gĶĒăț¢ğț¢ $$$$$$$$$· ####################- 3. ***（* 2. ** * *·- }• … • • šº， ºſ ſººſ （， ， ， ， ， ， ） （*~*~، ، ، ،- - - - - - -- --- » Ģ، ، ، ∞ · <！------··· • • • • •~--~--~|- ----~--~--~--~--~--~--~--~ }****ſe ? }***5:2 %, . , ， ， ， … . - Ž）， №. 3 . . . · • ××××, +, −, .，.::::::：::∞| （）، №. ！！ !; x））;S^*^®*** ، ، （~~~~.*.* （ `````|?！！！！！！！!！！！！！!！ :&& ſ.g.š;&（?：\ſ*$'· · ， ！ |- ·* . . . . . . . .· |-*********ſaeº. s. 2.） - ， : » …）.！ ſae; * ?. • - · · · · · · · · · ··---··· -- * * * * * w: * * * * ºss • • • • • •—• • • •~ ~ ~~~~ • • •º_º --~~~ ！ » 3 ---...， …， ... （:º） ++<！-- .……...…. ., …...………$+ ！！！-- . . . |- ſi \! £ ºj ſae § ºr " gº ſº ºf ºl, . ºfºº sº.” º sº > * * **** º „…，~（_） ）'_'，ae ：· ！№-----， º-º---********）ſae - six- Jºlliſºſ, iº YººHºº EIII ºffº III E LIBRARYºº Yor THE . tRNERsmºutlºw :-- :- -43. s wH t w W ! s Bº $ -: - E. : === E|{ C É = ------------------ -—— - sº - TITITITIIIHIII; miſſiń. | # sae aessae 4 42 G-B Se/.4, /, /7% Jº 3 R 273 / & 7 P. MAP or ºngº by Erhard O- 7/ve regions º ºrologº tº to the s A ºr ºr PL. I WORLD 90 grº are the ºwn our ow. Drawn by A. Vuillemin Rºs Nºw York - cº T H E EARTH: A DESCRIPTIVE HISTORY OF THE PHENOMENA OF THE LIFE OF THE GLOBE. By ELISEE RECLUS. TRANSLATED BY THE LATE B. B. WOODWARD, M.A., asp EDITED BY HENRY WOODWARD, BRITISH MUSEUM. * A Z Z U.S. 7" R A 7" E ZO BY TWO HUNDRED AND THIRTY MAPS INSERTED IN THE TEXT, AND TWENTY-THREE PAGE MAPS PRINTED IN COLORS. N E W Y O R K : H A R P E R & B R O T H E R S, PU B L IS H E R S, FRANKLIN SQUARE. I 873. o 4 || 30-7 3 22 C O N T E N T S. PART I. THE EARTH AS A PLANET. 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. . . . . . . . . . . . . . CHAPTER 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * @ e º e s & e º e & CHAPTER 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....... CHAPTER IV.-Geological Strata.—Conglomerates.—Sandstones.—Clays.—Limestones. —Fossiliferous Beds.-Sequence of Organic Beings.-General Classification of Strata. —Duration of Geological Periods. . . . . . . . . . . . . . . . . . .e. e. e. e s m e º e º e º e s a sº e o a s º e s • * e s e e s s a s 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . e = * * * * • * g g g g tº e º e s e º ſº e º ſº e º & e º is e º e º 'º - * PART II. ~! - THE LAND. CHAPTER VI. — Regular Distribution of Continents. –Ideas of Ancient Nations on this IPoint. — Hindoo Legends. – Atlas and the Giant Chibchacum. —Homer's Shield. — Strabo... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER VIII.-Division of the Land into the Old and New Worlds.—Double American Continent.—Double Continent of Europe and Africa.--Double Continent of Asia and Australia ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ** * * * * * * * * * * * * s a s & e s e CHAPTER 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 West. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . tº e º & Q e º e º º . . . . . . . . . . . . . . . . . * Page 13 I6 46 50 G4 iv. CONTENTS. CHAPTER XI.—Harmony of Shape in Oceans.—The two Basins of the Pacific.—The two Basins of the Atlantic.—The Arctic Frozen Ocean and the Antarctic Continent.—Con- trasts, an Essential Condition of Planetary Vitality... . . . . . . . . . . . . . o e e s e e º 'º e º e e s e º e º 'º 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER XIV.-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....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER XV. —IPlains and Deserts of the New World. —IIumidity of the American Continents. – Distribution of Savannahs and sterile Tracts. –The Prairies of North America.-The Llanos and Pampas........................ e e s e e s e o e . . . . . . . . . . . . . . . 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 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.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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. . . . . . . . . . . . . . . . . . . . . ................................ º 4 e e CHAPTER XIX. —Isolated Mountains.—Mountains in Groups.—Chains and Systems of Mountains. --The Beauty of Mountain Peaks. – Sacred Mountains. – Pleasures of Mountain Climbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................................... 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................................................ CHAPTER XXI.-Inequalities and Depressions in the vetical 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 Cañons.—General Arrangement of Valleys. –Amphitheatres. CHAPTER XXII. - 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 * * * * * * * * * * * * * * * * * * * o o o e º 'º - e < e < e < e < * * * * * * e o o o e s e o o e s o e o 'º e o e s e e s , , , , 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....... tº wº * * * * * * 9 tº o 'º e º o e º e s - e e s - e. e. e. e. e. e. e. e. e. e s 6 tº a e s a CHAPTER XXIV.-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 * * * * * * * * * * * * * * * * * * * * * c e s e e e s s a • * * * s • Pago 76 78 81 90 97 107 * 111 117 135 139 CONTENTS. CHAPTER XXV.-Mountain Chains of Central Asia.—The Kouen-Lun, the Karakorum, the Himalaya.—The South American Andes, a Type of the Bifurcated Qhain........ CHAPTER XXVI.-Gradual Cooling of the Air on Mountain Sides.—Difficulty of Ascents. —Limits of Man's Habitation.—Illness felt by Mountain Travelers... . . . . . . . . . . . . . . * * CHAPTER XXVII.-Gradual Subsidence of Mountains during the Lapse of Ages.—Sud- den Downfalls and Chaos.-The Fall at Felsberg.—Slow Action of Meteoric Agencies P A R T III. THE CIRCULATION OF WATER. CHAPTER XXVIII. —Snow-fall on Mountains. – Lower Limit of Snow. —Zone of Per- petual or Permanent Snow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER XXIX. —Influence of the Sun and Meteoric Agents on the Snow.—Avalanches. —Protecting Forests.—Defensive Works against Downfalls of Avalanches............ CHAPTER XXX. —Gradual Transformation of Snow into Ice.—Névés, or Glacier-reser- voirs.—Phenomenon of Regelation.—Crystals of Ice.—Glaciers of the First and Second Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER 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 CHAPTER XXXII. — Marginal, Transversal, and Longitudinal Crevasses. – Séracs. – Moulins.—Bridges of Snow.—Weins of fresh Ice. —Surface-streams on Glaciers. — Gouilles.—Lakes and Inundations.—Discharging Channels. . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER XXXIII.—Débris 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... . . . . . . . CHAPTER XXXIV. — Progress and Retirement of Glaciers. — Appearance of the Bed when abandoned by the Ice.—Roches Moutonnées.—Parallel Furrows............... CHAPTER XXXV.-Distribution of Glaciers over the Surface of the Earth............. 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 . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER XXXVIII.-Variation in the Discharge of Springs.-Estavelles.—Equaliza- tion of the Supply in Springs with deep Sources.—Intermittent Springs. ............. CHAPTER XXXIX. — Ascending Springs. – Artesian Wells. – Temperature of Jetting Springs.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . •e ſº tº tº * tº gº tº & tº º a tº tº £ tº tº tº & © tº e º 'º º e º e CHAPTER XL.-Cold and Thermal Springs.......... ~~~~ CHAPTER XLI.-Mineral Springs.-Incrusting Springs.-Metallic Weins.—Salt Springs 162 168 183 192 201 206 216 231 234. 238 CHAPTER XLII. —Subterranean Rivers. —The Spring of Vaucluse, the Touvre. —Sub- marine Affluents.-The Rios of Yucatan.—The “Mud-lumps” of the Mississippi..... - CHAPTER XLIII.-System of Subterranean Streams.—Joints and Fissures of Rocks.— Stalactites.—The Inhabitants of Caves.—The Mammoth Cave.—Caverns of Carniola and Istria tº gº tº tº ſº tº e G & º º ſº º gº tº * * g tº 'º º º e º e º ſº tº tº g tº $ tº e º 'º tº $ tº dº tº º º º is º ºs e º ºs e g g tº e '* tº e s tº 4 e º tº e s s a tº e s a - 251 Vl * CONTENTS. CHAPTER XLIV.-Rivers.-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 IIydrographical Systems of various Parts of the World........ . 271 CHAPTER XLVI. —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... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 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 is e º a s & G e º ſº tº e s tº º º & # * * * * * * * * * * * * * * & & g º º e º & s e . . . . 284 CHAPTER XLVIII.-Erosion of Lacustrine Dikes.—Cataracts and Rapids............. 296 CHAPTER XLIX. —Eormation 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 CIIAPTER LI.—Means of Preventing Floods.-Natural and Artificial Reservoirs. —Irri- gation Channels-—Embankments, and Cracks in them... . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.25 CIIAPTER 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.—Baising 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 CHAPPER IV.-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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ‘e & g e º 'º e g g º a c e s s tº tº $ tº $ tº w tº e º & © & 8 . . . 372 CIIAPTER 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. CHAPTEIR LVIII. Lakes acting as Regulators of the Rivers which pass through them, —Fresh-water and Salt-water Lakes.—The Caspian Sea. . . . . . . . . . . . . . . “. . . . . . . . . . . . . . 399 CIIApriºr LIX.—The Dead Sea.—The Salt Lakes of Asia Minor and the Russian Steppes. —The Great Salt Lake.—The Melr’ir . . . . . . . . . . . . . . . . . . . . . . " * * * * * * * * * * * * * * * * * * * * * * * * 407 Ciraptºn LX.–Marshes.—Swamps of North America.-Peat-bogs.-Unhealthiness of Marshes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ' ' ' ' ' ' is 9 e º e s e e ºr e º º ſº e s e ... . . 413 P A RT IV. SUBTERRANEAN FORCES. & Charten LXI.-Eruptions of Etna in the Year 1865.-Mutual Dependence of all Ter- restrial Phenomena.......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 CHArrºr 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 Citaptºn 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.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ** CONTENTS. V11 * CHAPTER LXIV.-Growth of Volcanoes.—Theories of Humboldt and Leopold Von Buch as to the Upheaval of Craters.-Disagreement of these Theories with the Facts observed CHAPTER LXV. —Number and Arrangement of Volcanic Outlets. –Form of Volcanic Cones and Craters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Ciraptor LXVI. —Composition of Lavas; Trachytes: Pumice-stone; Obsidian ; Ba- salts; Basaltic Colonnades... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXVII.-Sources of Lava; Stromboli; Masaya; Isalco; Kilauea.—Lateral Crevices in Volcanoes.—Eruption and Motion of Lava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Citapter, LXVIII.—volcanic Projectiles.—Explosions of Ashes.-Subordinate Volca- noes.—Mountains reduced to Dust.—Flashes and Flames proceeding from Volcanoes CHAPTER LXIX.—Streams of Mud ejected by Craters.-Mud Volcanoes.. . . . . . . . . . . . . . Ciraptºr LXX. —Volcanic Thermal Springs.-Geysers.-Spring in New Zealand.— Fumerolles.—Solfataras.-Craters of Carbonic Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXI.—Submarine Volcanoes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXII. – Periodicity of Eruptions.—Influence of Temperature on Volcanic Phenomena.—Extinction of Furnaces of Lava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * CHAPTER LXXIII.--Earthquakes.—Vibrations of the Ground-Various Hypotheses. . Page 440 445 468 475 480 48%) 497 500 CHAPTER LXXIV.-Earthquakes of Volcanic Origin.—Subterranean Downfalls.-EX- - plosions of Mines and Powder-mills . . . . . . . . . . . . . . . . . . . . . . ... e. e. e. e. e. e. e s is a tº e s tº * * * * * * * * * * * * CHAPTER LXXV. — Great Catastrophes. – Earthquake at Lisbon. — Area of Disturb- ance.—Earthquakes at Sea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXVII.-Secondary Effects of Shocks.—Springs.--Jets of Gas.-Fissures. —Depressions and Elevations of the Ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXVIII. — Periodicity of Earthquakes. –The Maximum in Winter. —The Maximum at Night. — Coincidence with Hurricanes. – Influence of the Heavenly Bodies..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ‘. . . . . CHAPTER LXXIX. — Slow Oscillations of the Ground. — Difficulties presented in the Observation of these Phenomena. –Causes of Error: Frosion of Shores, Swelling and Sinking of Peaty Soils.-Influence of Temperature.—Local Upheavals. . . . . . . . . . . . . . . CHAPTER LXXX. — Upheaval of the Scandinavian Peninsula; of Spitzbergen; of the Coasts of Siberia; of Scotland; of Wales..................... . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXXI.-Upheaval of the Mediterranean Regions.—Former Libyan Strait. —Coasts of Tunis, Sardinia, Corsica, Italy, and Western France....... . . . . . . . . . . . . . . . © CHAPTER LXXXII.-Coasts of Asia Minor.—Ancient Ocean of Hyrcania.-Coasts of Palestine and Egypt. --The Adriatic Gulf... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXXIII.-Subsidence of the Shore of the Channel, of Holland, of Schleswig, of Prussia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXXIV.—Upheaval of the Coasts of Chili and Peru.-Probable Depression of the Coasts of Ila Plata and Brazil.—Coasts of North America and Greenland. . . . . CHAPTER LXXXV. —Beefs of the South Sea. —Darwin's Theory as to Upheavals and Depressions... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHAPTER LXXXVI.-The Great Areas of Upheaval and Depression.—Mobility of the so-called Rigid Crust of the Earth. . . . . . . . . . . . . . . . . . . . . . . . . . . . ...................... 511 546 550. 556 ILLUSTRATIONS. [The Illustrations I. to XXIII., the titles of which are in capital letters, are printed in colors, their place being opposite to the pages indicated. The other cuts, designated as Fig- wres 1 to 234, are inserted in the pages as given.] NUMBER PAGI, NUMBER PAGI; I. MAP OF THE WORLD ................... . 1 || 31. The Mountains of Gavarnie........... 