always distinguished by a considerable development of the length of the upheaved ground, sometimes also have a dominant peak as their cen- tral culmination, on each side of which the summits of the ridge become gradually lower ; but there is no range where this regular arrangement is carried out with any thing like geometrical regularity. The greater part of the mountainous upheavals are found to present a collection of clus- ters, chains, and subsidiary chains, variously grouped, in which a long pro- cess of study is required for duly ascertaining the direction of the ridges. They must not be looked upon as chains, but as systems of mountains. Owing to the diversified character exhibited by these numerous groups of heights, both in their geological origin, the composition of their rocks, the general direction of their axis, the position of their peaks, the vegeta- tion which clothes them, the light which illumines them, and the atmos- pheric agents which waste them, every mountain is distinguished from its neighbors by certain characteristics of special beauty. From this very fact, among all this assemblage of summits, every peak, whether charming or magnificent, which rears its ravined sides above the base of upheaval, assumes an appearance of independent vitality, as if it enjoyed a distinct individuality. The sight of these giants towering up over a wide-spread horizon exercises a perfect fascination over the minds of some men, and they are urged by a kind of instinct, often quite unreflecting, to bend their steps toward the mountain, and to scale its acclivities. Through either the grace or majesty of their form, their bold profile standing out sharply against the clear sky, the girdle of clouds rolling round their rocks and their forests, and their incessant variations of light and shade gleaming through their ravines and recesses, mountains seem to assume an appear- ance of personality, and one is almost tempted to look upon their rocky masses as beings endowed with all the powers of vitality. Every moun- tain, the summit of which in its bold tracery stands out clear from the rest of the mass, seems to be so thoroughly an individual by itself, that in most cases a name has been given to it, often the half-poetic title of some hero or god ; and, in every-day language, we constantly attribute to it even human qualities. Mountains, in fact, are truly enough geographical individualities, and, by the mere fact of their position in the midst of plains, they modify in a thousand ways the climates and all the other phe- nomena of the districts round them. Farther, do they not exhibit within a limited space an epitome of all the beauties of the earth ? Various de- grees of climate and zones of vegetation are arranged in gradation on their slopes ; there, too, we may embrace in one comprehensive glance the most diverse features of the earth's vitality cultivation, meadows, for- ests, ice, and snow ; there, at eventide, we may see the fading radiance of the sunlight illuming the lofty peaks, and endowing them with a marvel- ous effect of transparency, as if the enormous mass were but a rosy-col- ored drapery floating lightly in the clear sky. SA CRED MO UNTAINS.- CL UBS. 1 1 9 In days gone by the people used to worship mountains, or at least ven- erate them as the seats of their divinities. All round Merou, the proud throne of the gods of India, every stage of humanity may measure its prog- ress by the side of other sacred mountains where the lords of heaven were wont to assemble, and where all the great mythological epopees of the life of nations have been brought to pass. The peak of Lofeu in China, and the volcano of Fusi-Yama in Japan, are both sacred mountains. The Sa- manala, or Adam's Peak, whence can be enjoyed a view full of grandeur over the well- wooded valleys of Ceylon, is also reverenced as a holy spot; and on its loftiest peak stands a wooden temple, fastened down to the granite mass by chains imbedded in the fissures of the rock. This, ac- cording to the Mohammedan and Jewish legend, is the spot on which Adam, driven out of the earthly paradise, came to do penance for many a long century ; here, too, the divine Buddha left the mark of his footprint when he took flight to soar up into heaven. To the Armenians, Mount Ararat is no less sacred than the Samanala is to the Buddhists, or the peak which towers over the sources of the Ganges is to the Hindoos. It was on one of the rocks of the Caucasus that Prometheus was bound down in punishment for having stolen the fire of heaven. For many an age Mount Etna was the citadel of the Titans ; the three brows of Olympus, which proudly rear their dome-like forms, were the magnificent dwelling- places of the gods of Greece, and when a poet wished to invoke Apollo, he turned his supplicating glance to the summit of Parnassus. If the pol- ished Hellenes thus venerated the mountains of their native country, how great must be the adoration which would be paid by ignorant barbarians to the mountain which bore upon its terraced ledges their miserable huts, much as a forest-tree carries a bird's-nest on its spreading-branches ! The mountain which affords them shelter seems to them to reign far and wide over the earth, and in it they proudly recognize their father and their god. In our day we have certainly ceased to worship mountains ; but, at all events, those that know them best seem to love them with a perfect love.* To scale the loftiest summits has at the present time become a complete passion ; every year important ascents are made by thousands, independ- ently of the minor expeditions which travelers undertake to the summits of a secondary class and of easy access. Alpine Clubs, or societies of mountain-climbers, composed in great part of some of the most energetic and most intelligent savants of Western Europe, have devoted themselves to the task of vanquishing, one after another, every mountain-top which had been hitherto considered inaccessible ; they carry away from them a stone as an emblem of their triumph, and they leave on them a thermom- eter, or other scientific instrument, in order to facilitate the investigations of any bold climber who may follow them. The Alpine Clubs have drawn up a list of all the peaks which are still rebellious, and have fully discussed the means of subduing them; they have also investigated multitudes of ascents, and, by their charts, their descriptions, and their numerous meet- * Vide Mountaineerin y, by Tyndall, and the various publications of the Alpine Clubs. 120 ings, they have largely contributed in throwing light on the architecture of the Alps. The collected traveling journals of the members of these va- rious clubs are unquestionably the source from which the most valuable information may be derived as to the rocks and glaciers of the loftiest mountaihs in Europe, and they also give us the most interesting narratives of difficult ascents. In the far-distant future, when not only the Alps, but also all the other accessible summits in the world, have become perfectly familiar, the records of the Alpine Clubs will form the Iliad of mountain- climbers ; and people will talk of the exploits of a Tyndall, a Tuckett, a Coaz, a Theobald, and of other heroes of this grand epopee of Alpine con- quest, just as the exploits of noted warriors were once the subjects of song. Whence proceeds the deep-seated joy which is felt in scaling a lofty summit ? In the first place, there is a great physical pleasure in breath- ing the fresh keen air, which has never been vitiated by the impure ema- nations of the plains. Man feels renovated by merely tasting this atmos- phere of life ; the higher he mounts up, the more rarefied becomes the air ; deeper inspirations are necessary to fill the lungs, the chest is swelled, the muscles are at full stretch, a cheerful flow of spirits pervades the mind. The pedestrian who scales a mountain feels himself his own master, and responsible for his own life ; he is not delivered over to the capriciousness of the elements, like the navigator who trusts his fortunes to the sea ; much less is he like the railway traveler a mere human package paid for, ticketed, and put in a carriage, and then dispatched at a fixed time, under the surveillance of employes in uniform. On alighting, he regains the use of his limbs and his liberty. His eye enables him to avoid the stones that lie in his path, to measure the depths of precipices, and to dis- cover the rocky projections and clefts which will facilitate the escalade of the cliffs. The force and elasticity of his muscles will enable him to leap over safely the deepest crevasses, to maintain his footing on the steep- est inclines, and to raise himself, step by step, up the most difficult pas- sages. On a thousand occasions during the ascent of a steep mountain, he must fully recognize that he is running a fearful danger should he ei- ther chance to lose his balance, or allow a sensation of giddiness to dim his sight, even for an instant, or should his limbs refuse their wonted serv- ice. This consciousness of peril, joined to the pleasurable knowledge of his activity and health, is the very sensation which, in the mind of the pedestrian, doubles his feeling of safety. With what joy does he after- ward relate the slightest incident of the ascent the stones rolling down the mountain slope, and plunging into the torrent beneath with a dead- ened sound ; the root to which he hung suspended when he scaled a wall of rock ; the streamlet of snow-water at which he quenched his thirst ; the first glacier crevasse over the brink of which he stooped, and yet dared to leap ; the long and weary slope up which he so painfully climbed, with his legs buried knee-deep in the snow ; finally, the culminating peak from which he saw, spreading away into the mist of the horizon, the immense panorama of mountain, valley, and plain. When the traveler looks back THE ASCENT OF MOUNTAINS. 121 from afar upon the summit which he conquered at the cost of so much exertion, it is with perfect rapture that he sees it again, or traces out with his glance the path that he followed, from the valleys at its base to its snow-clad peak. The mountain seems actually to look down and smile upon him from afar ; for him alone its snow glitters, and the fading sun- light illumines it with his last ray. With regard to the intellectual pleasure which mountain climbing af- fords, which, however, is intimately bound up with the material joys of the ascent, it is proportionately greater as the ftiind is more expanded, and the various phenomena of nature have been more successfully studied. The destructive action of water and snow is fully grasped by the scientific traveler ; he inspects the movement of the glaciers, and the rolling rocks or boulders making their way from the summits to the plain ; he traces out the enormous horizontal or inclined strata; he perceives the masses of granite upheaving the beds ; then, when he at last stands on some lofty peak, he can contemplate in its entirety the mountain edifice, with its ra- vines and its spurs, its snows, its forests, and its meadows. The hollows and the valleys which the ice, the water, and the tempest have carved in the immense relief, are clearly defined, and the whole labor accomplished during thousands of centuries by all the geological agents is plainly seen. By going to the origin of the mountains themselves, a surer judgment can be passed on the various hypotheses of savants as to the rupture of the earth's crust, the displacement of strata, and the eruption of granite or porphyry. And besides, without alluding to that meaner impulse of van- ity which instigates a certain number of men to distinguish themselves as mountain-climbers, there is a sentiment of natural pride excited when we compare our own littleness with the grandeur of the natural phenomena which surrounds us. The torrent, the rocks, the avalanches, and the gla- ciers, all remind man of his own weakness; but, by a natural reaction, his intellect and his will rise up in opposition to every obstacle. He takes a pleasure in conquering the mountain which seems to brave him, and in proclaiming himself the victor over the formidable peak, the first glance at which had filled his mind with a kind of religious awe. Owing to the increasing facilities of communication, and to the love of nature so much developed in modern society owing, too, to the example which has been set by bold mountain-climbers, the elevated regions of cen- tral Europe, where once but few travelers cared to venture, on account of the want of roads, the steepness of the inclines, the danger from avalanch- es, and the dread of the unknown, are nowadays become the great centre of popular attraction. These very mountains, so difficult of access, which tower up as a rampart between the north and south of Europe, have caused Switzerland to become the great rendezvous of nations ; and, during the season for traveling, bathing, and mountain-climbing, it enjoys a floating population of some hundreds of thousands a number which increases ev- ery year. Vevay, Lucerne, and Interlacken are like sacred cities to which every lover of nature must pay his pilgrimage. 122 THf: K CHAPTER XX. VARIOUS FORMS OF MOUNTAINS. POVERTY OF POLISHED LANGUAGES IN DESCRIBING THEIR APPEARANCE. RICHNESS IN THIS RESPECT OF THE SPANISH LANGUAGE AND THE ALPINE AND PYRENEAN PATOIS. THE NU- MEROUS PROVINCIAL TERMS EMPLOYED FOR VARIOUS SHAPES OF HILLS AND MOUNTAINS. MOUNTAINS vary singularly in their shapes, according to their height, their geological constitution, and the force and direction of the meteoric agencies that assail them ; so vast is the multitude of causes, in great part unknown, which have labored either in concert or in succession in carving out these projections of the earth, that every peak has its own special as- pect. It would thus seem almost necessary to employ a particular desig- nation, if not for every mountain, at least for each of the types to which we may be able to reduce the numerous shapes of the earth's protuber- ances. Unfortunately, our languages manifest a remarkable poverty in words well fitted to bring before the mind's eye the precise outlines of any particular summit. Whatever may be the appearance of two or more mountains and the geological composition of their rocks, the geographer and the author are compelled to avail themselves of the same terms in designating them, unless, indeed, they have recourse to a long description in cases where a single word ought to suffice. They are, in fact, obliged to make use of words altogether unsuitable, such as the term " chain," which is invariably applied to ranges of hills. The cause for this penury in exact geographical terms may be very eas- ily understood. Most of the cities in which the various languages were gradually refined are situated on very level ground, or among hills very slightly undulated. There can be no doubt but that the French nomen- clature in respect to mountains would have been much richer and more exact if, from Blois, Paris, and Orleans, lofty peaks had been visible in the horizon. The richness and the propriety of the terms employed by the southern Germans, the Spaniards, and Italians, when they wish to describe in one word various kinds of hills and mountains, are certainly derived from the fact that these nations have lived and formed their language in full view of lofty summits. M. de Humboldt, in his Tableau de la Nature, quotes the following terms employed by Castilian authors : pico,pioacho, mogote, cucurucho, espigon, loma, tendida, mesa,panecillo,farallon, tablon, pena, penon, penasco, penoleria, roca partida, laja, cerro, sierra, serrania, cordillera, monte, montana, montanuela, altos, malpais, reventazon, biifa, etc. all of which serve to designate the diverse forms of mountains, or THE FOBXS OF MOUNTAINS. 123 chains of mountains. It would be easy to still further enlarge this long list of names. The inhabitants of the Pyrenees and French Alps use in their dialects a great variety of expressions, each of which is especially devoted to some particular type of mountain, and consequently serves to depict to the mind's eye a perfectly different form. Many of these names, inherited from the ancient Celtic and Iberian dialects, well deserve to be admitted into the French written language, the more so that they are in customary use by all the French mountaineers from the sources of the Rhone to the Pyrenees. In the Alps of Queyras and Viso, lofty peaks with escarped sides which tower over all the neighboring summits are known by the name of brie or brec. Of this kind is the beautiful pyramid-shaped mountain of Cham- beyron (11,112 feet in height), which rises to the south of the valley of the Ubaye, in the midst of a circle of pointed summits of a less height. Fig. 20. " Brie," or Crest, of Monte Viso, seen from the East ; after Tnckett. Of this kind, too, is the Viso itself, at least on its northern face, for the other side ofcthe mountain presents too regular a slope to entitle it to the name of brie. Above the upper valley of the Guil, black cliffs rise up, fur- rowed by avalanches, then an enormous tower-like mass with perpendicu- lar sides, and at last the truncated peak crowned with its thick covering of snow. The apparently inaccessible terrace which so proudly overtops the Col de Valante, the secondary summits of Visoletto, and the rocks that have toppled down from the heights this is the brie of the Viso. To any mountaineer who has never set eyes upon this proud summit, this term will convey far more meaning than the vague designation of "mountain." In the same way, the old term pelve, now disused, which, however, we may still recognize in the names of the Grand-Pelvoux, the Palavas, the Pclvas, the Pelvo, and several other mountains in Dauphine, at once depicted to the mind's eye an enormous cone commanding all the neighboring sum- mits. The tncs and trues of the Pyrenees are also summits of lofty elevation, 124: THE EARTH. but not the highest points in the ridge ; they get this name on account of the bold outline of their upper cliffs, and not from their pre-eminence over the mountain-tops round them. As instances of these tucs we may cite those of Maupas, Montarque, and Mauberme, in the Central Pyrenees. The tuque, the truque, the tusse, and the tausse, all specify mountains with wider bases and more gentle slopes than those of the tuc / but now- adays these picturesque designations have been gradually displaced by the more general term of pic, which is applied without distinction to all pointed and almost inaccessible summits. It is a curious fact that the downs on the Atlantic sea-coast, which by the inhabitants of the intermin- able level of the French Landes are looked upon as real mountains, still retain this provincial name of tucs, although it has fallen into disuse for the giants of the Pyrenees. A few miles from Arcachon, a down of about 260 feet high has made such an impression on the imagination of the in- habitants of the Landes that, by an emphatic pleonasm, they have styled it the True de la Truque. Those very steep and pointed summits, which are generally designated by the exaggerated but rather striking name of aiguilles (needles), have, in most cases, received from the natives of the district much less ambitious appellations, the most common of which is pic. The Pyrenees also include, among some of their highest mountains, several piques / as the Pique Longue duVignemale (11,049 feet high) and the Pique d'Estats (10,104 feet high). The enormous cluster of the Alps of Pelvoux has for its cul- minating summit a pointed peak 13,461 feet high, which was once called the Barre des Ecrins. But in Savoy and French Switzerland summits of this form are principally known by the name of dent (tooth), almost sy- nonymous with the designation horn, which is used in Central Switzerland, starting from Mont Cervin or the Matterhorn,* that boldly modeled mass which Byron looked upon as his ideal type of a mountain. The dents are generally less pointed than the aiguilles, and are rounded off toward the Fig. 27. The Pic du Midi d'Ossau, seen from the northeast ; after V. Petit. * Coaz, Alpenclub, vol. ii. THE FORMS OF MOUNTAINS. 125 summit ; but the transitions presented by the mountain outlines are so gradual that it is difficult to establish any very strict classification. In consequence, great confusion prevails in the nomenclature, and the greater part of the summits in the Swiss Alps bear indiscriminately the name of horn. In the Tyrol, too, the term kogel (kegel, skittle) is applied to moun- tains of the most diversified shapes. The four-sided pyramids which spring up so numerously in some moun- tain ridges are called the caires, queyres, esquerras, or quairats of the Alps and Pyrenees. Certain peaks of this kind have given a name to an entire cluster of the French Alps that of Queyras. If the point of the pyramid Pig. 28. Einshorn de Splegen ; after Coaz. is replaced by an elongated ridge, the mountain-top then becomes a tail- lante (edge). If, on the contrary, the summit terminates in a cubical mass, it will be designated by the name tour (tower). Calcareous mountain re- gions are the localities where we chiefly find those enormous quadrangu- lar layers which seem as if they had been built in by the Titans. Few spectacles in Europe are equal in beauty to that afforded by a view from the Pic de Bergons over the limestone region of the Central Pyrenees, with its perpendicular walls, its snow-covered terraces, its tower-like heights, appearing to the glance almost inaccessible, and its carved-out gaps, like openings purposely made between battlements. A similar appearance is presented by the calcareous eminences of La Clape, near Narbonne, and by the sandstone mountains in several districts. The faces of these per- pendicularly hewn peaks are often designated by the very appropriate names parois (side -walls), or pareds, murs (walls), or muraittes (ram- parts). Tower-like peaks of comparatively smaller dimensions, which aopear as if they were edifices built on the mountain-tops, have received in the Pyr- enees the name ofptne, or bougn. The ttte (head) is a summit with regu- lar and gently inclined terminal slopes, springing up from a mass furnished Avith- steeper sides. If the roundness of the summit is developed in the form of a cupola, the mountain is then a sown (summit), or a ddme, as Mont Blanc, the giant of Europe. In German Switzerland mountains with flattened summits, as, for instance, the Rhigi, are known by the name of kiilm. In the Vosges the battons, and in the Black Forest the boelchen, 126 THE EARTH. . Fig. 29. The Gross-Glockner ; after Payer. represent mountains terminating in large summits, which seem blown out in the shape of a bladder. The bases of these mountains are generally very wide, and the slopes gently inclined. Pig. 30. L'Esquerra des Eaux-Bonnes, seen from the southwest ; after V. Petit. The names applied to summits of a secondary class are no less numerous than those given to the principal mountain-tops. A spur connected with a rounded summit frequently receives in the Pyrenees the appellation of turon, or turonnet ; and an escarped projection, extending with saw-like indentations (kamm, in German), takes the name of serre, or some deriva- tive of it, such as sarrat or serr&re ; it is the Spanish sierra in miniature. laiHon deCavanie Soum Pig. 31. The Mountains of Gavarnle, seen from the north ; after V. Petit NAMES OF MOUNTAIN PEAKS. 127 A motte (muotta in the Orisons) is a mountain almost isolated from the rest of the group, or even rising in the midst of a valley in an alluvial dis- trict. Finally, some mountain names point out the nature of their rocks or their vegetation. The Lauzet or Lauzieres mountains are composed of slaty rocks, and in the Pyrenees the numerous peaks called estibbre, or pradflre, are completely clothed with verdure. The vfordspuy,pui(/,pey, pech, or puck, are general terms which are applied indiscriminately to all the prominences either of mountain ridges or of the plain, from the Puig de Carlitte (9563 feet high) down to the smallest elevations. It is re- markable that the words which, in our more classical language, are most used to denote elevations of the surface, namely, montagne (mountain) and coUine (hill), are taken in quite a different acceptation in the idioms of the Fig. 32. Pine : Plz & Lun de Guscha ; after Coaz. inhabitants of the Pyrenees and Alps. "JfontaffntP means only a greater or less extent of pasture-land, and the term " colline" applies to the dales lying between two mountains. In addition to the names employed by the inhabitants of the Alps and Fig. 83. Tute: Wallenstock de Wolfenschiessen ; after Coaz. Pyrenees to specify various types of mountains, we must mention some which are made use of in the French tropical colonies, one or two of which, such as morne and piton, have found their way into literary language. In volcanic countries, the mountains of igneous origin,* with summits round- * Vide the chapter on "Volcanoes." 128 ed like a cupola, like the Puy de Dome, or pierced with a ci'ater like the Puy de Sancy, are almost all designated by local terms of very striking aptitude ; but the greater part of these words remain unknown to fame. Nothing can prove more decisively how much modern communities still adopt as their ideal a life altogether artificial, and without sympathy with nature. Happily, a kind of reaction is steadily setting in. Attracted by the beauty of the summits which once startled them, crowds of travelers now find their way to the mountains ; they learn to know them, to love them, and to describe them. Thus languages are enriched, and science gains a further store of information. INEQUALITIES AND DEPRESSIONS OF MOUNTAINS, 129 CHAPTER XXL INEQUALITIES AND DEPRESSIONS IN THE VERTICAL OUTLINE OF MOUNTAINS. ORIGIN OF VALLEYS, GORGES, AND OTHER DEPRESSIONS. LONGITUDI- NAL VALLEYS. TRANSVERSE VALLEYS. WINDING VALLEYS WITH PAR- ALLEL SIDES. VALLEYS WITH DEFILES AND GRADATIONS OF LEVELS. CLUSES AND CANONS. GENERAL ARRANGEMENT OF VALLEYS. AMPHI- THEATRES. THE OULES OF THE PYRENEES. MERE height constitutes but the most inconsiderable element in the beauty of mountains: the majesty as woM as grace of their appearance is chiefly due to the distortions and dip of their strata, the circular dells and glens which are hollowed out upon their slopes, their yawning de- files, their abrupt precipices, and, finally, the broad valleys stretched out at the base of the colossus, which, by the contrast that they afford, enable us the better to appreciate the magnificence of its proportions. Owing to the variety of outline and scenery caused by all these successive depres- sions, the mountain has assumed an aspect of grandeur and life which it must originally have wanted. Like a block of marble transfigured by the sculptor's hand, the mighty mass, once a monotonous plateau or mere dome of rock, has been gradually modified by meteoric agents incessantly affect- ing it, and has been converted into one of those mountains, in the proud profile of which our forefathers recognized the face of a god. We may easily figure to ourselves all the changes which have been effected in the form of mountains by the various depressions of the soil, if we visit cer- tain groups of heights, one side of which retains its old plateau-like as- pect, while the other, sinking abruptly toward the plain, has all the ap- pearance of an actual escarpment. There are many instances of this kind in the region of the central plateau of France, of Auvergne, the Jura Moun- tains, the Rauhe Alp in Wtirtemberg, and in Bavaria. On one side stretch long stony slopes ; the fields are all unfertile, and the prospect is uniform, and devoid both of movement and life. Then, all of a sudden, as we attain the edge of the ridge, we see opening out below us a succession of decliv- ities : hollows filled with water appear between the escarpments and the fallen rocks ; farther down in the increasingly misty depths we catch sight of terraces and ledges crowned with firs, and trickling rivulets glittering in the dells at the base of the cliffs. Far beneath our feet, at the very bottom of the gulf, lies the peaceful valley, like another world, with its winding river, its fields, its vineyards, its woods, and its busy towns. What, then, is the origin of the valleys, gorges, ravines, and all the oth- er depressions which we meet with in the elevated regions of the earth? This is a question which must be considered identical with an inquiry into I 130 THE EARTH. the origin of the mountains themselves, a point on which geologists are as yet very far from having come to any agreement. We can only state, in a general way, that some of these depressions are primitive features of the ancient conformation of the mountains, and owe their origin either to dis- turbances of the strata or faults in the rocks ; others have been gradually eaten away by time, or hollowed out by snow, ice, rain, and water-courses. Those who try to reconstruct in imagination mountain systems as they must have existed in preceding ages assert with certainty that some val- leys were contemporaneous with the mountain groups which surround them. They also feel warranted in boldly declaring that this glen or that ravine was cut out by meteoric agencies ; but, as regards a considerable number of the most important features of the mountain, doubt still con- tinues to weigh upon their minds. At all events, when extensive longitudinal valleys are included between two mountain chains which ai^parallel to each other, but different in age and geological formation, these valleys are indisputably of primitive ori- gin ; they are the hollow of the terrestrial crust formed naturally by the slopes of the two acclivities which rise on the right and left. The whole length of the valley itself must have been upheaved by the forces which were at work on both sides of it under the adjacent masses, and it has also been variously modified during the lapse of ages by the water-courses which have traversed it. In one place its hollows have been filled up, in another its rocks have been carried away the water having deepened it on one side to build it up on the other. But, notwithstanding all its modifications, the geologist none the less recognizes the valley to have been furrowed out in the same age as that in which the neighboring high mountain summits were formed. Thus the great depression of the lower Valais, which divides the peaks of the Finsteraarhorn and the Jungfrau from those of Monte Rosa and Mont Blanc, is certainly a primitive valley in all its essential features. For still stronger reasons, the vast cavity of the Lake of Geneva, which bends round between the Alps and the Jura Mountains, the lowest depths of which are but little above the level of the sea, must have had an existence at least coeval with all the mountains of Switzerland. Certain transverse valleys, which break abruptly through a mountain chain, and, as it were, cut it in two, must also belong at least most of them to the primitive mountain conformation. Of this kind is the charm- ing valley of Engadine, the slope of which rises almost imperceptibly up to the foot of the Maloggia (5941 feet), above which towers, 7352 feet higher, the summit of the Bernina. In the New Zealand Alps, Julius Haast dis- covered a still more astonishing transverse valley, as the foot of it, com- manded on both sides by peaks measuring 7800 and 9800 feet in height, was only at an altitude of 1600 feet, scarcely one fifth of the height of the chain. Finally, in all the mountain ranges composed of volcanic cones upheaved at intervals along the same fissure in the earth, large transverse valleys, which are, in reality, the remains of the former plain, are found in ORIGIN OF VALLEYS. 131 great numbers. This may be especially remarked in Java and in the Chil- ian Andes.* With regard to the ordinary transverse valleys which owe their origin to some depression in the face of the mountain, and merge into a larger valley or into a plain, being connected also with other glens which open out right and left into the thickness of the mountain, it is always difficult, and often impossible, to distinguish between the effects which must be re- ferred to the action of water and those which are to be ascribed to other causes which have co-operated in the formation of these gigantic furrows. Even in those spots where, on the two sides of the valley, the layers of rock all perfectly correspond, we are unable to tell whether the original fissure was not produced by a natural contraction of the beds, or by some sudden movement of the crust. It is, however, quite sufficient to note the geological labor accomplished every year by the torrent roaring along in its deep bed, in order to be convinced how mighty its action must have been during an immense cycle of centuries.f Buffon has established the fact that a great many winding mountain valleys are, from their origin to their outlet, walled in on each side by parallel escarpments. The projections on the cliff on one face correspond Fig. 84. Channel of the Bosphorua. * Vide the chapters devoted to "Rivers" and "Volcanoes. 1 t Vide the chapter on " Rivers." 132 THE EARTH. with the hollows on the other; the projecting and the re-entering angles alternate on either side, so that if the two opposite cliffs were suddenly brought close together, their windings and irregularities would mutually coincide. Other valleys, however, present an altogether different kind of formation : their sides, instead of running regularly in parallel curves, are in some places very wide apart, in others very close together. They thus follow a kind of rhythm very different to that of the first type of valley, and produce a succession of rounded basins, separated from each other by narrow passes. In the Pyrenees, the Jura, and the calcareous regions of the Alps, valleys of this kind are very numerous ; but we more often observe a combination of the two modes of formation. At certain points of their course, valleys run tortuously between parallel sides ; at others, they form successive basins. Thus the upper portion of the long channel of the Bosphorus, which may be looked upon as a valley, although now invaded by the waters of the sea, presents several stretches of water almost like lakes, while farther down the channel the indentations of the opposite banks are so regularly arranged that they might almost be fitted one into the other. The variations in the shape of valleys may be explained by the different natures of the rocks which the waters have had to hollow out. Wherever the material operated upon gravel, sandstone, granites, schists, or lavas are of an analogous composition, and thus every where present an equal amount of resistance to the action of the water, the latter is able to pur- sue its normal movement, and adopts a meandering course, which ap- proaches each bank in turn, thus communicating the windings of its bed to the valley it is hollowing out. On the contrary, when the rocks consist of strata of unequal hardness, or are traversed by obstructing walls, the water is necessarily compelled to spread out into a lake-like accumulation, in the mean time eating away the banks in a lateral direction, until the barrier being at last penetrated the sheet of water is poured down in a torrent to some lower level. In this way there has been formed, during a course of ages, a series of basins one above the other, some of which are still partially tilled with water, others entirely empty, all being linked to- gether by narrow defiles, through which pours the mountain torrent.* In- stances of a series of this kind of small basins of verdure, arranged like a succession of steps, are very numerous in all mountainous regions. We may mention the valley of Oo in the Pyrenees, and in the Alps the lofty valley of Isere, in which old lake-basins and gloomy gorges alternate with great regularity. The various channels or cuts which unite the various basins, and through which are precipitated the impetuous flood of the mountain torrent, are called in the Jura by the name of cluses, and in the Alps are designated as clus ; but in these countries they do not limit themselves to cutting through mere barriers of rock they pierce even through mountain chains. The basins of the Var and its water-courses are very rich in defiles of this kind enormous incisions carried right through the thickness of the lime- * Vide the chapters devoted to " Rivers" and " Lakes." CLUSES AND CANONS. 133 stone ramparts. Among these clus there arMome which are really formi- dable those of the Loup, between Grasse and Nice ; those of Saint Auban and the Echaudan, and others which afford a passage to the waters of the Vur ffid its tributaries. These are tremendous defiles; each side of the torrent is walled in with perpendicular or overhanging rocks several hun- dred yards high, and the summit of the escarpment is generally crowned with the picturesque walls of some ancient village. These narrow gorges, through which it is often found difficult to carry a road or even a path, must be classed among the most curious sights in France. The view of these gloomy passes is all the more striking as one comes upon them im- mediately after traveling over the fertile plains of the Mediterranean shores, studded with villas, gardens, and olive-groves. The clus of the Aube and its tributaries, those of the Upper Dordogne, the Tarn, and the Lot, are also formidable in their appearance ; but the most remarkable in the world are probably the canons of Mexico, Texas, and the Rocky Moun- tains, in which we see a river, almost without water, flowing at a depth of several thousand feet between perpendicular walls. According to New- berry, the geologist, the great canon of the Colorado is not less than 298 miles in length, and in several places its perpendicular sides rise to a height of 3300, 5000, and 60OT feet. In accordance with the size of the mountains, the nature of their rocks, the abundance of their snow and rainfall, the elevated valleys exhibit the most astonishing diversity of shape and aspect. In clusters of mountains where the torrents rush down to the plain over a very steep bed, and through sharp windings hollowed out in the body of the rocks, most of the tributary valleys, opening right and left of the principal ravine, are constituted altogether like the latter, except perhaps that they are still more winding, and the water in them runs more rapidly ; these, too, re- ceive the streams of smaller glens which are still steeper than themselves. Generally speaking, every tributary vale unites with the central valley at the precise spot where the latter presents the convex side of its windings. The result is, that valleys and their tributaries, as a whole, exhibit an ar- rangement which is very similar to that of a tree with a succession of branches. In calcareous mountains, Avhere the torrents run through a se- ries of basins one above the other, and communicate by means of cluses, the system of valleys shows a more rudimentary arrangement. In this case, each basin is also the point of junction for two lateral valleys oppo- site to each other, and ascending in a straight line toward the heights of the mountain. The ensemble of all these symmetrical depressions reminds one of the trees in gardens which are trained as espaliers, the opposite branches of which creep along their supp'orters in parallel lines. With regard to the dales, glens, ravines, and all the smaller depressions of a mountain, from those deep gashes which legends tell us were made by some giant's sword, down to those gentle and graceful undulations which resemble the folds of drapery, their variety is so endless that it would be impossible to classify them in any systematic order. Each mountain, having its own peculiar individuality, differs in the character THE EARTH. of its dales and glens, whicn^oo, have each their special aspect of majesty or grace. Almost every valley commences with a kind of amphitheatre of greater or less extent, hollowed out of the thickness of the central mass of the chain, and formed by the union of the ravines and gullies of the surround- ing mountains. The amphitheatres of a circular or elliptical form, which we come upon all on a sudden after having wandered along winding val- leys or on the sides of perpendicular cliffs, form a beautiful spectacle in all their calm and peaceful grandeur. We must visit the calcareous moun- Fig. 35. Circular Valley of Ourdinse. tain chains, such as the Central Pyrenees, with their perpendicular walls and deeply-hollowed basins, if we wish to see these wonderful amphithe- atres in full perfection. The most remarkable, on account of their vast dimensions and the snow-clad terraces which surround them, are the oules (boilers) of Gavarnie, Estaube, and Troumouse, which the slow action of centuries has hollowed out in the calcareous sides of the mountains of Mai-bore". Undulating tracts of pasture-land furrowed by torrents, pro- digious walls rising to 1500, or even 2000 or 3000 feet in almost perpen- dicular height, gigantic steps on which whole nations might find room to sit, cascades which either spread out over the precipice and float away in a diaphanous veil of mist or rush down into the valley like an avalanche, the high summits, glittering with unstained snow, which rear their heads high above the wall of cliffs, as if to look over into the inclosure all these features we find combined far in the recesses of these solitary mountains, so as to render the Pyrenean amphitheatre one of the grandest tableaux in Europe. DEPRESSIONS IN MOUNTAIN RIDQE8. 