126 II. GEOLOGICAL CHART OF THE WORLD 13 || 32. Pène : I’iz à Lun de Guscha.......... 127 1. Solar and Sidereal Day................ 18 || 33. Tete: Wallenstock de Wolfenschiessen 127 2. Orbit of the Earth around the Sun... 20 |34. Channel of the Bosphorus.............. 131 3. The Pyramid Mountain................ 33 |35. Circular Valley of Ourdinse........... 134 III. GEOLOGICAL MAP OF ENGLAND..... 37 ||36. The Pyrenees............................. 141 4. Paradoxides IIarlani................... 37 ||37. Luchon and Val d'Aran................ 142 5. The Weald of Kent..................... 41 |38. The Sierra de Marcadau............... 143 6. The World, according to Homer..... 49 |39. The Jura................................... 145 7. Proportions of Land and Water...... 50 |40. Valleys and Combes of the Jura...... 147 8. The Oceanic Hemisphere.............. 51 | X. THE ALPs. 9. The Continental Hemisphere......... 52 |41. Profile of Monte Rosa.................. 149 IV. North AMERICA....................... '52 |42. Valley of Cashmere..................... 152 10. Basin of the Pacific ..................... 53 |43. Great Landslip of Goldau.............. 161 11. Circumpolar Ocean...................... 54 |44. Limit of Permanent Snow............. 165 12. Circle of Inland Lakes and Seas..... 55 |45. Cornice of Snow.......................... 173 13. Semicircle of Deserts.................... 56 |46. Internal Banded Structure of Ice.... 175 14. Western Shores of the Mediterranean 57 | XI. THE MER-DE-GLACE .................. 178 V. SouTII AMERICA......................... 58 |47. Windings of a Glacier.................. 180 15. Terra Quadrifida......................... 61 48. Cascade of Glacier....................... 180 16. Mundus Tripartitus...................... 62 |49. Slope of the Mer-de-Glace............. 181 VI. EUROPE................................... 64 || 50. Marginal Crevasses in a Glacier...... 182 17. Circle of Junction of Continents...... 66 || 51. Intersecting Crevasses............... ... 183 VII. AFRICA.................................. 67 52. Transverse Crevasses, in Profile..... 184 VIII. Asia.................................... 71 53. Transverse Crevasses, in Plane....... 184. IX. AUSTRALIA AND ARCIIIPELAgo...... 73 |54. Longitudinal Crevasses, in Plane. ... 185 18. The “Landes” of Gascony............ 82 |55. Longitudinal Crevasses, in Profile. ... 185 19. Extent of IIeath-Smoke in 1857..... 84 || 56. Longitudinal or Terminal Crevasses. 186 20. The Black Lands of Russia........... 86 |57. Superficial Torrents of a Glacier..... 187 21. Oueld-Rir................................. 94 || 58. Chasms in Glacier, filled with Snow... 188 22. The Pampas.............................. 100 59. The Glacier of Giétroz, in 1818..... . 190 28. The Caussade............................ 113 | 60. Glacier Table............................. 193 24. Indented Plateau of Nantua........... 114 | 61. Lateral Moraines........................ 194. 25. Section of Africa...... “. . . . . ............ 115 XII. GIACIERS OF GEISBERG............ . 194 26. Crest of Monte Viso..................... 123 |62. Frontal or Terminal Moraines... . ... 195 27. The Pic du Midi d'Ossau.............. 124 63. Frontal or Terminal Moraines....... 195 28. Einshorn de Splugen.................... 125 | 64. Frontal or Terminal Moraines....... 195 29. The Gross-Glockner..................... 126 || 65. Frontal or Terminal Moraines....... 195 30. L'Esquerra des Eaux-Bonnes......... 126 | 66. Valley of Avoca, New Zealand...... . 195 *@ º • G. ILLUSTRATIONS. X NUMBER PAGE 67. Ribbons of Mud, Mer-de-Glace..... 196 68. Sources of the Arveiron............... 199 XIII. GLACIERS OF LANGTHAL............ 201 XIV. GLACIER OF VERNAGT............... 204 69. Glaciers of the Alps.................... 207 70. The Glacier d'Aletsch................. 208 XV. GLACIERS OF THE ADIGE............ 211 71. Ancient Glaciers of the Aar.......... 217 72. Ancient Moraine falling down....... 218 73. Ancient Glacier in the Himalayas. 220 74. Estavelles of Porrentruy.............. 228 75. Section of an Intermittent Spring... 230 76. Artesian System of Oued R'ir...... . 233 77. Natural Bridge of Panbouk-Kelessi 240 78. Saline Springs of Touzla............. 243 79. Vaucluse and the Sorgues............ 245 80. Course of the Touvre.................. 246 81. Mud Island in Course of Formation 249 82. Mud-Lump on Mississippi............ 250 83. Chasms of Carniola.................... 254 84. Grotto of Lueg, Illyria................ 255 85. Grotto of Adelsberg.................... 257 86. Grotto of Planina....................... 259 87. Cut of Riñihue, Chilian Andes...... 264 88. Difurcation of the Orinoco........... 265 89. Bifurcation of Valleys of the IRhine 267 90. Threshold of Sargans.................. 268 91. Marshes of Pinsk....................... 209 92. The Ponto-Caspian Isthmus......... 270 93. Sources of the Garonme............... 274 94. Iłasins of the Amazon and La Plata 277 95. Inclination of the Nile............... . 282 96. Slope of the Po, Tessin, and Oglio. 282 97. Circle of the Valley of Lys........... 286 98. The Igharghar......................... 288 99. Valley of Cogne ................... •e e º 'º - 289 100. Quadrangular Basin of Erosion..... 289 101. Erosion of the Bourgogne............ 291 102. Talus of Débris, Valley of Adige . . .293 103. Talus formed by Torrents........... . .293 104. Ancient Lakes and Defiles of Aluta 294 105. Lakes of Thun and Brienz...., ...... 294 106. Filling up of a Lake Basin........... 296 107. Deposits of the Rhone and Dranse. 297 108. Course of the Niagara................. 298 109. The Falls of the Zambesi............. 299 110. Rapids of Maypures, on the Orinoco 300 111. Cataract of Felou, Senegal........... 302 112. Profile of Cataract of Niagara....... 303 113. Islands in the Western Scheldt...... 307 114. Meandering of the Meuse............. 308 115. Meandering of the Seine.............. 309 116. Meandering at Luzech............... 310 TNUMBER PAGE XVI. Course OFTIIE MISSISSIPPI ...... 311 117. Old Channels of the Mississippi..... 311 118. Old Meanderings of the Rhine...... 312 119. Channel of Vicksburg................. 314 120. Diagram to show Guiding Banks... 315 121. Middle Course of the Rhine......... 316 122. Floods, Basin of the Amazon....... 3.18 123. Limits of Inundation of the Rhone. 323 124. Growth by Floods...................... 326 125. Subsidences of the Waters............ 326 126. Map of Fayoum........................ 330 127. Section across Fayoum................ 331 128. Dikes along the Rhine near Seltz... 333 129. Mean Heights of the Isere........... 335 130. Dikes by the Po........................ 336 131. Golemas by the Po..................... 337 132. Gap formed near New Orleans...... 338 133. Belts of the Senegal.................... 342 134. Old Course of the Adour.............. 345 135. Mouths of the Mississippi............. 350 136. Channel of Loutre...................... 351 137. Depths of Gulf of Mexico............ 352 138. Depths of Gulf of Mexico............. 352 XVII. DELTA OF THE GANGES........... 353 139. Delta of the Nile........... • . . . . . . . . . . . 354 140. Mouths of the Po...................... 356 141. Delta of the Rhone.................... 357 142. Height of Layers in Delta............ 359 143. The Mississippi at Plaquemine..... 361 144. Ancient Course of the Amou-Daria 362 145. Section of Bar of the Mississippi.... 364 146. Mouths of the Danube................ 370 147. Jetties of Soulina....................... 371 148. Middle Course of the Volga.......... 374 149. Left and Right River Banks......... 375 150. Radiation of the Gaves................ 376 151. Comparative Discharge of Rivers... 378 152. Iakes of Finland....................... 385 153. The Dombes............................. 386 154. Altitudes of Lakes, Italy............. 387 155. Altitudes of Lakes, Switzerland..... 388 156. Lake Maggiore.......... A * * * * * * * * * * * * * * 388 XVIII. LAKE GARDA....................... 388 157. Lake of Neuchâtel..................... 389 158. Valley..................................... 390 159. Cluse...................................... 390 160. Combe.................................... 390 161. Stages of Lakes in Valley of Oo.... 391 162. Lakes of Nors Elf...................... 392 163. Lake Stages of Estom Soubiran..... 393 164. Caspian Sea...… 401 XIX. TiHE BUGORs of THE CASPIAN.... 405 408 165. The Dead Sea and the Jordan......" ILLUSTRATIONS. xi Number PAGE | NUMBER PAGE 166. Section of Palestine ................... 409 | 201. Volcanic Region of New Zealand... 484 167. Lakes of Huiduck...................... 412 202. Section across Basins of Tetarata... 485 168. Salt Marshes of Paraguay............ 414 | 203. Island of Volcano...................... 487 169. Marshes of Corrientes................. 415 | 204. Isle of St. Paul ........................ . 490 170. Coulée of Monte Frumento.......... 421 | 205. Volcano of Taal........................ 491 XX. ERUPTIONS OF ETNA................ . 425 | 206. Santorin.................................. 492 171. Curve of Volcanic Islands............ 428 207. Kaimeni Group......................... 494 172. Equatorial Volcanoes.................. 429 208. Graham's Island, or Isle of Julia ... 495 XXI. VOLCANOES............................ 433 209. Coulée of Puy de Pariou.............. 499 173. Fracture, Etna and Vesuvius.........437 210. Area of Explosion at Mentz ......... 506 174. Section of the Island of Hawaii..... 438 211. Chart of Earthquake, Sept. 14, 1866 509 175. Isle of Palma............................ 441 212. Transmission of Earth-waves........ 512 176. Section of the Island of Palma...... 442. 213. Area of Earthquake of Viége, 1855 514 177. Volcano of Jorulla, Mexico.......... 443 214. The Runn of Cutch.................... 521 178. Series of Craters, IIawaii............. 445 215. Distribution of Earthquakes ......... 523 179. Auckland and its Volcanoes......... 446 216. Distribution of Earthquakes......... 524 180. Cone of Tuff........................... . 447 217. Distribution of Earthquakes......... 524 181. Cone of Tuff, and Crater of Scoria, 447 218. Distribution of Earthquakes......... 525 182. Volcano of Rangitoto.................. 447 219. Distribution of Earthquakes......... 525 183. Mount Vesuvius ........................ 448 220. Ilistribution of Earthquakes......... 526 184. Section of Vesuvius .................. . 449 | XXII. MAP OF UPIIEAvALS AND DE- 185. Section of Etna......................... 449 PREssross......................... 527 186. Mount Orizaba........................ . 449 |221. Elevation of Bed of Gulf of Bothnia 534 187. Profile of Orizaba................... ... 450 |222. Bank of Altenfjord..................... 535 188. Volcanoes of Java...................... 451 223. Biesbosch................................. 547 189. Flow of Łava at Mauna-Loa......... 455 224. Coast of Friesland..................... 548 190. Crater of Kilauea. ................ e..... 461 |225. Coasts of Puerto San Jorge.......... 550 191. Crater of Mauna-Loa................ . 461 226. Coasts of Coquimbo................... 551 192. Section across Craters of Rilauea. . 462 |227. Valley of Rio Santa Cruz............. 552 193. Nevado de Chillan ................... . 466 228. Keeling Atoll............................ 557 194. Regular Come of Ashes................ 469 220. Atoll of Ebon............................ 558 195. Cone of Ashes modified by the wind 469 || 230. Isle of Vanikoro........................ 550 196. Cone of Etna and Val del Bove.... 469 || 231. Section of Isle Vanikoro ............ . 560 197. Eruption of Coseguina............... . 471 |XXIII. Atoll, ARI........................ 560 198. Eruption of Timboro.................. 472 232. Growth of Coral ........................ 560 199. Crater of Sete Cidades............... . 476 233. Great Bank of Chagos................. 561 200. Crater of Demavend................... 480 234. Bridge of Adam, or Rama........... 563 CEO LOGICAL C Zºo ºn Mººs Zºº wo. anº and ºetaceous peº’s zºº of Maº Aºetº ººzºº ºw ºw º wo - L. º. º º lºw- º - - - - - __ --- - --- --- º º -d zo Meridia Drawn by A. Vuillemºn HARPER & BROTHE PL. II. RT OF THE WORLD º - -- roo rºa ---> ---> --> * nº - Eng 9 by Erhard NEW YORK 3. T H E E A R T H. PART I. THE EARTH AS A PLANET. CHAPTER I. SMALLNESS OF THE EARTH AS COMPARED WITH THE SUN AND FIXED STARS ; GRANDEUR OF ITS PHENOMENA.—FORM OF THE TERRESTRIAL GLOBE 3 ITS DIMENSIONS. - THE earth on which we dwell is one of the Iowest 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 the immense 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 ačrial 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 EARTHI 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 2 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 PLANET. 15 4. speed of which has been adopted in astronomy as a term 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 parasang, 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 mêtre, 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 are described from the equator to one of the poles. Owing to errors which the difficulties of actual measurements rendered inevitable, the ideal mêtre 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 kilomètres. 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 he did 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 Seele, 16 THE EARTH, AS CHAPTER II. MOTION OF THE PLANET. —DIUIRNAI, ROTATION AND ANNUAL REVOLUTION.— SIDE REAL AND SOLAR DAY. —SUCCESSION OF DAYS AND SEASONs.—DIF- FERENCE OF DURATION OF THE SEASONS IN THE TWO HEMISPIIERES.— PRECESSION OF THE EQUINOXES.—NUTATION.