135 CHAPTER XXH DEPRESSIONS IN MOUNTAIN EIDGES. DIVERSITY IN THE FORM OF PASSES (COLS). RELATION BETWEEN THE RESPECTIVE ALTITUDES OF SUMMITS AND PASSES. LAW OF DEBOUCHMENTS. REAL AND IDEAL SLOPES OF MOUNTAINS. ESTIMATED SOLID CONTENTS OF MOUNTAIN GROUPS. MOUNTAIN necks or passes (cols) that is, the hollows or depressions of the ridge or summit, are, like the valleys, to be attributed to diverse causes. Some are primitive features produced by the disturbance or rup- ture of the upheaved beds ; others are excavations of more recent origin, and are due to meteoric action and the crumbling away of the mountain mass. The variety of causes which have combined in the formation of these depressions sunk into the ridges, the varying force of resistance offered-by different rocks, and all the events of the incessant conflict carried on for centuries between the mountain summits and the air which surrounds them, have combined in giving to these passes the greatest diversity of aspect. Some are mere turfy or snow-clad bands, between two rounded brows ; others are themselves narrow ridges of sharp-edged rocks, com- manded on each side by pyramidal masses ; these are fourches (forks) and hourquettes of the Pyrenees. Others, again, are deep fissures carved out between perpendicular walls ; some, even, like huge gateways opening be- tween the valleys from opposite sides, are actual breaches, which we should be inclined to think had been effected in the living rock by the processes of sapping and mining. It has often been asked if there is not a constant analogy between the altitude of summits and that of the passes which indent their ridges. It might easily be foreseen that, as the mountains had been diversely worn away by the effects of storms, snows, and water, the depressions of the passes, which are the result of these long-protracted erosions, must be looked for at various elevations in the different groups. This, too, has been proved by M.William Huber, as the result of patient comparative in- vestigation. Thus, in the group of Mont Blanc, the proportion between the mean height of the summits and that of the passes is as 1'28 to 1 ; in the Monte Rosa group it is as 1'43 to 1 ; in the Jungfrau it is as 1*62 to 1. The relation between the highest summit and the lowest pass also differs very considerably in different systems of mountains. In the Todi group this proportion is as 2*68 to 1 ; it is only as 1'53 to 1 in the Tessinese Alps.* In a general way, the altitude of the widest and deepest passes of the Alps may be estimated at one half of the height of the surrounding * William Huber, Bulletin de la Societc de Geoyraphie, February, March, 1866. 136 THE EARTH. summits, while in the Pyrenees it is about two thirds. The more consid- erable depressions which divide the Alps into distinct masses, toward which tend a quantity of secondary passes, give, by the contrast which they afford, a peculiar character of grandeur and variety to the orographic system of Central Europe. The Pyrenees are much more uniform than the Alps in their architecture, and, in consequence of the relative heights of their passes, form one of the most beautiful types of the Cordillera which can be found upon the earth. It is a remarkable fact, brought to light by M. Huber, that the passes which are hollowed out the most deeply in the mountain mass debouch precisely in front of the most elevated peaks of the opposite group. Thus the pass of the Simplon (6594 feet) opens directly in front of the group of the Jungfrau (13,671 feet); and the Gemmi (7161 feet), the least ele- vated pass in the Bernese Alps, debouches in the valley of the Rhone, di- rectly in front of Monte Rosa (15,216 feet). In the same way, the pass of Lukmanier (6289 feet) faces the summit of Todi, and the pass of the Julier lies in the axis of the great Bernina group. It may, in fact, be no- ticed with regard to nearly all the principal passes that, on the other side of the valley, they are fronted by one of the highest mountains of the divergent chains which radiate round the central nucleus of the St. Gothard. To what cause, then, are we to attribute this general situation of the principal passes to which M. Huber has given the name of the " law of de- bouchments?" It may be explained in great part by the fact that the most elevated mountainous masses generally rest on the widest and most solid foundations; the torrents, consequently, pass round their bases, while on the opposite side the phenomenon of erosion becomes more active, and gorges are more and more hollowed out in the thickness of the chain. During the lapse of centuries, the differences in vertical outline between the escarpments of the two chains become very distinctly prominent. In the Pyrenees, this relation of summits and passes in two different moun- tain ridges can only be pointed out in a few instances, on account of the general simplicity of the chain and the comparative height of the passes. Nevertheless, here and there we find some unquestionable examples of this law ; thus the entrance of Venasque opens exactly in front of the Maladetta, and the deep depression of the pass of Puy Moren is opposite to the summits of the Fontargente group. Looked at in an entirely general point of view, this " law of debouch- ments" is nothing more than a particular instance of the law formerly pointed out by Buffon as to the serpentine form which is presented by all normal valleys. The salient angle of a chain corresponds to a hollow in the re-entering angle of the opposite chain, the summit rises opposite to a depression, and groups of very elevated peaks tally with some pass more depressed than any of the others. Now, if the curves of a valley render it very probable that an indentation of the ridge answers to the convex portion of the stream, we may assert almost to a certainty that the line of SUMMITS AND PASSES. 137 junction uniting two sharp bends of streams which are separated by a chain of mountains will pass through a deep deprasion of the ridge. The comparative studies which have been madei>y various geogrtphers, since Humboldt, as to the vertical outline of mountain chains, have been directed not only to the comparative height of passes and summits, but also to the mean inclination of mountain sides. The real slope of a moun- tain ridge is, as is well known, the tortuous and variously inclined line which is followed by a streamlet of water in its descent from the ridge to the plain below; but it is not this more or less regular curve which is constituted the actual side of the chain. It is, in fact, an ideal line pass- ing through the secondary summits, and over the passes and dales, and connecting the summits of the principal ridge with the base of the incip- ient acclivities in the adjacent plains. This ideal line is never so much inclined to the horizon as the appearance of the slopes and the sudden contrast between the heights and the valleys would lead one to expect ; painters, too, seem very naturally to exaggerate by one third, or even by half, the real relief of a mountain outline, so as to give the effect which they truly enough produce on the eye of the spectator. On the French side, the Jura the general incline of which is, however, very gentle from the crest of Mont Tendre to the town of Arbois, presents a total de- clivity of only 4288 feet that is, a gradient of about 2*6 in 100, which is but a moderate slope even for a coach road. The general inclination of the Pyrenees is much more rapid, since, from the summit of Mont Perdu to the plain of Tarbes a distance of thirty-six miles as the crow flies the declivity is 9980 feet, or a gradient of 5 '2 in 100. But even this is a much less rise than that of some of the high hills on mountain roads ; it is, too, very inferior to that of the railroad which winds in zigzags up the sides of Mont Cenis. The most abruptly inclined mountain side which can be found in Europe is that face of the Alps which is turned toward the plains of Piedmont and Lombardy ; from the summit of Monte Rosa to the district of Ivree, the mean slope exceeds 10 yards in 100, which to the eye produces the effect of an immense Babel of towers and pyramids placed one above another. Certain mountain 'groups in the New World have still steeper sides ; thus the Silla of Caraccas turns toward the Ca- ribbean Sea a real wall rising at an angle of 54 to the horizon ; this would be a cliff of an all but inaccessible character if it were not possible to scale it by zigzag paths through the gorges and ravines. It must, how- ever, be understood that the declivity of mountain sides is not exactly the same in every part of the mountain groups ; although very steep at one point, it may be tolerably slight at another, in accordance with the varie- ties of heights, rocks, and climates. The mean declivity is difficult enough to ascertain, on account of the great diversity of slope in different places ; but the total volume of a chain of mountains is a much more difficult thing still to find out, even approximately. Humboldt, taking as his basis the scientific data (which are still too incomplete) as to the heights of plateaux and mountains in 138 THE EARTH. various continents, has endeavored to estimate the cubical mass of sev- eral great mountain chakis. According to his calculations, the total mass of the Pyrenees, spread uniformly over the whole surface of France, would only raise the soil about 10 feet.* In like manner, if all the materials of the Alpine masses were equally distributed over the continent of Europe, they would only augment its height about 2l feet.f It would be very useful to renew these investigations, so as to arrive at results which would be more and more exact, as the orographical outline becomes better known. The most perfect calculation of this kind which has ever been made is probably that of Sonklar as to a portion of the Tyrolese Alps known un- der the name of the Oetzthal group. This mass would be represented by a solid body having a uniform height of 8333 feet, of which 5314 feet would be for the plateau or pedestal of the mountainous region, and 3019 feet would be for the whole of the peaks. J This mass, if spread over the whole of Europe, would only represent an increase of two feet in the height of the continent. We thus perceive that as regards the question of bulk, mountain chains are much less important than plateaux like Spain or Bavaria. * In Otte's translation of Humboldt's Cosmos, vol. i., p. 305, it is given as 115 feet. ED. t Cosmos, Faye's translation, vol. i., p. 353. J Sonklar, (Etzthaler Gebirgsgruppe. LAW OF MOUNTAIN CHAINS. CHAPTER XXHL HYPOTHESES AS TO THE GENERAL LAWS OP MOUNTAIN CHAINS. M. ELIE DE BEAUMONT'S THEORY OF PARALLEL UPHEAVALS. CHAIN OP THE PYRE- NEES TAKEN AS A TYPE OF THE CORDILLERAS OR LONGITUDINAL CHAIN. VARIOUS IRREGULARITIES IN THE CHAIN. THE PYRENEES AS AN ETH- NOLOGICAL BARRIER. SEVERAL geographers have fancied that they had discovered the law of the general arrangement of mountains, and, without so much as wait- ing until the whole surface of the earth became thoroughly known, have traced out, according to their own notions, ranges of mountains more or less hypothetical. Thus Buache, whose ideas were very prevalent for a long time, imagined that the chain of the Pyrenees was prolonged under- neath the Atlantic, then across the New World and the Pacific, and, again making its appearance in Asia, forming in succession the Himalaya, the Caucasus, the Balkhans, the Alps, and the Cevennes, finally returned to the point it started from. It was, in fact, the ancient image of the myth- ical serpent coiling itself round the globe and biting its own tail. We only need to glance at the maps which, at the present day, science enables us to trace out, in order to see how completely primitive this idea was as regards the harmony of the terrestrial configuration. It is, on the con- trary, by a singular variety of phenomena that the laws of nature are al- ways revealed. Of course it may be said, in a very general way, that the principal chains of mountains, interrupted here and there by gulfs, arms of the sea, or plains, form a kind of great circular cornice round the double basin of the Indian Ocean and the Pacific.* In like manner, it is certain that the mean altitude of the elevations of the ground, both mountains and pla- teaux, gradually diminishes as we leave the tropical regions and approach the poles. But how numerous are the exceptions which come under our notice when we study the endless variety of the geographical lineaments of the earth's surface ! Some countries seem a perfect labyrinth of plains, plateaux, and mountains, of every shape, form, and height. In one place we find granite peaks and domes of porphyry ; in another, ridges of schist, cut up into needle-like points ; limestone ramparts and basaltic cones of almost mathematical regularity of outline. The fact is this, that the se- ries of mountains which have been elevated during each period of the earth's existence have been added to by successive series of subsequent upheavals. Whatever the first rule may have been, it has gone through an incessant process of modification during the lapse of ages. * Vide above, p. 52. 14:0 THE EARTH. It becomes, therefore, the function of geology to decide as to the real order of arrangement of mountains by describing the history of their formation. M. Elie de Beaumont has endeavored to fulfill this great task, and, by a bold generalization of scientific facts, has succeeded in drawing up a theory of great simplicity. Taking as his starting-point the fact that the steeply-inclined sedimentary strata which stretch along the side of a mountain must necessaiily have been upheaved, while the strata which have remained horizontal have not been disturbed since their formation, the eminent geologist has thus been enabled to assign a relative age to each system of mountain chains. In fact, every chain which presents on its slopes the vertical beds of any geological formation, and at the base of which we find the strata of a later age, must evidently have been upheaved from the surface during the longer or shorter interval which separated the formations of the two series of strata. Now, if we compare the direc- tions of mountain systems of the same age, we find that they are nearly parallel in the set of their ridges. M. Elie de Beaumont has therefore classified various mountain chains according to their direction, and has in this way pointed out some very remarkable coincidences between ridges of upheaval separated from each other by thousands of miles. One most important fact which results from this classification of mountains is, that the most ancient systems are generally the least elevated. The Yosges date from a much more remote epoch than the Pyrenean chain ; the lat- ter was uplifted before the Alps, which also belong to an age much ante- rior to that of the Andes. Nevertheless, this geological classification of mountains is not so simple as it appears at first sight ; for it is often very difficult to determine the real axis of upheaval of mountain chains a fact which M. Elie de Beau- mont found an opportunity of convincing himself of in studying the sys- tem of the Esterel. A profound study of the earth's strata will correct all the false and incomplete elements which these theoretical ideas must con- tain. Geography, which confines itself to a description of the earth as it is in the present epoch, can only class the various chains of mountains ac- cording to the regularity of their shape, their vertical outline, and the im- portance which they assume in continents as the divisions of the water- shed, as the laboratories of meteoric agencies, and as a barrier between nations. Among the mountain chains which assume an almost perfect regulari- ty, we may mention the western portion of the Pyrenees. Just like a branch of a tree, or better still, a stalk of fern, is divided and subdivided right and left into small branches, leaves, and leaflets, so every knot in the ridge gives rise on both sides to transverse chains, similar in every respect to the mother-chain, except that they are much shorter, and sink by succes- sive falls down to the level of the adjacent plains. The transverse chains are also parallel, and separated from each other by deep valleys, down which glaciers rush, torrents roar, or footpaths wind. The valleys on CHAIN OF THE PYRENEES. 141 each side of the principal chain correspond closely and communicate with each other by a col, port, or passage, that is, a depression opening between two summits. Like the principal ridge, each subsidiary transverse chain is also composed of a succession of summits, separated from each other by passes, the height of which proportionately diminishes. Each summit gives rise to two lateral spurs, which are, in fact,-nothing but the rudiment of a tertiary chain running parallel to the principal one ; the secondary passes, too, serve to connect short ravines which empty their streams into the torrent of the principal valley. Fig. 36. The Pyrenees. The portion 01 the great Pyrenean chain which is comprised between the pass of Roncevaux on the west, and the port of Venasque on the east, may therefore be considered as the perfect type of a regular ridge of mountains. The eastern portion of the chain is not arranged in so order- ly a way: an examination of the lines^fthe ridge will prove that at sev- eral points it departs from the typicalilrm. The principal irregularity is to be found at about the centre of the chain, at an almost equal distance from both seas. We may there notice that the Pyrenean chain is not of a simple configuration ; but that, on the contrary, it is formed of two distinct lines, one of which is a continuation of the regular western chain ; while the other, divided into three parts by the Col de la Perche and the Col de Puymoren, commences on the shores of the Mediterranean, under the name of the chain of the Alberes ; at the Costabona group it crosses the more important transverse ridge of the mountains of Cadiz and Canigou, and, tending toward the east, forms the clumps of Andorre, Montcalm, and Mont Vallier ; then running parallel to the chain coming from the Atlantic, it terminates on the right bank of the newly-born Garonne. The Pyrenees may be compared to a regular chain which has been divided into two by some gigantic fault, the two halves of which, remaining fixed at each of their sea-coast extremities, have turned slightly and in contrary directions round these extremities, as if on pivots. 142 THE EARTH. Fig. 37. Lateral Ridge between the Valley of Luchon and the Val d'Aran ; after V. Petit. A transverse ridge, abutting at right angles to the northern chain, joins that of the south to the Col de Pallas ; another, likewise thrown out at right angles from the range of peaks in the southern chain, tends more to the west, and is only separated from the Mediterranean ridge by the nar- row defile of the Garonne. Thus the extremities of the two chains, and the two lesser chains which unite them, inclose on all sides a deep valley, resembling a terrestrial whirlpool, round which the mountains rise like enormous waves. This is the district of Aran, the centre of the Pyrenees. Although its rainfall flows, by means of the Garonne, into the plains of France, orographically speakingWr belongs to neither of the two basins. With a greater show of reason than the valley of Andorre, the district of Aran might have remained as a neutral republic between France and Spain, the two adjacent states. A second anomaly may be found in the fact that the highest summits are not situated on the principal ridge. Thus Mont Perdu, the Posets Peak, and the Maladetta rise to the south of the Atlantic chain of the Pyr- enees : the first of these mountains is connected with the central axis by several elevated passes, but the peaks of the Posets and the Maladetta, giants which front each other on each side of the Essera, form two almost completely isolated groups. On the north side only, some snow-clad ridges link them on to the principal system. Nevertheless, in spite of all these irregularities, resulting from the in- cessant labor of theagents which are at work in modifying the surface of the globe, the chain of the Pyrenees must ever be considered as an in- stance of a regular system of mountains, and, among all the ranges on the face of the earth, but very few can even be compared with it in the regular simplicity of its formation. The aspect of the Pyrenees is there- THE PYRENEES. 143 fore less diversified than that of the Alps and of several other mountain systems. The long range bounds the horizon with a uniform wall, in- dented with points like the edge of a saw (sierra), and, looked at from the plain, its subsidiary spurs are scarcely visible. Although the mean height of the central ridge of the Pyrenees exceeds that of the Alps by about 300 feet,* and the plains of France are lower than those of Switzer- land, yet this superior comparative elevation produces less effect on the spectator on account of the regular arrangement of the peaks and the sim- ilarity of their outlines. Few, if any, summits in the Pyrenees exceed by more than 2000 or 2500 feet the mean height of the ridge (8037 feet), while in the Alps many of the mountains rise more than 6600 and 8250 feet above the mean height of the range, and Mont Blanc rears its termi- nal point to an elevation of more than 15,700 feet. The mountains of the Pyrenees more generally assume the form of mere cones rising from the upheaved base. Some mountains, too, of considerable geological impor- tance as Neouvielle, and the mountains of Oo and Clarabide are scarce- ly to be distinguished by their vertical outline from the heights which surround them. Peaks which are plainly disconnected from the rest of the chain such as the Canigou, Mont Vallier, the Pic de Tabe, the Pic du Midi at Pan, and the Maladetta are not very numerous. In consequence of the simplicity of configuration which prevails in the Fig. 38. The Sierra de Marcadan, viewed from the Pic du Midi from the Northeast ; after V. Petit Pyrenean chain, we find in these mountains but few of those longitudinal valleys rising up to the right and left toward two parallel ranges of peaks, and pushing their arms of verdure into all the gorges and even to the mo- raines of the glaciers. In these mountains we see nothing but valleys which cross the axis of the ridge, and are steeply inclined down toward the plain. The passes where the incipient ravines of these valleys take their rise are often mere plateaux on the summit of the ridge, or else dark gorges hollowed out in the rock by the long-protracted labor of various atmospheric agencies. These passes are also more elevated on the aver- age than those of the Central Alps. It is therefore easy to understand why it is that, among all the natural ramparts in Europe, the Central Pyr- enees have always been the most insurmountable barrier of nations. Be- tween the Col de la Perche, near Montlouis, and the port of Maya, no* "far from Bayonne, a distance of more than 180 miles, the chain of the Pyre- nees is not crossed by any carriage-road. * Hmnboldt. 144 CHAPTER XXIV. MOUNTAINS OF CENTRAL EUROPE. CONTRAST BETWEEN THE ALPS AND THE JURA. THE JURA AS A TYPE OF A SYSTEM OF MOUNTAINS WITH PARAL- LEL CHAINS. APPARENT CHAOS OF THE ALPS. CENTRAL GROUP OF ST. GOTHARD. GROUPS OF MONTE ROSA AND MONT BLANC. THE ALPS CON- SIDERED AS A FRONTIER. THE great system of mountains which forms, as it were, the back-bone of Europe, and the ramifications of which, like the limbs of a body, deter- mine the very shape of the continent itself, is very different from the Pyr- enees in the richness and variety of its configuration, the intersection of its ridges, the number of its more isolated groups, and its frame-work of secondary chains. To the vertical outline and distribution of the Alps the glaciers of which supply, while they moderate, the water-courses of Western Europe the nations which inhabit the latter country owe indi- rectly much of their vitality and civilization. Standing up like the bas- tions of a fortification, the chief Alpine groups form a protection to the brave Swiss people. On the south, the ensemble of all the mountain groups sweeps in a vast semicircle round Northern Italy, and is linked on to the chain of the Apennines, which constitute the back-bone of the peninsula ; on the west, the spurs of the Alps form the most prominent feature of the French territory, and by their transverse chains modify the relief of the Jura ; on the north, the gradation of plateaux, which abut on the moun- tains of Switzerland, descend as far as the landes of Prussia ; finally, to the east, the Carnic Alps extend into Bosnia and Servia in calcareous ranges and plateaux, which are divided only by the Danube from the Transylva- nian citadel of the Carpathians, and, through the Balkhans and the Pindus Mountains, radiate out to the shores of the Black Sea and the ^Egean. The singular beauty of the Alps is still further enhanced by the contrast which they present to the mountains which surround them. The contrast is especially remarkable between the groups of the Central Alps and the ramparts of the Jura which form the western boundary of the natural territory of Switzerland. The chains of the Jura, more unpretending in height in comparison with those of the Alps, are nevertheless very curious in a geological point of view, and must be looked upon as the best type of one particular formation of mountains that of long parallel ridges. Carniola, Herzegovina, and Bosnia also possess chains arranged in a simi- lar manner. In America, too, we might point out the Ozark Mountains, and especially the Alleghanies, which extend over a still more considera- ble area than the Jura, but they have been much less studied. They are, besides, connected on both sides with granitic mountains ; and the princi- THE JURA AND THE ALPS. 145 pal mass of the system, which is often compared to long waves of the sea, is complicated with numerous irregularities. Fig. 31. The Jura. The European Jura occupies a very considerable area in the middle of the continent, from the banks of the Drome to the mountains of Bohemia. The central portion of this immense tract of land is all that is commonly understood under the name of Jura; for the more extreme points are very variously inflected and intersected by masses of distinct formations. Thus, in Savoy, the Mole and other peaks stand at the angles where the walls of the Jura intersect the Alpine chains. The Jura, properly so called, ex- tends from the southwest to the northeast, from the valley of the Rhone to that of the Rhine, presenting a slight convexity toward France. It consists of parallel and almost uniform ranges, which rise in successive gradations, tending from the west to the east. These ranges are like so many walls, with sloping declivities on one side, and terminating on the other in abrupt escarpments. Intermediate valleys separate these paral- K 14:6 THE EARTH. lei walls, the most eastward of which is by far the most elevated, and com- mands, in all its height, the plains of Switzerland. Hollows or combes, in the form of an amphitheatre, open out in the thickness of the Jura ram- parts, and here and there cluses, or transverse defiles, enlivened by tor- rents, cut right through the chains and divide them into isolated frag- ments. These fragmentary plateaux, which, in their extensions, follow uniformly the same direction, have been often compared to those species of caterpillars which creep along the ground in long processions. If we take no notice of the cluses which divide the walls of the Jura into so many bits, we may more poetically compare these mountains to the rip- ples produced by throwing a stone upon some liquid surface. The elongated brows of Mont Tendre, of Mont Noir, and the Weissen- steiri form magnificent observatories, from which one can study at ease the marked contrast between the Jura and the groups of the Oberland, bristling with its pointed summits, to the east of the Bernese depression. At first sight, these mountains seem to form a veritable chaos ; but this chaos appears much greater still when seen from one of the lofty summits of the Alps themselves. We then perceive, round the whole line of the horizon, points, pinnacles, and ridges, thrown together as if by chance, and almost innumerable ; they might well be called the congealed waves of an immense ocean. Very different from the Jura, the general formation of which is so striking in its regularity, the Alps appear to be nothing but a dreadful accumulation of disorder, and only a long course of study or personal survey will enable any one to become acquainted with the gen- eral arrangement of their ridges. It may then be seen that the ensemble of these mountains is formed by separate groups throwing out branches in every direction, like the rays of a star. Whilst the Jura, and the sys- tems of mountains belonging to the same type, are composed of parallel chains, the Alps are constituted by the juxtaposition of many groups with divergent chains radiating from them. M. Desor, taking as the basis of his classification of the Alps the various nuclei of granite and protogene which have pierced through the more re- cent rocks, has come to the conclusion that the Alpine system is composed of fifty distinct groups. This entirely geological division harmonizes in general with the results of a mere study of the vertical outline and direc- tion of the ridges ; but the number of groups must be considerably re- duced if those which are linked to one another by continuous ridges of great elevation are looked upon as forming parts of the same chain. The central mass, which is also the most impoi'tant in a geographical point of view, is that of the St. Gothard, situated between Switzerland and Italy, at the summit-level of the waters of the Rhine, the Tessin, the Rhone, the Aar, and the Reuss ; it is the knot or focus where the conver- gent ridges of the surrounding groups unite like radii. On the northeast stands the group of Todi; on the east, that of Rheinwald; on the west and south, the much more considerable clusters of the Finsteraarhorn and Monte Rosa. The latter group is linked on to Mont Blanc, rising more to TILE JURA AXD THE ALPS. 147 Fig. 40. Valleys, Cluses, and Combes of the Jnra. the west ; but at this point the Alpine system changes its direction, and, as a whole, bends round toward the south. The two first of the more im- portant groups which rise on this side are those of the Grand Paradis, commanding the plains of Piedmont, and that of the Vanoise and Grande Casse, dividing the Tarentese and Maurian valleys. A real chain bends round to the south, which is crossed by the Mont Cenis road ; the wind- ing ridges of these chains go on to join the groups of the Grandes Rous- ses and Belledonne on the west, that of the Grand Pelvoux on the south- west, and that of Monte Viso toward the south. The pyramid of Monte Viso is the magnificent boundary-stone which marks out the line of de- markation between the Alps of Dauphiny and the Maritime Alps; it is also the last mountain in the chain the height of which exceeds 11,500 feet. Beyond this point, the terminal branches of France and Italy, spread out like the leaves of a fan, gradually sink down toward, the sea. To the north of Nice andMentone, a small granite group rises to a height of more THE EARTH. than 9900 feet, and two of its highest summits, the Gelas and the Clapier de Pagarin, have small glaciers on their northern slopes. At this point the great curve of the Western Alps comes to a termination, and the in- termediate chain commences which unites the former to the ridge of the Apennines. The Eastern Alps, situated to the east of the St. Gothard, also assume a similar arrangement in groups. On the northeast of the Todi stands the Santis ; to the east of the Rheinwald are the groups of the Bernina, Sil- vretta, and the Ortelspitze ; then follow, tending from west to east, the groups of the Oetzthal, the Stubaier, the Gross-Glockner, and the moun- tains of Hallstadt, beyond which the Alps proper lose their primary im- portance. The summits of all these groups are more than 9900 feet in height, and are clad with snow ; like the western chains, they well de- serve the name of Alps (white) which the Celts gave to these mountains. Most of these Alpine groups exhibit a singular diversity of aspect, in all the various details of their relief. There is no feature in this mighty architecture which is devoid of its own special characteristics of beauty, and also there is no beauty which is not, by some unlooked-for contrast, individualized in each mountain. . In the first place, the central group of the St. Gothard, the knot from which radiate all the principal chains, is not very lofty, and is, in fact, of an altogether secondary class in comparison with the other Alpine groups. It is a quadrilateral mass, surrounded on all sides by deep valleys and the wide depressions of several passes on the west the Furka, on the north the Oberalp, on the east the Lukmanier, on the south the Nufenen, and is crowned by summits, the mean height of which attains 9678 feet ; the most important, the Piz Rotondo, not exceeding 10,488 feet in altitude. It is probable that, during the long course of ages, the upper waters of the Rhine, the Rhone, the Reuss, the Tessin, and the Toccia have had the ef- fect of lowering the mountains of St. Gothard somewhat below the sur- rounding summits. Another anomaly in the Alpine system is the fact that the mean eleva- tion of the snowy groups which rise east and west of the St. Gothard is not in direct proportion to the heights of their crowning summits. In fact, the true citadel of the Alps that which, by the form of its mountains, the number of its peaks, and the importance of its glaciers, deserves more than any other the title of the culminating group is the mighty bastioned rampart of Monte Rosa, the mean height of which is not less than 13,457 feet. The supreme diadem of this association of mountains is at a height of 15,216 feet, while Mont Blanc rises to 15,780 feet; but the group of summits which surround this highest point of Europe is only 12,657 feet in mean altitude, 800 feet less than the heights of Monte Rosa. Next fol- low in order of elevation the groups of the Jungfrau, 12,312 feet; the Ber- nina, 11,345 feet; the Grison Alps, 10,583 feet, and the Todi, 10,311 feet. Taken as a whole, the various groups of the central Alps decrease in height from west to east, and from south to north ; their southern slope is uni- Drawn "by A Vufllemin. ALPS PL. X. rtti Erhard STRUCTURE OF THE ALPS. 149 formly more abrupt than the northern declivities, which descend in long branches toward the valleys of the Rhone and the Rhine.* Considered in their ensemble, the Alps, like most mountains, serve as chains, ethnological frontiers, on one side to the French and Germans, and on the other to the inhabitants of Italy. The district of the Grisons, one of the most inaccessible of all the Alpine regions, which by the labyrinth of its five hundred valleys has been converted into the central citadel of Europe, served as a refuge to the Rhetian peoples, who still speak, though in a corrupted form, the language of their ancestors the contemporaries of the citizens of ancient Rome. The Alps, however, owing to their di- visions into numerous groups and to the comparative lowness of their passes, do not constitute an insurmountable barrier like the chain of the Pyrenees. On the mountains and in the valleys of Switzerland, men be- longing to three races German, French, and Italian are confederated so Skill 4 miles. Fig. 41. Profile of Monte Rosa. as to form a nation of brethren. German colonies, surrounded on all sides by a Latin population, have established themselves on the mountain sides facing the north ; for instance, in the Viege valley and in the Sette Com- muni in the environs of Bassano. Added to this, men of* the Latin race have colonized the southern slopes of the groups inhabited principally by Germans; finally, the ancient Attobroges, all alike nowadays speaking more or less impure French, inhabit the two sides of the Alps of Savoy and Dauphiny. While, in the Pyrenees, the ridge of the mountains dis- tinctly separates the two nations of France and Spain, it is, on the con- trary, the bases of the Piedmontese mountains which serve as frontiers, if not political, at least ethnographical, between two races. The valleys of the Italian side, traversed by the streams of the two Doires, the Cluson, the Pellis, and the Stura, have a population of the same stock as the val- leys of M aurienne, Queyras, and Durance. Besides, as Ami Bou6, the ge- ologist, long ago pointed out, longitudinal chains are those which form the least separation between peoples, owing to the resemblance of the cli- * William Ifuber, Bulletin de la Socictt tie Geographic, February, Mnrch, 18GG. 150 THE EARTH. mate on the two slopes; transversal chains, like the Pyrenees, are always the frontiers which are the most difficult to cross. For all the interchanges of commerce, as well as for the mutual inter- course of peoples, the Alpine groups are also much more happily arranged than the regular chain of the Pyrenees; and the traffic between the two opposite sides has always assumed a very considerable importance. Twelve carriage roads, some of which may be reckoned among the chefs cFceuvre of human industry, cross the ridges of the Alps, and form the means of communication between France, Switzerland, and Germany; a railway also, now some years finished, passes to the east of the Greater Alps through the Soemmering chain. Finally, four other railway lines are gradually pushing their way into the depths of the lofty central moun- tains, and, ere long, free communication will be established under the rocks and glaciers, and we shall be able to make the boast that we have leveled the Alps. MOUNTAINS OF VENTRAL ASIA. CHAPTER XXV. MOUNTAIN CHAINS OF CENTRAL ASIA. THE KOUEN-LUN, THE KAKAKORUM, THE HIMALAYA. THE SOUTH AMERICAN ANDES, A TYPE OP THE BIFUR- CATED CHAIN. THE chains of the Himalaya, the Karakorum, and the Kouen-Lun fill the same position in the continent of Asia as that occupied by the Alps in Europe. These three ranges of mountains have a common origin in the plateau of Pamir the " Roof of the World" from which also radiate to- ward the north and west the ranges of the Bolor and the Hindoo-Kuch. The triple rampart of Upper Asia is not less than 1550 miles in linear de- velopment, and its breadth, including that of the plateaux and intermedi- ate valleys, is toward the east, that is, toward Sikkim, about 620 miles. Jn each of the three chains the mean altitude of the summits exceeds that of any other ridge of mountains in the rest of the world ; this spot is, in fact, the culminating point of the earth. Between the two extreme sides the contrast is most decided. On the north, cold and arid steppes stretch away over an immense extent ; on the south lie spread out the burning and wonderfully fertile plains which are watered by the Ganges and its tributaries. The rocky and snowy ridges which tower up between the two regions form an ethnological barrier more mighty than the ocean it- self; they divide races of men and great systems of religion. There are but very few points at which the Buddhist Mogols thanks to "the great- er facilities which were afforded them, by their residence on the high plateaux, for crossing the mountains have made their way down into the Southern valleys of the Himalaya.* The northern chain, that of the Kouen-Lun, is very little known, and it can not as yet be stated positively whether it may not contain some sum- mits more elevated even than those of the Himalaya. It is, however, probable, from the information, that has been acquired by travelers as to various points, that the ridge of the Kouen-Lun is the least lofty of the three. The Karakorum, which is the middle rampart, is also that of which the mean height is the most considerable; and in its gorges the Indus and the Brahmapootra take their rise. At its base lies l^ie valley of Cashmere, which the Oriental posts celebrate as the " abode of happi- ness ;" its lovely blue lakes, surrounded with gardens, reflect the snowy peaks of fifteen or eighteen thousand feet in height. The torrents which flow from both sides of the mountains cross the parallel chains through prodigious defiles, which in some places reach a depth of thousands of feet. * Frferes Schlagintweit, Mittheilungen von Petermann, 152 THE EARTH. Fig. 42. Valley of Cashmere. The Himalaya, the best known of the three chains, has, however, been but slightly explored in comparison with the European Alps. It is pro- tected against all the attempts of explorers by the want of roads and evem paths ; by its impetuously-rushing streams, entirely unbridged ; by the inaccessible forests of its slopes ; by its formidable cliffs, and the height of its lofty summits, piercing through the clouds into the attenuated air, where man can scarcely draw his breath. On the face of the mountains a zone of variable width extends, like a barrier of death. This is the Te- rai, the unwholesome dampness of which, fostered by the rains of the mon- soons and the water descending from the Himalaya, steams in the sun in long-drawn out mists, creeping over the trees, and spreads, far and wide, fevers and pestilence. Finally, several of the mountain districts still be- long to native sovereigns, who oppose, either by force or stratagem, any advance of European travelers. It is not many years ago that observers were first able to measure the highest mountain in the chain, and proba- bly in the whole world. This is the Gaurisankar, or Tchingo-Pamari, the summit of which rises to a height of 29,002 feet, nearly twice the eleva- tion of Mont Blanc. In the same range, up to the present time, two him- THE HIMALA YAS.THE ANDES. 153 dred and sixteen summits have been measured, seventeen of which exceed 24,600 feet in altitude ; forty are about 23,000 feet, and a hundred and twenty more than 20,000 feet high. Next to the Gaurisankar, the high- est known mountain is the Dapsang (28,29f feet), in the Karakorum. The great peaks of the Himalaya, contemplated from one of the head- lands which stand out far into the plains of Hindostan, form one of the most magnificent spectacles which the eye of man can see and wonder at. From the village of Durjeling, which the English have built upon a ter- race more than 6000 feet above the level of the sea, in order to enjoy a cold and bracing air like that of their native country, may be seen rising, in all its formidable majesty, the colossus of Kinchinjinga, nearly five miles high. At its base, as if in the bed of a gulf of verdure, a white torrent of foam glitters through the palm-trees ; higher up, a chaos of wooded mountains, like the waves of a monstrous sea, are crowded and piled one over the other round the great tranquil summit ; above the multitude of secondary peaks rise the long slopes of the mountain, first tinged with an aerial blue softer than that of the sky, then with a bright white, sparkling like silver. From one snowy ridge to another, the eye rises at last to the culminating point, from which the bold climber, if he ever reaches it, might see stretched out at his feet a prospect as extensive as that of the whole of France.* Spectacles as grand as that of the Kinchinjinga, seen from Durjeling, are numerous enough in the Himalaya, especially in the eastern portion of the chain, where the summits attain their principal elevation, and where the defiles of the valleys are most deeply hollowed out. But, although these mighty mountains of Upper Asia are more majestic than the Euro- pean Alps, they do not generally present an equal variety of aspect, an equal grace of outline", or charm of landscape. In all its grandeur, the Himalaya is uniform ; its peaks are loftier, its snows more extensive, its forests deeper ; but there are fewer cascades and lakes ; there are no pleas- ant lawns and scattered groves; and we fail to notice the picturesque chdlets nestling down in the glens or hanging over the brink of the preci- pices. The South American Andes, which in 1824 that is, before the discov- eries of Webb and Moorcroft were looked upon as superior in elevation to the Himalaya, are, in fact, 6600 feet lower in mean height. In sublim- ity they are exceeded by the Asiatic mountains, in variety of site by the European Alps; but they are distinguished, especially in the volcanic re- gions, by regularity of form. Added to this, they constitute a chain which, in a geographical point of view, is really unique, on account of the har- mony which they exhibit with the continent which they crown with their snowy ridges. This long range of mountains, so remarkable by its enor- mous length (about 4350 miles), and by the great height which its peaks maintain, over a space of about 50 degrees of longitude, is, however, less regular than it appears at first sight. The principal characteristic which * Hooker, Himalayan Journal. 154 THE EARTH. distinguishes the Andes from every other mountain system is found in the numerous forks, or rather bipartitions, of the Cordillera. In that part only of their extent which stretches from the frontiers of Chili to those of Venezuela, the Andes divide eight times, forming large inclosures, each containing a plateau between the two lines of peaks. At some points, in- deed, the Andes separate in three scarcely divergent branches. From the southern point of America, as far as the other side of Acon- cagua (22,420 feet) the giant of the Chilian Andes the principal chain throws out to the east but very unimportant groups. There are only some low ridges running above the Pampas parallel to the principal ridge. About the 30th degree of latitude these uplands augment in number and height, and then form a vast plateau, from which, in a northeasterly direc- tion, branches off the great sierra of Aconquija. Other sierras rise on the enormous mass of the plateau between the mountains of Aconquija and the great fork of the Bolivian Cordillera, in the 22d degree of latitude. The western range, composed of broad domes of a regular shape, ap- proaches the shore of the Pacific, while the eastern chain, throwing out several important branches into the eastern plains, curves round the great plateau of Bolivia, with its long row of serrated and snowy peaks, among which towers the Illampu or Sorata (24,812 feet), the highest mountain in America. North of the lake of Titicaca the two chains are united by a transverse rampart, but they continue to extend in a northwest direc- tion parallel to the coast. Although the eastern Cordillera is pierced in a great many points by rivers which are tributaries of the Amazon, it can still easily be recognized by the general direction of the fragments which compose it. At the knot of Cerro de Pasco the two Cordilleras again unite, but only to divide again immediately into three chains, one of which, tending to the northeast, merges in the Pampa del Sacramento, while the two oth- ers, inclosing between them the deep valley of the Maranon, unite at the extreme angle near the southern frontiers of Ecuador. More to the north, we have several small plateaux covered with virgin forests ; then, on the other side of Loja, the two Cordilleras again separate their two parallel ridges of snow-clad summits. Here, too, lies the magnificent ter- race of Ecuador, divided into three distinct plains by the cross groups of Assuay and Chisincha. Two of these plains, those of Tapia and Quito, form the magnificent avenues of volcanoes rendered celebrated by La Condamine, Bouguer, Humboldt, and other learned travelers. On one side rise Chimborazo, Carahuirazo, Illinissa, Corazon, and Pichincha ; on the other, Sangay, the most formidable volcano in the world, Tunguragua, Cotopaxi, Antisana, and Cayamba, which crosses the line of the equator.* North of the equator, the two chains unite in forming the group of the Pasto plateau, which stretches nearly up to the .second degree of latitude. At this 'spot commence three distinct Cordilleras, which are not destined again to unite into another knot of mountains. The western Cordillera * Vide the chapter on "Volcanoes." THE ANDES. 155 disappears close to the Gulf of Darien, between the valleys of the Atrato and Cauca. The central Cordillera, on which rise the mighty summits of Purace, Huila, Tolima, and Herveo, divides the Cauca basin from that of the Magdalena ; lastly, the eastern Cordillera, or the Suma Paz (supreme peace), bending round to the west of the plateau of Bogota, forks out into two chains near Pamplona, one of which terminates in the vicinity of Maracaibo, under the name of the Sierra Negra, while the other, variously ramified, bounds on the north the llanos of Venezuela, and, forming the proud Silla of Caraccas, runs along the sea-coast, and pushes out as a promontory to the Bouche du Dragon, which separates it from the moun- tains of the island of Trinidad. This point forms the termination of the chain of the Andes. The immense and spirally inflected extent of the Cordillera has for its culminating summits three peaks Chimborazo, So- rata, and Aconcagua placed about 1240 miles apart on the mighty ridge ; but the summits which are higher than Mont Blanc may be reckoned by hundreds. This enormous mountain chain seems to form so intimate a part of the very construction of the continent, that numbers of the inhab- itants of its plateau and slopes look upon it as the back-bone of the whole world ; they can not fancy any country which is not commanded by the Cordillera of the Andes.* * Jules Remy, Nouvelles Annales des Voyages, February, 1865. 156 THE EARTH. CHAPTER XXVI. GRADUAL COOLING OP THE AIR ON MOUNTAIN SIDES. DIFFICULTY OF AS- CENTS. LIMITS OF MAN'S HABITATION. ILLNESS FELT BY MOUNTAIN TRAVELERS. BY uplifting their summits into the higher regions of the atmosphere, mountains penetrate through zones of ever-increasing cold, and, owing to this gradation of successive temperatures, nature assumes a marvelous va- riety of climates and floras.* The sides of every lofty mountain present a kind of epitome of all the phenomena which are exhibited in the im- mense space comprehended between the plains at its foot and the icy re- gions of the pole. The solar rays have actually more heating power on the soil of moun- tains than in the plains, as is shown by direct observation, and also by the marvelous colors of the sweet-smelling Alpine flowers ;f therefore the gradual cooling of the temperature on mountain slopes must be attributed to the rarefaction of the successive layers of air. The investigations and experiments of natural philosophers have proved that the air affords a much easier passage to luminous than to dark radiations. The result of this fact is that the heat poured down by the sun during the daytime readily traverses the whole depth of the atmosphere in its way to warm the surface of the planet, while the heat radiated from the ground during the night can only escape into space in very small quantities. The lower layers of the atmosphere thus act as complete screens in arresting the ra- diation from the surface of the earth, and preventing the cooling of the planet. By this very fact, however, slopes and summits of mountains are, in proportion to their elevation, the more easily deprived of the heat which warms the plains at their base, and they mount into tracts of air which are the more chilled in proportion as they are vertically distant from the denser atmospheric layers lying below. J Thanks to this progressive dimi- nution of temperature in the aerial waves which bathe them, mountains, already so beautiful in their outline and the majesty of their forms, add to the magnificence of their appearance by the contrast between their forests and their glaciers, their pasture-lands and their snows* What, then, on the average, is the proportion according to which the temperature falls in ascending from the base to the summit of a moun- tain ? It is a difficult matter to settle it exactly, for aerial currents of va- rious temperatures lie one above the other in the heights of the atmos- * Vide the chapter on " The Earth and its Flora." t Ch. Martins. Helmholz, La Glace et les Glaciers. J Tyndall, The Glaciers of the Alps. LIMITS OF MAWS HABITATION. 157 pbere, and sometimes we may rise from a comparatively cold zone to one that is much warmer, as some of the aeronautic expeditions of Mr. Glaisher have strikingly proved. Nevertheless, when the sky is clear and the air is calm, the decrease of the temperature takes place with a regularity which is sufficiently certain to enable us to calculate the law respecting it, at least approximately. Just above the sui-face of the ground, an ele- vation of 143 feet corresponds, on the average, to a fall of one degree Fahrenheit ; at the height of about 3000 feet, it takes an increase of height of 294 feet to effect a diminution of heat amounting to one degree Fahr- enheit ; and in proportion as we mount higher and higher, the interval in- creases, so that at about 30,000 feet of elevation the temperature sinks only one degree Fahrenheit for every space of 1055 feet.* The real rate of the decrease of heat can not be so easily ascertained on the slopes of mountains, on account of the influence of the ground and the ice. But we may state generally that on the Swiss mountains the temperature of sum- mer decreases one degree Fahrenheit for every vertical space of 290 feet ; in winter the same fall of temperature takes place for every 439 feet of increased height.f The extreme cold of very lofty mountains renders them completely un- inhabitable for man. No traveler has ever set his foot on the mighty summits of the Karakorum and the Himalaya. The principal summits of the Andes Sorata and Aconcagua are equally inviolate; and even among the more unpretending summits of the Alps there are still a con- siderable number on which, up to tHe present time, the snows and the gla- ciers have formed a sufficient barrier against any attempted ascents. The highest point that the mountain climber has yet attained is the summit of Ibi-Gamin, a mountain of Thibet, which rises 22,079 feet above the level of the sea. Even at this considerable height the brothers Schlagintweit, who accomplished this exploit in 1856, still found themselves more than 6500 feet below the culminating point of Gaurisankar. Since this date, Mr. Glaisher's balloon has reached an elevation of more than 13,000 feet higher in the cold atmosphere of Great Britain. In all mountainous regions the permanent habitations of man cease at a limit far below the most elevated points reached by the bold mountain climber. St. Veran and Gurgl, the most highly-placed villages of France and Germany, are situated at the respective altitudes of 6591 and 6197 feet; but in Switzerland the Hospice of St. Bernard, built many centuries ago to shelter travelers when benumbed with the cold, is much more ele- vated its height iS 8110 feet. There is another convent that of Hanle, inhabited by twenty Thibetian priests, which is the most elevated cluster of houses in the whole world; it is situated at a height of 14,976 feet.J None of the villages of the Andes, except perhaps that of Santa-Anna, in Bolivia, have been built at so great a height. * Zurcher, Annuaire ,Sci>jiert de Schlagintweit, Mittheilungen von Petermann, 1865. Heck, Geographisches Juhrbvk von Behm. 158 THE Travelers who venture to ascend the slopes of a lofty mountain not only have to suffer all the rigors of cold and run the risk of being frozen on their route, but they may also experience most painful sensations, ow- ing to the rarefaction of the air. It is, in fact, very natural that, at an elevation at which the pressure of the atmosphere is reduced to one half or even to one fourth that of the plains below, a certain uneasiness should be caused by the sudden change, and the more so. that some of the other surrounding conditions, such as the caloric and the humidity of the air, also become modified. Undaunted climbers like Tyndall, who have never felt in their own persons the effect of this mal de montagne, expressly deny that this exhaustion proceeds from any thing else than mere fatigue. M. Jules Remy, too, has noticed only one mountain of the Andes on which the phenomena of the puna or soroche are always developed in the organ- ism of living beings ; this is the Cerro de Pasco, the height of which does not exceed 13,966 feet. Horses, mules, asses, and oxen are also, like man, subject to the peculiar influence of these localities, while at much more considerable altitudes the usual state of health suddenly returns. There- fore, in this region of the Andes, emanations from the ground, and not the rarefaction of the air, are the cause to which we must attribute the incon- venience felt by travelers.* However, the investigations made on the sub- ject by Robert de Schlagintweitf can, leave no doubt in our minds that this mountain ailment is really felt generally, in other regions of the An- des as well as on the Cerro de Pasco. Usually, indeed, the effects of the soroche are felt at a much lower elevation on the slopes of the Cordilleras than on those of the Himalaya. In the latter mountains the traveler does not begin to suffer from the attacks of this ailment until he has reached a height of 16,500 feet, while on the Andes a large number of persons are affected by it at an altitude of 10,700 and 11,500 feet. . Added to this, in the South American mountains the symptoms are much more serious ; to the fatigue, headache, and want of breath, which are likewise experienced on the Himalaya, are added giddiness, sometimes fainting-fits, and bleed- ing from lips, gums, and eyelids. J At the same elevation as the paramos of the Andes, or even as the lofty summits of the Himalaya, the aeronaut who, however, is spared- all the fatigue of climbing rarely suffers any inconvenience ; but at 30,000 to 40,000 feet the malady shows itself, and, if the balloon continued to rise, the aerial voyager would infallibly perish. Therefore, at but a very few miles above our heads lies the region of death, and into this terrible zone the loftiest mountains of the earth ele- vate their white summits. * A scension du Pichincha,Nouvelles Annnles des Voyages, etc., Febniary, 1865. t Zeitschr.fur Erdkunde, 1866. % Humboldt, Pceppig, Moritz Wagner, Philippi. SUBSIDENCE OF MOUNTAINS. 159 CHAPTER XXVIL GRADUAL SUBSIDENCE OF MOUNTAINS DURING THE LAPSE OF AGES. SUD- DEN DOWNFALLS AND CHAOS. THE FALL AT FELSBERG. SLOW ACTION OF METEORIC AGENCIES. THE formidable mountain citadels which tower up so high over the habitations of man, along the sides of which creep clouds and thunder, do not, however, escape a slow but certain process of sinking so soon as the upheaving force which pushed them out of the earth has ceased to act. Assisted by the force of gravity which is constantly tending to level the surface of the ground, meteoric agents are unceasingly persistent in the destruction of mountains. They open valleys and gorges, they hol- low out passes, they undermine their summits, either by sudden down- falls, or, more generally, by a slow and continuous erosion. Sooner or later, the Andes and the Himalaya, those mighty continental ridges, will become mere ranges of hills, like many another ancient mountain chain, which, too, once formed the back-bone of a world. Great mountain downfalls, although of no very great importance in a geological point of view, are among the most tremendous phenomena of planetary vitality : whenever such a catastrophe has occurred, tradition has handed down the recollections of it for long centuries. No event is calculated to produce a more forcible effect in the popular mind. Per- pendicular or overhanging rocks, which seem to hang suspended over the plains, suddenly become detached and rush headlong down the mountain side ; in their rapid fall they raise a cloud of dust like the ashes vomited forth by a volcano ; a horrible darkness is spread over the once pleasant valley ; and the cataclysm is known only by the trembling of the ground and the crushing din of the rocks striking together and shattering one an- other in pieces. When the cloud of dust is cleared away, nothing but heaps of stones and rubbish are to be seen where pastures and cultivated land once were ; the stream flowing down the valley is obstructed in its course and changed into a muddy lake ; the rampart of rocks has lost its old form, and on its sides, from which some d&bris are still crumbling down, the sharpened edges point out the denuded cliff from which a whole quarter of the mountain has broken away. In the Pyrenees, Alps, and other important chains, there are but few valleys where we may not no- tice these chaos-like heaps of fallen rocks. The principal catastrophes of this kind which have taken place in the mountains of Europe during the present era are facts which are well known. Southward of Plaisance, in Italy, the ancient Roman town of Velleja was buried about the fourth century by the downfall of the only too-well-named mountain of Rovinazzo, and the large quantity of bones and coins that have been found proves that the subsidence of the rocks was so sudden that it did not even afford the inhabkants any chance of 160 THE EARTH. escape. Tauretunum, another Roman town, situated, it is said, on the banks of the Lake of Geneva, at the base of one of the spurs of the Dent d'Oche, was completely crushed in A.D. 563 by a downfall of rocks ; the declivity that it formed may still be seen advancing like a headland into the waters of the lake, which at this spot is not less than 520 feet deep. A terrible flood-wave, produced by the deluge of stones, invaded the op- posite shores of the lake, and swept away all the habitations fromMorges to Vevay every town and every village on the banks was demolished ; and they did not commence to rebuild them until the following century. Geneva itself was in part covered by the water, and the bridge over the Rhone was swept away. According to MM. Troyon and Morlot, howev- er, these disasters were caused by a landslip which fell from the Gram- mont or Derochiaz across the valley of the Rhone, just above the spot where it flows into the Lake of Geneva. The effect of this was the for- mation of a temporary lake, and the shores were devastated by an inun- dation at the time of the destruction of the natural barriers by the accu- mulated water.* The great downfalls of rocks which have taken place during historical periods, in the Alps and neighboring mountains, may, in fact, be reckoned by hundreds. In 1248, four villages situated at the base of Mont Granier, not far from Chambery, were buried under a mass of calcareous rubbish, which the water-courses have now ravined out and moulded into little hillocks ; small pools, known by the name of abimes, are dotted about amongst these heaps of debris, which are nowadays covered with cultiva- tion. In 1618 the downfall of Monte 'Conto buried the 2400 inhabitants of the village of Plurs, near Chiavenna. Two out of the five peaks of the Diablerets fell down, one in 1714, and the other in 1749, covering the pas- tures with a layer of debris more than 300 feet thick, and, obstructing the course of the stream of Lizerne, formed the three lakes of Derborence which are now existing. In like manner, the Bernina, the Dent du Midi, , the T)ent de Mayen, and the Righi have overspread with their fragments vast tracts of cultivated land ; but no catastrophe of this kind has left more fearful reminiscences of horror than" the fall of a section of the Ross- berg on the 2d of September, 1806. This mountain, situated to the north of the Righi, in the centre of the peninsula-like space formed by the lakes of Zug, Egeri, and Lowerz, consists of a compact conglomerate, lying on beds of clay, which hinder the infiltration of the surface water. At some unknown epoch the falling rubbish of a mountain spur destroyed the vil- lage of Rotten ; but in 1 806 the catastrophe was still more terrible. The season which had just terminated had been very rainy, and the clay strata had gradually changed into a muddy mass ; at last, the rocks above, los- ing their supporting basis, began to slip down the mountain side, plowing up the ground in front of them like the bow of a ship pushes up the water before it. Suddenly a general break up took place. In a moment, an enormous mass, carrying with it forests, meadows, hamlets, and inhabit- ants, rushed down into the plain. Flames, produced by the friction of * Bulletin de la Societe" Vaudoise. FALL OF MOUNTAIN MASSES. 161 the rocks striking and rubbing against one another, broke in fiery jets from the half-opened mountain. The water deposited in the deep beds, suddenly converted into steam, burst out with explosive force, and show- ers of mud and stones were vomited out as from the mouth of a volcano. The charming plains of Goldau (the Vallee d'Or), and four villages, inhab- ited by nearly a thousand persons, disappeared under the heaps of debris; the Lake of Lowerz was partly filled up; and the furious wave which the falling mass drove up on to the banks swept away all the houses on it. The catastrophe occurred in so sudden a way that the very birds were killed as they were flying in the air. The portion of the mountain which slipped down was not less than two miles and a half long, by about 350 yards wide and 35 yards thick ; it was a mass containing more than fifty- four millions of cubic yards.* Fig. 43. Great Landslip of Goldau. Whatever may be the geological importance of these fearful mountain downfalls, still they are but phenomena of a secondary class in compari- son with the results produced by the slow and gradual action of various atmospheric agencies frost, air, and rains. These are the incessant and indefatigable workers which, by their continual labor, have enlarged the first clefts open here and there in the thickness of rocks, and have hollow- ed out all the net-work of passes, amphitheatres, combes, defiles, cluses, glens, and valleys, the endless ramifications of which add so much variety to the mountain structure. Owing to these operations, continued with- out intermission during the long centuries of geological periods, the lofti- est summits are being gradually lowered, and the materials derived from their slopes are spread far and wide over the plains, or borne down to the waters of the ocean. * Henri Zschokke. OttoVolger, Erdbeben der Schweiz. L PART III. THE CIKCULATION OF WATER. CHAPTER XXVIII. SNOW-FALL ON MOUNTAINS. LOWER LIMIT OF SNOW. ZONE OF PERPET- UAL OR PERMANENT SNOW. THERE are few sights more charming than that of the clouds sweeping in long trains over the sides of a mountain, and leaving behind them on the slopes a covering of fresh-fallen snow. We may often notice that the lower portion of a cloud breaks up into showers, and inundates with rain the less elevated slopes, while higher up the colder vapors are discharged in flakes of snow. A line, which is sometimes uncertain, but is usually pretty definitely traced across the declivity of the mountain, marks out the limit of temperature above which the clouds fall in snow, and runs with remarkable regularity above the verdant tracts which have been watered by the rain. This lower snow-limit is traced round the mountain side at different elevations, according to the seasons. In winter it gradually descends to the base of the Alps and Pyrenees ; in spring and summer it rises little by little toward the summits, and even mounts above them when they do not reach any very great elevation. For the most part, however, the higher mountain chains have their ridges always covered with snow, and a line may be drawn across their declivities, changing more or less in va- rious centuries and years, above which the snow never entirely melts. This is the so-called snow-line, or limit of the perpetual snow ; it would be better described as the limit of permanent snow. Above the lower snow-line the snow is constantly being partially melt- ed and then again renewed ; thus the bed of snow-flakes becomes gradu- ally thicker and more heaped up, owing to the fall of the temperature in these high regions. More snow, in fact, falls than the rays of the sun and the heat of the earth can dissolve in one warm season ; enormous masses, therefore, fill up alt the gorges and ravines, and drifts of several yards in depth cover those rocks and cliffs which are not too steep to allow the snow to accumulate on their slopes. All lofty mountains are, therefore, clad with veils of snow ; but it is certain that if they rose to a still more considerable elevation into the regions of air, they would ultimately, and indeed before long, reach a limit-line above the very snow itself. In fact, SNOW-FALL ON MOUNTAINS. 163 the cold regions of the higher atmosphere contain only a very small pro- portion of misty vapor; and the scanty flakes of snow which would fall on summits 45,000 to 60,000 feet high (if any such existed) would be soon swept away by the wind or melted by the solar rays. On the sides of a mountain of this elevation there would be a belt of permanent snow, bounded on the lower side by a region of pasture-ground, and on the upper by tracts of desert perfectly devoid of vegetation.* According to Tschudi, the quantity of snow which falls on that portion of the Alps which is above a height of about 10,800 feet is comparatively very small. Most of the clouds charged with snow-flakes discharge their burden on the mountain slopes at elevations of 7600 to 8600 feet. At these heights moisture falls sometimes also in the form of rain; but at 10,000 feet the clouds but rarely assume the shape of showers, and at 12,000 feet they bring nothing but snow. Observations made in the Alps prove, however, that the quantity of snow falling on different mountains varies singularly, according to the altitude and the aspect of the slopes; and in each par- ticular locality^ according to the climatic circumstances of the year. At the Hospice of Grimsel, situated at a height of 6148 feet, M. Agassiz no- ticed a fall of snow in six months of winter amounting to 57 feet equiv- alent to five feet of water. Some years afterward, in the same place, W. Huber, the engineer, ascertained that the thickness of the bed of snow was 59 feet during a period of double this duration. On the St. Bernard, at 8110 feet of altitude, the thickness of snow has varied during twelve years (from 1847 to 1858) from 11^ feet to 44 every year. This would give a difference of one and four in a yearly snow-fall on the same point of the mountain.f It appears that on the St. Gothard, at an elevation of 6867 feet above the level of the sea, the annual deposit of snow is more considerable than on the St. Bernard ; for in one night's time the thick- ness of the fallen snow was sometimes increased as much as 6^ feet. J The snow which falls on the mountain summits is but seldom composed of those elegant shapes, the marvelous configuration of which we so much admire in the valleys. It usually consists of small granules as fine as dust, slender needles of ice, and stars with almost imperceptible rays ; it is, in fact, sleet, and not snow, properly so called. It often happens that the slightest change in the direction of the atmospheric currents substi- tutes a fall of granular snow for one composed of flakes, or produces the reverse phenomenon. We can not, however, as Agassiz has pointed out, establish any well-defined distinction between the two different kinds of sleety or flaky snow. It is very difficult, or, indeed, impossible, to fix the altitude above which beds of snow may always be perceived on various groups of mountains. This limit varies according to the aspect and inclination of the slopes, the nature and color of the rocks, the force and average direction of the winds, the quantity of the snow which falls, and all the meteorological * Hiimbolclt, Tyndnll. t Bibliotheque de Geneve. I Eugene Flaclmt, La Traverste det Alpes. THE EARTH. phenomena of the region into which the summits rise. It is, therefore, only approximately, and entirely in a general way, that we can venture to point out the height of this unsettled line, fluctuating, as it does, from year to year, and from century to century, under the combined influence of solar heat and atmospheric agencies. According to the brothers Schlagintweit, the so-called limit of perpetual snow in the central Alps would fluctuate between 9000 and 9240 feet of altitude; and for the group of Mont Blanc, between 9400 and 10,200 feet. Nevertheless, it is very certain that in September, 1842, a neighboring mountain to the Jungfrau the Ewigschneehorn, the German name of which signifies peak of eternal snows showed nothing but the bare ground on all its slopes.* In like manner, in 1860 and in 1862 the summits of the Alps presented only partial stains of white snow, and tourists could cross the Strahlech (10,993 feet) without walking for a single instant on any snow, either fresh or hardened.f In 1855 Sonklar could not perceive a trace of snow on the Hangerer, a mountain in the Austrian Alps, which rises to a height of 9994 feet.J Similarly, in the autumn of 1859, the summit of the Cha- berton (10,295 feet), near Mont Genevre, was completely bare of snow. With regard to the Pyrenees, in which the limit of permanent snow would be from 9000 to 9240 feet in height, it is certain that the Montcalm, which rises to an elevation of 10,101 feet, is topped by a kind of plateau which is often perfectly clear of snow during the hot season, and even dotted over with bunches of grass. On the Spanish side of the Pyrenees, toward the middle of August, nothing but the bare rock is to be seen, except in the deep hollows which the south wind can not penetrate. The ideal snowy zone with which geographers clothe the lofty Pyrenean peaks has, in fact, no absolutely permanent existence. The same thing may be likewise affirmed of a large number of mount- ain chains that we are accustomed to class with those which are crowned by perpetual snow. The ideal line, therefore, which is traced in most atlases as fixing the limits of the snowy zone on the outline of mountains can only be considered as having an approximate value. According to Durocher, the line of perpetual snow, which passes at a height of 13,731 feet over the sides of the equatorial Andes, would be only 705 feet lower than on the great mountains of Mexico Popocatepetl and Orifcaba. There is another phenomenon which is much more surprising still : in the southern hemisphere, south of the Peruvian Andes, this snow-line ceases to sink, and even rises to more than 16,500 feet of altitude. On the pla- teaux of the Chilian and Argentine Andes, between 22 and 33 degrees of south latitude, where the temperature naturally falls much lower than in the corresponding regions of Ecuador, the mean limit of snow is actually higher ; which, nq doubt, is owing to the great dryness of the winds. Thus travelers have seen the slopes of the Cordillera of Mendoza on the * Desor, Nouvelles Excursions. t Dollfuss-Aussett, Materiaux pour I'Etude des Glaciers, vol. v. f (Etzthaler Gebirgsgruppe. LIMIT OF PERMANENT SNOW. 165 22d degree of latitude swept perfectly clear of snow up to the height of 13,200 feet; at four degrees farther north no white surface is seen to glitter on the Sierra Fa mat ma (14,764 feet). In the Tropic of Capricorn, the Sierra de Zenta, the summits of which rise 16,404 feet above the level of the sea, is but very rarely covered with snow even during the winter, and the layers of flakes which are brought by the clouds im- mediately melt. Lastly, according to Pentland, the western slopes of the Bolivian Andes, which are very seldom blown upon by damp winds, exhibit no instances of perpetual snow at a less height than 18,370 feet. In a general way, any humidity that falls evaporates without giving rise to the smallest rivulet of water, or even without moistening the ground. Toward the middle of the day, the clouds may be seen from afar floating up from the heights of the mountains like smoke, and disappearing at an immense altitude in the deep azure ; these are the snows of yesterday re- ascending into the atmosphere in the form of vapor.* The astonishing contrast, as regards the lower snow-limit, between the northern slopes and the southern side of the mountain chains of Central Asia, must be attributed to the unequal distribution of the rain-fall. The climate is naturally much more rigorous on the north side of the Hima- laya than in the valleys turned toward the south, and yet in the former Fit;. 44. Limit of Permanent Snow in South America. the snow-covered tracts do not descend nearly so low. This contrast is so striking that every traveler has remarked it, and has even exaggerated its importance, until the recent explorations of the brothers Schlagintweit. According to Hooker, the botanist, on the southern sides of the Himalaya the mean limit of perpetual snow exceeds 13,943 feet, and on the opposite slope rises to 18,589 feet of altitude ; so that precisely the coldest side is denuded of snow at a point 4646 feet higher than the declivities exposed * Martin de Moussy, Confederation Argentine, vol. i. THE EARTH. to the burning sun of Hindostan. The comparative observations of the brothers Schlagintweit have considerably reduced this enormous differ- ence between the two slopes.' For the southern and northern slopes, these travelers have ascertained the mean limits to be respectively 16,049 feet and 17,237 feet, which reduces the total difference to 1188 feet. But farther on in these regions the contrast may be made more considerable, for in Thibet many mountains, at an altitude of even more than 20,000 feet, may be seen denuded of every snowy particle. Lately, in accordance with Humboldt, this great height of the snow-limit on the northern slopes of the Himalaya was attributed to the reaction of the solar rays after falling on the plateaux of Central Asia ; but the brothers Schlagintweit, by showing that Thibet is actually a large valley of mountains, and not a plateau, have put it beyond doubt that the cause of this contrast between the snowy slopes must be sought for in the system of winds. On the north, the aerial masses which sweep over the Himalaya after having traversed the whole of Central Asia are perfectly dried up ; but on the south, the monsoons which rush stormily through the gorges of JSTepaul and Sikkim are charged with an enormous burden of moisture, which falls in snow on the high summits and in rain on the valleys beneath. On the mountain chains which extend to the north of the Himalaya the mean limit of perpetual snow descends regularly as the chains lie far- ther north. In the Karakorum, where this ideal line is higher than in the Himalaya, on account of the great dryness of the air, the respective alti- tudes are, in the southern chain 19,225 feet, and in the northern slope 18,438 feet; in the Kouen-Lun they are, on the south, 15,640 feet, and 14,960 feet on the north. As regards the other chains of Central Asia no exact observations have been made, except for the Altai', in which the mean limit of perpetual snow is at 7034 feet. In a general way it is allowed that about the 75th degree of north lat- itude the snow-limit coincides with the level of the sea; but, as Richard- son has shown, no arctic regions have yet been discovered which in the height of the summer are covered with a permanent layer of snow, and very probably none such exist.* Therefore, as regards these polar coun- tries, as well as for most of the mountains in the temperate zones, the ex- pression of " perpetual snow" ought to be erased from scientific phraseol- ogy. We must also refrain, notwithstanding the example set us by many meteorologists, from laying down any general law in reference to the mean limit of snow ; for the atmospheric phenomena in the various parts of the world are not yet sufficiently well known, and the distribu- tion of heat, the direction and humidity of the winds, vary quite as much as the forms of the continents themselves. The more important point, therefore, is, not the mere recognition of the uncertain and variable line of the lower snow-limit on mountain slopes, but the establishment, as regards the most varied points, of the mean quantity of snow which falls annually on the sides and summits of mount- * Vide the chapter on "Climates." VARIATION 1ST THE SNOW-LINE. 167 ains, these facts being derived from observations carried on season after season and year after year. In like manner, as regards a river, neither the low-water mark nor the point reached by the highest floods is the fact which is the most essential to ascertain, for these levels relate but to an instant of fluviatile vitality, and their sole value is only as a means of comparison with other such levels ; the more useful questions are the mean discharge of the flow of water, and the resultant presented by the incessant fluctuations of the stream. CHAPTER XXIX. INFLUENCE OF THE SUN AND METEORIC AGENTS ON THE SNOW. AVA- LANCHES. PROTECTING FORESTS. DEFENSIVE WORKS AGAINST DOWN- FALLS OF AVALANCHES. THE accumulated layers of snow do not remain forever on the sides and summits of mountains. Since every year, on the average, 33 feet of snow fall on the mountains of the Alps, these peaks would, in fact, in the course of a century, increase 33,000 feet in height, if the humidity falling from the clouds in the form of snow-flakes was not evaporated into the atmosphere, or did not find its way down into the valleys below. The heat of the sun and meteoric influences commence the work of clearing away the snow. It has been calculated that the solar rays will melt as much as 20 to 28 inches of snow in a day, especially when the upper layers are not very dense, and allow the heat to penetrate to some depth under the surface. The rain and tepid mists which the winds con- vey on to the mountain slopes also lend their aid in thawing the snowy layers, and sometimes indeed with more effect than the rays of the sun. The cold winds likewise assist by blowing up the snow into whirlwinds, and thus transferring it to lower slopes where the temperature is higher. There is not one violent wintry squall which does not remove thousands of cubic yards of snow from the summits of lofty mountains, as may easily be seen from below, when the peaks beaten by the wind appear to smoke .like craters, and the powdered flakes are dispersed in whirlwinds. The warm and dry winds, however, effect still more than storms in di- minishing the masses of snow which lie heavy on the summits. Thus the south wind, which is called fohn by the Swiss mountaineers, will in twelve hours melt or cause to evaporate a bed of snow three quarters of a yard thick. It " eats up the snow," as the proverb says, and brings spring back again on the mountains. Next to the sun, the fohn is the principal climatic agent in the Alpine districts. It would be very important if we could establish the average propor- tions of the masses of snow which fall upon the mountains which are lost by melting and evaporation respectively. In valleys where the sides are composed of hard rocks which retain the water on the surface, it would suffice to measure the annual discharge of the torrent, and to compare it with the quantity of rain-water and snow which has fallen in 'the basin during the same period, and we should approximately ascertain all that has been lost en route, being drawn from it either by the innumerable roots of the plants growing in it, or directly by evaporation. At all events, it is certain that this latter cause of diminution is very important, MELTING OF MOUNTAIN KNOWS. 