—PLANETARY PERTURBA- TIONS. — MOVEMENT OF THE EARTH TOWARD THE CONSTELLATION IIIER- 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 cast—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 earth 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, such 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 rºw 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 aphelton, 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 Encke, 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. - t 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, is 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 šuddenly extinct, 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 fixed star, is comparatively near to the earth. While the latter is perform- * Wide the chapters as to “Rivers,” “Currents,” “The Atmosphere, and Winds.” B * 18 THE EARTH. 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 ". and in order that the earth should present to it exactly the same pºtion 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 round 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. Amédée Guillemen, Le Ciel. From this work wo have borrowed the above plate. - * ORBIT OF THE EARTEI. 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 ºstronomical year commences on the 20th of March, at the exact moment 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, the 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, where 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 234° 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 zone 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. - I8 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 póſtion 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 round 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. Amédée Guillemen, Le Ciel. From this work wo 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 ºstronomical year commences on the 20th of March, at the exact moment 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-poſht of spring, the earth continues its translatory movement. In consequence of the inclination of its axis, the 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, where 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 233° 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 233° 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 zone 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. - 22 - THE EARTH, of 66° 32' to the plane of the terrestrial orbit, turns round with a slight lateral motion, so as always to point to a nºw region of the sky; if it were prolonged indefinitely it would describe a circle amid the distant stars. As the axis of the earth is constantly changing its direction in this way, the plane of the equator must vary exactly to the same extent in its po- sition as regards the sun. In fact, every year the exact moment of the March equinox anticipates by about twenty minutes the time at which the corresponding equinox fell in the year preceding. Each revolution of the earth round the sun brings a fresh advance of twenty minutes in the de- termination of the equinox; and as, during the long course of ages, the axis of the earth does not intermit in this swaying motion, the time must come, after a period of 12,900 years, that the conditions of the seasons will be altogether changed. The hemisphere which hitherto received the larger proportion of heat will receive the lesser share, and that half of the globe which had endured the larger number of wintry days will now, in its turn, enjoy the more lengthened period of Summer. Then, after a second period of 12,900 years, during which the relation between the seasons of the two hemispheres is being gradually modified, the axis of the earth completes its round of swaying, which has lasted for 258 centuries, and the position of the globe in respect to the sun being nearly the same as at its starting-point, a second cycle of seasons will then commence. We might call this period the earth's great year, if, at the end of it, the earth were in an identical position to that which is occupied at the com- mencement; but this is not the case. The attraction of the moon, and the disturbances caused by the vicinity of certain planets, are incessantly modifying the curve described in the starry fields of space by the earth's axis, and complicate it with a multitude of spirals, the various periods of which do not coincide with the great period of the swaying of the axis. The successive undulations form a continuous system of interwoven spi- rals. “It is a manifestation of the infinite.” f But even this is not all. In addition to all the motions of the globe which we have already pointed out—its diurnal rotation, its annual rev- olution round the sun, the rhythmical swaying of its axis, proved by the precession of the equinoxes, the nutation or more rapid swaying which is caused by the attraction of the moon—we must now notice the enormous translatory movement which is dragging it through endless tracks of space in the train of the sun. Not many years ago, this motion was en- tirely unknown to astronomers, and, yet it is going on with inconceivable rapidity—a rapidity more than double that of the course of the planet round its central luminary. In one second of time the earth moves about forty-four miles toward the point of the heavens where we find the con- stellation of Hercules. During one year only, she travels 1882 millions of miles in this direction. Does this enormous distance—which light it- * Jean Reynaud, Terre et Ciel, Stone, James Croll, Carrick Moore, Lyell, and Le Hon. # According to Bessel. Wide Humboldt's Cosmos, Faye's transl., part i., p. 162. Struve estimates the annual movement at 149 millions of miles only. IMMENSITY OF ST24 CE, 23 self would take two hours and five minutes in traversing—form part of an ellipse described by the whole planetary system round some centre of attraction—a centre which Maedler, the astronomer, has fancied that he has discovered in Alcyone, in the midst of the Pleiades? Or is it, as Ca- rus” supposes, a portion of an orbit which has for its focus (like the curves of multiple stars) a centre of gravity common to many stars—nothing but a mathematical point everlastingly changing in infinite space? We can not tell; but certainly this movement of the globe we live on, and its prog- ress through the unfathomable depths of space, must give us an idea of the immense variety of the motions which make the heavenly bodies gy- rate like particles of dust in a whirlwind. Our own little earth itself is carried on from space to space, and never closes the cycle of its revolutions. Ever since the time when its particles were first grouped together, it has been describing in space the infinite spiral of its ellipses, and thus will it go on turning and oscillating in ether until the moment when it will exist no longer as an independent planet. For the earth, too, must have an end; like every other body in the universe, it comes into existence, and lives only to die when its turn comes. Already its annual motion of rotation is diminishing in speed;f certainly this slackening of pace is not very obs servable, since no astronomer from Hipparchus to Laplace has yet exactly defined it. . But, unless some cosmical force acting in a contrary direction compensates for the loss of speed caused by the fiction of the tides against the bed and the shores of the ocean, the impetus of our planet will every century diminish. After various catastrophes which it is impossible to foresee, the earth will eventually completely change its course of action, and lose its independent existence, either uniting itself with other plan- etary bodies, or breaking up into fragments; or it will perhaps terminate its course by falling like a mere aerolite upon the surface of the sun. * Natur und Idee. f Meyer, Joule, Tyndall, Adams, Delaunay, 24 THE EARTH, CHAPTER III. JARIOUS OPINIONS AS TO THE FORMATION OF THE EARTH.—LAPLACE’s IIY- I’OTIILSIS ; GRAVE OBJECTIONS RAISED TO IT.—TIIEORY OF A CENTRAL FIRE; OBJECTIONS TO IT. TIIE origin of the earth is lost in the dark night of our ignorance. From the observations and deductions they have made, none of our sci- entific men have been enabled to afford us any exact information as to the way in which our planet was formed, although new stars are constant- ly showing themselves in the infinity of space. The telescope serves only to demonstrate the appearance of these celestial bodies, and fails to dis- close to us the mode of their formation. On one occasion only, in Decem- ber, 1845, astronomers had the good fortune to witness the division of a comet—that of Biela ; they saw it, in fact, break asunder and form two nuclei of unequal sizes, which traveled on into space, one following the other. But this isolated fact will not justify us in assuming a similar mode of formation as regards all the heavenly globes, and in asserting that the stars and planets are produced by a kind of bipartition or duplication. The human intellect is still compelled to be content with mere hypothe- ses as to the origin of our own and other planetary globes. All cosmog- onies, from the legend of the savage, who imagined that the earth sprang from a sneezing fit of his god, down to the theory of the great Buffon, ac- cording to which the planets of the solar system are the fragments launch- ed into space by a collision between a comet and the sun, the vague con- jectures of the ancients, and the ideas struck out by modern science—all alike are mere suppositions more or less plausible and ingenious. The hypothesis which at the present day still receives the most cre- dence is that which was first proposed by Kant, the philosopher (1755), and, having been developed by Herschel, was taken up and largely des- canted on by Laplace in his Eagosition du Système du Monde. So great is the authority of this illustrious geometrician, that a great number of persons erroneously look upon his hypothesis as a clearly demonstrated scientific fact. It is, therefore, hardly permissible to omit giving some description of it, even in the briefest sketch of the primitive history of the carth. Taplace supposes, in the first place, that the space in which the solar system now moves was filled by a gaseous cosmical matter of a high tem- perature, the dilation of which was excessive, compared even with the most rarefied gases: This enormous nebula incessantly radiated heat around it, and thºs supplied a portion of its caloric to the surrounding space; it therefore necessarily condensed gradually round a central point, THEORY OF LAPLACE. 25 destined one day to become our sun. The particles of gaseous matter, being mutually attracted to one another, were not only subject to the mo- tion of condensation, but were also hurried on in an immense circle round the axis of the system. The loss of caloric and the consequent concentra- tion of the spheroidal mass had the effect of increasing the speed of rota- tion. At the same time, the centrifugal force was proportionately in- creased, and, under the influence of this force, the atmospherical mass, be- coming flattened at the two poles, assumed gradually the form of a disk. The attraction which had hitherto retained in their place the molecules of the circumference, and had prevented them from rushing off into space, was 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- bulsive force communicated to its molecules, its motion became twofold; it continued its revolution round the sun, and began to turn round on its OWI) {\,X1S. § The formation of satellites is similarly explained by the gradual shrink, ing of the gaseous mass of the elementary planets. The rings separated 26 TIHE 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 6500 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. Ibut, unsubstantial and ačrial as it was, our carth 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 I3elgian 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 * Erposition du Système du Monde, p. 450. FORMATION OI" PLANETS. 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 distant nebulae, 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 nebulae, 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 the 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 must 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, would 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- via 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 fost-bound sea. This first scoria was succeeded by a second, and them by others; next they would unite 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 within 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 scoriae, was again united; the cooling process would tend also to slowly thicken it. After a lapse of time, which must have been immenscly protracted, since the interval' during 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,f the pellicle at last became firm, and the erup- tions of the liquid mass within ceased to be a general phenomenon, local- * Exposition du Système du Monde, p. 475. t IIclinholz. 28 THE EAIRTH. 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 ačrial 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. IIenceforward the igneous planet was externally clothed with a triple covering, solid, liquid, and gaseous; it might therefore become the theatre of life.” Vegetables and lowly forms of animals were called into exist- enco 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 fossil 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.”? § 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 carth, 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 Jouvencel, Les Commencements du Monde, p. 37 seq. f Daubrée. f IIumboldt's Cosmos; Studer's Physikalische Geographie, vol. ii., p. 37, etc. MUTABILITY OF ITS SURFACE 29 may be given by a sheet $f 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 of fusion 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 carth 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 * Expériences du Conservatoire des Arts et Métiers, 1864. f Wide the chapter as to “Upheavals and Depressions.” 