169 for even during calm weather, and at three or four degrees below freez- ing-point, the superficial surface of the snow constantly supplies to the atmosphere a certain portion of aqueous vapor. Under the influence of the sun and wind evaporation increases very rapidly. But these slow and gradual means are not the only causes of the dimi- nution of the mountain snows ; they also sink down in masses into the valleys, and thus expose themselves directly to the influence of heat. The masses which thus rush down the slopes are avalanches, likewise called in the Alps lavanges and challanches. The greater part of these downfalls of snow occur with great regularity, so much so that an old mountaineer, who is clever at discerning the signs of the weather, can often announce by a mere glance at the surface of the snow the exact time at which the subsidence will take place. The path of the avalanche is completely marked out on the mountain side. At the outlets of the wide mountain amphitheatres in which the snows of winter are accumu- lated, narrow passages open, hollowed out in the thickness of the rock. Like torrents, only that they appear but for a moment and are suddenly gone, the masses of snow which are detached from the upper declivities rush down the inclined beds afforded them by the narrow passages, and descend in long trains, until, arrived at the ledge of their ravine, they pour out over the slope of debris. Most mountains are furrowed over their whole extent with vertical channels, down which the avalanches rush in the spring. These falling masses become actual tributaries of the streams which run below ; only, instead of flowing continuously as the rivulets of the cascades, they plunge down all at once, or in a succession of falls. On slopes where the inclination exceeds 50, the snows not only de- scend through the passages hollowed out here and there on the mountain sides, but they also slide en masse over the escarpments. Their gradual progress being more or less rapid, at first they accumulate in heaps when they meet with any obstacle in the less sloping portions of their track, until, becoming animated with a sufficient momentum, they at last break forth with a crash, and dash down into the depths below. The particular way in which each avalanche descends is, of course, varied according to the shape of the mountain. On perpendicular escarpments the snow on the upper terraces is slowly impelled by the pressure of the masses above it, and plunges over, straight down into the abyss below. In spring and summer, when the white layers, softened by the heat, are falling away every hour from the lofty summits of the Alps, the mountain climber, standing on some adjacent headland, may contemplate with admiration these sudden cataracts dashing down into the gorges from the heights of the shining peaks. How many thousands of travelers, seated at their ease on the grassy banks of the Wengemalp, have witnessed with excla- mations of pleasure the avalanches rolling down to the base of the sil- very pyramid of the Jungfrau ! First the enormous bed of snow is seen to plunge forth like a cataract, and lose itself in the lower stages of the mountain ; whirlwinds of powdered snow, like a cloud of bright smoke, 170 THE rise far and wide into the atmosphere ; and then, when the snow-cloud has passed away and the whole region has again assumed its solemn calm, the thunder of the avalanche is suddenly heard reverberating in deep echoes in the mountain gorges, one might fancy it was the voice of the mountain itself. All these downfalls of snow are phenomena in the economy of mount- ains, no less regular and normal than the flowing of the rainfall into riv- ers, and they form a part of the general system of the circulation of wa- ter in every basin. But in consequence of the superabundance of snow, its too rapid melting, or some other meteorological cause, certain excep- tional avalanches, like the inundations caused by river -floods, produce most disastrous effects by laying waste the cultivated grounds on the lower slopes, or even by swallowing up whole villages. Catastrophes of this kind and the falls of rocks are the most formidable occurrences in the vitality of mountains. The avalanches known under the name "of poudreuses are those most dreaded by the inhabitants of the Alps, on account not only of the rav- ages immediately arising from them, but also of the whirlwinds which frequently accompany them. Before the newly -fallen layers of flakes sufficiently adhere to the former snow, the mere tread of the chamois, the fall of a branch from some bush, or even a resounding echo, is suffi- cient to disturb the unstable balance of the upper sheet of snow. At first it slides slowly over the hardened mass beneath, until, reaching a point where the slope of the ground assists its progress, it rushes down with an increasingly rapid movement. Every moment it becomes aug- mented by fresh beds of snow, and by the debris, stones, and brush-wood, which it hurries along with it. It makes its way over the ledges and passages, tears down the trees, sweeps away the chalets which lie in its path, and, like the downfall of the side of a mountain, plunges into the valley, sometimes even reaching the opposite slope. All round the ava- lanche powdery snow rises in broad eddies ; the air, being compressed laterally by the sinking mass, roars right and left in actual whirlwinds, which shake the rocks and uproot the trees. Thousands of trunks may sometimes be seen thrown down by nothing but the wind of the ava- lanche, when the latter traces out for itself a wide path across whole for- ests, and, as it passes, sweeps away the hamlets in the valley.* The avalanches de fond are generally less dangerous than those we have just spoken of, because they are formed at a more advanced season of the year, when the greater part of the superficial snow is melted, and the remainder of the mass is able to run through its regular passages. As their name indicates, these avalanches are composed of the whole thickness of the snow-field. Lubricated, as it were, by the rivulets of water which cross them and flow over them, the beds of snow lose their adherence to the ground, and slide in one lump, like marine icebergs de- taching themselves from a field of ice. Under the pressure of these mov- * Tschudi, Le Monde des Alpes, vol. ii. DEFENSES AGAINST AVALANCHES. ing masses, the snow below at last yields, and the avalanche, loaded with water and mud, earth and stones, rushes through the passages and over the rocks ; at last, finding its way into the valley, it dams up the stream with a kind of dike, which sometimes resists the weight of the water till the middle of summer, and the gray or even blackish mass becomes so com- pact that it assumes the hardness of rock. It is, in fact, a glacier in miniature. Thickly-planted trunks of trees are the best protection against ava- lanches of every kind. In the first place, the snow which has fallen in the wood itself can not very well shift its place ; and then, when the masses descending from the slopes above dash against the trees, they are unable to break through so strong a barrier. After having overturned some few of the first trees, their progress is arrested, and the intermingled heaps constitute a fresh obstacle for future avalanches. Small shrubs, such as rhododendrons, or even heaths and meadow grass, are very often sufficient to prevent the slipping of the snow, and where people are imprudent enough to cut them on the mountain slopes, they run the risk of clearing the way for this formidable scourge. The danger is still more imminent if a screen of trees is cut down in one of the protecting forests. The task is then begun for the avalanche, which soon undertakes to complete the rest of the labor by tearing up all that still remains of the former woody rampart. A mountain which stands to the south of the Pyrenean village of Aragnouet, in the lofty valley of the Neste, having been partially cleared of trees, a tremendous avalanche fell down, in 1846, from the top of a plateau, and in its fall swept away more than 15,000 fir-trees. The protecting woods of Switzerland and the Tyrol used to be defend- ed by the national bann, and, as it were, " tabooed." They were, and still are, called the Bannwadder. In the valley of Andermatt, at the northern foot of the St. Gothard, the penalty of death was once adjudged on any man found guilty of having made an attempt on the life of one of the trees which shielded the habitations. Added to this, a sort of mystic curse was thought to hang over this impious action, and it was told with horror how drops of blood flowed' when the smallest branch was broken off. It was true enough that the destruction of each tree might perhaps be expiated by the death of a man. The inhabitants of some villages which are threatened with avalanches endeavor to find a substitute for trees in long stakes or piles driven into the ground to resemble fir-trees. This is what they call clouer I 'avalanche (nailing up the avalanche). At the same time, they hew steps at inter- vals, almost like a staircase, so that the snow falling from the cliffs may be arrested in its course or partially broken up. In some localities, too, they construct lateral walls on purpose to contain the flow of the ava- lanche, as if it were a banked-up river; and if, after all these precautions, the houses are still threatened, they furnish them, like the piles of a bridge, with spurs or buttresses, made of stone or hardened snow, which, by sprinkling, is gradually changed into ice.* * William Hubcr, Les Glaciers. 172 THE EARTH. The village and the great establishment of the baths at Bareges, in the Pyrenees, used to be menaced every year by avalanches rushing down from an elevation of 4000 feet, at an angle of 35 degrees. The inhabit- ants, therefore, were in the habit of leaving vacant spaces between the two quarters of Bareges, so as to allow a free passage to the descending masses. Lately, however, they have endeavored to do away with the avalanches by means somewhat similar to those employed by the Swiss mountaineers. They have thrown up banks about 10 or 12 feet broad on the sides of the ravines, and have furnished these banks with an edg- ing of cast-iron piles. Basket-work, and, here and there, walls of mason- ry, protect the young growing trees, which are gradually improving un- der the pi-otection of these defensive works. In the mean time, until the real trees are strong enough to arrest the course of the snow, the artificial trees have well fulfilled the end they were destined for. In 1860, the year when the defensive works were finished, the only avalanche which slid into the ravine did not exceed 400 cubic yards in bulk; while the masses which used to fall down upon Bareges sometimes attained to more than 90,000 yards in volume. CHANGE OF SNOW INTO ICE. 173 CHAPTER XXX. GRADUAL TRANSFORMATION OF SNOW INTO ICE. NEVES, OR GLACIER-RES- ERVOIRS. PHENOMENON OF REGELATION. CRYSTALS OF ICE. GLACIERS OF THE FIRSf AND SECOND ORDER. BY a succession of partial changes affecting the millions of frozen par- ticles, the snow of the high mountain summits is changed into ice, and the white flakes falling on the peaks become those rivers of bluish crys- tal which slowly make their way down between the sides of the -gorges. Imperceptibly the field of snow^ is changed into neve, and then into gla- cier ; afterward becoming in succession stream, river, and wave, it finally, under the form of aqueous vapor, recommences its eternal circuit. The alteration of opaque snow into transparent ice is one of the most interesting phenomena of planetary vitality. The newly-fallen flakes be- gin by first settling down and hardening. Then, when the rays of the sun have raised the temperature of the snow-field to melting-point, a number of small drops penetrate into the subjacent layers, and, being again assailed by the cold, freeze into small envelopes, irregularly-crys- tallized round solid molecules, and become cemented all together into a compact mass. The snow may thus become *">.'_,; ^; ^, - ' very lianl, :md on the edu'e of many of the ^lY li precipices it forms a kind of overhanging pent- house, which resists for a considerable time the effects of the weather without giving way. We borrow from Forbes the design of one of these elegant cornices, with its brilliant pend- ants of ice. In the end, the entire thickness of the snow- field changes its structure and becomes a mass of granules, from which the air is partially ex- pelled by the successive freezing and melting Fig. 45. CoruIceofSnow. , * , . , T *i produced by the solar heat. In this way are formed the hard and granular beds of former snow, which lie upon the upper slopes of all lofty mountains ; these whitish or dull gray masses are known in the Alps and Pyrenees by the name of neves. In winter, when the temperature often remains below the freezing-point, even during the day-time, the snow on high summits maintains its powdery state ; but as soon as it is subjected to the first breath of spring, it begins to assume a granular form.* The first change in the particles of snow is but the prelude to still * Desor, -V' uretlei Excursions et St jours dans les Glaciers. THE EARTH. more important modifications. The heat of the sun continues to melt the surface-layers, and thus causes drops of water and laminae of ice of an increasing size to penetrate into the neve. Simultaneously the snow, compressed by its own weight, ultimately expels by mechanical force the greater part of the air which it contains, and gives to the opaque granules of the neve the structure and transparency of ice. The pressure of the superincumbent- layers is the principal agent in the transformation of beds of snow. The brothers Schlagintweit and Tyndall state that by the com- pression of fresh snow they succeeded in obtaining slabs, of transparent ice ; but there is scarcely a child who has not amused himself in trying the same experiment by kneading a snow-ball with his fingers. Under the tread of the pedestrian, the coating of snow which sticks to his shoes ultimately becomes a piece of ice.* In consequence of this gradual transformation, the mass of neve becomes more and more indurated and compact. A cubic yard of snow weighs on the average 1871bs. ; but the same volume of neve weighs more than half a ton, and the various modifications to wljich the snow is subject in becoming transparent ice ultimately give it a weight of about 1980 Ibs. per cubic yard. The material which constitutes the glaciers is twelve times lighter than water when it commences its course, but at the end of its career it is only one tenth or one twentieth part inferior in weight to an equal liquid volume.f Notwithstanding these successive changes, the whole thickness of the mass of neve is composed of strata of varying regularity, which are the beds of snow deposited in successive winters. Each of the superimposed beds exhibits on its surface a kind of gray or yellowish crust, which is formed by the mixture with the snow of bits of stone, dust, and even the remains of insects ; under this crust extends a thin layer of glazed ice, caused by the freezing of the water which had melted on the surface. The strata of the neve, being thus arranged one above the other like the beds in a calcareous rock, are, in proportion to their age and the weight that is laid upon them, all the more compact and ice-like in their texture. In many places these strata may be perceived at the edge of the neve; for wherever the rocks rise above the upper snow-limit a kind of cleft may be noticed in the neve, owing partly to the rending force exercised by the whole mass .on the upper beds, and still more, perhaps, to the flowing of the water which trickles round the base of the rocks which are warmed by the sun. Below the neve, which is, in fact, the reservoir in which the ice begins to form which afterward is to feed the glacier properly so called, the frozen masses continue to become gradually modified as regards their internal structure. It is very true that a great part of the ice, which is melted by the rays of the sun, the rain, or the mild breath of warm winds, remains in a liquid state, and in the form of rivulets finds its way through * William Huber, Les Glaciers. t Dollfuss-Ausset, Materiaux pour servir a I' Etude des Glaciers. FORMATION OF GLACIERS. 175 the crevices of the glacier, and joins the stream which flows over the rocks' below. But there is another agent at work as well as the sun in the process of melting the ice in the very heart of the layers. This agent is the pressure exercised by the upper masses on the ice lying beneath them. Natural philosophers have, in fact, proved that the melting temperature of ice lowers forty-two ten thousandths of a degree (Fahr.) for every at- mosphere* of pressure. At the foot of rapid slopes, where the enormous weight of the layers above compresses the ice with the force of a large number of atmospheres, the liquefying point of the mass is considerably lowered, a greater or less amount of latent heat is set free, and a portion of the ice must melt and pass into water. Thus-, in consequence of this pressure, cells and liquid veins are here and there opened in the interior of the glacier, the mean heat of which is, however, only a mere fraction of a degree lower than the freezing-point. The protracted and numerous experiments of Agassiz have proved that in a deep hole sunk to a depth of 200 feet in solid ice the thermometer marked on the average 31 24' (Fahr.), and that only in winter, and quite exceptionally, the temperature was lowered to 28 24' (Fahr.) ; in the open air the cold was most intense. Owing, therefore, to the comparatively high temperature of the ice, small Fig. 46. Internal banded Structure of Ice. veins of water are formed which penetrate its entire mass. Nevertheless, the particles of ice which divide the thin films of water remain separate only for an instant ; for even under a slight pressure, very much less than that which is brought to bear upon glaciers, two morsels of ice surrounded by water immediately approach one another, and unite to form a single lump. Even in warm water two pieces of ice which are melting continually strive to combine, and the isthmus which joins them forms and reforms until the last solid particles have disappeared. This is the great fact which was discovered by Faraday, and brilliantly demonstrated by Tyn- dall, who has given it the name of regdation. This phenomenon takes place at 'every point in the thickness of the glacier. Particles of ice approach one another, and unite across the little veins of water which permeate it in every direction; fresh liquid films are formed under the pressure above; fresh unions take place between the divided morsels of ice ; and, by this continual process of change, the air contained in the mass of that which once was snow is gradually expelled. Thus it happens that the whole mass ultimately assumes an almost perfect transparency and a beautiful azure color. It is, however, the case every winter that * A weight equivalent to that of a column of wnter of about 32 feet. 176 THE EARTH. the clefts on the surface of the glaciers are filled up with fresh masses of snow. These new layers, to which an intermixture of air-bubbles gives a whitish tint, are dragged and thrown forward by the general move- ment. In several glaciers, where mighty crevasses disclose the internal structure of the whole mass, it is wonderful to see the alternate stratifica- tions of gray snow and the blue belts of ice, just like the beds of a forma- tion of rocks. On high elevations neve and glacier are intermingled together. In climbing Monte Rosa, Zumstein saw, down in a crevasse of neve, real glacier ice, at a height of 13,989 feet, less than 1300 feet below the summit. Nevertheless, whatever may be the modifications which the snow un- dergoes, it is a matter of fact that, even in the lower parts of glaciers, granules are found similar to those of the neve, only these grains have be- come transparent and free of air-bubbles, and in their long course toward the valleys have considerably increased in size. Some of them are as large as a chestnut, or even a hen's egg. These granules of ice are some- times very irregular in shape, owing to the enormous pressure to which they have been subjected, sometimes in one direction and sometimes in another; but the phenomena of polarization which they present to the light prove that they are really crystals,* and the whole glacier is an ac- cumulation of granules confusedly packed together. From the moment when the snow-flakes fall in the shape of needles and stars, to the time when they are reai*ed up in blue walls, it never ceases, under all its va- rious aspects, to retain a crystalline character. The snows which are thus transformed into ice by the effects of press- ure form the enormous masses which cover the mountain sides and fill up whole valleys. Some of these glaciers those of the Pyrenees, for in- stance only extend over the upper slopes of the mountain, and do not descend through the gorges as far as the cultivated grounds at its base. These are the glaciers which Saussure calls Secondary or summit glaciers. There are other fields of ice which also take their rise on lofty peaks, and, flowing out into the mountain amphitheatres, make their way into the lower valleys, uniting, on each side of their beds, with the ice of other tributary gorges; these are glaciers of the first order. There are some which extend to a length of 12, 18, or 30 miles, and attain a thickness of several hundred yards. These are easy to class ; but in nature the transi- tions are so gradual that, as regards the greater number of glaciers, it is impossible to point out precisely in which category they ought to be classed. The distinction established by geologists is purely artificial. * Sonklar, (Etzthaler Gebirgsgruppe. EXPERIMENTS. 177 CHAPTER XXXL ilOVEMENT OF GLACIERS. EXPERIMENTS AND THEORIES. CONVEXITY OF THE CENTRAL PART OF A GLACIER. ITS SUCCESSIVE WINDINGS. FRIC- TION OF THE ICE AGAINST THE BOTTOM AND SIDES OF THE BED. THE GLACIER GAUGE. INCLINATION OF THE GLACIER BED. THE Alpine mountaineers, from time immemorial, have been aware of the fact that glaciers move onward, and convey masses of rock from the mountain summits down into the valleys ; but it was unknown to most geographers, shut up as they were in their gloomy studies. At the end of the sixteenth century, Simmler announced this marvelous fact, and other savants repeated it after him ; but it was not generally known until the end of the last century, after the publication of Horace de Saussure's travels. This traveler, one of the first of that generation of energetic men who knew well how to combine scientific inquiry with skill, strength, and endurance, and could also both hit upon and unravel the mysteries of nature, verified the movement of glaciers, and attempted to propound a theory for it. He was, however, content with stating his ideas in a general way, without making any direct experiments to verify them. This, however, fell to the share of Hugi. In 1827 he had a little hut built on the glacier Unteraar, at the foot of the promontory of Ab- schwung. In 1830 the hut was 110 yards lower down; by 1830 it had traveled 780 yards; by 1841 it had reached a distance of 1561 yards from its first position ; its movement, therefore, had been at the rate of 112 yards a year. Since that date, a great number of experiments of the same kind have been made by other explorers. The measurements made so carefully by Agassiz on the upper tributaries of the same glacier, the Aar, the Finsteraar, and the Lauteraar, have proved that the two masses have shifted their places, one from 52 to 89 yards, the other from 34 to 81 yards each year, according to the various positions of the measure- ment-marks on the surface of the glacier. The motion was ascertained to be the more rapid in proportion as the marks were nearer the central por- tion of the field of ice. Thus this important fact was brought to light, that the mass of the glacier occupying the centre of the bed descends more quickly than the portion situated in the vicinity of the two sides. Henceforth the matter was set at rest that, without any exaggeration of language, a glacier might be literally assimilated to a river.* This, how- ever, is an idea that had already been suggested by M. Rendu, an excel- lent observer of the mountains of Savoy. In a work on glaciers, pub- lished in 1841, he stated that there was a perfect resemblance between the Mer-de-Glace, in Savoy, and a river, and that it would be impossible * Complex Hi iiilus de F Academic des Sciences, 29th of August, 1842. M 178 THE EARTH. to point out any phenomenon in any of the streams which might not be found in the other. To what cause, therefore, are we to attribute this gradual descent of the river of ice in its rocky bed ? At all events, it is certain that it is not a mere sliding of the mass over its lubricated bed, for it has been several times proved that above the zone in which the mean temperature of the ground is below the freezing-point, that is, at about the height of 6600 feet in the Central Alps, the layers of the glacier are frozen to the ground, and can not detach themselves from it by the mere force of grav- ity. On their lower surface they melt but slowly, except at the spot where the rivulet flows, which gathers all the surface-water sinking through the crevasses. There are also instances of a stream running by the side of a glacier from the neve to the terminal moraines without be- ing able to penetrate the solid wall of ice adhering to its bed of rocks.* Since the investigations and experiments of Tyndall, it has become more than probable that the real cause of the onward motion of rivers of ice must be sought for in the formation of innumerable fissures, and in the reconstitution of all the broken fragments into a fresh mass. Regela- tion is taking place in every part of the glacier at once, and, as may be easily understood, the particles of ice compressed by the masses above them must always move in the direction of the slope when they shift their position in order to coalesce anew. This descending movement and the junction of the particles are taking place at the same time as regards millions and millions of broken granules, and from this very cause the whole body of the glacier descends in the gorge which serves as its bed. Under the pressure of the enormous weight which pushes it forward, the ice ultimately becomes so moulded as to fit perfectly into its channel of rocks, just as if it were a pasty mass. If the gorge becomes narrow, the glacier assumes a more elongated shape in order to make its way into the defile ; if the mountain sides widen out in a basin, the glacier spreads out like a lake in the broad hollow. This remarkable plasticity of the ice under pressure has caused several distinguished natural philosophers (as James Forbes) to believe that the frozen mass, although so brittle, is of a viscous nature, and flows in the same way as treacle and honey. Spring-time is the season in which the river of ice descends toward the valley with the greatest rapidity. Then the phenomena of liquefaction and regelation take place with the greatest frequency on the elevated neve. Innumerable rivulets of water, set free from their icy prison, widen the crevasses and lubricate the slopes on which the solid river has to glide slowly down. The blocks of ice, glued to the sides of their bed by the frosts of winter, regain their liberty. It is probable that in summer the progress of a glacier is at least double as fast as it is during the cold sea- son. Thus, according to Tyndall, the progress of the Mer-de-Glace, near Montanvers, is on the average about 13 inches a day in winter, and more than 24- inches a day in the summer ; but, between the extreme rates of speed, the difference is much more considerable. Every variation of tem- * Sonklar, (Etzthaler Gebirgsgruppe. THE MER DE GLACE & ITS AFFLUENTS P1 .xi her ih 1 o> m ^^ * cs 3 *- a) ^t-^ w KO ^C-5S 3QOCTT ^5u^ c>> S:S Fig. 74. " Estavelles" of Porrentruy. Higher up still, the escarped ravine of Rochedor commences, where, dur- ing the whole year, the rivulet, running sometimes below and sometimes above the surface of the ground, passes through a series of chasms. At one place it springs up suddenly to the top of the rocks, and then as sud- denly disappears, only to gush forth again at some distance down the ra- vine.* The estavelle which is the most remarkable in France for its abundant flow of water during the rainy seasons is situated, like the springs of Por- rentruy, on one of the slopes of the Jura. It is called the Frais-Puits, and rises at the opening of a little valley about two miles and a half southeast of Vesoul. In ordinary seasons, a spring of some importance that of Champdamoy is the sole outlet for all the rain that falls in the basin ; but when the subterraneous caverns are not capacious enough to contain the whole of the accumulated liquid mass, it flows out through the orifice at Frais-Puits, about a mile and a quarter above Champdamoy. Sometimes, indeed, it is a perfect river which rushes forth from this abyss. It inundates the meadows of Vesoul over an extent of several square miles, and floods the little stream in the valley, influencing even the Saone, which receives the surplus of the sudden overflow. The Frais-Puits, in conjunction with another estavette, a tributary of the Vesoul stream, has been known to discharge the enormous quantity of 133 cubic yards of water per second, equivalent to double the liquid mass of the Seine at its passage under the bridges of Paris. We thus see that very heavy rain has the effect of causing springs to gush forth in spots where, in a general way, they do not exist ; but we must also notice that every precipitation of moisture, even the most in- considerable, has its proportional influence on the discharge of fountains * Fournet, Hydrographie Souterraine. INTERMITTENT SPRINGS. 229 and springs. The nightly freezing of melting snow, the increasing intens- ity of the solar rays, the intermittent activity of the phenomena of evap- oration taking place on the surface of the soil in fact, every meteoric agency, incessantly tends to modify the action of water springing forth from the earth, and causes it to change every day and even every hour. It must, however, be understood that springs are all the less subject to the influence of the rain, sun, and wind the farther the subterranean streams have traveled, and the deeper they have descended into the bow- els of the earth. All the hinderances which the percolating water is sub- ject to from the friction of its liquid particles against the rocky sides of its underground course, and all the delays which it is forced to submit to in the cavernous lakes, have this result that the sudden variations which the changes of the seasons cause on the surface of the ground are modified and weakened in these subterranean beds. Down in these depths the sea- sons seem to blend one into the other, and their effects are mutually coun- terbalanced. Owing, therefore, to the long and winding channels which feed them, springs are able, as it were, to regulate themselves, and to fur- nish, during the whole year, a supply of water which varies but very slightly. In a certain number of thermal springs rising from fissures which descend to a very considerable depth in the earth's crust, the equi- librium of the liquid mass is so perfectly established that any variation answering to the different seasons can scarcely be perceived. There are, however, certain hot wells, replenished from reservoirs with which they find rapid and easy means of communication, which show a great variety in the amount of their discharge, according to the quantity of rain or snow which has fallen in the country. Thus, in July, 1855, after a long succession of stormy weather, the hot wells at Pfeffers, in Switzerland, sprung out in such abundance, both from their usual source and also from several other clefts in the rock, that they were obliged to let a great quan- tity of the water flow away into the Tamina without making any use of it. The following year, on the contrary, the hot wells received such an in- considerable supply that it was feared that they would dry up altogether.* The springs which cause the most astonishment are those which for a time flow plentifully, and then all at once cease running, but, after an un- certain lapse of time, again make their appearance. One might almost fancy that some invisible hand alternately opened and shut the secret flood-gate which gave an outlet to the subterranean stream. The cause for this phenomenon of intermission is easily explained. When the water brought by the underground stream is collected in a capacious cavity in the rock, which communicates with the exterior surface through a siphon- shaped channel, the liquid mass gradually rises in the stone reservoir be- fore it rushes out into the air. It is necessary that the reservoir should be filled up to the level of the siphon, in order that the latter should be primed, and that the water should flow out as a spring into the external basin. If the water in the reservoir is not replenished with sufficient ra- * Otto Volger, Erd\eben in der Schweis, vol. iii. 230 THE EARTH. Fig. 75. Section of an Intermittent Spring. pidity, and is unable to keep at least on a level with the external outlet, the jet of water will immediately cease, and can not recommence until the upper part of the liquid mass has again risen up to the highest point of the siphon. After an indefinite period of repose, the spring then enters on a new phase of activity. The comparative durations of the intermissions vary according to the capacity of the retaining reservoir, the height and the diameter of the siphon, the position of the outlet-channel, the abundance of the subterra- nean water, and the force of the evaporation. Nevertheless, the action of each spring is incessantly modified by the frequency or scarcity of rain, and the jet of water increases or shortens the duration of its appearance. Occasionally springs which are generally intermittent are recruited by subterranean channels to an extent sufficient to enable them to flow with- out interruption for weeks or whole seasons. At other times, after long periods of dryness, the spring entirely ceases to gush out; and the visitor who, on the faith of some old book, stands waiting, watch in hand, for the predicted appearance, runs a good chance of gazing vainly for many a long hour upon the dried-up basin of the fountain. It also often happens that the fall of rocks, or the opening of fresh clefts, alters the course of the subterranean stream and destroys its periodicity. Thus the Buller- born, a spring in Westphalia, which formerly burst out of the ground about every alternate four hours with sufficient force to turn the wheels of several mills, has now, since the commencement of the eighteenth cen- tury, become a much less considerable stream, but runs constantly.* * Von Klceden, Handbuch der Erdkimde. ASCEXDIXG tiPBIXati. 231 CHAPTER XXXIX. ASCENDING SPRINGS. ARTESIAN WELLS. TEMPERATURE OP JETTING SPRINGS. THERE are many of these subterranean streams which, before they break forth in springs, do not flow over beds continuously sloping inthe direc- tion of their current, as is the case with water-courses on the surface of the ground. There are some indeed which first descend into the bowels of the earth, either by a uniform declivity or by a series of cascades or rapids, and ultimately reascend from the depths toward the surface, or jet out vertically from the ground. Let us follow in our imagination a rill of melted snow trickling down from the mountain side through the crev- ices of the earth to a depth of some hundreds or thousands of yards be- low the surface of the ground. So long as this water does not meet with any impervious stratum, it continues to sink toward the lower abysses. But if its progress is arrested by a bed of retentive clay or any other layer through which it can not pass, it will spread out over this layer, and will follow all its inflections. Should this stratum curve gradually upward to- ward the surface of the ground, or should it even rise suddenly, the sub- terranean stream will reascend, as if in a tube, so as to place itself in a po- sition of equilibrium with the other liquid masses which continue to de- scend from the heights. Added to this, in obedience to the law which compels liquids to seek the same level in all connected reservoirs, a rivulet of water will never fail to dai't forth as a spring as soon as it finds an outlet below the cav- erns in which the water is collected from which it proceeds. Likewise, if the spot where the gushing out takes place is on a much lower level than that of the feeding reservoirs situated above, the liquid jet must necessa- rily shoot up in a column above -the surface of the ground. This is the case at Chatagna, in the department of the Jura, where a natural^ d 1 eau springs up to a height of 10 or 12 feet. In the grotto of Male-Mort, near Saint-Etienne, in Dauphinc, the jet of water is not less than 23 to 26 feet in height.* But the water of the fountains being always more or less charged with sediment, the deposit accumulates in the form of a circular hillock around the orifice, thus almost always ultimately raising it to the level of the top of the liquid column. As an instance of these rising foun- tains, we may mention the famous springs of Moses (A'ln Musd), which gush out in a charming oasis not far from the shores of the Gulf of Suez. These springs, the temperature of which varies from 70 to 84 (Fahr.), . now flow from the top of several small cones of sandy and slimy debris which they have gradually thrown up above the level of the plain. They are also shaded by olive and tamarind trees. At a certain distance from * Fournet, Hydroloyie Souterraine. 232 THE EARTH. the spot where these small streams gush out, there is a line of dried-up cones. These are the former fountain-heads, which are now abandoned by the water on account of their too great elevation.* This phenomena of the springing up of deep-lying water from the bow- els of the earth is a fact established beyond all doubt by direct observa- tions; for, many centuries ago, the absolute necessity of finding springs of water in arid countries disclosed to the nations inhabiting them the exist- ence of these sources ascending from the depths of the earth. In the des- erts of Egf pt and Algeria, the natives, from the most remote antiquity, had learned how to bore wells 30, 40, and even 90 feet into these liquid veins, and thus, in the very midst of the sands, they caused the rising col- umns of water to spout out, casting life and riches all around them. The inhabitants of certain valleys in Affghanistan and Arabia, fearing to lose a drop of the precious water which comes down to them from the 'moun- tains, have had the foresight to take possession of the brooks at their issue from the gorges, and to inclose them in subterraneous tunnels, inclined ac- cording to the general slope of the soil. The water, thus protected from the heat of the sun, does not evaporate at all en route; it reaches the foot of the declivity almost without waste, and, ascending by a vertical well into the outlet-reservoir, flows immediately into the irrigation trenches. The greater part of these channels are pierced here and there with aper- tures, through which the cultivators of the banks of the river draw the water necessary for their crops. Some of these subterranean streams are not less than 36 miles in length. They are rudimentary imitations of the very work which nature herself accomplishes in order to elaborate her springs and cause them to gush out from the surface of the soil. Thanks to the efficacious means of boring which modern ingenuity has placed in the hands of geologists, men do not content themselves with piercing the beds of clay, sand, and stone to any trifling depth, but pene- trate hundreds of yards, in order to give an upward egress to the veins of water which have descended from the mountains or distant plateaux. By means of the second-sight which study gives him, the savant can point out beforehand with almost perfect precision the course of the subterranean waters, and even the quality of the fluid. Thus the engineers bored through the soil in the environs of Calais in the hope (which was justified by the result) of touching upon the waters which had come from the hills of England under the Straits of Dover, and making it spring up in their wells. They have also dug with perfect confidence in the precise spot where saline or medicinal waters flowed under the ground. In the Alge- rian Sahara, the engineers mark beforehand, in the middle of the barren and arid desert, the place where an abundant spring ought to gush out, and ^very blow of the boring-rod brings to the surface a jet of water, which is soon surrounded by tents and the budding palm-trees of an oasis. Thus, although the sight of man can not penetrate through the beds of rocks piled one above another, yet the subterranean course of the streams is none the less visible to his mind's eye. Besides, these subterranean * Mittheiltinyen von Petermann, 1861. ARTESIAN WELLS. TEMPERATURE. 233 watero act exactly in the same manner as those which flow on the surface of the soil ; they also carry along their alluvium, and thus contribute their part toward modifying the relief of the globe. In many places, especially at Tours, the artesian wells have ejected the remains of plants, branches, moss, snail-shells, and other debris which the rains had probably carried away some weeks previously into the depths of the earth. AtElboeuf the water of a well contained living eels.* Many artesian wells reach a very considerable depth. The celebrated well of Grenelle is not less than 1771 feet deep, and the water which rises from the bottom of this abyss also ascends 91 feet. The salt water which rises from the artesian spring of Neusalzwerk, near Minden, proceeds from a depth of 2394 feet. A spring of sulphurous water at Louisville, in Ken- tucky, rises in a bore 2086 feet deep, and the water leaps up 170 feet from the orifice. A well dug at St. Louis, on the Missouri, to supply a sugar refinery, exceeds 2624 feet in depth. The quantity of water which it is possible to obtain from the various borings is very considerable, and, in many cases, would be still larger if the ascending tubes had a wider diam- eter. The spring of Neusalzwerk yields 321 gallons a minute; an arte- sian well of the Ouqd R'ir, that of Sidi-Amran, supplies in the same space of time 884 gallons, or 5 cubic yards. That of Passy, at Paris, yields 7. cubic yards. In some spots, a large number of artesian wells unite into one single rising column, the waters of two or more sheets of fluid rising one above another. Thus, at Dieppe, in boring a well 1092 feet in depth, they came successively upon seven very abundant water-bearing strata. I G20 miles. Fig. 70. Artesian System of Oued R'ir; after Dubocq. In all artesian springs the temperature rises the farther the well de- scends below the level of the sea. The jet from the well of Grenelle marks 82 (Fahr.), 64 (Fahr.) more than that of Passy ; that is to say, that at this point of the terrestrial crust the increase of heat is 1 (Fahr.) for each interval of 55 feet in depth. The thermometrical study of other artesian springs has given results differing little from this, and it can be strictly stated that for every space of from 40 to 55 feet of vertical height the temperature increases on an average 1 (Fahr.) from the surface of the soil to the lowest beds which the excavations of man have yet penetrated.! In the springs of Sahara the increase of temperature is, according to M. Ville, l c (Fahr.) to 36 feet of depth. * BufF, Physik Jer Erde. t Vk above, p. 30. 31 . 234 THE EARTH. CHAPTER XL. COLD AND THERMAL SPRINGS. As artesian wells only differ from natural springs in the change of direc- tion given to their waters, the same laws must apply to all subterranean currents, consequently the depth to which the water descends into the bowels of the earth may be approximately ascertained by the temperature of a spring. It may be confidently affirmed that, in a general way, cold springs that is to say, those the mean temperature of which is lower than the heat of the soil descend from mountains, and that thermal springs proceed, on the contrary, from beds lying deep in the interior of the earth. In the innumerable multitude of springs, either cold or thermal, which rise from the earth, we may observe the whole range ,of possible tempera- tures from freezing-point up to the boiling-point. A spring which flows from the side of the Hangerer, in the Oetzthal, at a height of 6742 feet, is only 1 warmer than ice.* On the Alps, the Pyrenees, and all the other chains of snow-clad mountains, near the summits small rills of water are very frequently met with, the temperature of which is scarcely higher than that of melting snow. Even at the bases of mountains, and especially those of a calcareous nature, a great number of springs are found which are much colder than the surrounding soil. Geologists who have applied themselves to the study of subterranean hydrography have had many op- portunities of proving the truth of the fact that drainage- waters at first maintain a temperature considerably lower than that of the rocks. This is so because, in addition to the water, the air also enters the. subterranean channels and circulates in all the net- work of clefts and crevices, and, by incessantly gliding over the wet sides of the channels, produces a rapid evaporation of moisture, and, in consequence, refrigerates the surface of the rocks and even the stream itself. The temperature, therefore, of springs which proceed from the interior of cavernous mountains is always several degrees lower than the normal temperature of the soil. The greater number, however, of subterranean rivulets which flow at a small depth below the surface of the rocks or earth, and gush forth in 'springs after having slowly traversed a slightly inclined extent of ground, ultimately acquire a temperature scarcely differing at all from that of the soil The simplest means of approximately ascertaining the mean tem- perature of any particular spot is to plunge the thermometer into the spring-water ; for, as the extremes of heat and cold are inoperative at a depth of only a few yards below the surface of the soil, the greater num- * Sonklar, (Etzthaler Gelirgsyruppe. THERMAL SPSIXGS. 235 her of liquid veins are not liable to the changing influences of the outer air, and, in consequence, show at their emerging point the real average cli- mate of the locality. In winter the Sorgue of Vaucluse seems to smoke, on account of the rapid condensation of its vapor, which is cooled by the atmosphere. During the severe winter of 1819 to 1820, when the Rhone was completely frozen over, and might be safely crossed from Avignon to Villeneuve, M. F. de Lanoye tells us, the whole extent of the Sorgue re- mained perfectly free from ice. Springs which have a higher temperature than the soil are called ther- mal springs. These are the springs the depth of which may be roughly estimated by calculating a descent of 55 feet for each degree (Fahr.) be- yond the normal heat of the surrounding soil. Thus the springs of Plom- bieres, which have a temperature of 149 (Fahr.), would take their rise 5413 feet below the surface; those of Chaudes-Aigues, the heat of which is found to be not less than 178 (Fahr.), issue from beds situated 6889 feet from the surface of the soil ; lastly, the gushing rivulet of Trincheras, in Venezuela, which marked 206 (Fahr.) at the time of Boussingault's visit in 1823, would proceed from rocks at a still more considerable depth. It has been the subject of direct observation in the wells of the Geysers, in Iceland,* that the deep water in the interior of the earth may attain a temperature considerably above 212 (Fahr.) ; but on reaching the surface, this boiling water, nearly all of which jets forth in the vicinity of volca- noes, must necessarily be transformed into steam. It must, moreover, be remarked, that the high temperature of several springs is owing to acci- dental causes. When the volcano of Jorullo made its appearance in 1759, two small rivulets the rios of Cuitimba and San Pedro were covered with intensely heated scoriae, and reappeared farther down their course as thermal springs. In 1803 the lava was still warm, as the temperature of the springs measured by Humboldt exceeded 149 (Fahr.);f but travelers who have recently visited the district of Jorullo aver that the water flow- ing from the base of the volcano has gradually cooled since the commence- ment of the century, and that soon it will have reached the normal tem- perature of the surrounding soil. In the same way the water of Bertrich- bad, in Luxembourg, has gradually discontinued to be either warm or min- eral in its character ever since the lava of a small eruption has ceased to come in contact with the burning furnace which produced it.J It is to be remarked that nearly all thermal springs which do not owe their high temperature to the vicinity of volcanoes issue forth from faults which open on the surface of masses of a crystalline nature, and principally at the side of modern eruptive rocks which have been thrust up through older strata. This must evidently be the case, for in piercing the terres- trial crust the upheaved matter has broken through the parallel layers which detained the sheets of water, and by this rupture of the strata has opened channels by which the springs can ascend toward the surface of * Vide the chapter on "Volcanoes." f Humboldt, Cosmos, 1st Part. t Poulett Scrope, Volcanoes. 236 THE EARTH. the soil. One fact, also, that proves the existence of these deep fissures whence thermal waters spring is that their temperature sometimes changes suddenly in consequence of earthquakes which obstruct the former faults, or else open them out to far greater depths. At the time of the earth- quake at Lisbon, the temperature of a spring of Bagneres de Luchon sud- denly rose, it is said, from 46 to 122 Fahr. (?), and since that date, now more than a century ago, the action of the spring is not modified. It is also said that the thermal springs of Bagneres de Bigorre suddenly be- came cool at the time of the great earthquake in 1660.* The influence of rains and seasons has much less effect upon thermal waters than upon cold springs which proceed from the upper layers of the soil. A great number of warm springs, however, undergo certain changes in their yield of water, which must be without doubt attributable, at least partially, to the same causes as the variations in the discharges of super- ficial streams. In Auvergne, in the Pyrenees, and in Switzerland, several springs, perfectly protected against any infiltration of rain-water, flow in much greater abundance at the very same period when the adjacent tor- rents become swollen. It is true that the increase of thermal water must be partly caused by the lateral pressure exercised by the cold waters sat- urating the soil and forcing back all the small scattered rills toward the central spring. But the liquid mass proceeding from deep beds is also much stronger (for the temperature of deep springs increases simultane- ously with the yield), doubtless because the subterranean rivulets, when increased in volume, are less retarded in their course, and lose less heat in mounting toward the surface of the ground. At, Brig-Baden, in the Val- ais, the water, the mean temperature of which is in autumn and winter from 71 to 72 (Fahr.), rises to 113 and 122 (Fahr.) when the breath of spring melts the ice on the Jungfrau.f Many of the phenomena, however, exhibited by thermal springs are still rather difficult to explain. The greater number, therefore, of savants who devote themselves fo the study of subterranean hydrology admit that the tension of gases which are pro- duced in the interior of the earth plays a principal part in the emission of thermal waters. Most thermal springs contain mineral substances in solution ; there are, however, a certain number which are almost as pure as rain-water such as, for instance, the celebrated waters of Plombieres, which do not even contain 33^ of salts; also that of Gastein, Pfeffers,Wildbad, and Baden- weiler.J The springs of Chaudes-Aigueg those in France which have the highest temperature, 15 8 to 176 (Fahr.) contain only a small amount of mineral substances. The inhabitants of Chaudes-Aisrues use the water o to prepare their food, to wash their linen, and to warm their houses. Wooden conduits, erected in all the streets of the town, supply, on the ground floor of each house, a reservoir which serves to heat it during cold weather, and thus dispenses with fires and chimneys. In summer, small * Lyell, British Association at Bath, 1864. f Filhol, Eaux des Pyrnes. % Bnff, Physik der Erde. THERMAL SPRINGS. HEAT UTILIZED. 237 sluices, placed at the entrance of each conducting tube, stop the warm water alid throw it back into the rivulet which flows at the bottom of the town. M. Bertbier, a chemist, has calculated that the heat furnished daily by the springs is equal to that which the combustion of more than four tons and a half of coal would produce. It is sufficient to give a comfort- able temperature to the interior of the houses and to warm the streets themselves. The snow, which falls in great abundance during winter, melts immediately after its fall.* There are not perhaps in the world any thermal springs the heat of which is better utilized. * Allnrd aud Boucomout, Euux Tliernio-minerales d'Aweryne. 238 THE EARTH. CHAPTER XLL MINERAL SPRINGS. INCRUSTING SPRINGS. METALLIC VEINS. SALT SPRINGS. SPRING- WATER, cold as well as hot, is rarely, if indeed ever, pure from all admixture ; thousands of samples analyzed even in our time by chem- ists do not furnish a single instance of spring-water which does not con- tain a greater or less proportion of calcareous or rnagnesian salts. The purest water that the French chemists have yet found is that of the Dome, a small river of Ardeche, and this may almost be compared to distilled water. In the other mountainous regions of Central France, water, con- sidered quite excellent in its character, is charged with two, three, four, or even ten times more calcareous matter. The water of the Seine contains, on an average, thirty-six times more extraneous matter, and some wells at Paris and Marseilles, the water of which is, notwithstanding, used for drinking, are 250 to 350 times less pure.* Among the various substances which spring-water brings to the surface, those which are most common proceed from the strata which serve to con- stitute the very frame-work of the globe. Chalk, especially, occurs in dif- ferent proportions in most springs, either under the form of sulphate of lime, or, more often, as carbonate of lime. Water which contains carbonic acid in solution is charged with calcareous matter dissolved away from the sides of the rocks through which it passes ; then,-by means of evaporation, it redeposits the stony substances which it previously held in solution. Hence arise all those calcareous concretions which form around so many springs ; also the stalactites in caverns, and even those dangerous incrus- tations which accumulate in the boilers of locomotives. Nearly all countries of the world possess some of these curious springs, which cover with a calcareous crust any object placed in their waters. Among these incrusting springs, those of Saint Allyre, near Clermont, Ri- voli, and San Filippo, not far from Rome, have justly become celebrated. These latter have, in a space of twenty years, filled up a pond with a bed of travertin 30 feet thick, and, in the neighborhood, entire strata of this same rock may be seen having a depth of more than 328 feet.f The springs of Hammam-Mes-Khoutine, in the province of Constantine, are also very remarkable on account of the considerable amount of their deposits. This water, which rises at a temperature of 203 (Fahr.), and from which a high column of steam always rises, is frequently compelled to change its point of issue on account of the dense beds of travertin which are gradu- * Robinet, Discussion stir las Enux Potables. t Lyell, Princijdes of Geology. INCRUSTINO SPRIXOS. 239 ally deposited upon the soil. Most of these deposits are of a dazzling white hue, striped here and there with bright colors, and are developed in mammillated strata ; other concretions, accumulating gradually round an oriffce, have taken the form of cones, and are like the small craters near a volcano, some of them rising, to a height of as much as 33 feet; lastly, there are masses of travertin which stretch out in a kind of wall below the flow which deposits them. One pf these walls, which is interrupted at in- tervals by heaps of earth upon which large trees grow, is not less than 4921 feet long, 66 feet high, and, on an average, from 33 to 49 feet wide.* . The thermal waters of Algeria are, however, surpassed in grandeur and beauty by the springs of the ancient Ionian city of Hierapolis (holy city), which at the present time flow in the solitary plateau called Panbouk- Kelessi (Castle of Cotton), on account of the cotton-like aspect of. the white masses of travertin of which it 1 is composed. On reaching this spot from Smyrna, something like an immense cataract may be seen in the dis- tance, 328 feet high and 2 miles wide ; this is formed by the walls which the water has gradually constructed, column after column, and layer after layer, by flowing over the edges of the plateau and gushing out on the slopes. Here and there, real cascades glitter in the sun, and their spark- ling surfaces light up the dead whiteness of the crystal walls. As a spec- tator ascends the declivities, the masses deposited and carved out by the water appear in all their strange beauty ; one might fancy that they were colonnades, groups of figures, and rude bas-reliefs which the chisel had not yet perfectly set free from their rough coverings of stone. And all these calcareous deposits which have been fashioned by the cascades dur- ing a succession of ages open a multitude of cup-like hollows with fluted edges fringed with stalactites ; these graceful reservoirs some of which are shaded with yellow or veined with red, brown, and violet, like jasper or agate are filled with pure water. Higher still follow two steps of the plateau on which stood the ancient thermal edifice and the Necropolis of Hierapolis. There, whitish masses cover the ancient tomb-stones and fill up the conduits. The ground is crossed in various directions by the for- mer beds of rivulets, which have gradually stopped up their own courses by depositing concretions upon them. Above one of the widest of these dried-up channels, the magnificent span of a natural bridge displays its graceful form, like an arch of alabaster, streaming with innumerable sta- lactites.! At what date did this majestic structure take its rise, and how many years and centuries did the process of its formation last? No one knows. According to Strabo, the channels of the baths of Hierapolis were soon filled up by solid masses, and if Vitruvius can be believed, when the proprietors of the environs wished to inclose their domain, they caused a current of water to run along the boundary-line* and in the space of a year the walls had risen. Silica, which is still more important than chalk in the formation of ter- * Grellois, Lrs Dfydts Calcaires de Hammam-Mfs-Kltoutine. t Tchihatchef, I^e Bosphore et Constantinople. THE EARTH. Fig. 71. Natural Bridjre of Panbouk-Kelessi- after Tchihatchef. restrial rocks, is also sometimes deposited on the edge of springs, but in very small quantities ; only those waters which are of a very high tem- perature can dissolve silica in sufficient quantities to form a deposit round their outlet, and produce beds of any considerable thickness. Among the springs which are charged with silica, the best known are the Geysers of Iceland, the boiling waters of which deposit round their orifice circular lay- ers of siliceous concretions several yards high.* Other volcanic springs are no less active, and even at a long distance from any volcano there are few thermal springs which do not contain silica in quantities more or less perceptible. Concretions and crystallizations formed by thermal waters in the very interior of fissures or lines of fault have geologically more importance than external deposits, and can be produced at a much lower temperature than in the open air. M. Daubree has seen these phenomena in action at the springs of Plombieres. The ancient Roman masonry which was used for storing and supplying water is filled with zeolites or siliceous crystals, ev- idently owing to the prolonged influence of the water and its slow chem- ical reaction on the calcareous cement and the bricks. The intimate struc- ture of these materials has been modified by this water, the heat of which does not, however, exceed 140 to 158 (Fahr.). It is doubtless a similar chemical action, due to these thermal waters, which has produced in all * Vide chapter on "Volcanoes." MINERAL VEINS. 241 the fissures of Plombieres the vein of quartz, opal, and fluor spar which are found there. The enormous deposits of a quartz-like nature in an ad- jacent valley, that of Roches, are results of the same geological work.* It is probable that at 33,000 or 39,000 feet deep in these abysses, where the water, still retaining a liquid state, may attain to a temperature of 500 to 600 (Fahr.), the chemical operations of subterranean waters are ac- complished with much more activity than in beds near the surface. Most geologists think that thermal vapors can dissolve not only those metals which melt at low temperatures, such as tin and lead, but also copper, gold, and silver. Veins containing metals are probably only fissures in which these thermal vapors have become cooled, and have then deposited the metallic substances with which they were charged. Gold, silver, and copper remain in the depths of the earth, and the waters bring up to the basin of the spring nothing but a small quantity of salts, silicates, and gases. Then follow the gradual movements of the crust and the geolog- ical revolutions which cause the metallic veins to rise to the level of the ground, or, at least, which bring them nearer to the surface.f The various dislocations of the terrestrial strata, the cooling of the wa- ters, and, perhaps, in many instances, the obstruction of channels by de- posits of ore, explain why, in the present period, so small a number of thermal springs issue from metalliferous beds. Nevertheless, many lo- calities might be mentioned where this phenomena takes place at the present time. A spring at Badenweiler, in the Black Forest, issues forth at a few yards from a vein of sulphuret of lead. In the granitic plateau of Central France other springs are likewise found to be associated with this metal. Various thermal waters in the Black Forest, like those of Carlsbad and Marienbad, are in close connection with veins of iron and manganese. Oligiste iron is found in the fissures of the springs of Plom- bieres and Chaude-Fontaine. In Tuscany sulphureous fumaroles proceed from the veins of antimony. In France and Algeria the waters of Syl- vanes and Hammam R'ira issue forth from beds of copper. Lastly, near Freyberg, a voluminous thermal spring has been discovered in a vein of Ever.} Among the mineral substances which some springs bring to the surface of the soil, the most important, in an economical point of view, is common salt. This substance, being one of those which dissolves most readily in water, all the liquid veins which pass over saline beds become saturated with salt ; therefore springs of this kind, which flow in great abundance, give rise to salt-works of more or less importance. The masses of com- mon salt which make their way every year from the interior of the earth may be estimated at thousands of tons. The springs of Halle, which rise on the northern slope of the Alps of Salzburg (Salt Town), and are man- aged with the greatest care, annually produce 15,000 tons of this mineral. * Daubrde, Bulletin de la Sociiti de Giologie, 1859. t Lyell, British Association at Bath, 1864. J Pnubrtfe, Bulletin de la Societi de Geologic, 1859. Q 242 THE EARTH. The salt springs of Halle, in Prussia, which have been worked from time immemorial by a company, furnish 10,000 tons of salt every year. Other parts of Germany also yield for consumption thousands of tons of white salt, which, is produced by the evaporation of saline springs. The mass of salt furnished by the single artesian well of Neusalzwerk, near Minden, in Prussia, represents every year a cube measuring 78 feet on each side.* Though not so rich as Germany in saline springs thus turned to account, most of the civilized countries of the world possess salt-works which are also very important. France enjoys the springs of Dieuze, Salins, and Salies ; Switzerland, those of Bex ; Italy has the springs in the environs of Modena, and many others besides. In England, near Chester, there are some mines of rock-salt in w r hich numerous liquid veins issue forth which are impregnated with salt. Lastly, the United States have the celebrated springs of Saratoga. But how" many saline springs, still more abundant, flow uselessly along in the solitudes of the world ! Not far from the " spot where Troy once stood" is the valley of Touzla- sou, which owes its name (Salt Water) to its numerous salt springs. The mountains which rise around its circumference are variously shaded with blue, red, and yellow, and the rocks are incessantly decomposing under the action of the liquid salt which oozes out from, and trickles down their sides. The plain itself is covered with a variegated crust, while jets of boiling water, saturated with salt, burst forth in every direction. Here and there pools are found, the moisture of which, by evaporating in the sun, leaves upon the soil beds of salt as white as snow. Near the mouth of the valley springs become more and more numerous. Lastly, in the place where the clifls approach near together, so as to form a defile, a magnificent spout of water jets out from one side of the rock. This jet is not less than a foot in diameter at the orifice, and falls again after having described a parabola of more than a yard and a half. Other springs shoot out on both sides, the constant temperature of which is more than 212 (Fahr.) ; these, together with the principal jet, form a rivulet of boiling and steaming water. It would be easy to extract from these springs an enormous annual supply of salt ; but the negligence of the Turkish gov- ernment, who have appropriated the valley of Touzla-sou, has prevented more than one thousand tons a year being obtained, f Springs of salt water are used for the treatment of diseases as well as for the extraction of salt. They constitute one of the most important groups of medicinal waters, according to the various susbstances which they contain in solution. The other springs made use of, on account of their healing virtues, have been classed under ferruginous, sulphureous, and acidulous springs. These waters also contain, in different proportions, a variable quantity of gases and salts which they have dissolved in their passage over subterranean beds of every kind. It is probable that the proportion of gases dissolved in the water fluctuates with all the varia- tions of temperature and pressure of the surrounding air. It even ap- * Buff, Physik der Erde. t Tchihatchef, Le BospJiore et Constantinople. HOT AND SALINE SPRINGS. 243 pears that a simple movement of the liquid is sufficient to alter the con- stituents of the w%ter as regards its gaseous elements ; but, on the whole, the chemical composition is tolerably permanent, and there is no doubt as to the particular virtue of every spring which renders it fit for the treatment of one or many special diseases. Thanks to this healing power, of all the resources of which science, still imperfect, is yet ignorant, medicinal wa- - a Fig. 78. Saline Springs of Touzla. ters serve as a guide to a more familiar acquaintance with nature, for every year thousands and hundreds of thousands of visitors are attract- ed by them to the most picturesque and majestic spots on the face of the earth. In fact, mineral springs, which, for the most part, are also thermal, hav- ing flowed from deep beds, nearly all issue forth at the point of contact between older rocks and more modern formations. Now these points of contact are especially found in mountainous countries, which also receive from the atmosphere larger quantities of water than plains do. Mineral springs are most numerous and abundant in mountain valleys, and there, consequently, the great thermal institutions are established. In Europe the chain of the Pyrenees is probably the richest in mineral, sulphureous, saline, ferruginous, and acidulous springs. According to Francis, the en- gineer, in 1860 more than 550 mineral springs, 187 of which are used, flow- ed upon the French slopes of the Pyrenees. These waters supplied 83 244 THE EARTH. hot baths in 53 localities, the principal of which are Bagneres de Bigorre, Luchon, Eaux-Bonnes, and Cauterets. The most abundant springs, those of Graus d'Olette, form a sort of mineral stream, yielding more than four gallons a second, or 2322 cubic yards a day. In Algeria the spring of Hammam-Mes-Khoutine yields 6 gallons a second. There are regions, some volcanic and some not, in which nearly all the springs are thermal and mineral ; springs of pure and fresh water being so rare, they are there considered to be most precious treasures. One of these regions comprehends a large part of the plateau of Utah. In this place numerous thermal springs issue forth, to which have been given the vulgar names of the Beer, Steam-boat, Whistle springs, etc., and into one of which the Mormons plunge their neophytes. The springs which are not thermal are loaded with saline and calcareous matter. It is only in spring, at the time when the snow melts, that the springs, which then be- come very abundant, yield comparatively pure water. During the dry season, salt and carbonate of lime become concentrated in the nearly ex- hausted springs, and give to the liquid flow an unpalatable taste. Pal- grave, the traveler, informs us that all the springs of the country of Hasa, in Arabia, are also thermal. It can readily be understood that when all these substances escape from the interior of the rocks, together with the water which holds them in so- lution, they must leave empty spaces in the earth. During the course of long centuries whole strata are dissolved, and, under a form more or less chemically modified, are brought up from the depths and distributed on the surface of the soil. The thermal waters of Bath, which are far from being remarkable for the proportion of mineral substances they contain, bring to the surface of the earth an annual amount of sulphates of lime and soda, and chlorides of sodium and magnesium, the cubic mass of which is not less than 554 cubic yards.* It has also been calculated that one of the springs of Loueche, that of Saint Laurent, brings every year to the surface 8,822,400 pounds of gypsum, or about 2122 cubic yards; this quantity is enough to lower a bed of gypsum, a square mile in extent, more than five feet in one century. But this is only one spring, and we have reckoned one century only ; if we think of the thousands of mineral springs which gush from the soil, and of the immensity of time during which their waters have flowed, some idea may be formed of the import- ance of the alterations caused by springs. In time they lower the whole mass of mountains, and no doubt, after these sinkings, violent oscillations of the earth may often have taken place.f * Ramsay. Lyell, British Association at Bath, 18G4. t Otto Volger, Ueber das Phanomen der Erdbeben, ~\ ol. ii. SUBTERRANEAN WATER-COURSES. 245 CHAPTER XLH SUBTERRANEAN RIVERS. THE SPRING OF VATJCLUSE, THE TOUVRE. SUB- MARINE AFFLUENTS. THE RIOS OF YUCATAN. THE " MUD-LUMPS" OF THE MISSISSIPPI. IN regions where the strata are pierced with wide and deep caverns, and especially in calcareous countries, the waters sometimes accumulate in sufficient quantities to form perfect streams with long subterranean courses. At their issue from the caverns, these waters form a contrast with the rocks and hills around, all the more striking because the latter are completely devoid of moisture, and fearfully sterile, while on the brink of the limpid stream the fresh verdure of plants and trees is at once de- Fig. 79. Vaucluse and the Sorgues. veloped. Like a captive, joyous at seeing the light once more, the water which shoots forth from the sombre grotto of rocks sparkles in the sun, and careers along with a light murmur between its flowery banks. Among these subterranean streams, the most celebrated, and doubtless one of the most beautiful, is the Sorgues of Vaucluse. The vaulted grotto from which the mighty mass of water escapes opens -at the mouth of an amphitheatre of calcareous rocks with perpendicular sides. Above the spring rises a high white cliff, bearing on its summit a ruined tower of the Middle Ages; the rock is every where sterile and bare; there is nothing but a miserable fig-tree, clinging to the stone like a parasitical plant to the bark of a tree, which has plunged its roots into the fissure of the cave, and greedily absorbs with its leaves the moisture which floats like a mist above the cascades of the spring. After heavy rains, the liquid mass, which is then estimated at 26 or even 32 cubic yards a second, flows in a 246 THE EARTH. wide sheet high above the entrance to the cavern, which is then altogeth- er inaccessible. When the waters are low, they flow bubbling across the Fig. SO. Course of the Touvre. barrier of rocky debris which obstructs the entrance ; at that time it is quite possible to penetrate under the arch, and to contemplate the vast basin in which the blue waters of the subterranean stream spread out be- fore they leap into the open air. Soon after its issue from the cave and amphitheatre of Vaucluse, the Sorgues is divided into numerous irrigation- channels, which spread fertility in the country over an area of more than 77 square miles. The subterranean course of the affluents which form the stream is not ascertained ; but it is known that most of them commence 12 or 15 miles to the east, in the plateaux of Saint Christol and Lagarde, which are pierced all over with avens or chasms, into which the rain-water sinks and disappears. In another part of France there is a second important subterranean stream, which is much less known but no less remarkable than that of Vaucluse ; this is the Touvre of Angouleme, continuing the course of the Bandiat, the waters of which, like those of the Tardoire, are swallowed up in several abysses at distances varying from 3 to 7 miles to the east and northeast. The three principal springs of the Touvre flow slowly out of a deep cave, hollowed out at the base of an escarped cliff; another spring bubbles up in a basin of rocks ; the third emerges from a sort of boggy SUBMARINE OUTLETS OF RIVERS. 247 meadow intersected by drains. At the outlet of their subterranean courses these three enormous springs immediafely form three streams, which re- unite, leaving between them two long peninsulas of reeds and other aquat- ic plants. Below the junction, the Touvre, which is here more than 100 yards wide, passes round a rugged hill, and, dividing into several branch- es, turns the numerous mill-wheels of the important gun-foundery of Ru- elle ; then, after a course of five miles, it flows into the Charente at a small distance above Angouleme. Among the hundreds and thousands of trav- elers whom steam annually conveys over the bridge of the Touvre, there are few who are aware of the curious nature of the source of the river of limpid water over which the train passes in its noisy career. Omitting to mention the streams which accidentally pass under the strata of rocks during a small part of their course, or of the subterranean outlets of certain lakes,* a multitude of other instances might be brought forward of masses of water, more or less abundant, which appear above ground after having traversed a considerable distance under the earth. Of this kind is the graceful spring of Nimes, the blue transparent water of which, reflecting the foliage of pines and chestnut trees, glides in its gentle ripples over the semicircular steps of an old Roman staircase. Of this kind, too, is the spring of Veneran, near Saintes : this spring, which was formerly sacred to the Goddess of Love, gushes from the ground in a gorge of rocks, and, passing through a mill, the wheel of which it turns, it suddenly disappears, being swallowed up in an abyss ; thus it appears on the earth to work but for an instant. Numbers of water-courses do not reappear on the surface of the soil after being swallowed up in the earth, but flow straight to the sea by means of subterranean channels. On nearly the whole extent of the con- tinental shores, and principally in localities where the coasts are of a cal- careous nature, the outlets of submarine tributaries ma y b e noticed, some of which are perfect rivers. Most of the springs of the department of Bouches du Rhone jet up from the bottom of the sea, but at various dis- tances from the shore. One of them, that of Porte Miou, near Cassis, forms on the surface of the sea a considerable current, which drifts any floating bodies to a great distance.! At Saint Nazaire, Ciotat, Cannes, San Remo, and Spezzia, other streams also issue from the midst of the salt waves, and attempts have even been made to measure approximately their discharge. M.Villeneuve-Flayosc estimates at 24 cubic yards a second the quantity of water discharged into the sea by all the hidden affluents of the Mediterranean between Nice and Genoa. Some of the submarine springs of Provence and Liguria proceed from enormous depths. The ori- fice of the spring of Cannes is 531 feet below the level of the sea; that of San Remo rises from a depth of 954 feet ; lastly, at four miles to the south of Cape Saint Martin, between Monaco and Mentone, another stream of fresh water empties itself under a bed of salt water, near 2296 feet deep.J * Vide the chapter on "Lakes." t Mareigli, Histoire Physique de la Mer. $ Villeneuve-Flayosc, Description Gtologiqve du Par. 248 THE EARTH. The coasts of Algeria, Istria, Dalmatia, and the Herzegovina also pre- sent numerous instances of submarine streams ; on the eastern shores of the Adriatic the traveler may even have the pleasure of contemplating the delta of a considerable river, the Trebintchitza, visible through the sea-water at the depth of a yard. The abundant springs of fresh water which pour out into the open sea to the southwest of the Cuban port of Batabano are well known, since Humboldt described them, and it is ob- served that the lamantins, or sea-cows, which dread salt water, delight in frequenting these parts. Lastly, the Red Sea, which does not throughout its immense circumference receive a single permanent stream flowing on the surface of the ground, nevertheless receives some which spring from the bottom of its bed. The shores of the United States, the calcareous soil of which is probably pierced with caverns from the very centre of the continent, perhaps are the coasts which pour into the sea the most abun- dant subterranean rivers. Near the mouth of the stream of St. John, a submarine stream of perfectly pure water spouts in bubbles as far as one to two yards above the level of the sea. Off the Carolinas, and Florida, salt water has been known to change into brackish water under the influ- ence .of the sudden increase of its subterranean affluents. In the month of January, 1857, all that part of the sea which is adjacent to the southern point of Florida was the scene of an immense eruption of fresh water. Muddy and yellowish water furrowed the straits, and myriads of dead fish floated on the surface and accumulated on the shores. Even in the open sea the saltness diminished by one half, and in some places the fishermen drew their drinking-water from the surface of the sea as if from a well. It is affirmed by all those who witnessed this remarkable inundation of the subterranean river that, during more than a month, it discharged at least as much water as the Mississippi itself, and spread over all the strait, 31 miles wide, which separates Iey West from Florida,* On the coasts of Yucatan, the fresh waters which take a subterranean course down to the sea do not appear to flow like rivers which have a narrow bed and attain considerable speed, but more in the form of a wide sheet of liquid with a nearly imperceptible current. Cenotes open here and there over the sui-face of the country ; they are a kind of natural draining-well or hole, not very deep, into which the inhabitants descend to draw spring water. At Merida and in the environs the subterranean water is found at a depth of 26 to 30 feet ; but the nearer we approach to the sea, the thinner the layer of rock becomes which covers the liquid veins ; on the sea-shore fresh water is found nearly on a level with the soil. The height of the veins varies several inches, according to the quan- tity of rain ; but in every season, the mass of water descending from the plateau of Yucatan is poured into the sea through innumerable outlets. Over a great extent of the shore of the peninsula, these hidden springs furnish collectively a mass sufficiently large to counterpoise the waters of the sea. Under the pressure of the marine current which runs along the * Raymond Thomassy, Essai sur rilydrologie. ORIGIN OF "MUD-LUMPS," ETC. 249 coast, there is formed, between the open sea and the liquid mass which has made its way from the land, a littoral bank like those barriers which the waves construct before the mouths of rivers.