30 THE EARTH, those who assume the existence of a central file, our planet is to be con- sidered as actually a liquid mass, as the external crust 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 débris torn away from the surface of the soil, which they bear with them. Lastly, M. Bischoff, having ascertained from the principal soundings that 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- 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 more than in metallic veins.” In the Artesian well at Neuffen, in Wür- tomborg, 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. In the mines of Saxe, the increase of heat, according to Reich, is one degree for every 76 feet. Still, the carth 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 six e 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 Wärmelehre, p. 169–171. # Collegno, Geologia, p. 26. f Bischoff, Wärmelehre, p. 254. The learned German professor endeavors even to trace out in various countrics chthonisothermes, 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 propolº 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 ačrial layers, that the decrease of heat would continue up to the midst of celestial space, and that at miles above the 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 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 the 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. Nevertheless, the recent experiments of M. Delaunay on glass 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 attractions 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 Waltershau- Sen, the historian of Etna, to harmonize best with the volcanic phenome- na, is, that there is no actual central fire, but only internal seas of red- hot molten matter scattered about in various parts 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. f L'Espace Celeste et la Nature Tropicale. f Wide the chapter on “Volcanoes.” 32 THE EARTH, CHAPTER IV. GEOLOGICAL STRATA. – CONGLOMERATES. — SANDSTONES. — CLAYS, - LIME- STONES.–FOSSILIFEROUS BEDS.—SEQUENCE OF ORGANIC BEINGS.—GEN- Jº RAL CLASSIFICATION OF STRATA.—DURATION OF Glº OLOGICAL 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 order of seniority. The geologist who descends the shaft of a mine sunk vertically into the earth may, as it were, traverse the 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 Îeport, has been revised by M. Marcou, the geologist, who was the first to bring under notice the existence of this remarkable mountain (Fig. 8). TIIE CRUST OF THE EARTEI. 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. Gº- sº Fig. 3. The Pyramſö 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 waves, supply either to rivers or direct to the sea masses of débris, which, spread out into shingle-strands or beds of pebbles, are gradually changed into solid conglomerates. The crystallino rocks, pulverized by atmospheric agencies and the fiction 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 the 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 cre 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 trage behind them, and the piled-up masses of their remains arº, 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 future 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 insulſed 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 JºA RITY OF ORGANIC IºEMAINS. 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 crustaceae, 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 which 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 EARTH, 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 2 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, Lycopodiaceae, and Calamitede, 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 Rhaetic beds of Somerset, and even in the Trias, at the termination of rocks of Palaeozoic 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 palaeontologists 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 Genève, Archives Scientifiques, Aug., 1866. Wallich, North Atlantic Sea-bed, p. 95. Lyell, Darwin, Gaudry, Carpenter, etc. . - CEOLOGICAL MAP OF EN CLAND - PL. III. º - 3. 7 lºw nº ºn. 5 I N V) Modern Bedº N. wº/ Tertiary do * * A. Gretaceotzo do - - wºrwtowºc do & - ºw and Pºzºan do. %) Awesowie Bea'a Øystal/ºne & Erwoºre do sº - - IRIS H H ANN Anol-resex -- - ºf 1. Dºwn by A. Vuillemn after Ramsay Engº by Erhard ºn & B ROTHERS 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- ceae, 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 palaeontology 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 Jºozoon Canadense (if indeed, it exists at all, except in the imag- ination of certain geologists) and the Braintree trilobite (Paradocides º º º º wº wºn - --- ºn º º ºº Žº º º º Fig. 4. Paradoxides Harlani. Warſan?), 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,” 1868) fully accepted the Darwinian Theory.] * Bronn, Albert Gaudry, Owen, Hermann von Meyer, Lartet. 38 - THE EARTH iferous beds, including the Mountain limestone rôcks 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 débris, 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 2 The solution of this problem is one of the great tasks of science?” * Marcou, Roches du Jura, p. 240. MODIFICATION OF THE EARTH'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 GIEOGRAPHY. 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 18 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 particles, 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 shiftings 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 TIII) EAJETII. 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 more shoal; then, perhaps, that islets, and then islands made their appearance, and, grouping themselves into archipela- gos, ultimately united into continents. Iłut 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 the globe where the 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 ſound 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 & J. VIDENCE O/?' I'OSSILS, 41 * * **** ****** * * * *f, *, * s ºf Tºº, sºft,” sº, s sº * - ºf jº.º.º.º.º.º.º.º.º.º.’, •e * • * "Tºº §§§§ § § * tº: N * Y. § § N §§ § – à : – *-:-- §º * •. *s & i º § sº :- * * & Cretaccotts Bear. gº Jurassée Bedr. Fig. 5. The Weald of Kent and the opposite French Coast. 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, swe 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 land joining England and Ireland, Ireland and Spain, and even Europe and America. In exploring the lignite beds of the Tertiary formation in Europe, geo- ogists have, in fact, found fossil tulip-trees, the remains of the Louisiana cypress (7%taxodium distichum), seeds of the Robina nuts of a United States species, leaves of the maple, oak, poplar, pine, magnolia, Sassafras, and tax- us; also of the Sequoia—those giants of the Californian forests, and other * Albert Gaudry, Animaux fossiles de Pikermi. - f Murchison, Anniversary Address, 1863. ºf Edward Forbes. \º 42 TLIE EARTLI. 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- timent, 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 miass 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- ſerent 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. IFinally, 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- mind 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 * Unger, Die versunkene Insel Atlantis. Oswald IIeer, Klee, Gaudry, etc. OLD CONTINENTS. 43 Archaeopteria 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 IIolland is the place where we now find the only living representatives of Trigonia which once inhabited the Jurassic seas.” Round the inland sca 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 Zöne, 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 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 Silurian 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, Marcou, Oswald IIeer, 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 * Marcou, Roches du Jura, p. 331. f Joches du Jura, p. 326 seq. f Manual of Geology. § Roches du Jura, p. 335 seq. | Tertiàr-Flora der Schweiz. 44 * ſº 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 débris 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 fiaced Stars those distant luminaries which nevertheless move through ether with so prodigious a rapidity? IRocks, 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. Iły 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 'ast 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 carth 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. G ENESIS 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 ages. P A R T II. T H E L A N D. CHAPTER VI. REGULAR DISTRIBUTION OF CONTINENTS.—IDEAS OF ANCIENT NATIONS ON TIIIS POINT.-IIINDOO 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 the 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 IReynaud, Terre et Ciel, p. 26. HARMONY OF THE CONTINENTS. 47 q 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, just 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 eternal 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—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 pºst', 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, dnd sometimes spreads his wings to glide over º 48 TEIE 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-vita, 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 crost, 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 IIercules—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 Researchēs, p. 12. EARLY IDEAS OF THE EARTH, 49 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 castern PEGION OF DARENESS Galactophagi Hippomolgi §§ ºr ºf : Yºğ ë% § fº §º {{#iºsº §§§ §jº * º º §§3% º . §§ §§ §§§. § º 2::$ **: 㺠sº tº: *N Şāś); % % § º º & ſº § ; º § sſº) §3. % º º §§§4% º 'º ºś Sº º º §§ §: :S º § º W º -- º º .*-ºs º- ºr sº ºr zº: :***.*.*.*.* : $ºś *ś Fig. 6. The World after the poetic accounts of IIomer. 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 AIRRANGED 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, halfway 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. tº | The principal accumulation of water is in the southern hemisphere, and * Dove, Zeitschrift für allgemeine Erdkunde, Jan., 1862. IANA AND WATER. 51 Q 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- --~~~~-- C - No. 9. Continental Hemisphere. forence 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. PL. IV NORTH AMERICA ºſ; №tº §3. Ø *o \， \\ 2a Drawn by Avenuemºn - Enzº ºf Erhard 12 r Duguay Trouin CONTOUR OF THE LAND. 5 3 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 wº 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 of Darien the great chain begins again, and, plunging the rocks which form its base deep into the waves of the Pacific, extends & S www.ſº s\º º ſº O Fig.11. circumpolar 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 uniº 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 J2OLAJ3 CITECLE). 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 zºr-------. ...A. ----- - - - - - - º - - 4 * - * *~~ * vº º e--". *- - &ruºcº 27.0. KTV # * & } 7%.<- #f gº. " A. $3 ** * o ~ - Frry: 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 Behring's Straits would have for its almost regular circumference the northern * Wide 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 cpoch, 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 *** {, r”y, &Z • ?, ? w º %. £º. O ~ *.* ºthº: Fig. 13. Somicircle 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 CQI'- 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, I) ESERTS 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 Cobi, 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 5. % -- % - - *::::. ºA' % 3% ºf º #$$$$$$. - sy," • * … - . ~ * . . . - º ! --Rºº. . . . . . ,” ... * M. i. º. t §§§ % *::::::: \ ºr !," º º: .. 9 * .* rºx7, 26. Sºº ºğ.3.;tº 22; .,, V. ‘’ *:::: * ~ y i. §§§º ~.ºr 325': '*N K*A*śſ/?=: - \# ---º' ºy Nººnºtºº ºki' tº fit - - s3gºść. sº {e * * - ‘e. 24 x w • rºtº-' YNºh f: Fº ºf clº - sºto § º jº" %:S --- % % - à * - Yº -...-. f**: - ------ ~ É ~~ .* * ~ 4. *** * T.2, s - - Sº • !; ºf *::::::::: - * ***.........” n . - 9 - - §§%+3. «w. i * w º § º: º $: }º ºn r {{ KºščSè: ~ % ra . §§º t 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 Ciel, Eclaircissements scientifiques. 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. - PL. V. SOUTH AM ERICA ºo 60° West of Paris 72 & Drawn by AVuillemm too Eng? by Erhard ºr Dºuay Troum - NEW - - - B ROTHER H A R PER º * ( . cº- *... DIVISION OF THE LAND, . 59 CHAPTER VIII. 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-4-some in a circular direc- tion round 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. Nevertheless, 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 60 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 Iſla SSGS. 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 if, 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 which 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 characters. 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 castern 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 castern 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 I) OUBLE CONTINEWTS. • 61 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.} 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. In 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. - &s £º- Rººs c Y T H 1 #& 3.j §§§ A §§ §§§s===s--- śā *ś -*--~~ Fig. 15. Terra quadrifida. 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 l'Algérie. t Sallust, Bell. Jug., c. 17; Von Hoff, Veránderungen der Erdoberfläche. 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. 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, which 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 are 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 tyhole 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. CHAINS OF THE HINDU. KUTCH. 63 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. 64 THE EARTH, CHAPTER IX. PRINCIPAL ANALOGIES PETWEEN 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.–IRHYTHMICAL AIRRANGE- 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 |- ſ！ ： ºngº by Erhard W. Yºº - º - Nº. ||-|| __，|-2！！!！！！|- º ºn- - a -º Drawn by A Mullemun HAR PER & B R PYRAMID FORMS. wº 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-Nor, Tengri-Nor, Koko-Nor, and Oubsa-Nor; and on the west 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, find 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 Cordilleras properly so called. Africa, too, has several basins without outlet, the 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. 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, Tasmaania 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 Fuego, which is itself divided into numerous islets by a labyrinth of * Wide the Map of the World, Pl. I. f Jean Reynaud, Terre et Ciel. E | 66 -- THE FAIRTH. Fig. 17. Circle of Junction 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 Storms,” 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. * Iſouzeau, De la Symétrie des Formes des Continents. ſºn was Nº. º º - º - Cape Verd Islands º Gui, tº ºr- tº hiſ in tº a * - - - \ ºu º Drawn by A. Vuillemin Mºulian a ni Paris |A || || || || Nºw Yoº 12ENINSULAS, 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 débris 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. , at 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 newesten Arbeiten über das Mammuth, Mittheilungen von Petermann, ix., 1866. \ 68 THE EARTET. 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 mu- 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- means 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. 69 CHAPTER X. TNUMEROUS 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 N.E.W. —THE TRANSWERSE POSITION OF THE AXES OF AMERICA AND THE OLD WORLD.—CONTRASTS OF CIVIMATE IN THE WARIOUS 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 the contrary, 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 EARTEI. peninsula, is four 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. AIREA OF CONTINENTS. FIRST PAIR. North America........................................... 7,953,315 square miles. South America........... • • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6,949,674 “ “ - SECOND PAIR. Purope..................................................... 3,822,320 “ “ Africa..................................................... 11,244,958 “ “ THIII&D 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 OCC&I). . CONTINENTAL RADII. FIRST PAIR. t North America. .......................................................... 1087 miles. South America........................................................... 931 “ SECOND PAIR. - Europe .................................................................... 478 miles. Africa ...................................................................... 1118 “ THIRD PAIR. Asia......................................................................... 1491 “ Australia. .................... tº e º is e e º 'º p tº e e º tº g º g g g & ſº e & & © & tº e º te e º 'º º º ſº tº e º tº e º g tº e ($15 & 4 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 ačri- al currents. Europe is so variously articulated that she enjoys a more considerable extent of coast-line than either South America or Africa it- №： PL. VIII \，\！---- &\№- №.| \ HAEPER & Brothers. Nºw York JEXTENT 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 Indo-China. 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 6ther 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. ve IFIRST PAIR. - North America......................... , 9 tº º e º 'º º & tº e º 'º e e < e < e < e < e < * * * * * * * * * 29,969 miles. Sāth America......................................................... 16,012 “ SECOND IPAIR. Europe................................................................... 19,825 “ Africa.................................................................. 12,561 “ THIRD PAIR. Asia.............................. • * * * * * * * * * * * * * * * * * * * * * * * * * * @ e º e º e º e º ſº tº e s = 35,886 “ Australia.......................- * * * * * * * * * * * * * * * * * * * * * * * * * * : e. e. e. e. e. e. e. e. e. e. e. e. e. e. 8,947 “ PROPORTION OF SEA-COAST TO SURFACE. FIRST PAIR. North America ....................................... 1 mile to 265 square miles. South America ....................................... 1 ‘‘ ‘‘ 434 “ & C SECOND IPAIR. - Europe.................................................. 1 * * * * 192 “ 44 Africa................................................... 1 ‘‘ ‘‘ 895 “ & C THIRD PAIR. Asia..................................................... 1 ‘‘ ‘‘ 469 “ & 4 Australia............................................... 1 * : * : 332 “ & 4 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 the 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 Geraës, 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 clevated 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 Iſumboldt 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- ment must present about a third of the elevation of Asia—the latter be- ing approximately estimated by IIumboldt at 1162 feet. º - 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 IPrussia as far as the frontiers of France and Belgium. Over this im- mense area, the level of the ground is so uniform that from N ini-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 THE ADJACENT ARCHIPELACO PL. IX. *§§M ſae № ） ----\\ …T Tºſ T. |- | | né" by Erhard. - - F brawn by A. Vuillemin. - NEW YORK - I?LATEA U.K. 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.* º On account of the plateaux existing in Europe being so few, the mean elevation of this continent is 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 law 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 are 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, Europa. f Guyot, Earth 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 striking 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 world 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 Drazil. 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 s, winds, and all the other atmospheric phenomena. 76 THE EARTH, CHAPTER XI. IHARMONY OF SHAPE IN OCEANS.–TIIB TWO IRASINS OF THE PACIFIC.—THE TWO IRASINS OF THE ATLANTIC.—TIII, AIRCTIC FIROZEN OCEAN AND THE AN- TARCTIC CONTINENT.—CONTRASTs, AN ESSENTIAL CONDITION OF PLANET- ARY WITALITY. g 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 enormous 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 Ritter 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 TEIE POLAJ3 REGIONS. º 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 with 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 which 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 with 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 sock 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 work, and by studying 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. GIENERAL ASPECT OF PIAINS.—ALLUVIAI, PLAINS.—CULTIVATED PLAINS.— Iſ NIFORMITY IN UNCULTIVATED PLAINS.—VARIETIES IN APPEARANCE PRO- DUCED BY CLIMATES AND DIFFERENT PIIYSICAL 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 of the large level plains and the continental deserts. Thus the western and eastern regions of the Sahara, the Neſoud 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 reaches 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 masses 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 the work of mocking genii. Although all the bare plains on the various continents resemble one an- other in the curvature of the ground, the circularity of the horizon, and 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, 80 'I'll E 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 FRENCEI LANDES. 81 CHAPTER XIII. THE FRENCH LANDES.–THE BRANDES AND THE ALIOS.—THE CAMPINIE. — THE HEATHIS OF HOLLAND AND NORTHERN GERMANY.—THE PUSZTA OF HUNGARY. — THE GRASSY STEPPES OF RUSSIA. - THE SALT STEPPES OF THE CASPIAN AND THE ARAL.-THE TUNDRA.S. 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 landos 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 brandes 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 onº Come upon large patches of furze 82 THE EARTH, anfi 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 gº Fig. 1S. The “Landes” of Gascony. spring up in the spongy earth around the water. And this is all. Por- 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 generál it is very much mingled * TIII, LANDES OF GASCONY. 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 Médoc under the denomination of “alios” 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 al?08, 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 alios, 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 allos, 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. ISut, 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 acres; 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 Deua Mondes, 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 the north wind passes over these immense fires it car. ries with it smoking particles of the smouldering turf hundreds of leagues away from IIolland, and sometimes even to the centre of France, Switzer. #=#=#= - ** E === == &########E=== ==#2 ~ E º EE =#EE º:#FFFFE Eß -Y ; : Fig.19. Extent of the IIeath-smoke in 1857. land, Bavaria, and Austria. . This is the origin of those dry fogs, or north- orn fogs, which give a yellowish tint to the atmosphere, and SOIn Ctimes half hide the face of the sun.” IIowever, 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 away in long eddies toward the west, was perfectly visible as far as Maremmes, a distance of about 125 miles in a straight line. - - t * Emile de Laveleye Revue des Deur Mondes, Jan., 1864. M. de Laveleye thinks that the name of “brandes,” given in Gascomy to the high-growing species of heath, is derived from the habit they have of burning them. In German, brand signifies burning. 12LAINS OF FIUNGARY AND /ē USSIA. - 85 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 allos 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 of jern-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 Puszta, so 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 bring down from the surrounding mountains, is very fertile, and in the cultivated districts yields abundant crops. Vast extents, which are 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 Tchornośjom (black earth), thus named on account of the color .*. soil, is still in great part a sea of grasses, varied only here and there by vil- lages, cultivatº 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 débris 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” i 86 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 mat- 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 Tchormosjom there are, here and there, some oases of the same nature which are cqually remarkable for the richness of their £2,5 . 36 º: : º - l Nº. iº %||||W[º §§ ºf º e §º º § § § §§§ §Wº º g §§§ %. —º - - *s. Š *% -- Fig. 20. The “Black Lands” of IRussia. vegetation; but the greater part of the steppes are former sca-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. * Ruprecht, Bulletin de l'Académie de Pétersbourg, vol. vii., No. 5. TIIE RUSSIAN STEPPES. 87 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 sca 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 Yāk. 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 the 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 caten 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 into 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. Iſere and there ravines, hol- lowed in the Soil by the torrents of rain-storms, have to be crossed with great labor; then some marsh, with Yts 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, 88 THE EARTH, columns of dust; at the side of the car the débris of withered plants may be seen strangely bounding along by thousands and by millions; these Tacers 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 in order to pay it a visit, and each time they hang an article of their clothing upon its branches. From this custom the name of Sinde- richagatch, or “rag-tree,” has been given to the desert poplar.f The plains of southern Siberia, which extend castward as far as the Al- tai Mountains and the lake of Dsai-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. f Zaleski, La Vie des Steppes Kirghizes. f IIumboldt, Asie Centrale and Tableaux de la Nature. IPLAINS 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 water which sparkle during several months in the marshy depressions of the soil.* * Wrangell. 90 THE EARTH, CHAPTER XIV. SEMICIRCLE OF DESERTS PARALLEI, TO THE SEMICIRCLE OF LANDES AND STEPIPIES.—TIIR. SAILARA.—SANDS, IROCKS, OASE.S.—THE DESERTS OF ARA- I3LA.--THE NEFOUD.—DESERTS OF IRAN AND THE INDUS.—THE DESERT OF COIBI. At a great distance to the south of this zone of landes, prairies, steppes, and tundras, which extends in an irregular semicircle from France 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, Cobi, 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 real South, 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 cstimated at 2000 feet; but the lev- cl 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- “Wide above, p. 56, Fig. 18. f Carl Ritter. I) ESERT 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. 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, 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. Off 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.S A current of sand is, therefore, constantly passing across the desert from northeast to southwest. The débris 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. f Vide in vol. ii. the chapter on “Dunes.” # Duveyrier, Exploration du Sahara, vol. i., p. 9. § Carl Ritter, Erdkunde. | Georges I’ouchet, Dongolah et la Nubic. 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.