* This embankment, which protects the coasts of Yucatan like a breakwater, is not less than 171 miles long, and is cut through by the sea at two or three points. The channel, which stretches like a wide river between the bank of alluvium and the Yucatan coast, is, not without reason, designated by the inhabit- ants by the name of stream, or rio.\ Among the remarkable phenomena which perhaps owe their existence to subterranean water-courses, we must mention the sudden or gradual appearance of those hillocks of clay (" mud-lumps") which rise, to the great danger of navigators, either in the middle of the bar of the Missis- sippi, or in the immediate vicinity. Like small volcanoes of mud, the " mud-lumps" generally appear under the form of isolated cones, allowing a rill of dirty water to escape from their summits. Some of them are ir- regular on their surface, on which lateral orifices here and there show O ' themselves, some in full activity, others abandoned by the springs which formerly gushed from them. The water of some " mud-lumps" is loaded with oxide of iron or carbonate of lime, which, with the agglutinated sands, form hard masses, having the consistence of perfect rocks. These hillocks vary both in their height and shape. The greater part remain hidden at the bottom of the water, and even their summits do not reach the level of the river or sea; others hardly raise their heads above the Fig. 81. Mud island in course of formation. waves ; the most considerable, however, rise to a height of 6, 9, or even 19 feet, and their base covers an area of several acres. M. Thomassy is of opinion that the mouths of the Mississippi probably owe to one of these hillocks the name of Cabo de Lodo (Mud Cape) which was given to them by the Spanish pilot, Enriques Barroto. It is evident that the " mud-lumps" were not formed by the alluvium of the river, as several geologists at first supposed. The great elevation of some of the mud hillocks above the flood-waters and tides suffices to ren- der this hypothesis inadmissible. The sudden way in which most of these water-volcanoes make their appearance, the anchors of vessels, and the re- mains of cargoes which have been found on their surface, their conical form, their terminal craters, and all the springs, " which seem to spout out as if from a subterranean sieve," indicate, on the contrary, the existence of a subterranean force always at work to upheave this band of hillocks. Messrs. Humphreys and AbbotJ think that this power consists in the dis- * Vide chapter xliii. t Arthur Schott, Mittheilungen von Petermann,]8G6. J Report on the Mississippi liicer. 250 THE EARTH. charge of hydrogen gas proceeding from the alluvium of the Mississippi. According to these engineers, great masses of vegetable products trunks of trees, branches, leaves, and seeds brought down by the waters of the river, drift upon the bar ; these are afterward covered up, and, as it were, imprisoned under a bed of mud, and, fermenting, produce gases whicli ultimately distend their covering, and, puffing it up into a multitude of cones, escape into the air, after having pierced the soil which held them captive. This hypothesis sufficiently explains the upheaval of the soil and the ex- istence of the inflammable gases which are occasionally discharged from the craters of the " mud-lumps," but it leaves unexplained why the mud poured from the sides of the craters is transformed into a hard and com- pact clay, devoid of vegetable matter. M. Thomassy is of opinion that the hillocks of these bars are the orifices of regular artesian wells natural- Fig. 82. "Mud-lump," with bubbling springs at its summit (southwest passage of the Mississippi). ly formed by a sheet of subterranean water descending from the plateaux of the interior and flowing below the Mississippi and the clayey levels of Louisiana.* However this may be, the mode in which these mud hillocks are formed is well enough known to render it easy to clear them away from the mouths of the Mississippi and to protect the interests of naviga- tion. When a cone of clay makes its appearance on the bar, a charge of powder is introduced into it and explodes it. Thus, in the year 1858, the southwest passage was cleared of a "mud-lump" which formed a consid- erable island ; a single charge was sufficient to annihilate the whole. The island suddenly sunk ; in its place a wide depression was formed, the cir- cumference of which resembled that of a volcanic crater; at the same time an enormous quantity of hydrogen gas was discharged into the atmos- phere. * Geologic de la Louisiane. Essai sur FHydrologie. SYSTEM OF UNDERGROUND RIVERS. 251 CHAPTER XLIH. SYSTEM OF SUBTERRANEAN STREAMS. JOINTS AND FISSURES OF ROCKS. STALACTITES. THE INHABITANTS OF CAVES. THE MAMMOTH CAVE. CAVERNS OF CARNIOLA AND ISTRIA. ABOVE the springs, the course of subterranean rivulets is generally in- dicated by a series of chasms or natural wells, which disclose the stream beneath. The arches of caves not being always strong enough to support the weight of the superincumbent masses, they necessarily fall in some places, leaving above them other spaces into which the upper beds suc- cessively sink. The debris of the ruin is afterward cleared away by the water, or dissolved, atom by atom, by the carbonic acid contained in the stream, and gradually all the loose rubbish is carried away. In this man- ner, above the subterranean rivulets, a kind of well is formed, which is designated in various countries by very different names. They are called sinks in the United States ; dolinas in Carinthia ; catavothras in Greece ; pots, entonnoirs, and creux in the Jura ; embues, embucs, goules, gouilles, gourgs, gourgues, betoirs, boit tout, anselmoirs, emposieu, avens, scialets, ra- gages, garaged, in southern France ;* swallow-holes, sand-pipes, sand-galls, etc., in England. By means of these natural gulfs it is possible to reach the subterranean streams, and to give some account of their system, which is exactly like that of rivulets and rivers flowing in the open air. These streams also have their cascades, their windings, and their islands ; they also erode or cover with alluvium the rocks which compose their bed, and they are sub- ject to all the fluctuations of high and low water. The only important difference which superficial waters and subterranean currents present in their phenomena is that these streams in some places fill the whole section of the cave, and are thus kept back by the upper sides, which compress the liquid mass. In fact, the spaces hollowed out by the waters in the interior of the earth are only in a few places formed into regular avenues, which might be compared to our railway tunnels. Throughout its thick- ness, the rock opposes an unequal resistance to the action of the water, on account of the diversity of its fissures, its strata, and its particles. When the faults are numerous and the strata not very compact, the current grad- ually hollows out vast cavities, the ceilings of which fall in, and are car- ried away by the water almost in single grains. Where beds of hard stone oppose the flow of the rivulet, all it has done during the course of centuries has been to hew out one narrow aperture. This succession of widenings and contractions, similar to those of the valleys on the surface, * Fournet, Hydrologie Souterraine. 252 THE EARTH. forms a series of chambers, separated one from the other by partitions of rock. The water spreads widely in large cavities, then, contracting its stream, rushes through each defile as if through a sluice. On account of these partitions, it is very difficult, or even impossible, to navigate the course of subterranean rivers to any considerable distance, even at the time the water is low. When it is high, the liquid mass, de- tained by the partitions, rises to a very high level in the *large interior cavities, and often reaches the roof above. Sometimes when, through the clefts of the rocks, a communication exists between the cave and some hollow above, the surplus water from the subterranean streams makes its appearance there. Thus the Recca, which flows beneath the adjacent plateau of Trieste, does not always find space enough to flow freely in its lower channels, and Schmidl has seen it ascend in the chasms of Trebich to a height of 341 feet. It may be understood that the pressure of such a column of water often shatters enormous pieces of rock, and thus modifies the course of underground streams. When the water, impelled by force of gravitation, seeks a new bed in the cavernous depths of the earth, and disappears from its former channels, these are at first much easier of access than they formerly were ; but ere long, in most caves, a new agent intervenes, which seeks to contract or even completely obstruct them. This agent is the snow-water, or rain, which percolates, drop by drop, through the enormous filter of the upper strata. In passing through the calcareous mass, each one of these drops dissolves a certain quantity of carbonate of lime, which is afterward set free on the arch or the sides of the cave. When the drop of water falls, it leaves attached to the stone a small ring of a whitish substance ; this is the commencement of a stalactite. Another drop trickles down, and, trembling on this ring, lengthens it slightly by adding to its edges a thin circular deposit of lime, and then falls. Thus drop succeeds drop in an infinite series, each depositing the particles of lime which it contains, and forming ultimately a number of frail tubes, round which the calcareous deposit slowly accumulates. But the water which drops from the stalac- tites has not yet lost all the lime which it held in solution ; it still retains suflicient to enable it to elevate the stalagmites and all the mammillated concretions which roughen or cover the floor of the grotto. It is well known what fairy-like decorations some caverns owe to this continuous oozing through the vaults of their roofs. There are few sights in the world more astonishing than that of these subterranean galleries, with their dead-white columns, their innumerable pendants #nd multiform groups, like veiled statues, all yet unstained by the smoke of the visitor's torch. These stalactite caverns can only retain this primitive beauty on the condition of not being given over to idle curiosity. But yet how large is the number of those vulgar admirers who, under the pretense of loving nature, seek only to profane her ! When the action of the water is not disturbed, the needles and other deposits of the calcareous sediment continue to increase with considerable STALACTITES FLORA AND FAUNA OF CAVES. 253 regularity. In some cases, each new layer which is added to the concre- tions may be studied as a kind of time-measurer, indicating the date when the running water abandoned the cave. At length, however, the soft con- centric layers disappear, and are replaced by forms of a more or less crys- talline character ; for in every case where solid particles exist, subject to constant conditions of imbibition by water, crystals are readily produced.* Sooner or later, the stalactites, increasing gradually in a downward direc- tion, meet and unite with the needles rising from the surface of the ground, and, forming by their number a kind of barrier, obstruct the narrower passages and close up the defiles, separating the cavern into distinct cham- bers. Any objects which lie on the surface of the ground in these drip- ping caves gradually become hidden by the calcareous concretion which thickens round them. Generally speaking, when geologists find in these grottoes the remains of men or animals the former inhabitants of the mountain caves they are covered with a crust of stone, slowly deposited by the dripping water. In 1816, in one of the caves of Adelsberg, a skel- eton probably that of some bewildered visitor was discovered, which the stone had already enveloped in a white shroud ; but these bones have now, for some years, been firmly fixed in the thickness of the rock, added to, as it constantly is, by fresh layers ; indeed, the lateral cave itself will soon be filled up by stalactites, and will cease to exist. In like manner, the skeletons of three hundred Cretans, who were smoked to death by the Turks in 1822 in the cave of Melidhoni, are gradually disappearing under the incrustation of stone which has enveloped them with its calcareous layers, f In the gloom of these dark recesses there is still some little manifesta- tion of life. Since, however, plants of a higher order are unable to dis- pense with light, fungi form the only vegetation which we meet with, and even these growths of darkness do not always arrive at their full develop- ment ; they often present monstrous and anomalous forms, which puzzle the botanist, and hinder his attempts at classifying them. Some fungi never reach any further development than a mass of confusedly organized cells ; others grow so as to cover a considerable surface. The Fauna, be- ing more independent of light than the Flora, reckons a much larger num- ber of representatives in these caves. Not only do these subterranean cavities serve as places of refuge for various birds, and as dens for several kinds of beasts of prey, such as foxes, badgers, hyenas, which carry thither the prey which they have caught (as our ancestors the troglodytes once did), but they are also inhabited by several families of animals which only exceptionally, or through accident, ever emerge from the depths of the caverns. Among the latter there is at least one mammal, a species of bat, J which is found in the caves of Istria, the Apennines, and the Algerian mountains. The subterranean pools and streams of Central Europe also contain several varieties of a strange reptile the Hypochthon, or Proteus * Knhlmann, Presse Scientijiqve, 1 8G5. t Perrot, L'lle de Crete. I Minioptervs Schreiberrii. 254 THE EARTH. the eyes of which, being useless in the darkness, are almost aborted. Insects are the class which is best represented in these subterranean re- gions, but none present those vivid colors which the light of the sun con- veys to most of their congeners. All are clad in a dull garb which bjends with the dark shades of the rock. The most curious of these insects is a species of fly (Phora maculata) which never uses its wings, and various Coleoptera (Anophthalmus), in which the eyes are entirely wanting. Then follow spiders, centipedes, crustaceans, and molluscs. M. Schiner, who has made a special study of the Fauna of caves, enumerates twenty-three spe- cies of animals which inhabit the caverns in the vicinity of Trieste alone ; but these species form, doubtless, but a very small proportion of the sub- terranean tribes which live in the caves scattered far and wide over the whole earth. It is said that the caves in Kentucky contain a species of blind crayfish ; also whitish rats, of a very large size ; and lizards, wan- dering gloomily in this world of darkness; and, lastly, a species of yellow cricket, which crawls like a frog, guiding its course by means of enormous antennae. One of these Kentucky caves, called the " Mammoth Cave," is the lar- gest which is at present known. The whole of its extent has not been as yet fully explored, for it may be almost called a subterranean world, having a system of lakes and rivers, and a net-work of galleries and pas- sages without number, which cross and recross one another, going down to an immense depth. From the chief entrance to the farther recesses of Fig. 83. Chasms of Carniola. the cave, the distance is reckoned to be not less than 9| miles, and the whole length of the two hundred alleys that have been traced out in this enormous labyrinth is 217 miles in extent. This "Mammoth Cave" once CAVERNS OF CAENIOLA AND ISTBIA. 255 served as a retreat for savage tribes, for skeletons of men of an unknown race have been found buried in it under layers of stalactite. This district, which is the most remarkable among all the calcareous countries of Europe for its caves, its subterranean streams, and its abysses, is unquestionably the region of the Carniolan and Istrian Alps, which ex- tends to the east of the Adriatic, between Laibach and Fiume. The whole surface of the country, as in certain plateaux of the Jura in France, is ev- ery where pierced with deep boat-shaped cavities, at the bottom of which the water forms a kind of whirlpool, like the water flowing out of the hold of a stranded ship. Many mountains are penetrated in every direction with caverns and passages, just as as if the whole rocky mass was noth- ing more than an accumulation of cells. On one steep cliif-side may be noticed all kinds of perforations at different heights arched portals, and orifices of fantastic shape ; on another there are numbers of springs of blue water gushing from the caves, or from the rocks heaped up at the foot of the cliflf, and forming rivulets which disappear a little farther on in the fissures of the ground, as if through the holes of a sieve. The whole surface of the plateaux, whether bare or covered with forests, is scattered over with wells, or funnel-shaped holes communicating with subterranean reservoirs. The geography of the underground labyrinth of the Illyrian caves is as yet only sketched out, and yet a considerable number of sa- vants, at the head of whom stands M. Schmidl, have devoted many years of their lives to this study. Thanks to their investigations, some of the passages in these caverns, especially those of Lueg, are almost as well known as the corridors and chambers of a palace. Fig. 84. Grotto of Lueg, Illyrla, One of the Istrian rivers, the subterranean course ot which, although still unknown as regards a great number of points, has given rise to a most continuous course of investigations, is the celebrated Timavus (Ti- mavo), which falls into the sea near Duino, about twelve miles to the north of Triesta Virgil's description* no longer applies to the mouths " Fontem superare Timavi IJnde per ora novem vasto cum murraure mentis It mare pncruptum, et pelago premit arva sonanti." 256 THE EARTH. of the Timavo ; at present they do not reach the number of nine, because either the extermination of the woods of the Carso has diminished the mass of the water, or the action of the stream and the alluvium of the delta have modified the form of the shore. But still it is a magnificent spectacle to see the outlet of the three principal torrents of water, which rush foaming out of the heart of the rocks, and are navigable from their mouths to their very source. A river of this importance must certainly receive the drainage of a vast basin, and yet all the neighboring valleys seem perfectly devoid of rivulets, and their surface presents little else but the bare rock ; in fact, the whole of the rain and snow-water runs away through underground caverns. We do not meet with any tributary until we reach a spot 21 miles southeast of the mouth of the Timavo. This tributary, known under the name of the Recca, is lost in the rock under a high arch on which stands the village Sant Canzian ; it appears again at the foot of two precipices, and then ingulfs itself in the depth of the rocks by a series of beautiful cascades, beyond which explorers have not traced it. Farther on, the course of the subterranean torrent is only indicated by abysses opening here and there in the midst of the plain. In 1841, M. Lindner, who was seeking in every direction for springs of water to sup- ply the city of Trieste, the inhabitants of which were threatened with drought, formed the idea of sending some miners down into the chasm of Trebich, situated about four miles to the northeast of the city. After eleven months of labor the miners at last reached the floor of the lower cave, 1062 feet below the surface of the plateau, and there, in fact, they found the Recca of Sant Canzian flowing at their feet. The descent into this cave is by means of ladders, and it is thus rendered accessible by the work of man. The most remarkable net-work of caverns in this region of the Alps is that which spreads out from the southwest to the northeast across the Adelsberg group of mountains, between Fiume and Laibach. The princi- pal cave is especially curious on account of its size, the variety of its cal- careous concretions, and the torrent which runs roaring through it ; cer- tainly its vast compartments, its innumerable white and rose-colored pend- ants, its abysses wrapped in shade, and the eternal echo of its rushing wa- ter, would produce upon visitors a much more striking effect if its pro- prietors had not conceived the untoVard idea of decorating their property with rustic or Chinese bridges, elegant staircases, and pyramids adorned with sentimental inscriptions. North of the town of Adelsberg the traveler passes along the base of a hill with steep and bare sides, bringing into view the sharp edges of its highly-pitched calcareous beds. On the right the stream of the Poik winds peaceably in the valley ; and then, its course being arrested by a headland, turning suddenly, it flows into the interior of the mountain through a kind of high portal, opening between two parallel beds of rocks. Unless the water in the stream is very low, it is impossible to follow it over the accumulation of rocks upon its bed ; but on the right, at a height QROTTO OF ADELSBERG. 257 of a few yards, there is another entry, through which the traveler may de- scend dry-shod into a vast cavity or chamber, where the Poik again ap- pears issuing from its narrow passage of rocks. At this point the cave divides; on the north the stream, the depth of which varies, according to Fig. 85. Grotto of Adelsberg. the season, from a few inches to 30 or 33 feet, buries itself in a winding avenue, which has been traversed in a boat as far as a point 1027 yards from the entrance ; on the northeast, a higher avenue, discovered only in 1818, pushes its way far into the heart of the mountain, branching out in vari- ous directions, into narrow passages and wide compartments. This por- tion of the grotto, which appears to have been the former bed of the Poik, is the most curious part of the Adelsberg labyrinth ; it affords wonderful groups of stalactites, especially in the Salle du Calvaire, the vaulted roof of which, having the enormous span of 210 yards, has dropped upon a hil- lock of debris a perfect forest of stalagmitic columns and white needles. R 258 THE EARTH. The full length of the principal cave is not less than 2575 yards ; but very probably some other and still longer avenues may yet be discovered. Although it is impossible to go in a boat along the subterranean por- tion of the Poik for a greater distance than 1027 yards, by traversing the surface of the calcareous plateaux we can at all events trace out the sub- terranean stream by means of the funnel-shaped hates which open above its course. One of these gulfs, the Piuka-Jama, is situated about a mile and a half to the north of the entrance of the Adelsberg caves; the only way to descend into this is by clinging to the branches of the shrubs and sliding down by the assistance of a cord fastened to the top of the rocks. By these means the entrance to a kind of air-hole may be reached, from which the Poik is visible foaming over its bed of rocks, and only a slope of debris is to be descended to reach the edge of the stream. . It can only be followed in the down-stream direction for about 275 yards; but it can easily be ascended for a distance of 495 yards by passing under a high portal with lofty pillars, and in this way a point can be reached which is less than a mile from the place where the stream disappeared in the cave of Adelsberg. Farther down the stream the Poik is not visible again until it emerges from the mountain, where it is known under the name of the Planina ; it rushes out through a circular arch at the base of a perpendicular bluff crowned with fir-trees. It really is the Poik, as is proved by the equal temperature of water and the sudden increase of its liquid mass after a storm has burst at Adelsberg ; but the stream always issues from the cave much more considerable in bulk than it is when it enters, owing to the tributaries which pour into it on both sides during its subterranean course of five to six miles. One of these rivulets, which comes down from the plateaux of Kaltenfeld, joins the Poik at a little distance from its outlet. Above the confluence the principal stream can be ascended in a boat to a distance of more than 3500 yards, which, with the other explored parts of the subterranean river, makes about three miles. Below the point of out- let the stream is partially lost in the fissures of its bed, and then, joining the Unz, goes on and empties itself into the Danubian Save. About a dozen miles to the southeast of the Adelsberg and Planina caves extends a large plain surrounded on all sides by high calcareous cliffs, at the base of which nestle seven villages. In this hollow, the most elevated portion of which is under cultivation, the remainder being cov- ered with rushes and other marsh plants, there are to be found more than 400 funnel-shaped holes resembling those in other parts of Carniola. These dolinas, the average depth of which is from 40 to 60 feet, have each their special name, such as the " Grand Crible" (great siev.e), the " Crible- d-froment" (corn sieve), the "Tambour" (drum), the " Cuve" (tub), the; "Tonneau" (cask), pointing out the form or some remarkable peculiarity of each abyss. During extremely dry seasons there is only one of these cavities which contains any water ; but after continuous and heavy rain, the water of a stream which is swallowed up in the rocks a little above THE LAKE OF JESSERO. 259 the plain rises with a roaring noise in each of these wells. Torrents es- caping from all these open " cribles" form in the wide space hemmed in by the cliffs a sea of blue and transparent water. This is the lake of Jessero or Zirkuitz, the lacus Lugens of the Romans. The surface of the sheet of Fig. Mi. Uruiiu of Pluuiua. water extends over an area of 14,826 acres; at the time of great inunda- tions, this extraordinary temporary lake, thus vomited out by the under- ground river, is not less than 24,711 acres. The water runs away through 260 THE EARTH. a subterranean channel, and, further on, empties itself into the Unz, below the Planina. Lacustrine basins of this sort, first emitted, and then again absorbed by a subterranean water-course, are rather rare ; there are, however, some other remarkable instances of them in Europe. Thus, in the Oriental Hartz, in the midst of a beautiful spot surrounded by fir-trees, the charm- ing lake called Bauerngraben (Peasants' Ditch), or sometimes Hungersee (Lake of Famine), sometimes makes its appearance ; but when this mass of blue water has filled but for a few days its basin of gypsum rock, it is suddenly swallowed up, and flows away by subterranean channels into the stream of the Helme. The celebrated lake of Copa'is, in Boeotia, may likewise be compared to the Zirknitz lake, at least as regards certain por- tions of its basin. NAMES OF WATER-COURSES. 261 CHAPTER XLIV. RIVERS. VARIOUS DENOMINATIONS OF WATER-COURSES. DETERMINATION OF THE PRINCIPAL BRANCH AMONG THE AFFLUENTS OF A RIVER. RIVER BASINS AND WATERSHEDS. FORKS OF CERTAIN RIVERS. GEOGRAPHERS have long discussed, and are still discussing, the precise import of the names which are used to designate running waters. How are we to lay down any distinction between a river and a stream, or be- tween a stream and a rivulet ? Obviously no absolute difference can ex- ist, as all water-courses are alike composed of liquid masses impelled by their own weight over an inclined bed. The only relative difference which at first sight it seems easy to establish consists in the greater or less quantity of water which each bed contains ; but even this mode of estimation must vary in every continent and in every country, according to the importance of its hydrographical system. Many a European river would seem nothing but a slender rivulet, and would scarcely be thought worthy of a name, if it were situated in the immense basin of the Ama- zon. Added to this, the mass of water alters its bulk according to the various seasons. Many rivers in tropical regions which flow very abun- dantly during the rains, are during the dry season often entirely dried up, or changed into a series of pools. All the phenomena of nature being full of diversity, she has omitted to furnish any fixed rule for the classification of water-courses; but some geographers, desiring, at any rate, to assume an appearance of authority in matters relating to the earth, have given the name of river (fleuve) to the liquid masses which empty directly into the ocean, and apply the name of stream (riviere) to mere affluents which are themselves fed by tributaries of the second order, or rivulets. In virtue of this purely scho- lastic distinction, the Argons, the Seudre, and the Leyre would be rivers, while the Tapajoz and the gigantic Madeira would only have the right to the title of streams. Our ancestors, the Celts of Western Europe, who understood much more about nature than many of our modern savants, employed the same name (although variously modified by use) for distin- guishing water-courses of all sizes, viz., the Rhine, the Rhone, the Arno, the Orne, and the Amon. All running water was in their eyes a river. The principal difficulty which systematical geographers meet with is that of determining, as regards each basin, which is the chief branch ; that is, which is to be considered the river par excellence, all the other water- courses being mere tributaries. IK some cases, certainly, it may readily be perceived to which artery of the river-basin the pre-eminence unques- tionably belongs; but more generally it is difficult, or even impossible, to 262 THE EARTH. pronounce with any certainty on this question. Is it the Seine or the Yonne, the Adour or the Gave-de-Pau, the Rhine or the Aar, the Inn or the Danube, the Mississippi or the Missouri, the Maranon or the Apurimac (Ucayali), which has the best right to impose its name on the principal artery which bears onward to the sea the mingled water of the two riv- ers? Does the point in question chiefly depend upon length of course? If it does, the Saone and the Rhone are only tributaries of the Doubs, which has a total development, from Mont Rizoux to the Gulf of Lyons, exceeding that of the Rhone by 93 miles. In like manner, the Mississippi would thus become a tributary to the Missouri, which has a course more than 1615 miles longer an excess which is equal *o three times the length of the Seine. In deciding which of the upper tributaries is the principal water-course, would it be more to the point to compare the quantities of the liquid supply which each brings to the common fund ? In this case, the Yonne, the Aar, and the Inn are rivers which are fed by the Seine, Rhine, and Danube respectively. Ought we not rather to consider the more or less rectilinear direction, and the comparative geological unity'of the valley of each affluent, as the principal signs which should determine the real river? Then the Rhone and the Seine are nothing but seconda- ry water-courses in comparison with the Saone and the Yonne, and the Yonne itself must yield its pre-eminence to the Cure. The savant who devotes himself to the unthankful task of seeking out the principal branch in a river system has therefore to take account of the most diversified points of detail : the average mass of water, the length of the course, the general direction of the valley, and the geological nature of the soil; but, whatever may be the result of his investigations, he must ultimately yield to the all-powerful authority of tradition. For it is tra- dition, and not science, which has invested rivers with their titles and dig- nity ; it is the voice of our ancestors, founded on a thousand circumstances in connection with mythology, the history of conquests or colonization, agriculture, navigation, or even on various natural phenomena, which has arbitrarily decided to give the pre-eminence to some particular water- course over the other rivers of the same system. It is now too late to try to change the hydrographical nomenclature. But, even were it possible, this alteration would be almost entirely inef- ficient, for the vitality of nature will not accommodate itself to the strict classifications to which pedants would seek to restrict it. It is only by pure abstraction that we come to consider a river as an isolated existence. In reality, it is the aggregate of the streams and rivulets which flow into it from all the points of its basin ; it unites the millions of rills which are set free from the ice, or trickle from the crevices of the rocks ; it is made up of the innumerable springs which ooze out from the ground saturated with rain or covered with snow. A river is in a constant process of change, and every tributary takes its sbfcre in this work of transformation. The entire drainage area, and not any particular affluent, ought, therefore, to be considered as the real river. We must take into account the Mis- ORIQDf OF XAMES OF RIVERS.-RIVER SYSTEMS. 263 souri, the Ohio, and the Red River, no less than the Mississippi, extending its long and constantly increasing peninsula of mud into the Gulf of Mex- ico ; also the Tapajoz, the Rio Negro, and the Madeira, flowing with the Solimoes into the vast estuary of the Amazon. In like manner, to use the language of the sailors of the Bay of Biscay, the " two seas" of Garonne and Dordogne unite their waters to compose the " Sea" of Gironde. Those names of rivers which are formed by the contraction of the desig- nations of their chief tributaries are, indeed, the only terms which are geo- graphically correct. We may mention, as examples, the names of the Somme-Soude, the Thames (Thame, Isis), the stream of Gyronde (Gyr, Onde) in the Upper Alpfe, and, better still, that of the Virginian river Mat- tapony (Mat, Ta, Po, Ny). The aggregate of the arteries of a river system may be compared to the branches and twigs of an immense tree. The Rhine and the Mississippi remind one of the oak by the majesty of their shape and the magnitude of their branches, thrown out at right angles to the parent stem. The Nile, with its long trunk devoid of lower boughs, and crowned with its plume-like terminal branches, recalls to our mind the palm-tree of the oasis. These comparisons, it is true, have no scientific element in them, but still they do not fail to present themselves to the eye, and geographers, as well as artists, must be to some extent struck by them. Almost all those portions of continents on which the humidity of the atmosphere falls in the shape of snow and rain have their system of rivers, into which all the water is emptied which is not, immediately after its fall, absorbed by the earth or sucked up by the roots of plants. But when the surface of the ground is almost or quite horizontal, the rain-water can not find a sufficient amount of slope to enable it to flow down toward the sea, and consequently spreads out in stagnant pools. Thus, in the pampas of the Argentine Republic where, however, the annual rainfall is greater than that of France the prairies are dotted over with lagunes having no outlet, and the Vermejo, the Salado, and the Pilcomayo the great rivers descending from the mountains of the northwest are not replenished by a single tributary from the plains through which they pass.* Lofty mountain chains, the peaks of which tower up into the sky, cross- ing the very tracks of the clouds, collect in proportion a much larger share of moisture than the plains, and consequently give rise to the most abundant streams of water. Nevertheless, as low-lying countries, or those possessing a moderately elevated vertical outline, embrace an area much more extended than that of mountainous districts, these flat regions are the localities where rivulets spring from the earth in the greatest number. In a general way, the ravines or dells in the plains in which the water of river-sources is collected are representations in miniature of the deep gorges and the hollows of erosion existing in high mountains. But among the incipient river affluents there are some which take their rise on level plateaux, or in some trifling depression of the ground ; there are others, * Martin de Moussy, Confederation Argentine. 264 THE EARTH. especially in the great plains of Russia, which issue from lakes or marshes, which spread out in vast sheets in the centre of the country. Thus the watershed that is, a ridge separating two slopes, or perhaps a mere ideal winding line, on each side of which the water flows in an opposite direc- tion is developed under the most diversified conditions. A river basin that is, the area which is traversed by all its affluents may be bounded on one side by the jagged ridge of some mountain chain, on the other by the gentle undulations of a range of hills, further on by an almost imper- ceptible rising in some low-lying plain. In certain localities, indeed, it is necessary to level the soil in order to ascertain the exact spot where the " divorce of the waters," as the ancients used to call it, actually takes place. Added to this, even in the mountains, the ridge line, or the highest elevation, is very far from uniformly coinciding with the watershed which separates two drainage areas. Mountains exhibit such infinite variety in their original form, and the agents which denude them have hollowed out their sides in ways so diversified^ that some rivers actually take their rise on the contrary side of the mountain to that which they are about to wa- ter. The most remarkable instance which is to be found on the earth of sud- ' den interruption in a mountain system is probably the astonishing cut of Rinihue, situated in the Chilian Andes, near the fortieth degree of latitude. Fig. 87. Cut of Rinihue, in the Chilian Andes. According to the unanimous evidence of the aborigines and the Chilian peasants of the country, the stream ofHuahuum, which takes its rise in the high pampas of Buenos Ayres, empties its waters into the Pacific after having crossed the chain of the Cordilleras. Issuing from the lake Neltume, the stream then penetrates into a defile, where it is known under the name of the Caillitue. It is certain that further down it is replenished BIFURCATION OF RIVER-COURSES. 265 by a stream flowing from the Andine lakes of Panguipulli and Cafalquen, and that the combined liquid mass flows on and empties itself into the lake of Riiiihue, which is a tribiftary of the Pacific Ocean. The Indians assert that the whole extent of the Huahuum and Caillitue are navigable, and are only interrupted by one single rapid. Unfortunately, the scien- tific explorations of this region have not yet gone beyond the banks of the lake Rifiihue. It appears that in this part of its development the chain of the Andes owes its form to the action of the subterranean agents, which have raised cones of eruption at intervals along the volcanic line of fault.* Several river-basins exhibit rather a curious phenomenon. The water- shed line, traversing high mountain chains, plateaux, and marshes, and separating two hydrographical systems, is interrupted by breaches or gaps, through which the water can flow out of one basin into another. On reaching this breach, the flow of water, being attracted by two inclines, forks out into two streams running in contrary directions, and sometimes toward two different seas. Thus, in Columbia, the Upper Orinoco divides Fig. 88. Bifurcation of the Orinoco. into two rivers, one of which empties into the Atlantic immediately to the south of the Antilles, while the other, known by the name of the Cassi- quiare, runs to the southwest toward the Rio Negro, a tributary of the Amazon. The river, therefore, which collects the waters of the upper ba- sin of the Orinoco is a tributary of two seas at the same time ; it assists in turning the whole of the Guianas into a great island, surrounded on one side by the ocean, on the other by a channel navigable along a double incline, having its summit level at the foot of the high mountain of Duida. * Frick, Mittheilungen von Petermann, ii., 1864. 266 THE EARTH. This phenomenon of bifurcation, which has been rendered famous by the journey of Humboldt and Bonpland, is also found, although certainly on a less magnificent scale, in several other countries of the earth, some moun- tainous, and others only slightly undulating. In some places, owing to the kind of indecision which is produced in the liquid mass by the double attraction of the two inclines, man has been enabled to regulate at his will the course of the two diverging streams, or even entirely to do away with the bifurcation by means of a dam, or some other hydraulic works. But to make up for it, in a multiplicity of other cases human ingenuity has been able to utilize the depressions of the surface so as to draw off later- ally an arm of a river, and thus create an artificial fork.