# 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 rāgle, 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- cr'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 storics 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- mess after having undergone all the direst tortures of heat and thirst. IIappily such adventures are rare, even if the accounts of them are at all * Daniel, IIandbuch der Geographie, vol. i., p. 446. f Duveyrier, Exploration du Sahara. OASES IN 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 fact, 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 temperature (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 oasis 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, are 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 aërral 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 verdure 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.S 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 houses on the most unproductive land in the oasis, and even on the very * Carette. f Erploration du Sahara, vol. i., p. 110. † Derived from the ancient Egyptian word owahe, signifying “habitation.” § Vogel. 94 THE EARTH, 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-Rºir. 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. ARABIAN 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 Wafowds, 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- erything that is movable on the face of the globe. The parallel furrows of 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 * Wide the chapter on “Labor of Man.” * Carette. f Wide the chapter on “Rivers.” 96 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, occupy- ing a quadrilatºral 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, Cobi 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 Cobi, just the same as in all other deserts. Dut 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 Riahkta to Pekin, there are only five trees for a distance of 400 to 500 miles, which is the width of the desert in this part of Mongolia. The Cobi, 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 thé area which was formerly occupied by a now vanished gulf. * Gifford Palgrave, Journal of the Geographical Society, 1864. f IRussell-Killough, Seize milles lieues, p. 111. IPLA INS OF THE NEW WORLD. 97 CHAPTER XV. PLAINS AND DESERTS OF THE NEW WORLD.—COMPARATIVE IIUMIDITY 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 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 * Wide the chapter on “The Earth and its Flora.” G 98 , THE E.4/3TH, 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- ics of the United States are the pampas of the La Plata and the llamos 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 llamos 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, owing 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 Régions Equinoziales. : : ; : 100 THE EARTH. § | # § º” yo 65 2.6 Cordova, growing smaller in proportion to their distance from the mount- Fig. 22. The Pampas. 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 Plata 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. diminution of rains, and the increase of evaporation during the present geological period, have resulted in severing the river into two parts. Tho 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, or a solitary tree spared by the hatchet of the gaucho. Pools, some brackish or 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 Chaco, 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 OF UTAII.—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 scorie, 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- * Wide 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 the 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.} - 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. Tegions 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 Rémy, Voyage au Pays des Mormons. f 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 clapse 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 simply 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 flores 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-IRosa, which was completely cleared of Salt * Dollaert, Antiquities. DESERT OF ATA CAMA. 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 déðr's from the adjacent Cordilleras. Saltpetre is also procured from the pampa 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- ing, and that a stream issued from the midst of the firebrands and cinders. 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 the pampa 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 lbs. 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 1860.* - 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 guanoſ—that is, heaps of the almost exhaustless droppings of all the sea-birds 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 wabstance constitutes a most important element of national com- * Bollaert, Antiquities, pp. 155, 240, f Derived from the word huanu. 106 THE EARTH, merce. 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. PLATEAUA AND PLAINS. 107 CHAPTER XVII. DIFFERENCE BETWEEN IPLATEAUX AND I’IAINS.–MATERIAL IMPORTANCE OF PLATEAUX IN THE ECONOMY OF TIII, GLOBE. —DISTRIISUTION OF ELIE- VATED REGIONS ON TIII. 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 inequalitics 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, into 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. Ilow-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 - THE EARTEI. 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 would have as its effect uni- versal stagnation and death. Supposing that men could exist on such an carth 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 * Conversagóes sobre o Amazonas, fº PLATEA UK AND PLAINS. 109 º the Pterodactyl spread his sluggish wings over the reed-beds. It 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 obeans, 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 mesºn 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 that, 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. 110 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 high lands 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 clouds 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. - * Wide the chapter on “The Earth and its Flora.” THE GREAT IPLATEA Ux OIP CENTRAL ASIA. 111 * CHAPTER XVIII. TIII, GIREAT PLATEAUX OF CENTRAL ASIA AND TIII, GATE OF THE HINDOO- KUTCII.-PLATEAUx OF EUROPE ; THEIR SYMMIETRICAL ARRANGEMENT.- PLATEAUx OF THE TWO AMERICAS.–SIMILARITY BETWEEN THE CLOSED BASIN OF BOLIVIA AND THE DISTRICT OF. UTAII.—PLATEAU X 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. 112 THE EARTEI. 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- ment 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 cast 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. 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- Cls, 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 Causses, 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 Ritter, Erdkunde. t Carl Ritter, Europa. PLATEA U.K 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 }* E. Of Pari S º sº § 3% º, -º-; $ * ... º S º § *S*% f 2.” A ,” & & & 4 º, Ś.); * * º ºš § | ! 3º42 7.T. = Tº..." Sº YTA®g. y º * * ***'...' §§* º hº § º --~~~ ** & 3. 3. E. , YººTºlſº &y, Ś),\\\\\!/.4% ºft %iº º %\% *Y.3% sº Kºś" º jº % & :: º31*. § %3/\ §§ Zocº %| 3 : *% yº 2” W ſº § §§ | §. §§ - - § 3. & \ f. § £º ; :”. §§. § º $º # * : ** * ** -ºxºS$s. º w *_ *ºf . , ; : Ş (*º fi ſ㺠% # § º # tº #% $ à. 3: : .iº, 2 - sº • wº 3, Rºžđ * * * w - 㺠º żº. 3 - - * * º - §§ % ** * 3,6′... ºr tºº £ tº * * Alſº §:7% - * 2 \; sy-s: º, ºh” ! .º.º sº, fºr - ºfºº gº tºº r %\{ſº} S㺠º ºsºft, ºf 23%-º ºrº s 2:8, 5& ſº ; %X.2% ºf Ş ſº % : # "tº $º 53 ºn . Sº * ... %X% ššfſ: ...tº º 33, Aºi : 2, § sº.”. Sº, - % % ! %2. #|N N %ᚺ ** * § § | º &# º; *@; º 3:?") . £2: V'i §ºf , § Sºjºſº, ..º...&#r Žsº X?'º º NY/N º &º sº §: A\\ S$ WM Wi º, 2 *. sº º - St. }} - r § | §§ rºſ, */ •. - W. Nili, , § āşş Sº ſº ãºſ. ºgº - t - - .*º %. 3% ($g %Nº ºr à. §%\º. º iº’ \% - ɺ º w Will/2, sº ºSº wº lº £ºš, Atº SSW a=ſº º s - flirºsiſ? 4& - \}\},\ºmºyº ºlº º ** §§§ sº Iſº º §§ §º % $º § $ ºº: ºl s''...atlacº §§’ x & s &. *ś § § CŞ £ºš - * &arnºś 4% §§ E. º * \\ f Nillſ, is - . 2× Nºa § - N - § Nº"º, */X-5% K: §º \ f SM'ſ. s: § * } * ; : sº 2 -3%: à §% º § 'llº); ºſ º 'º §§ 5\ = $ſ. g **śrºğWººs twº º sº. º. º. ºº §§§ 3.3, A ...Alſºs; • * ~ *:N. 'Yº. *\ºma º }% § “º sº... .º. * * ..."; º(sº §§ %3 %.é Žſº #x{# *RSS , % * sº º §-ºff * †, , àº, , ; Śº Øl gº º &º sº §º- º . : & łº, % Sº, §3. - S {sºlſ|||ſ|[.3%|W3%, à §§§ $ $ $º ºšš º % º W º §§ § | % ! º §§- às". s § §§ §: § Sºlº 㺠‘’S$ lº), §: % sº §§ %flº § § sº §§ ğ. § S. ºš lºſs º §§§§ {& §§§ 22 §§%\}. Sº - }% |\}ºš ºš $%; % §N *} |\% ºft W; \\ ºff. & # Ž s: º #. § § • , 2. \ "Nºs . . #ſº, .. Z! !%is §Nº Sº N º - % §'ſíšš(§.N. *: *. |SN %|}.3°SS$ $#&# & , , § { a A * - * **** 1. a §º - #g: N º - * * * . º, ºil * 2, §:E ===3:2%(WSS: S. % .* - º s.S.Nº.: Wºlińºf S& § ãºs iſ %% º º ~- 'WN sº s §/\% ºš *º sº § --> ºWN & Ç x :Sºsis:-- sº §§§ §§§ºS º $S * * **** ºššº § •. % W ..º. 2: §: Sº ź Š Sºº. - º º S §: - %. := - A. i # Š * % 3:5 º § sºlſ/; Nºë:S i ØSãAS$º sºft\{. ºśīlīlīš 㺠ñº º : Zºº,2/1,2 mºſº §§§s}|\NS 4, tº.…--º 'ſºft #º, S$ſº ex 㺠ſº 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 Pasto, Antioquia, Cundinamarca, and Caraccas. Farther south, the two chains of the Andes and the Cor- ſ?LATEA UN OF AMERICA AND AFRICA. 115 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 elevation 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 iº & tºs Qo : roº o? º TO 3.5° &go Sºon º 2 * * * - & So ºt § º * &e "sº § Fig. 25. Section of Africa from Cape de Verde to Tadjura. 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 116 - 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 distribution 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. 117 CHAPTER, XIX. ISOLATED MoUNTAINS.—MOUNTAINS IN GROUPS.–CHAINS AND SYSTEMS OF MOUNTAINS.—THE BEAUTY OF MOUNTAIN PIEAKS.–SACRED 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” (Höllenberg). 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” (Himmelberg): 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 I18. 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- momena 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 offect of transparency, as if the enormous mass were but a rosy-col- ored drapery floating lightly in the clear sky. SACRED MOUNTAINS.–CLUBS. 119 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 popées 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 pftiest 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- * Wide Mountaineering, by Tyndall, and the various publications of the Alpine Clubs. 120 THE EARTEI. 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 mountains 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 epopée 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 cmployés in uniform. On alighting, he regains the use of his limbs and his liberty. IIis eye cnables 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 escahade 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 ci- ther chance to lose his balance, or allow a sensation of gidºliness to dim his sight, even for an instant, or should his limbs refuse their wonted serv- ico. 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 knec-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 TIIſ; 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 ſading 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 mind 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 massos 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. IIe 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 facilitics 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 TIIE JEARTET. CHAPTER, XX. VARIOUS FORMS OF MOUNTAINS. — POVERTY OF POLISHED LANGUAGES IN DESCRIBING THEIR APIPEARANCE.-RICHNESS IN THIS RESPECT OF THIE SPANISH LANGUAGE AND TIII. ALPINE AND IPYRIENIEAN PATOIS.—THE NU- MICROUS PROVINCIAL TERMS EMPLOYED FOR VARIOUS SIIAIPES OF IIILLS 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, picacho, mogote, cucurucho, espigon, loma, tendida, mesa, panecillo, farallon, tablon, peña, peñon, peñasco, peñoleria, roca partida, laja, cerro, Sierra, Serrania, cordillera, monte, montaña, montañuela, altos, malpais, reventa2007, buſa, etc.—all of which serve to designate the diverse forms of mountains, or THE FORMS OF MOUNTAINS. 123 chains of mountains. It would be easy to still further enlarge this long list of names. º 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 IRhone 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 Orºc or bree. 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. Rºsº §§ §h 2-ºxº~~SN §§§ * `, sº º º “º * , Šºš § *. tº §§ §§ Sº --- ºº: ty º º §§§ gº 4-º • . . . -->Jºººº - ... &; 2." * . * . .xº~ ** * * *. Fig. 20. “Bric,” or Crest, of Monte Viso, seen from the East; after Tuckett. Of this kind, too, is the Viso itself, at least on its northern face, for the other side of the mountain presents too regular a slope to entitle it to the name of bric. 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 bric 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 Pelvas, the Pelvo, and several other mountains in Dauphiné, at once depicted to the mind's eye an enormous cone commanding all the neighboring sum- mits. - The twcs and trucs 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, Montarqué, and Mauberme, in the Central Pyrenees. The tugue, the truque, the tusse, and the tausse, all specify mountains with wider bases and more gentle slopes than those of the twc ; 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 Pyrences. 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 Truc de la Tºuque. 