* In Europe only, numerous instances may be mentioned of natural bifur- cations. In Sweden a small lake, which is situated at a height of more ' O than 3300 feet at the foot of the lofty mountain of Sneehattan, simultane- ously feeds the stream of Lougen, which descends toward Christiania, and that of Romsdal, which empties itself into the Molde Fjord, between Ber- gen and Trondjhem. Added to this, the marsh of Kol, on the plateau of Hardanger, gives rise to eight rivulets, each diverging in its own particu- lar direction.f In like manner, on a rocky plateau situated at a height of about 2640 feet to the east of Puy de Carlitte, in the Eastern Pyrenees, we find the little pool of Las Dous (the Two) emptying its waters simultane f ously into an affluent of theTet du Roussillon and into the rivulet of An- goustrine, a tributary of the Segre and the Ebro. Central Italy affords a still more curious instance of bifurcation. It appears unquestionable that, at the time of the Romans and during the first centuries of the Middle Ages, the Arno was divided into two branches, one of which emptied itself directly into the sea, while the other, crossing on the south the valley of Chiana, fell into the Paglia, a tributary of the Tiber. J When the river Arno, gradually sinking its northern bed, ceased to flow into the valley of Chiana, the water which descended from the lateral ravines in this almost horizontal depression flowed to a very slight extent on one side into the Tiber, and on the other into the Arno ; but more often it stagnated in wretched marshes, which were a constant source of fever. These marshes have now disappeared, thanks to the splendid hydraulic works undertaken since Torricelli's time by the Tuscan engineers for the amelioration of the valley. By means of the alluvium brought by the torrents on both sides into the settling basins, an artificial watershed has been created in the mid- dle of the valley, giving the water two very perceptible slopes, inclined in contrary directions. One of the tributaries of the basin of the Seine also once offered an instance of constant bifurcation ; at Moeurs the Grand Morin divides into two streame, one of which flows down to the Marne, and the other feeds the Superbe, an affluent of the Seine. But lately, ow- ing to the destruction of the woods, the sources have become diminished; * Vide the chapter on "The Labors of Man." t Fritsch, Mittheilungen von Petermann,vo\. xi., 18(16. t Salvagnoli Marchetti. Simonin, L'Etrurie et les Etrusques. RIVER-BASINS AND WATERSHEDS. 267 the double communication of the water only takes place in an artificial way by means of a dam.* Among phenomena of a like nature, we must also class the division .of the contents of a river into two branches, which, flowing separately each in its own valley, ultimately reunite at a considerable distance below the point of bifurcation. It is not improbable that, at a recent geological pe- riod, the Rhine was thus divided into two branches, embracing in its Fig. 89. Bifurcation of the Valleys of the Rhine. course an immense island of rocks and mountains comprehended between the lakes of Wallenstadt, Zurich, and Constance, and the present conflu- ence of the Aar and the Rhine. In the earth's history the two valleys may be looked upon as having an equal title to be considered the axis of the river-basin, as they have both served as the river-bed, either simulta- neously or in turn. Between Meyenfeld and Sargans, at a height of 1580 feet, the Rhine doubles round suddenly to the northeast, and, penetrating a narrow defile, runs down to the Lake of Constance, which it crosses, and flows on to join the waters of the Aar and the Limmat at about 93 miles below Sargans. The latter town is situated on an isthmus of pebbles and peat, which divides the present bed of the Rhine from its former bed, which tends toward the northwest. If this isthmus, which is only about 16 feet high, were to disappear, the river would again divide into a fork, and one of its arms would flow on to empty itself into the Lake of Wal- lenstadt, and thence into the Lake of Zurich and the valley of the Aar. Various hypotheses have been propounded to explain the formation of * Plessier, Formation de* Plateaux et des Valk'es de la Brie. 268 THE EARTH. this isthmus which has severed the river-basin into two parts, and forced the whole body of the Rhine to flow into the Lake of Constance. It is Fig. 90. Threshold of Sargans. probable that this mass of pebbles is a portion of a slope of debris brought down by the torrent of Seez from the recesses of the gorge of Weiss-tan- nen (White Firs), and deposited at the outlet of the lateral valley.* So long as the river was able to clear a way through these heaps of stones, a portion of it followed its old course toward the Lake of Wallenstadt ; but, being constantly impeded by the ever-growing barrier, it was ultimately compelled to open a new outlet toward the north. A great number of examples of this double flow of portions of one mass of water toward different basins are afforded by low and marshy plains. The marshes of Pinsk, in Volhynia, serve as a common source to various affluents both of the Vistula and the Dnieper, thus forming a link between the Baltic and Black Seas. In spring, when the snow melts, and toward the end of autumn, after the heavy rains, a series of lakes, wet marshes, and temporary rivulets connect the inland Caspian with the Sea of Azof and the Euxine. The water of the Kalaous, coming down from one of the rugged valleys of the Caucasus, divides, and forms a temporary channel * W. Huber, Report of the Geographical Society, February and March, 1 866. CHANGES IN THE COURSE OF RIVERS. 269 between the two basins, which were, indeed, once united in one and the same ocean. Fig. 91. Marshes of Pinsk. The two principal river-systems of North America those of the Missis- sippi and the St. Lawrence are likewise blended together for a few days after a prolonged rain-fall. Even before the construction of the canal which at present unites the two rivers, small boats could sometimes pass from the Chicago River into the Illinois, and thus cross the scarcely-indi- cated watershed which divides the basin of Newfoundland from that of Mexico. In a recent period that is, about 4500 or 5000 years ago the union of the two river-basins, which has now become but temporary, ap- pears to have been of a permanent character. The calculations and ob- servations of Sir Charles Lyell, Schoolcraft, and many American geolo- gists, render it very probable that, at this epoch, all the upper affluents of the Mississippi and the St. Lawrence fed a lacustrine reservoir, the vast sheet of which, situated about 600 feet above the level of the ocean, stretched toward the north as far as the mouth of the Wisconsin, and on the east joined the Lake Michigan, covering all the intervening peninsulas. The centre of the continent was occupied by a sea as large as our Medi- terranean, which emptied itself into the ocean by an immense delta, each arm of which was one of the greatest rivers of the earth.* The bifurcations of water-courses do not, however, all take place on the surface of the ground ; and if the deeper layers could be disclosed to our view, it is probable that we should find the majority of river-basins would afford' instances of subterranean derivations. In a country like France, in which geological exploration has seriously cpmmenced, a considerable number of these curious phenomena have been discovered, although they * Humphreys and Abbot, Report on the Mississippi River. 270 THE EARTH. Fig. 92. The Ponto-Caspian Isthmus. are in general but little noticed. Thus, in the Basses Pyrenees, the Gave d'Ossau forms a fork at the foot of the high hill of the Sevignac. One arm, running to the northwest, flows on to join the Gave d'Aspe, and forms the Gave d'Oloron ; but the other buries itself under the rocks, and reappears about five miles to the north, in two very strong springs, the stream re- sulting from which, called the Neez, empties itself into the Gave of the same name, not far from Pau. In like manner, in the centre of France, the Haute-Vezere sends one of its arms under the ground, for a distance of about three miles, to feed the stream of the Isle, which meanders through its deep valley in long parallel windings. ORDERLY DISTRIBUTION OF RIVERS, 271 * CHAPTER XLV. THE HYDROGRAPHICAL SYSTEMS OF VARIOUS PARTS OP THE WORLD. THE great difference which exists between continents as regards both their vertical outline and their extent of area gives to the water-courses in each part of the world the most diversified directions and characteris- tics. In every place the general plan of the hydrographical system va- ries in proportion to the height and bearing of the mountain chains, the length and inclination of their slopes, the geological nature of the regions which it waters, and the annual quantity and distribution of the rain-fall. But, since the continental masses, both in their general outline and in their different parts, present an evident equipoise in their forms ; since the clouds and winds are in full obedience to constant laws ; the result is, that the rivers themselves are arranged on the surface of the earth with a remarkable degree of order, which is all the more beautiful in that it so considerably deviates from any symmetrical regularity. The graceful windings of a river, its long and almost quivering curves, and the intri- cate bends of its innumerable tributaries, prevent our noticing the rhythm of its system, and how this system prevails from one end of the world to the other. On our earth physical laws are but rarely manifested in all their inflexible simplicity. Owing to the vitality which pervades every thing, they often assume a character of beauty, and through this very beauty they not unfrequently evade the notice of man. A study of the map, with regard to the distribution of rivers over the surface of the earth, brings before our view, at a glance, this fact that the water-courses which are tributaries of the Atlantic exceed consider- ably, both in number and importance, those which belong to the great Pacific Ocean. This sea, the greatest of all seas, receives directly only five considerable rivers the Cambodin, the Yantse-kiang, the Hoang-ho, the Amoor, and the Columbia ; but the comparatively narrow channel of the Atlantic is the reservoir into which the most enormous rivers of the earth pour their contents the Uruguay and the Parana, the River of the Amazons, the Orinoco, the Mississippi, and the St. Lawrence, without reckoning the Congo, Niger, and Gambia, all the water-courses of West- ern Europe, and, by the intervention of the Mediterranean, the Nile and the Danube the two great rivers of the ancients. This unequal distri- bution of rivers is a result of the semicircular arrangement of the Andes, the Californian mountains, and those of Kamtschatka and Siberia, all round the basin of the Pacific. The western side of South America is excessively poor in rivers. All over this narrow belt, which is on the average not one tenth as wide as the opposite Atlantic side, and is, be- 272 THE sides, rarely visited with rain, there are at most but two or three rivers which are navigable. The streams of Chili and Western Columbia would scarcely merit the name of rivulets in the basin of the gigantic Marafion. In a hydrographical point of view, the continent of Asia may be di- vided into three entirely dij&nct systems those of the north, the centre, and the south. The first is the great plain of Siberia, which is gently in- clined toward the Frozen Ocean, and the whole extent of which is crossed by three parallel rivers, certainly among the largest, but also, perhaps, the least used by man, of all the water-courses in the world. In the cen- tre of the continent there are several closed basins, consisting of plateaux more or less desert, the streams of which are lost in some lake, or evap- orate during their course. The southern and eastern countries of Asia are the portions of the continent which show a genuine vitality thanks to the sea which bathes them, the deeply indented shape of their penin- sulas, the varied productions of their soil, and, above all, to the numerous water-courses which traverse them. The most remarkable of these rivers are arranged in pairs, so as to constitute three groups of twin currents. These are the Tigris and Eu- phrates, the Ganges and Brahmapootra, the Yantse-kiang and Hoang-ho. In each of these pairs, the two rivers take their rise side by side in the bosom of the same system of mountains, and, bending their course in op- posite directions, each describes a vast semicircular line all across the continent, and ultimately again unite before they empty themselves into the sea through the same delta. There is another point which still far- ther augments the analogy between these double fluviatile arteries, viz., that each empties its waters into one of the three seas situated to the east of the three southern peninsulas of Asia. The Shat-el-Arab flows into the Persian Gulf, to the east of Arabia ; the Ganges into the Bay of Bengal, to the east of India ; the Chinese rivers into the Pacific Ocean, which stretches to the north and east of the Indo-Chinese peninsula. In order to understand the general features of the river-system of the Asiatic continent, there is a fourth group of allied rivers which we must also notice the Indus-Sutlej. Certainly these two rivers of the western regions of Hindostan unite their waters at a rather considerable distance from their mouth ; but their lower course has entirely the character of a delta. The Indus and the Sutlej were probably once separated, and be- came united in consequence of the alteration of their course, and the con- siderable elongation of the delta common to both which received their alluvium. In like manner, at the time of Alexander the Great, the mouths of the Tigris and Euphrates were situated at a good day's march from each other; but at the present day the two river-arms coalesce at some considerable distance from the sea, and form together the Shat-el-Arab. The Indus and the Sutlej may, therefore, be classed among the double rivers, as their sources lie very close to one another ; their courses take an entirely different direction, and they also have a common outlet. As the waters of this fourth group of rivers descend from the same mountain DIVERSITY OF RIVER-SYSTEMS. 273 range which gives rise to the Ganges and the Brahmapootra, we might even say that in the north of Hindostan there is a double system of al- lied rivers which at their sources are almost joined. The four most con- siderable currents of water in India, taking their departure from nearly the same point, flow away in opposite directions, and, after describing enormous circuits, unite in pairs, as if to obey some double law of har- mony and contrast the Indus and the Sutlej to the east, the Ganges and the Brahmapootra to the west. They are the four animals of the Indian legend the elephant, the stag, the cow, and the tiger which spring down from the same mountain peak into the green plains of Hindostan. The contrast offered by Europe proper so rich in mountains, peninsu- las, and deep indentations of the coast to the vast plain of an almost Asiatic character which distinguishes Eastern Europe, shows itself equal- ly in the river-systems of the two halves of the continent. In Western Europe the Alps and the other chains of mountains radiating from them determine the characteristics of the water-system. In the Sclavonic countries, inhabited as they are by peoples hardly emerged from barba- rism, the great rivers, such as the Volga, the southern Dwina, the Niemen, the Bug, and the Dnieper, all take their rise in the marshy or slightly undulating regions which occupy the interior of Russia. Certainly they roll down a very considerable mass of water ; but in their historical im- portance they are very inferior to the rivers which spring from the Alps, and, flowing in every direction, water the various countries of Western Europe the principal theatre of modern civilization. The Alpine group of streams is that to which it is chiefly material to devote a separate study. From the sides of the St. Gothard, the centre of the Alps, three rivers, not counting the Reuss, take their rise the Rhine, the Rhone, and the Tessin falling respectively into the North Sea, the Mediterranean, and the Gulf of Venice. Two other water -courses, which do not pre- cisely descend from the St. Gothard itself, take their rise in its vicinity. These are the Aar, the principal tributary of the Rhine, and the Inn, a stream more important than the Danube the name which it assumes be- low the point of their confluence. Here, then, are five rivers which radi- ate toward four seas from one single group of the Alps ; but as isolated rivers, and not in the form of. double systems, like those of India and China. However, these distinct water-courses, especially the Rhone and the Rhine, present some remarkable peculiarities. These two great ri^ ers, nearly equal in volume, flow each in a diametrically opposite direr- tion ; then, turning suddenly toward the north by an abrupt bend, and crossing a lake of considerable dimensions one the Lake of Geneva, the other the Lake of Constance cross the parallel chains of the Jura either in rapids or cataracts, and, finally emerging from the mountainous regions, flow, the one directly to the north, toward the German Ocean, the other directly to the south, toward the Mediterranean.* Other groups of the same mountain chain, such as those of the Viso * W. Huber, Bulletin de la Sociite de Geographie, 18G6. s 274 THE EARTH. and the Levanna, near Mont Cerris, form secondary centres for the radia- tion of streams ; but, as regards their hydrographical importance, none of them can be compared to the central group of the St. Gothard. The great rivers of peninsular Europe which are not fed by the Alpine snows flow to the north of the almost continuous line of mountains which is formed across the continent by the chains of the Pyrenees, the Ce- vennes, the Jura, the Alps, and the Carpathians. The rivers which descend to the south are smaller, on account of the more contracted area which is afforded them in Europe by the Mediterranean slope. But it must be remarked that the line of summits does not exactly mark out the water- shed where the waters divide, some flowing to the north, the others to the south ; there is, in fact, a complete mutual invasion of the opposite basins, and their respective interpenetrations fit, as it were, one into the other. A river flowing to the north receives affluents from the southern side of the mountains, and another flowing to the south receives those from the north. Thus, on the Tatra (Carpathians) the water-shed is far from coinciding with the line of summits, and cuts across the chain of mountains. The Arva, coming from the north, penetrates the mountain- chain, and flows on into the Theiss ; while the Poprat, taking its rise in the south, hollows out a bed for itself through the gorges, and runs on to Fig. 93. Sources of the Garonne. ioin the Vistula.* In like manner, the Garonne rises in the glaciers of We Maladetta, to the south of the principal chain of the Pyrenees, and makes its way into the district of Aran and the plains of France ; but to effect this it is compelled to cross the base of the mountain of Poumero through a subterranean gulf 4376 yards long. The water, which disap- pears on the Spanish side in the high valley of Essera, reappears on the other slope of the mountain at a point 1980 feet lower down. The rising spring, the water of which thus pierces right through the rocks of Poumero, was once held sacred ; it is called the " Goueil de Joueou" (Jupiter's eye). * Carl Hitter. NORTH AMERICAN RIVERS. 275 In North America the same radiation of rivers exists as in Europe, but it spreads round three centres, two of which are mountain groups, and the other a merely gradual and imperceptible rising of the plain. In the ter- ritory of Idaho, between the 43d and 44th degree of north latitude, a great peak towers up to a height of 13,779 feet, to which Lieutenant Rey- nolds has given the name of " TJnion Peak," because the water from its melted snows, being soon increased and converted into important rivers, flows toward the Colorado on the south, the Missouri on the north, and the Columbia on the west.* More to the south, but still in the angle formed by the valley of the Colorado and those of the tributaries of the Missouri, the Rio Grande del Norte takes its rise, thus completing the system of radiation of large rivers round an elevated group of the Rocky Mountains. Nine degrees farther north, in the vicinity of Murchison Peak, several of the more important springs rise which feed the Fraser River, the Columbia, the Saskatchevan, the Athapasca, and the Macken- zie. According to Antisell, three of these rivers are fed by the snow of the same mountain. The sources of the Mackenzie and the Columbia take their rise at a distance of about 200 yards from each other ; and in fourteen paces or so a man may walk from the origin of the Columbia to that of the Saskatchevan. These, then, are the spots whence the radia- tion takes place of the great rivers on the northwest of the continent. The radiating centre of the rivers of the plain is situated a little to the west of Lake Superior, in the vicinity of the Red Lake, Lake Itasca, Lake of the Woods, and several sheets of fresh water which are scattered over the highest part of the lower plateaux of North America. Thence spring forth the sources of the Mississippi proper, those of the St. Lawrence, and the Northern Red River, a tributary of the great Lake Winnipeg, which communicates with the Mackenzie River and the Frozen Ocean by a se- ries of sheets of water. The radiating centre of the river-system of the plains serves to link together the two centres of the Rocky Mountain chain. It forms the complement of them. The three regions of the American river sources are mutually linked to- gether by the two principal affluents of one {fpat river. Thus, the gigan- tic development of the upper branches of the Mississippi connects the lofty groups of the Idaho mountains with the marshy plains of the Min- nesota ; as the Missouri it is classed as a mountain current, and as the Upper Mississippi it is a stream of the plains. The river, therefore, which unites all these waters is essentially double in its character. The Mac- kenzie River also presents this appearance of duality, although in a lass degree, as it receives affluents both from the lake region and also from the chain of the Rocky Mountains. In like manner, the two principal branches of the Columbia, the Serpent River and the Columbia proper, take their rise respectively in the two groups of summits, whence the streams radiate toward various points of the continent. South America is par excellence the country of rivers. There roll down * Humphreys and Abbott, Antisell, etc. 276 THE the immense Amazon, navigable for more than 3000 miles ; the mighty Parana, signifying by its name " The River" pre-eminently ; and the Ori- noco, surnamed " the Father of Waters," the drainage area of which is not one third so extensive as that of the Mississippi, although the latter river pours down a much less considerable body of water. On account of the narrowness of the Pacific slope, alUthe great water-courses of South America flow over the plains situated to the east of the continent ; but they do not all take their rise in the chain of the Cordilleras. The Orino- co takes its rise in the mountains of Guiana, the Maranon in the Andes, the Parana and the greater part of its tributaries spring from the high plateau^ in the interior of Brazil. These rivers, therefore, do not radiate round the same centre ; on the contrary, they belong to two basins which are perfectly distinct, and, indeed, cross one another at right angles. The basin of the Amazon tends, in fact, from west to east, while the plateaux and plains in the middle of the continent, forming a basin in the direction of the meridian transversal to that of the Amazon, are watered on the north by the Orinoco and the Rio Negro, on the south by the Tapajoz, the Madeira, the Paraguay, and the Parana. The distinguishing feature of the river-system of South America is in the fact that the three princi- pal rivers are interwoven by means of an almost continuous line of run- ning water, which extends from north to south from the mouth of the Dragon to the estuary of the Plata. More than half a century ago Hum- boldt placed the matter beyond all doubt that the Cassiquiare empties its water both into the Orinoco and into the Rio Negro. The communica- tions between the Tapajoz and the Paraguay are not so perfect, but they nevertheless exist in several places. According to M. de Castelnau, the proprietor of the Estivado farm irrigates his garden by turning the water from an affluent of the Paraguay into the bed of the Tapajoz, and makes the little channels flow at his will toward either the northern or southern side of the continent. In like manner, there is a stream near Macu which at the time of inundations is divided into two currents, one forming a part of the Plata system, and the other belonging to that of the Amazon. Farther to the east, the R^pGuapore, an affluent of the Madeira, and the Jauru, a tributary of the Paraguay, take their rise in a plain which is periodically inundated during the rainy season. At the foot of the Boli- vian Andes a similar intermingling of basins takes place, as regards the Marmore and the Pilcomayo. Thus, the Caribbean Sea and the mouth of the Orinoco are connected with the estuary of the Plata by a series of rivers, streams, and marshes. The numerous water-courses which proceed from the central plateau of the continent are all set in an aspect parallel to the Tapajoz and the Madei- ra. The chief affluents of the Orinoco, on the contrary, follow the same di- rection as the River of the Amazons. We are, therefore, correct in saying that the river system of South America comprehends two basins crossing one another. The Rio Magdalena, the Atrato, and the other streams of Guiana, are all rivers with distinctly limited basins; but it must be re- AFRICAN RIVERS. 277 Fig. 94. Interlacing Basins of the Amazon and the La Plata. marked that they all flow from the south to the north, in the same direc- tion as the southern tributaries of the Amazon. In that portion of the earth which is the most massive and the least ar- ticulated in its shape an harmonious correspondence is found between the water-courses and the continent itself. As long as the greatest part of Africa was an unknown region, geographers were able to attribute to its rivers all kinds of imaginary courses ; they could, as their fancy dictated, make the Nile, the Niger, and the Congo take their rise from one common source, or interweave in a complete net-work all the tributaries of these great rivers. But the discoveries of modern travelers will now warrant us in forming some general idea of the African river-systems. This land, so devoid as it is of peninsulas and of deep indentations in its coasts, does not, probably, present more than one centre of radiation for its waters, which centre is situated about the middle of the continent. From this point descend the Chary, the Binue a tributary of the Niger various streams falling into the Congo, and some important affluents oi the Nile. Still, the principal branches of the large rivers take their rise at enormous distances from one another, and in the general features of their courses exhibit only some transient and slight similarities. The basin of the Nile is partly separated from that of the Niger by a great depression, the cen- tre of which is occupied by the Lake Tchad. In like manner several lakes and their affluents are interposed between the three basins of the Nile, the Zambesi, and the Congo ; lastly, a small independent inland sea the Lake N'gami having its own special system of tributaries, fills up the space between the basins of the Zambesi, the Orange River, and the Lim- popo. There is another point which distinguishes African rivers from those of other countries ; this is an absence of any extent of ramitica- 278 THE EARTH. tions. In this characteristic they resemble their mother-continent a gi- gantic trunk without peninsular branches. From Assouan to Rosetta, a length of seven degrees, the Nile does not receive a single visible affluent ; nevertheless, it must necessarily be replenished by several underground tributaries, for its liquid mass is much more considerable in Egypt than in Nubia.* Australia is even poorer in rivers than the east of the African continent itself. With the exception of the Murray, its affluent, the Darling, and a few other rivers that are navigable at all times, the greater part of the water-courses in Australia can scarcely be said to exist except during the rainy season, and in summer their beds are only indicated by pools of stagnant water at intervals. Their special characteristic appears to be periodicity. The general features of the river-systems of each part of the world may thus be shortly summed up : Northern Asia is distinguished by rivers of simple character. In the south and east they are allied. Europe is distinguished by two centres from which the streams radiate one situated in the midst of vast plains, the other in the heart of the highest mountains of the continent. North America is characterized by a radiation of the rivers from three centres, two of which, being elevated groups in a mountain chain, are linked together by the third, occupying a marshy rising in the plains. South America is characterized by the crossing of two mutually trans- verse basins and the continuous union of the river-systems. Africa is distinguished by the comparative independence of its water- courses and their poverty in tributaries. Australia, by the small number of its rivers and the periodicity of their existence. The form of each continent, and the phenomena of climate peculiar to them, have thus determined the rise of rivers which are modeled on a par- ticular type in each division of the world. As all continental masses dif- fer one from another, the circulating system of each naturally harmonizes with the general features of the regions which the running waters trav- erse and vivify. * Elia Lombardini, Essai sur VHydrologie du Nil. THE RIVER AMAZON. 279 CHAPTER XLVI. THE RIVEE OF THE AMAZONS. DIVERSITY IN THE CHARACTER OP WATER- COURSES. UNITY OP THE LAW WHICH GOVERNS THEM. EQUALIZATION OP THEIR SLOPES. UPPER, MIDDLE, AND LOWER COURSES OF RIVERS. IN. like manner as the hydrographical systems of each continent pre- sent in their special features the most marked contrasts, so the rivers of each country and the various tributaries of each river. They are distin- guished by the length of their system, the winding of their course, the abundance of their water, the nature of the soil which they pass through, the color and character of their alluvium, the general inclination of their bed, and the shape and number of their meanderings. Thus, only men- tioning the basin of one single river, we may reckon among the tributa- ries of the Mississippi the Clear-water River, the Mud River, and the Blue, Green, Yellow, Red, Black, and White rivers. Names designating other physical properties besides that of the color or purity of the water are also very numerous in the tributary valleys of the American rivers. The same kind of names occur in most river systems ; and, indeed, noth- ing would be more easy than to give to every water-course some name relating to its general aspect, its characteristics, or some of the local cir- cumstances which distinguish it, such as gulfs, cascades, or defiles. Like the trees of a forest, so also an infinite diversity is shown in all the run- ning waters which moisten the surface of the earth. The chief cause, however, for this infinite variety in rivers must be sought for in the geo- logical constitution of the soil through which they flow. Thus, among the old schistose and gneissose rocks, rivers are more often characterized by the abundance of their liquid mass and the winding of their bed. In calcareous districts the water-courses are less richly supplied, more rectilinear, and generally bounded on each side by steep escarpments. Any sudden bend in the course of a river usually indicates some important modification in the geological nature of the strata. We may mention as examples the elbows of the Rhine at Basle and Bingen, those of the Rhone at Lyons, of the Danube at Ratisbon,of the Elbe at the outlet of Saxon Switzerland. In South America all the great rivers flowing into the Atlantic describe a broad curve toward the east when they leave the valleys of the Andes and make their way into the tertiary formations of the continent.* The river par excellence, the glory of our planet, is the great stream of the Amazons, which, next to the great upheaval of the chain of the An- des, forms the principal feature of the Columbian continent. This mov- * Ami Boud. 280 THE EARTH. ing fresh-water sea, which takes its rise at a short distance from the Pa- cific, and empties itself into the Atlantic through an estuary measuring 186 miles from promontory to promontory, serves as a line of division be- tween the two halves of South America, and, like a visible equator, sepa- rates the northern" hemisphere from the southern along a length of about 3000 miles. Every thing belonging to this great central artery is on a colossal scale. In its immense basin, embracing an area of 2,700,000 square miles, it collects two or three thousand times as much water as the Seine. In different parts of its course this immense river is known under various names, as if it were composed of distinct streams set end to end, and, together with its tributaries, its furos , or false rivers, its igarap'es, or lateral arms, offers scope for steam navigation of more than 30,000 miles. It is so deep that sounding-lines of 150, 200, or even 300 feet, have failed to measure its depths, and frigates can ascend it for more than 1000 leagues. Its width is so great that in some places it is impos- sible to see the opposite bank, and at the mouths of the Madeira, the Tapajoz, the Rio Negro, and some other of its great affluents, the distant horizon closes in upon the water just as in the open sea. It is replenished by dozens of rivers which scarcely find their equals in Europe, and many of them, being yet unexplored, still belong to the realms of fable. In several places its banks serve as limits to two distinct Faunas, and many species of birds will not venture to cross the broad sheet. Like the sea, it is inhabited by cetaceans ; like the sea, too, it has its storms, and dur- ing a tempest the waves will rise to several feet in height. When 'we sail over the gray water of the estuary at the mouth of the river, we feel tempted to ask, says M. Ave-Lallemant,* whether the sea itself does not owe its existence to the enormous tribute which the rolling current is in- cessantly bringing down to it. The difference in the motion produced by the movement of the waves or by the force of the current is the only thing which points out on which domain a voyager is sailing that of the fresh or salt water. Even in late years, the greater part of the inhab- itants of the shores of the Amazon white, black, or red men alike are in the habit of fancying that the great river surrounds the whole uni- verse, and that all the nations of the earth are denizens of its banks, f Certainly, the difference is considerable between the mighty South . American river and some slender stream ; as, for instance, the Argens, which is crossed by a bridge with a single arch, and can readily be waded through by travelers. But whatever may be the comparative impor- tance and the discrepancy of aspect in these rivers, they are none the less governed by the same laws. The geographer can describe them all to- gether by forming an outline of an ideal river, the course of which would afford the combined phenomena of all the streams which traverse the globe. The function of rivers in the plan of nature is incessantly to renovate * Reise durch Nord-Brasilien. t Bates, The Naturalist on the River Amazon. ACTION OF RIVERS ON THE LAND. 281 the surface of continents, to convey the life and the alluvium of lofty mountains down to t^e plains and the coasts of the ocean. It has often been said that a landscape can not be really beautiful when it is destitute of the rippling motion of a lake, or the presence of running water. The fact is, that man, whose life is so short, and, in consequence, so restless, has an instinctive horror of immobility. To make him fully appreciate the vi- tality of nature, it is requisite that motion and sound should bring it home to his senses. Only by a course of long reflection can he duly estimate the long-protracted movements of the terrestrial crust ; he therefore needs to view the rapid bounds of the water leaping down in cascade after cascade, or the harmonious undulations of the waves. More than this, he also demands the contrast between the stable and the unstable, between restlessness and rest. This is the cause why a field of snow as far as the eye can reach, a desert without water, a sky without clouds, or a shore- less ocean fail to excite in him any thing better than a gloomy or melan- choly admiration. |p the presence of these spectacles man feels himself crushed, while in a narrow valley, with its streams of running water, he is fully conscious of his own vitality. On our earth, water is, par excellence, the symbol of motion. It flows and flows on forever, without rest and without fatigue. The lapse of centuries can not dry up the slender rill of water trickling from the fis- sure of a rock, and fails to silence its soft and clear murmur. It leaps down joyously, in cascade after cascade, to mingle with the impetuous torrent ; then, blended with the calm and mighty river, it flows on, and loses itself at last in the immense and mysterious ocean that tomb in which every water-borne fragment finds a temporary grave till the re- solved elements enter again into the vast bosom of nature and reassume fresh forms of vitality. Motion is only another word for action. Water does not merely flow through a bed hollowed out ready for it ; it is inces- santly eating away, undermining, corroding, washing away, and moving the earth and the rocks which hem it in or oppose its course. Pebble by pebble, and grain by grain, it is carrying the mountains into the sea. Wa- ter, as Pascal says, is " not merely a road in motion, it is also a traveling continental mass which, in the centuries of yesterday, was covered with the eternal mountain snow, and will in the ages of to-morrow be fixed on the sea-shore, to augment the domain of man." Rivers carry out the circula- tion of solid as well as of liquid matter; they are like the blood, ever-flow- ing life-renewers. It is, then, requisite that we should study carefully the mode of operation which rivers adopt in their renovating action on the continents they traverse. Every current of water is constantly tending to equalize its slope, to increase it where it is almost imperceptible, and to diminish it where it is too rapid. The whole course of the river, from its mountain source down to its junction with the sea, may be compared to an avalanche fall- ing from the heights of some snow-clad peak. The masses which sink down into the valleys modify gradually in their fall the outline of the 232 THE EARTH. cliffs. The projections are broken down, the fissures are filled up, a gracefully curved slope of debris abuts against the yertical walls, and ex- tends in a gentle incline down into the plain. Owing to all these exca- vations and fillings up, the passage through which the avalanche makes its way ultimately assumes an outline of considerable regularity. Al- though less abrupt in its progress, less violent in its effects, and gliding over a gentler slope than the avalanche, still the river adopts a very sim- ilar course of action ; it clears away the obstacles before it, and fills up any depressions, appearing as if it endeavored to provide for itself a uni- form incline down to the sea. The portions of a river's course where this equalization of its incline chiefly takes place are naturally those where the declivity of the bed is Fig. 95. Inclination of the Nile from Khartoum to Damietta. most rapid, and where the waters consequently attain their highest rate of speed. It may be generally asserted that those portions of the river- beds which are distinguished by the most abrupt incline are also the most elevated; for in almost all the countries of the earth the plains lie round the circumference of the land, and the mountains rise far in the in- terior. Most rivulets and streams take their rise thousands of feet above the level of the sea, and descend first through a very steep bed, some- times intersected by precipices, or even interrupted by lacustrine basins. * 4 5} I-. o M S t. M oj I 1 S ! t - C ** v ^ . }z5P ~-~ ^ r *'j> ^m isoor ~ "~ ~" - L'X^. ^"^ -^.- 6 *^1 - '-" Lf**\ of S Fig. 9e. Slope of the Po, the Tessin, the Oglio, and the Miucio. On reaching the lower plains, the running water, now converted into a considerable river by the tributaries which have joined it on both sides from the valleys of the mountain-system, extends in long and peaceful windings across the more or less sloping ground which serves as a ped- COURSES OF RIVERS. 283 cstal for the mountain chain. This is its middle course, during which the river receives its principal affluents descending from other mountain chains, or the high ground which commands it laterally. Then, below the last hills, its lower course begins ; the fresh water descends slowly down to the sea, and, not far from the mouth of the river, is arrested in its course twice every day by the salt tide which meets it. The Rhine is a magnificent example of a river in which the three divis- ions of its course are regularly developed.