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 du Vignemale (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 Peña foratata ſº 'I Col. de Pombº. º ºº 3. ..' ... * 8 % {} gº º tº ..!. W. 3' yº §: º Q *::::A; tº \\ – ::\Sº º - % - F. . . . . * * | - ? Fig. 27. The Pic du Midi d'Ossau, seen from the northeast; after W. Potit, tº * Coaz, Alpenclub, vol. ii. THE FORMS OF MOUNTAINS. 125 summit; but the transitions presented by the mountain outlines 3.1°C 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, que/res, esquerras, or quałrats 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 sº º z % º º º SN ºrm º g **ś ~~~ sºsº Slºr sº->~~~~ •º **- * . Fig. 28. Einshorn de Splugen; 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- Iar 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 murailles (ram- parts). - Tower-like peaks of comparatively smaller dimensions, which appear as if they were edifices built on the mountain-tops, have received in the Pyr- enees the name of pène, or bougm. The tâte (head) is a summit with regu- lar and gently inclined terminal slopes, springing up from a mass furnished with steeper sides. If the roundness of the summit is developed in the form of a cupola, the mountain is then a soum (summit), or a dome, 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 Kulm. In the Vosges the ballons, and in the Black Forest the boelchen, 126 -> THE EARTH, S : Nº...: &z •l \ ºº. º N. ** . º º, \ º, sº tº Nº §2. * % jº º, ºx º § ſº "ſh # ſº hº 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. gºš ..º à ſº £º - % N § zº º: 3 º º, sº 2% ºf § 2. §§ ºſ--" eleº *\ zºº º º º } •. º º 2 º' Wººd L^ º £3% w ºz. º 2 *** .” ... • 24.3% ºftºffº Zºº” .' " sº % ºf § Coldo Tºrto, ºf ſº ** f . º ºf ſ. ſ - º fº 23&º flº * * É º ºf FY ºff 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 Serrère , it is the Spanish Sierra in miniature. *rº Cylindro de Marboró 2–~~~º 3.322 2,258 brèche deBoland - laruºſºde à Taillon Tourt dºbors C ~~~T 3% s de Marboré …—ºſº/ā ** º §ºs lº. 'Ad Ž sº *: Tº 2 ü gº ºt *; tºº - º - > %; ' 'º º É i. Rºwi ºr. * º §: ſº *-*— 22 A::P iji * =º, º ~\\ Cirque. ~z de Gavarnie Fig. 31. The Mountains of Gavarnie, seen from the north; after W. Petit. NAMES OF MOUNTAIN PEAKS. 127 A motte (muotta in the Grisons) 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 Lauzières mountains are composed of slaty rocks, and in the Pyrenees the numerous peaks called estibère, or pradºre, are completely clothed with verdure. The words puy, puig, pey, pech, or puch, 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 colline (hill), are taken in quite a different acceptation in the idioms of the Fig. 32. Pène: Piz à Lun de Guscha; after Coaz. inhabitants of the Pyrenees and Alps. “Montagne” 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 \\ º AW º § S. \ : fºsº -* ,” Fig. 33. Tête: 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- * Wide the chapter on “Volcanoes.” {} 128 THE EARTH, ed like a cupola, like the Puy de Dôme, or pierced with a crater 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 XXI. INEQUALITIES AND DEPRESSIONS IN THE VERTICAL OUTLINE OF MOUNTAINS. —or 1GIN OF VALLEYs, GoRGES, AND OTHER DEPRESSIONS.–LONGITUDI- NAL vALLEYS.—TRANSVERSE WALLEYS.–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 well 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 Alivergne, the Jura Moun- tains, the Rauhe Alp in Würtemberg, 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 are 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 IIaast 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 ORIGINT OF WALLEYS. 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 ISuffon 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 26°40' $3% % §§ §§ § w ºv; à \\ i. |\ N }}|{{ SºS YºYXNº. º % |º § Sºº-ºº: º º §:BE: - º * * Fig. 34. Channel of the Bosphorus. * Vide the chapters devoted to “Rivers” and “Volcanoes.” f Wide the chapter on “Rivers.” 132 THE EAIRTH. 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 irregularitics 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 cating 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 filled 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 Pyrences, and in the Alps the lofty valley of Isère, in which old lake-basins and gloomy gorges alternate with great regularity. f 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 War and its water-courses are very rich in defiles of this kind—enormous incisions carried right through the thickness of the lime- * Wide the chapters devoted to “Rivers” and “Lakes.” CLUSES AND CANONS. 133 stone ramparts. Among these clus there are some 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 War and 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 caſions 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 caſion 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 6000 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, where the torrents run through a se- ries of basins one above the other, and communicate by means of claſses, 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 supporters 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 134 THE EARTH, of its dales and glens, which, too, 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- º §§ %mº §ººl ºff / % jº. tºº º º. 3 \ §§ \ \ | §§ § * §: § § *...'", § N ſº {\ f §§ º \ •v º %|º º / §§§ §§ §§ : § | sº sº % Nº |\l Xºlºſſº Wºº. . .” - S --> * Nº # § º º º º § º º ſº. Sº §ººftº % ºf 㺠S(\;=#|\}\}'}\%\}\}'}\}\}. sº§§§§§ "N sº sº º % ºf º § - §§§§ºğNº. %\Nºš § §§ - º % NWhº'NW// \ J *ś%%iſ sºft|\Nºæſſ. º º S3% Rºž .3 㺠º #º % §§§§§§§§ §ſ º Nſ. wº sº sº §º ºš - $WNi ffºr % § f º §§ SNS y \\ º \ §§§ º - º ºff - §§§ §§§ sº § §§ j & §§ º żº §§§ §§ º N § M(II) § sº § l § |W \\ N º ºº º Zº - Ø º §§ |Š § §§ º º: º | %š § §§ % § § % º §§ - § \ - ſ §§ 2%|{\ Ş §§ º wº Nº. ſº ſº s § # - §§§ w º ºft|\º: §§ §§§§ %3&tº sº If \"\\ º º S. Sº §§ N § º Š º ſºº sºº º à |\ tº " †N} \º º #! § º § §º º : º º N - §§§ §§§ fº Fig. 35. Circular Valley of Ourdinse. 32 sº 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, Estaubé, and Troumouse, which the slow action of centuries has hollowed out in the calcareous sides of the mountains of Marboré. 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. 2) EPRESSIONS IN MOUNTAIN RIDGES. 135 CHAPTER XXII. OEPRESSIONS IN MOUNTAIN RIDGES.—DIVIERSITY IN THE FORM OF PASSES (COLs).-RELATION IBETWEEN TIIIE RESPECTIVE ALTITUDES OF SUMMITS AND PASSIES. —IAW OF DEBOUCHIMENTS. IRIZAL 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 Illa,SS. 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 l; 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 Société de Géographie, 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- wated 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 depression of the ridge. The comparative studies which have been made by various geographers, 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 99.80 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 Ivrée, 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, tº various continents, has endeavored to estimate the cubical mass of sev- eral great mountain chains. 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 21% feet. 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. 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 Otté's translation of Humboldt's Cosmos, vol. i., p. 305, it is given as 115 feet.—ED. f Cosmos, Faye's translation, vol. i., p. 353. † Sonklar, CEtzthaler Gebirgsgruppe. IAW OF MOUNTAIN CHArys 139 CHAPTER XXIII. HYPOTHESES As To THE GENERAL LAWS OF MOUNTAIN CHAINS.—M. ELIE DE, BEAUMONT's THEORY OF PARALLEL UPHEAVALS.–CHAIN OF THE PYRE- NEES TAICEN AS A TYPE OF THE CORDILLERAS OR LONGITUDINAL CHAIN. —VARIOUS IRREGULARITIES IN THE CHAIN.—THE PYRENEES As AN ETH- INOLOGICAL BARIRIER. 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 Cévennes, 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 éarth'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. * Wide above, p. 52. º \ 140 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 necessarily 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 Vosges 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. º Fº 2, ſº § 2 ** - - º ". * . . . . . . . - - sº * - ‘...." º' - *: ſº Wºlfº %.º.º. - sº - -, *::: f * $ º § ſ * * *::s : * ºfºº Yº §§ - : ºr ** { º ºº: **-*::F. hºws.º. *. * ºº: * - 3 || || 3: - * * ~ S.$.".º. ºº -> º ... ** * * * * tº º º ºg .*.*.* º * *...* iſ tº §: º, J2 º' ºr ºf 4 tº: - E. -- - - - - ... º.º. **…* : ***** - Q *.*.*.x.y. 3, , ſº º, ºr, ºf º; sº º, R. l ſº . - ºf , .ºg * : Y. gº º( : º ~ º Yū . § º º ... º. º. sº º A sº ****t º º ºg º Q * 'º d Čkºº, º Sº sº Mººg. Æ { º A. --> : tº is - - º º º § {ſº bºº §§§§ sº s - w *3% ſ º Ž º, Yº! ; g ! º º º … 3 gº . § *...* E - º º % º 3. º 3. tº & 2 • ** Fig. 36. The Pyrenees. The portion or 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 of the ridge will prove that at sev- eral points it departs from the typical form. 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 Alböres; 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, a §. §: | | * **** a. * $º ºilº **; A 23 iſ: **- ſº * * iñº * * # § j; Sºft \S.ºss *** *** *-*. - ^^xº~ * 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 speaking it 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 clevated 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 the agents 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 thé 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 Néouvielle, 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 Pau, and the Maladetta—are not very numerous. In consequence of the simplicity of configuration which prevails in the Fig. 3S. The Sierra de Marcadau, 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, not far from Bayonne, a distance of more than 180 miles, the chain of the Pyre- nees is not crossed by any carriage-road. * Humboldt. 144 THE EARTH, 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 GIROUP OF ST. GOTHARD. –GIROUPS OF MONTE ROSA AND MONT BLANC. -TIIIE 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 Carmic 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 AEgean. 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, Herzogovina, 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. l 3. º { \,; I WT's “ º * “, Q. º tº - º NZ - Šºć"N . | º - ºğ ſh:S {{*; * : T !ſ { \ Wº kº gº.); Băieşº *Q/º à §§ º “(y” -, ºº: º tw: - t - - •. º: & Yeº : \; ‘. t jºtº, i. *. ** º %, * * Aft 3. *g, *y- - - , ºf º *::: {\ 's SJSºº- § W S ' f : . s . Sºr * >...." - -tº 2% & X. & h •. sº ºn.'…??-wº gº.º.e , zºº WLKºl, Q sº & Ayºu’l: *Wºno,...,tº * ** *ws ź wrºſº , *. tºº.º.º. ººº-ººººº ſº c &º > …º.2% º 1SN §§ - º ... * * * ,”)? --- : { :** * |- 's j ; Fig. 39. The Jura. The European Jura occupies a very considerable area in the middle of the continent, from the banks of the Drôme 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 Mòle 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- JK 146 TEIE EARTII. lel 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- barts, 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 cluscs 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- stein 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 cast 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 muclei 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 ſiſty distinct groups. This entirely geological division harmonizes in general with the results of a more study of the vertical outline and direc- tion of the ridges; but the number of groups must be gonsiderably re- duced iſ those which are linked to one another by continuous ridges of great clevation are looked upon as forming parts of the same chain. The central mass, which is also the most important 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 I&hine, the Tessin, the IRhone, the Aar, and the IReuss; it is the knot or focus where the conver- gent ridges of the surrounding groups unite like radiº. On the northeast stands the group of Todi; on the cast, that of Theinwald ; on the west and south, the much more considerable clusters of the Finsteraarhorn and Monte IRosa. The latter group is linked on to Mont Blanc, rising more to TIIE JUIRA AND TIME ALI’S. 147 30 ń. // | § f \ A º º :* § { * tº, . º *- º yº d 22 tººlſ. %; ſ § º §§§ tº & º § W º §§ ºSt. % §§ | Øſ º ſº . ſº §§§ Exº ſº . º § sº º §º sº º §§§ sº ſ *. º Fº N &|ºğ §§§ sº. tºº • * * º º º ºś SºğyAN& º * sº . . . . Ø § - tº: §§ Nº § * & § º § M. 3S ... • Ş. ****): Jº, º w sº . •º º f º/ºšŠ § lºss. - º sa.gº . - §: * ; §§ §§ ºğ .* ºlº 3% §§§ § §§ wº §§§º - f W. § § % ºššº sº ºxwº : §§ §: ºr a .# º t 3. ſº § i º ãº. - - .* §§ .* º 4 gº 3° to §§§ º # §§ § sº º: ſº \ § & 2. §§§2. ** º §§.St. §§ §§ § s'. $ º N à. WNº. Hiſ liſti, º, X', 'NN'``N.: My S. Sºº º/ºr Jºžº T ; : W. T.T.T.ſº sº §§§ § § §º ñº; ºść Šºš § ºšº * , , §§§ ºft.*.N ºSS. Tº gº ºyº w ,\ ^'''I'', & NNW § § *z, *, *, *. º "...º.º.º. º º * f *, * : || QNº $º º - & ×3. º º § s $ ºt. º tºº, º sº, sº Mºš 3. 3. - º º Yº...sº $º * § §§tº: if "A.” ºšš º' W. j ſ' ºº g W . %; § i. º h *::º 3.x. 3 ºr ºš Š Asºº % KNS § §§ ; * §: § - * - %3a, §§§ §::A; 2 * * :33%;\º º - - - A*... .". Tº ºš. ſº SY} 3. º % | ‘ī §. §§ * º |ſº º § sº º * t Mºść. Žºº &º $º *AW', Zºº "º */ $n #. lſ * N £ºğ : A ‘i’s § :*::: A wº-ºº::yº. .. § & §:/º d * * **** * ºf: ºf , . . . . §§ §§ § N, tº . . . . . --- - . . . “. . § º * * * * , f § d º”. % ºs %. º Fig. 40. Valleys, Cluscs, and Combes of the Jura. 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 in- 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. round to the south, which is crossed by the Mont Cenis road ; the ing ridges of these chains go on to join the groups of the Grandes ses and Belledonne on the West, that of the Grand Pelvoux on the west, and that of Monte Viso toward the south. A real chain bends wind- Rous- south- The pyramid of Monto Viso is the magnificent boundary-stone which marks out the line of do- 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 fect. 13cyond 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 and Mentone, a small granite group rises to a height of more 148 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 Säntis; 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 Thine, 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- THE ALPS º- º º º º º . al º º º - º . - d | º/ - º º º º ººº º - º ... - º º - º º --- %."