* The upper course, the whole of which is included in the Alpine regions, bends round in a vast semi- circle to Laufenburg and Basle, where the rapids cease. The middle course, remarkable for its regularity, rolls on uniformly to a point below Mayence, where the Rhine is compelled to open a passage across the Odenwald and other hills ; then, below the Siebengebirge, between two low banks of alluvial origin, commences the lower course, which ulti- mately terminates in the muddy estuaries of Holland. But for one river where the three divisions of its course are marked with so much distinct- ness, how many there are which exhibit no marked difference between the various portions of their bed ! How many there are, indeed, which are even calmer ad less inclined on the plateaux of the interior than in the vicinity of the sea ! How many there are, especially, which as rep- resented by some of their affluents are entirely rivers of the plain, while in other tributaries which descend from the mountains they ex- hibit all the characteristics of torrents ! These are differences essential to the fluviatile system and to its geological operations. * Carl Kilter, Europa. 284 THE EARTH. CHAPTER XLVH. MOUNTAIN TORRENTS. INEQUALITIES OF THEIR BEDS AND OF THEIR DIS- CHARGE OF WATER. TEMPORARY STREAMS. FILLING UP OF LAKES. EROSIONS, GORGES, AND SLOPES. TORRENTS OF THE FRENCH ALPS. THE principal features which distinguish the mountain torrent from the water-course in the plain is the irregularity of its bed, its mode of action, its discharge of water, and its sedimentary matter. Among the gentler features of the plain, the stream runs but slowly, and all the changes of slope, curve, and level take place in gradual transitions ; but, on the con- trary, in narrow winding gorges it is violent, impulsive, and uncertain. Rocky angles project abruptly across the water ; the declivity is inter- sected with precipices ; the liquid mass poured down by the torrent may sometimes be compared to that of a river, but at other times it forms only a slender rivulet, or even dries up altogether. Lastly, most mount- ain streams are sometimes as pure as crystal, and at others are loaded with so large a quantity of alluvium that they are more like avalanches of debris. The turns and twists of the gorges are so much the more sud- den as the rocks through which they are cut are higher, harder, and more irregular in their stratification and fissures. The water dashing against some projection springs back at right angles on the opposite rock, to be again driven back, and thus descends toward the valley in a series of zigzag falls. In these rugged gorges, where the pathway seems suspended from the ledges of the opposing cliffs, on either side overhead may be seen the abrupt fissures where the torrent has cut a passage; and not only is this mass of water and foam incessantly cast from one side to the .other by the obstacles which hem it in, but it is very often temporarily kept back by the barriers of debris which crumble down across its course. When the dam, composed of stones and blocks of rock, affords no interstices through which the water can glide, the latter gradually rises in the form of a lake, and then makes its way as a cas- cade over the wall of rubbish, which by degrees it hollows out down to the level of its old bed. But usually the avalanche which pens back the torrent consists of a mass of snow, dust, and broken stones ; the water kept back by this more plastic dam slowly converts it into a kind of pasty mass, and forces its way through a subterranean outlet. In the spring, when a good many avalanches are falling from the sides of the Alps, it is curious to trace the course of the torrent, visible here and there, in the gorges. The water may be seen diving down under some grayish or dark mass, joining with its graceful curve the two opposite sides of the ravine. The entrance of the gulf forms a kind of porch orna- MOUNTAIN TORRENTS. 285 merited with icicles, down which the melted snow trickles or falls drop by drop. Above the torrent which is roaring in the depths below, the mass of debris is intersected in some places with crevasses, and the closely-packed snow presents a bluish edge, like ice ; wells open in it at intervals, at the bot- tom of which the foaming waves may be indistinctly seen careering along. In ravines and defiles where the slope is uniform the torrent-water af- fords some degree of regularity in its volume ; but when the declivity is unequal and broken, and especially when, as is the case in most of the calcareous districts, it is composed of horizontal layers intersected by precipices, the liquid mass is incessantly changing in width and depth. In the level or gently inclined portions of its bed the water, flowing slowly, spreads out into a wide stream, until, reaching the edge of the cliff, it suddenly tumbles over, and, losing in volume what it gains in speed, seems nothing but a slender thread of foam gliding over the face of the rock. Below the fall a new basin opens out, often hollowed in the shape of a tub, in which the water, now to all appearance unstirred by the slightest current, reposes quietly as in a lake. A great number of the valleys in the Alps, the Jura, and all mountainous countries, owe their picturesque beauty to this succession of pools of quiet water and graceful cascades. This series of gradations constitute the successive planes of elevated valleys.* The variations which are found in the discharge of a torrent stream are really enormous, even in those mountainous countries where, owing to the accumulation of the winter snow upon the heights, the water never entirely dries up. During severe cold, when the snow above is frozen on the ground, and numbers of rivulets are converted into solid ice, the main stream of the valley sends down only an inconsiderable liquid volume, and a traveler may easily cross it by jumping from stone to stone ; but on the arrival of the earliest warm weather, when the rain and the sun, assisted by the south wind, melt the snow and cause it to slide down in avalanches, the masses of water which are discharged into the torrent from all sides change it into a formidable river, running some- times, Surell tells us, at a speed of 46 feet a second more than 30 miles an hour. It spreads out widely over its basins, flows over the meadows, and often washes away farm-houses, trees, and even the vegetable mould. In the defiles, on the contrary, it is compelled to gain the requisite space in height, as it can not find it in width, and its level suddenly rises 60, 80, or even 120 feet. All this may easily be noticed in the narrow Ital- ian valley-streams fed by the snow from the Mont Blanc and Monte Rosa groups. The Sesia, the Dora, and many of their affluents, before they empty into the plain, pass through dark gorges, where the liquid mass of the flood-water, ten times deeper than its width, descends with the ra- pidity of an avalanche. Looking forward to these rushes of water, the mountaineers, in many places, have dug out their paths more than 150 feet above the bed of the torrent. * See above, chapter on " Valleys," p. 132. 286 THE EARTH. Fig. 9T. Circle of the Valley of Lys. The Var may be mentioned as an instance of this astonishing fluctua- tion in the discharge of its torrent-waters. At its outlet, the liquid mass of this river varies from 37 to 5240 cubic yards of water in a second; this difference is as 1 to 143, and the proportion would be still larger if the fluctuations were measured above the confluence of the Vaire, the Tinee and the Vesubie.* In the level countries of Western Europe, the difference presented between the high and low water levels is, on the av- erage, scarcely one tenth of that afforded by the Var. In great rivers, such as the Mississippi, the difference between high and low water is as 1 to 4 only. As a standard of comparison between the floods of a torrent and those of a lowland river in the same climate, we may mention the Upper Loire and the Somme. Above Roanne, the basin of the Upper Loire, at its first outlet from the mountains, comprises an area of 2470 square miles, and the stream discharges during exceptional floods 9549 cubic yards of water a second rather less than four yards for each mile of surface. In its highest floods, the Somme sends down 117 cubic yards of water a quantity which, if it was spread over its drainage area, would render the floods of the Upper Loire 84 times more considerable than those of the Somme ;f and doubtless a comparative study of the inun- dations of all the water-courses in France would disclose still greater * Villeneuve Flayosc. f Belgrand, Anuales des Fonts et Chaussees, 1854. FLUCTUATIONS IN RIVERS. 287 variations between the system of torrents and that of the lowland rivers. In the tropical regions, where the rainy season is succeeded by the season of drought, the greater part of the mountain rivers only run during half the year; they are alternately considerable rivers and dry ravines. Thus some valleys those, for instance, of the Sierra Nevada de Santa Marta exhibit a daily fluctuation in the discharge of their streams, ow- ing to the storms which the gusts of the trade-winds rarely fail every afternoon to dash against the heights. In the evening all the gorges are filled with masses of raging water, and the traveler finds himself com- pelled to put a stop to his journey ; he bivouacs on the edge of the river, and is lulled to sleep by the noise of the cataracts roaring over the rocks ; when he wakes up at dawn next day, all he sees is a slender rivulet of water, only visible here and there among the masses of gravel But the torrents which must be instanced as the most striking types of the merely temporary water-course are the ouadys in the Sahara and the plateaux of Arabia, and the liquid masses which sometimes roll down the quebradas of Bolivia and the Argentine pampas. All round the Red Sea, embracing an extent of more than 1550 miles of coast-line, there does not exist one permanent stream. All the ouadys which, during heavy rains, flow into the sea, convey 1;o it only the surplus of the surface-water which the sand of the desert was not able to absorb. In a general way, before the complete disappearance of these streams, most of which run over a bed of subterranean rock, they ooze up imperceptibly through the sand, and show themselves in pools stagnating in the passes of the defiles. In- stances of streams thus converted into a chain of ponds are very numer- ous in deserts all over the world in Arabia and Algeria, in the Caspian steppes, and in the North American solitudes. In these regions the ground on the plateaux and in the plains is fur- rowed with valleys exactly like those found in t"he country that is well watered with rivulets, streams, and rivers. The river-system exists in full force, and for hundreds of miles the traveler may trace wide hollows, perfectly developed, which would contain rivers like the Danube or the Rhine, and on either side debouch the stony stream-beds of the lateral valleys. Nevertheless, these deep and winding depressions, hollowed out by the temporary waiter-courses, generally contain nothing but pebbles and sand ; water is altogether wanting except during the season of the periodical rains. One of these waterless rivers, the Roumah, which con- nects its bed with the Euphrates, not far from the mouths of the Chat-el- Arab, is not less than 750 miles in length. The only permanent ele- ments, so to speak, of its vast drainage area are a few springs and rivu- lets flowing from the mountain sides round the circumference of its basin. In the upper part of their course, these torrent-waters assist, as we have said, in modifying the relief of the terrestrial surface ; but these 288 THE EARTH. magnificent operations of erosion, which crumble away mountains, or, at least, by enlarging the clefts, ultimately convert mere fissures into open- ings of such important dimensions both in width and depth, are not the work of the torrents alone. The latter, in fact, are scarcely the chief agents in the work ; they do little else than clear away the stones and ^'.y^^w.. -aVv . :. ~ S ! . -.-. -' Fig. 98. The Igharghar. debris fallen from the heights above. All the meteoric phenomena of the atmosphere among which, however, snow and rain may certainly be con- sidered as the real orign of torrents contribute to the work of destruc- tion, and detach from the mountain-sides masses of debris, which accumu- late at the foot of the rocks in more or less inclined slopes. The torrent EROSIVE ACTION OF TORREXTS. 289 into which this debris crumbles down washes away all the sand and light- er matter, until the time when, swelled by rain and melted snow, it rolls down toward the valley the great blocks of rock that have fallen into its bed. It is difficult to restrain a feeling of dread when we pass along the ba'nk of a flooded toirent and hear, above all the uproar of the water, the dull thunder of the masses of stone dashing one against the other as they are hurried along under the rushing water, yellow with the earth which it washes away. Thus, year aftsr year and century after century, the torrent clears away whole mountain sides which have crumbled down into it rock by Fig. 99. Valley of Cogne. rock, and this great work of erosion is incessantly going on. In some mountain groups, where the rocks are easily shifted by the action of the weather, nothing is left but a mere skeleton of those former proud heights which once towered up toward heaven. But in the regions where the mountain strata are of a compact formation, and the water consequently takes some considerable time to penetrate them, all that we notice in the way of dilapidation are large holes which the torrents have gradually hollow- ed out in the body of the rock. Where two mountain rivulets form a junction, it is very seldom that the three headlands which overlook the confluence do not leave at their base a small triangular valley, whence the Fig. 100. Quadrangular basin of erosion ; p J ' after Sonklar. water leaps down into the lower gorge. In like manner, when two streams proceeding from directly opposite ravines fall into the main stream of the valley at the same spot, the little plain T 290 THE EARTH. of erosion which is found at their confluence generally assumes a quad- rangular form. It must, however, be understood that the dimensions and the outlines of these basins must vary infinitely according to the force of the torrents, the hardness of the rocks, and the energy of the agents that attack them. Ultimately, the surface of the country, having been carved out by the water for an unknown number of centuries, completely changes its aspect; the mountains and the plateaux are swept down by the rivers, and little else remains but the isolated landmarks of the an- cient piles. There is probably no country in the world where this devastation goes on more rapidly than in the French Alps. The mountains of this region, and especially those which inclose the basins of the Durance and its tributaries, are in general composed of very hard rocks alternating with other beds, which easily give way under the action of the water; in every place we may notice immense cliffs resting upon bases without any solid consistence. The marls, the disintegrated schists, and the other fri- able matter are gradually washed away, and their fall precipitates that of the compact layers at the summit, which suddenly fall down or glide slowly into the valleys.* It is, however, the improvidence of the inhab- itants, and not so much the geological constitution of the soil, which is the principal cause of the devastating action of the streams. In the mountains of Dauphiny and Provence, the slopes, most of which are now so bare, were once covered with trees and various plants which kept back the surface-water resulting from the rain or melting of the snow, by absorbing a great part of the falling moisture, and thus retaining the coating of vegetable earth over the beds of crumbling rock. During the course of centuries, the trees have been cut down by greedy speculators, and by senseless farmers who wished to add some little strips of land to the fields in the valleys and to the pastures on the summits; but when they destroyed the forest they also destroyed the very ground it stood on. The rain or snow, being now no longer kept back upon the slopes by the roots of the trees, descends rapidly into the valley, driving before it all the debris torn away from the sides of the mountain. The tooth of thte goat and the sheep helps to lay bare the rootlets of the herbaceous plants and the brush-wood ; bit by bit, the whole of the thin coating of vegetable earth is removed, the bare rock shows itself, and deep ravines are hollowed out in the cliffs, and are traversed in the rainy seasons by furious torrents which once did not exist. The water which used slowly to penetrate the earth, conveying fertilizing salts to the roots of the trees, now serves no other purpose than that of devastation. When the forests are gone, great furrows of erosion may be noticed opening out at inter- vals on the slopes ; these furrows often correspond to ravines situated on the other side of the mountain, and in a comparatively short space of time they ultimately sever the ridge of the mountain into distinct peaks, uniformly surrounded by a slope of rocks or fallen earth : summits of this * Scipion Gras ; Rozet ; De Ladoucette ; De Ilibbe. EhOSIVE ACTION OF TORRENTS. 291 kind are being forme' 1 every year. In some localities there is not a sin- gle green bush over a space of several leagues in extent ; the scanty gray- Fig. 101. ValWs of Erosion of the Bourgogne. / colored pasturage is scarcely visible, here and there, on the slopes, and ru- ined houses blend with the crumbling rocks that surround them. The stream in the valley is generally nothing but a scanty rill of water wind- 292 THE EARTH. ing among the heaps of stones; but these very heaps of shingle and rock have been carried down by the torrent itself in the days of its fury. In many parts of its course, the Haute Durance, which is generally not more than 30 feet wide, seems lost in the midst of an immense bed of stones, a mile and a quarter wide from bank to bank. The Mississippi itself does not equal it in dimensions. The devastating action of the streams in the French Alps is a very cu- rious phenomenon in an historical point of view ; for it explains why so many of the districts of Syria, Greece, Asia Minor, Africa, and Spain have been forsaken by their inhabitants. The men have disappeared along with the trees ; the axe of the woodman no less than the sword of the conqueror have put an end to or transplanted entire populations. At the present time, the valleys of the Southern Alps are becoming more and more deserted, and the precise date might be approximately estimated at which the Departments of the Upper and Lower Alps will no longer have any home-born inhabitants. During the three centuries that have elapsed between 1471 and 1776, the vigneries of these mountainous regions have lost a third, a half, or even as much as three quarters of their cultivated ground, and the men have disappeared from the impoverished soil in the same proportion. From 1836 to 1866, the Upper and Lower Alps have lost 25,090 inhabitants, or nearly a tenth of their population. At the present time, in an area of 3860 square miles, embraced between Mont Thabor and the Alps of Nice, there is not a single group of inhabitants which exceed the number of 2000 individuals. Barcelonnette, the most considerable place, has more than once been in danger of being carried away by the stream, the bed of which is higher than the streets of the town; the latter certainly would be still less populous were it not that the numerous functionaries necessary in every sub-prefecture tend to give it an artificial life. Without the employes and the custom-house officers, who almost consider themselves as exiles, the whole extent of a great portion of these mountainous regions would be nothing more than a gloomy solitude. It is the mountaineers themselves who have made and are seeking to extend this desert, which separates the tributary valleys of the Rhone from the populous plains of Piedmont. If some modern Attila, traversing the Alps, made it his business to desolate these valleys forever, the first thing he should do would be to encourage the inhabit- ants in their senseless work of destruction. Is it necessary that man must ultimately rid the mountains of his odious presence, so that the latter, left to the kind offices of beneficent nature, may again some day recover their forests of fir-trees and their thick carpet of flower-studded turf? Although the torrents lower the mountains, on the other hand they ele- vate the plains ; but their deposits, not being pulverized into clays and sand, are often the means of bringing another disaster on the inhabitants, who find their fertile land covered beneath enormous masses of rocks and pebbles. In fact, when a stream empties itself into a valley which has a moderately inclined slope, and the former consequently experiences a sud- TALL 293 den check in its progress, it deposits over a long extent of descent all the debris which it conveys in its water or rolls down before it. The masses of rough alluvium accumulate on both sides of its course, so as to form a rising, with regular slopes abutting against the escarpments of the mount- Fig. 102. Tulua of Debris in the Valley of the Adige. ain. Even in places where the stream once rushed down into the valley in rapids or cascades, its tendency always is to conceal gradually every irregularity in its old bed under the ever-increasing slope of rocks, peb- bles, and sand. The deep ravine of the upper valley is succeeded by a long embankment, which, continuing the incline, pushes out far into the principal valley, and forces the stream to describe a considerable bend round the base of the cone of debris. Some of these banks attain very important dimensions ; they accumulate to an enormous extent at the outlet of each lateral ravine opening into the elevated valley of the Adige, to the south of the (Etzthal group. One, that of the Litznerthal, is 1036 Fig. 103. Talus formed by Torrents. feet in height at the outlet of the ravine, and extends 4148 yards in length as far as the Adige, with a mean slope of 4 46' ; the curve of the river which winds round its base is not less than five miles in length. When the streams empty their waters into a mountain lake, and not into a valley, the debris which they carry down accumulates at the upper end of the lacustral basin, forming a slope much more abrupt than the mass of stones deposited at the entry of a ravine. In fact, at the outlet of the latter the water of the torrent continues to flow over the masses which it has heaped up; fresh materials are continually being brought down, some of a small, others of a large size, which serve both to prolong the slope and to render it more and more uniform with that of the plain below. In lakes, on the contrary, a separation immediately takes place in the various debris brought down by the current. The blocks of stone and pebbles fall by their own weight into the depths of the water, and form a kind of moraine, which incessantly pushes on into the quiet water. 294 THE EARTH. Fig. 104. Ancient Lakes aud Defiles of Aluta. The lighter alluvium, which is held in suspension by the liquid mass, is partially carried on by the current toward the middle of the lake ; but the greater part of this matter is soon dropped on each side of the em- bouchure, and ultimately extends in horizontal promontories above the . accumulated mass of heavier* rubbish. Thus the bed of the stream, with **' t.ofP.r Fig. 105. Lakes of Thun and Brienz. FLUVIATILE DEPOSITS. 295 its steep slope of stones in front, bordered by its layers of lighter allu- vium, incessantly encroaches on the lake. A large number of lakes have thus been gradually filled up altogether; in several high mountain valleys, where lakes exist at intervals one above another, all the basins have in turn been filled up. In other places the upper pools only are choked, and the work is going on in one of the low- er lakes, which, sooner or later, will ultimately be converted into a hori- zontal plain. By very carefully measuring the annual deposits of a tor- rent, and ascertaining, by boring, the depth of the former lakes which they have filled up, the number of centuries might be approximately esti- mated which this immense work has taken. Also, sounding the depths of the basins which are still full of water would show the duration of ages which will be required to fill up their abysses. At the foot of the great group of the Bernese Alps, on the isthmus of Interlachen, so well known to travelers, it would be comparatively easy to make the experi- ments necessary for the solution of this problem, which would also in- form us approximately as to the duration of the geological period during which the streams have flowed down from the mighty group over which towers the Jungfrau. For this calculation it would be necessary to measure the present deposits of the furious Lutschine, and to estimate the enormous solid mass of the isthmus of Interlachen, which has been thrown down by the stream as a kind of dam between the two lakes of Brienz and Thun, which once formed only one lacustrine basin. 296 THE EARTH. CHAPTER XLVIH. EROSION OF LACUSTRINE DIKES. CATARACTS AND RAPIDS. WHILE crossing the lakes situated at the bases of the mountains, the waters of the torrent become tranquilized, and their course regulated ;* they emerge from the basin in streams of a less turbulent shape, and, flowing on to join other water-courses, descend with them quietly to the sea. But even the outlet-stream of the lake, although usually more peace- able than the water-course above, accomplishes its special geological la- bor, and is also employed in the task of doing away with the lacustrine basin. The water, impelled by its own weight, constantly wears away the layers which form the lower margin of the lake. The edge of this margin being gradually destroyed by the liquid mass, sinks by slow de- grees, and the average level of the water in the lake sinks also in the same proportion. Thus, at the two extremities of the basin the river is Fig. 106. Filling up of a Lake-basin. carrying on two kinds of work, contrary in appearance, but which have both an equivalent result in reducing the area of the lake which the river crosses. Up above, it gradually elevates its bed, and gains on the lake by filling it up with alluvium ; down below, it lowers the brink, and, by this constantly increasing waste-gate, gradually drains out the water. The two stream-beds, the upper and the lower, will ultimately meet in the middle of the lake, and the latter will cease to exist. This is the double phenomenon which has been going on for ages in the Lake of Ge- neva. This crescent-shaped sheet of water certainly once extended as high up the stream as the place where the town of Bex now stands, ll miles from the end of the lake ; it also extended down the stream in nar- row basins as far as Ecluse, 9 miles from the outlet of the Rhone. It must, however, be understood that the outlets of lacustrine reservoirs are not the only places where the rapids and cataracts of a river crumble away the rocks so as to lower the up-stream and elevate the down-stream beds. However hard may be the strata which form the bed of a rapid, the eddying waters ultimately penetrate the stone, and deposit the debris below the gulf that the furious shock of the torrent has hollowed out at * Vide the chapter on "Lakes." FILLING UP OF LAKES. 297 Fig. 107. Alluvial Deposits of the Rhone aud the Draiise. the foot of the rocks. In like manner, cascades and cataracts incessantly wear away the ledges from which the mass of their water pours down to the bottom of the abyss, carrying the great stones with them in their Tall, and, destroying layer after layer, they continually retrograde toward the source of the river, and tend to convert themselves into mere rapids, which, in some thousands of years or perhaps centuries, are destined to assume a perfectly uniform inclination. This is the ideal, so to speak, of every river to do away with the irregularities of its course, and to flow down toward the sea, describing a regular parabolic curve. This ideal, however, is never perfectly attained, on account of the diversity of rocks in its course, the changes in its bed, the disturbances or elevations of the ground, and other circumstances of various kinds which may cause a de- viation in its current. But whatever may be the obstacles which oppose the leveling of the declivity, still every river intersected by falls and rap- ids is constantly at work in effecting the general uniformity of its slope. In their magnificent beauty, cataracts and rapids only yield the pre- eminence to hurricanes aud volcanic eruptions. Of the former, there are some in Europe which are very remarkable: such as the falls of the Rhine at Schaff hausen ; the four cataracts of the Gotha-Elf at Trollhata (dwell- ing of sorcerers) ; the Hjommel-saska (the hare's leap), where the river Lulea plunges over in a body from a height of 264 feet ; and the Riu- kan-fos (roaring cascade), which falls at the outlet of the Norwegian lake Mjosvand in a single jet of 885 feet. The most celebrated water-fall in the whole world is that of Niagara " the falling sea" the constant thunder of which may sometimes be heard 12 miles off. Above the cat- aract the river, which discharges on the average 1 300 to 1 400 cubic yards of water a second, breaks against the shore of Goat Island, and divides into two rapidly inclined currents. Even at this point the mass of water 298 THE EARTH. is impelled by such velocity of move- ment that engineers have not yet been able to sound its depth, and they have similarly failed to do so below the cataract. On reaching the edge of the cliff, the two halves of the river one 655, and the other 295 yards wide take their final leap, and describe their vast para- bola, 147 feet and 160 feet in height. A gloomy passage, penetrated by furious gusts of wind, opens be- tween the wall of rock and a sheet of water, 18 to 33 feet in thickness, which curves widely overhead like an immense arch of crystal. Col- umns of iridescent vapor spring from the whirlpool of the roaring waters, and half hide the two white masses of the cataracts. At every instant of the day, following the path of the sun, the great rainbow painted on the wavering and misty spray shifts its position, and thus modifies the aspect of the fall. The various seasons, each in their turn, add some feature of beauty to the magnificence of the spectacle. The trees still left on Goat Island and the cliffs contrast with the whiteness of the water in summer by their verdure, in autumn by the more varied colors of their foliage. In winter, stalactites, glittering in the sunlight like immense strings of diamonds, hang down from all parts of the rock, and serve ^,s a frame-work to the two great plunging sheets of water. In spring, when the ice breaks up, a formidable spectacle is presented by the blocks of ice, like mountain fragments, crowding together at the edge of the cataract, and crashing against one another as they glide over the enormous curve of water which is sweeping them along. Other great water-falls in different parts of the earth afford similar phe- nomena, and several of their number may even rival Niagara in their beauty. Among these we may mention, in North America, the magnifi- cent falls of the Missouri, the Columbia, and the Montmorency. Of like beauty, also, there is in Brazil, not far from Bahia, the wonderful cataract of San Francisco, known by the name of Paulo Affonso. At the foot of a long slope over which it glides in rapids, the river, one of the most con- siderable of the South American continent, whirls round and round as it enters a kind of funnel-shaped cavity roughened with rocks, and, sudden- ly contracting its width, dashes against three rocky masses reared up like towers at the edge of the abyss; then, dividing into four vast columns Fig. 108. Course of the Niagara. FALLS OF THE ZAMBESI. 299 of water, plunges down into a gulf 246 feet in depth. The principal column, being confined in a perpendicular passage, is scarcely 66 feet in width, but it must be of an enormous thickness, as it forms almost the whole body of the river. Half way up, the channel which contains it bends to the left, and the falling mass, changing its direction, passes un- der a vertical column of water, which penetrates through it from one side to the other, and, breaking it up into a chaos of surges, converts it into a sea of foam. Sometimes the white misty vapor may be seen, and the thunder of the water may be heard, at a distance of more than fifteen miles.* This turbulent cataract is very different in character from the majestic falls of the Zambesi, the existence of which Livingstone has made known Fig. 109. The Falls of the Zambesi. to the world. Above the precipice the river is calm, and flows over a gently inclined bed; some islets, covered with cocoa-nut trees, are reflect- ed in the clear water. A large island, called " the Garden," on account of its rich vegetation, divides the Zambesi into two branches, and the general features of the landscape are full of grace. All on a sudden, without the least transition,, the ground comes to an end beneath the water, and the two liquid masses, one of which is 1858 and the other 546 yards wide, plunge down to a depth of 348 feet into the gaping fissure of a vast mass of basalt. They then escape by a narrow and winding chan- nel, which the river itself has hewn out of the rock during the lapse of many centuries. Ten columns of vapor, answering to ten great projec- tions on which the body of water dashes itself to pieces, rise in eddies * Ave-Lullemant, Reise durch Nord-Brasilien. , 300 THE EARTH. from the foot of the precipice, and float, like the smoke' of a conflagration, far away above the surface of the river. They vary in height according to the state of the water and the atmosphere ; but, generally speaking, they do not rise less than 1000 or 1150 feet above the brink of the gulf.* On account of these clouds of spray and vapor, the natives have given to the cataract of the Zambesi the name of Mosi-oa- Tounya, or "Thunder- ing Smoke." With regard to rapids, we find them on most rivers at different points Fig. 110. Rapids of Maypures on the Orinoco. of their course ; either at spots where cataracts once existed, or at the mouths of streams which carry down with them large quantities of de- bris, and pile them up like dikes across the current. The American rivers * Baines, Exploration in Southwest Africa. FALLS AND RAPIDS. 301 are the principal localities where these rapids may be contemplated in their full beauty. Humboldt was the first to describe the raudales of Atures and Maypures, where the Orinoco, changed into a mass of foam, pours down innumerable cascades over a chaos of rocks and banks with dark sides crowned with foliage and verdure. Each mass of granite, resembling in its shape some ruined tower or castle, is surmounted by a group of palms or densely-foliaged trees. Every stone below the level which the river reaches during flood-time is covered with alluvium, on which the mimosa, with its delicate leaves, grows abundantly; also ferns and orchids, with their charming flowers. They are perfect little gar- dens surrounded with foam, reminding one of the rocks covered with flower-studded turf which spring up in the midst of some of the glaciers in Switzerland. A cloud of vapor hovers over the river, and the rainbow shines through the verdant hues of innumerable bowers of foliage. This o ^ is the lovely spectacle which the Orinoco affords for a distance of several miles along each of its two rapids. The fall is not considerable, that of the rauclal of Maypures being scarcely 30 feet ; but still the slope is very difficult to overcome, and in a width of 2841 yards the navigable channel is sometimes not more than 18 feet.* About the same time as that when Humboldt and his friend Bonpland visited the rapids of Atures and Maypures, Azara examined the great salto of Maracayu, where the river Parana, which, just above, is 4590 yards wide, is suddenly contracted into a deep channel only 66 yards across, and, sliding over an inclined plane of 60, forms a fall of 56 feet of vertical height. The narratives of travelers have also made us acquaint- ed with the rapids of the Madeira, the Huallaga, the Ucayali, and several other rivers, down which the canoes of the savages used to glance like arrows in the midst of the foam. In North America the most celebrated rapids are those which the St. Lawrence forms at its issue from Lake On- tario; but all-powerful steam has succeeded in overcoming them. The European rapids are not so imposing, on account of the inferior quantity of the river discharge, and also because the general relief of the continent is much more gentle than that of the New World. We may, however, mention the rapids of the Shannon, above Limerick, the porogs of the Dnieper, and the whirlpools (strudeln) of Bingen, which were so danger- ous before the rocks were blown up which impeded the course of the Rhino. Among the most imposing rapids in France, both on account of their bulk and the fury of their foaming water, and also of the calm so- lemnity of the surrounding landscape, are those of the Gratusse, formed by the Dordogne, some miles above Bergerac. In surveying both falls and rapids, there is one point that especially impresses the. mind ; it is that, in a general way, immediately the water has emerged from its state of turbulent effervescence, it assumes an un- broken surface, and spreads out into wide calm sheets, known in Spanish America under the name of remansos. On one side we look down on the * Humboldt, Vvyage aux Regions Equinoxialu. 302 THE EARTH. giddy chaos of the liquid masses dashing against one another as they rush along ; on the other we see a pool of water almost still, or at most slowly rotating. Here the long gentle eddies seem unable even to move the straws and twigs which incessantly float round and round in the same circle; higher up the stream, the river in its impetuous career sweeps away trunks of trees, tears up the stones of its bed, and notches out the edge of the cliff over which it falls. This contrast becomes still more striking when we reflect that the cataract once descended at the very spot where this tranquil sheet of water now lies, and that during a long course of ages the fall has continually retrogaded. The high ver- tical rocks which hem in the two banks of the river belong to the same geological formation, and the parallel lines of their strata exactly corre- Fisj. 111. Cataract of Felou, SeiieguL spond on both sides. The traces of the current which has eaten away the stone are still visible, and the marks of the work slowly accomplished by the water can be distinctly traced out by the eye. The immense cavity which extends like a dark passage below the fall has been hollowed out by the cataract scooped out, so to speak, grain by grain. The rate of speed at which the fall shifts its position might serve to estimate approximately the age of the river itself. If geologists had studied this retrograde movement for a sufficient number of years, they would know the exact degree of resistance afforded by the rocks through- out the whole length of the cavity ; they would be able to say with cer- tainty how many centuries the present system has lasted with regard to every river which is interrupted in its course by a cataract. But this comparative study of water-falls has scarcely commenced, except, perhaps, WEARING AWAY OF FALLS. 303 in the case of Niagara and some other of the great water-courses of North America. According to Hall, Lyell, and other geologists, the Falls of Niagara have receded three miles and a half in the space of about 35,000 years. The erosion of the edge of the precipice is now taking place at the average -rate of 12*183 inches a year.* This is a tolerably rapid a. Niagara Limestone. c. Niagara Marl. 6. Clinton Group. d. Medina Sandstone. Fig. 112. Profile of Cataract of Niagara ; after Marcou. movement of retrogression, which, however, is explained by the nature of the rocks ; these latter are composed of calcareous strata resting on beds of soft and friable marl. The water penetrates into these layers, and, slowly undermining them, washes them away, thus throwing down the upper strata in massive blocks, which are carried away by the cataract. The observations of M. Marcou have established the fact that the volume of water is constantly diminishing in the fall on the American side, and that, in consequence, the rocks there have scarcely been encroached upon for some twenty years. To make up for it, the great cataract is rapidly receding up stream, and even now it no longer assumes the graceful semi- circular form which obtained for it the name of the " Horse-shoe Fall." In an interval of time which may be estimated at eight or ten centuries, the cliff of the cataract will probably be lowered as far back as the little islets of the Three Sisters ; the whole liquid mass will then rush down the current which runs along the Canadian shore, and the branch on the American side, no longer receiving any water, will gradually dry up ;