º º Drawn by A Wuillemin. 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 # 2% * . # # - A º : % outh 0 1 2 3 4 miles. {-1–1–1–1–1–1–1–––. 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 Viége 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 Allobroges, 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 Maurienne, Queyras, and Durance. Besides, as Ami Boué, 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 IIuber, Bulletin de la Société de Géographie, February, March, 1866. 150 THE EA RTH. 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 d'oeuvre 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. A- MOUNTAINS OF CENTRAL ASIA. 151 CHAPTER XXV. MoUNTAIN CHAINS OF CENTRAL ASIA.—THE KOUEN-LUN, THE KARAKORUM, THE HIMALAYA.—THE SOUTH AMERICAN ANDES, A TYPE OF THE BIFUR- CATED CHAIN. TIIE chains of the Himalaya, the Karakorum, and the Rouen-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. In 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 the valley of Cashmere, which the Oriental posts celebrate as the “abode of happi- mess;” 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. g - s * Frères Schlagintweit, Mittheilungen von Petermann. 152 THE EARTH. † 72 r ſ *A reºs **'.//, §§§º º , ºf "zºº D **NWºº % º 3% º § § # § º % - t § wº .… ... - º º % * * p §§º ğ.3% § The height, are ºftee. * & Nº.3% %3% § & | W §§ E. º r % º ſ º: ź%%jº 3 : 321 º % § | % º #º & %/º ſ/fººl % %; § % *****, º 2/hiſ º S lº ſº | r % § % % N SSº W | ºf ºğ § § ºn." Ng §§ §. W WS º º A. ſº §|\{!!}} B §ºl/#| 2%|\º §§§ § #|ſº %; § §º Zºr- \\ ſº {\% : § W \S$ *... ---, --- ... º. - ſº § A. SWh/.4 _/º §§§ w \; \ § ; §º % | ſº Wº. %iºš *º sº ſº §§§º i. sº| % º % % s º § } % º §ºſºft\!\! º %% ºft Rºž)}|{\| < Scsº sº sº \| ſº %iº º ſº% º NS: #/. Nº. §D \ W º #º {} % Nº. \\ § \ ޺ M º §ft. ^*- */º W w º % § = < * , | 7. % §§§ §§§ sº ºftº # #: . %." SWº º ſº º $º 㺠W §§§)\! º, º º % § *º §§ §.3% º W % * § - % ń. - | }\ | N Š : st-º % ſº :- 㺠% # ſº ..º w % º º º | SS VS º, *.. yº. ^n 2% łºść. ºb Nº 2 3 - • sº §§ §§3%\ % wº ºğ §§ º W § ** Tºrº § º § N wº, § |: sº ºš º *Iº wº º: º ; - # %. 3% 㺠- £ - ſº | - §ººl ºś % Wºźſº %). 2. * W. º * . - ë. % %Nº | • . #} Bººtſ, % º wº §º § º: § Sº % Ø º % %26; .**** * '''', * “lº, **** - º - º * y Ž. - º * Nº 3% tº: - º º- º: - ź 2 ić |Aiºi, àº'à%% jºš Şāś sº }}| | f \ #}}º, º gº ºS$ % % º º àſº 33% A £2 * 㺠\% º º, º º ºf %: É' ** * * * , * iº ſ N º % § º, %X&/º: º sº3WAW'º ‘’Fºº º 2. Sº º- 㺠". ! : ". ; ~ § j ſº ...,\ ...º.º." - $. º - &º. Auſt º 33 *Wyº Q º $ºs, #ſº º ºt. Ø º %], *.ſº | * \2? t " *%.º —a 72 . 73 I'ig. 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 even 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- raï, 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 postilence. 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 hun- THE HIMALAYAS.–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 (28,297 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 Rinchinjinga, 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 aërial 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 chálets 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- cries 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, loss regular than it appears at first sight. The principal characteristic which * IIooker, 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 Dolivia, 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- ors, inclosing between them the deep valley of the Marañon, 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 IPasto 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 AWDES. 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 Puracé, Huila, Tolima, and Herved, 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 EARTEI. CHAPTER XXVI. GRADUAL COOLING OF THE AIR ON MOUNTAIN SIDES.—DIFFICULTY OF AS- CENTS. – LIMITS OF MAN's HABITATION.—ILLNESS FELT IBY 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; 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. Thanks to this progressive dimi- nution of temperature in the aërial 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 ačrial currents of va. rious temperatures lie one above the other in the heights of the atmos. * Wide the chapter on “The Earth and its Flora.” # Ch. Martins. IIelmholz, La Glace et les Glaciers. f Tyndall, The Glaciers of the Alps. LIMITS OF MAN'S HARITATION. 157 phere, 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 surface 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 61.97 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. None of the villages of the Andes, except perhaps that of Santa-Anna, in Bolivia, have been built at so great a height. Š * Zurcher, Annuaire Scientifique, 1864. f Helmholz, La Glace et les Glaciers. f Robert de Schlagintweit, Mittheilungen von Petermann, 1865. § Reck, Geographisches Jahrbuk von Behm. 158 THE EARTII. 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 puma 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, omamations 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 Schlagintweití 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 clevation on the slopes of the Cordilleras than on those of the IIimalaya. 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 IIimalaya, are added giddiness, sometimes fainting-fits, and bleed- ing from lips, gums, and eyelids. At the same clevation 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 aërial 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. * Ascension du Pichincha, Nouvelles Annales des Voyages, etc., February, 1865. f Zeitschr, fir Erdkunde, 1866. f Iſumboldt, Poeppig, Moritz Wagner, I’hilippi. subsidency of MoUNTAINS 159 CHAPTER XXVII. GRADUAL SUBSIDENCE OF MOUNTAINS DUIRING TIII. IAPSE 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 offect 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 débris 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 inhabitants 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—from Morges 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.” a 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 Chambéry, 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 débris, 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 débris 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 Dent 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 1806 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 Société 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 Vallée d'Or), and four villages, inhab- ited by nearly a thousand persons, disappeared under the heaps of débris; 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.” Yººl ºW § & º Uğyº º §§ \º Sºº - - § *Nº. º §§§N | jgºšN - §§§ ºu, t - º: tº } 㺠§§ § J '''S' ſº § W. § Mºs: - º, ". ºs. º * a y [* * * W . Nº § \ Š Žº §§ t; º sº º º &Nº. § Šºššº w ğ% º § § ğ sº 5%; tº 2…nº §§ º tº: t &" jº Ž. w - 2 ſº º ſº § § ºfº s jº º - s º źsº º: #: º º > * sº - - º ſº - s - g - -- - ... rºtarº $% º \ ŽišNú º -: § † Jº § º; ("Zºº º º ºlºſ/ º §º §§§ ſºft §ºś º § º N ºrs tº º º º º Nº. hº º §§ ºt Rºš º % % -- | Hºus ſ %% ºft|{\|iff * #º sº º º W ºº % §º. 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, Otto Volger, Erdbeben der Schweiz. L - PART III. THE CIRCULATION OF WATER. CHAPTER XXVIII. SNOW-FALL ON MOUNTAINS.–LowRR LIMIT OF SNow. —zoNE of PERPET. UAL OR IPERMAN ENT 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 all 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, SNO W.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 114 feet to 444 every year. This would give a difference of one and four in a yearly snow-fall on the same point of the mountain. 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 64 feet. 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 * Humboldt, Tyndall. - t Bibliothèque de Genève. f Eugène Flachat, La Traversée des Alpes. 164 THE EA RTH. 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 namg 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. 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. Similarly, in the autumn of 1859, the summit of the Cha- berton (10,295 feet), near Mont Genèvre, 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 Orizaba. 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 maturally falls much lower than in the corresponding regions of Ecuador, the mean limit of Snow is actually higher; which, no 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 Eccursions. # Dollfuss-Aussett, Matériaux pour l’Etude des Glaciers, Vol. v. f OEtzthaler Gebirgsgruppe. LIMIT OF PERMANEWT, SAWOW. 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 Famatina (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 s i i | i i: fº: i i i j i i S582 yº Fig. 44. Limit of Permanepºt 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, Confédération Argentine, vol. i. 166 THE EAJRTEI. to the burning sum 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 aërial 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 Nepaul 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- * Wide the chapter on “Climates.” a. TVARIATION IN THE SAVO W. LIVE!. 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. - 168 THE EARTH, 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 frôm 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 fêhn 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 SWOWS. 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 débris. 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 dr 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 Wengernalp, 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 EARTH, 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 débris, 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 chálets 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 A VALANCHES. 171 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 intermingked 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 Bannwgelder. 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 clower l’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.* w * William Huber, Les Glaciers. 172 THE EARTII. The village and the great establishment of the baths at Baróges, in the Pyrenecs, 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 Baréges, so as to allow a free passage to the descending masses. Tately, 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 protection 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 Baréges sometimes attained to more than 90,000 yards in volume. º - CIIANGIE OF SNOW INTO IOE. 173 CIIAPTER XXX. GRADUAL TRANSTORMATION OF SNOW INTO ICE.-Níðvíºs, OIR GLACIEIR-ICES- ERVOII&S.—IPIIISNOMENON OF I&EGISLATION.—CRYSTALS OF I.C.E.-GLACIERS OF THIS ITIRST AND SECONI) 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 mévé, and then into gla- cier; afterward becoming in succession stream, river, and wave, it finally, under the form of aqueous vapor, recommences its cternal 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 hard, and on the edge of many of the 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- iš) * § | field changes its structure and becomes a mass {\ - of granules, from which the air is partially ex- pelled by the successive freezing and melting 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 névés. 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, Nouvelles Eccursions et Séjours dans les Glaciers. Tig. 45. Cornice of Snow. A 174 - 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 névé, 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 névé 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 névé becomes more and more indurated and compact. A cubic yard of snow weighs on the average 187 lbs. ; but the same volume of névé weighs more than half a ton, and the various modifications to which the snow is subject in becoming transparent ice ultimately give it a weight of about 1980 lbs. 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 névé 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 mévé, 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 ºvévé; for wherever the rocks rise above the upper snow-limit a kind of cleft may be noticed in the névé, 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. - - I3elow the névé, 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 IIuber, Les Glaciers. - # Dollfuss-Ausset, Matériaur pour servir à l'Etude des Glaciers. FORMATION OF GLACTERS. 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 f 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 regelation. 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 water of about 32 feet. 176 - THE EA RTH. the clefts on the surface of the glaciers are filled up with fresh masses of snow. These nºw layers, to which an intermixture of air-bubbles gives a whitish tint, àre 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 névé and glacier are intermingled together. In climbing Monte Rosa, Zumstein saw, down in a crevasse of névé, 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 77606, 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 reared 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 XXXI. MOVEMENT 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 1836 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 * Comptes Rendus de l'Académie 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. - º To what cause, therefore, are w&o attribute this gradual descent of the river of ice in its rocky bed 2 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 0600 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 névé 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 névé. 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- * Somklar, CEtzthaler Gebirgsgruppe. TH E M E R DE GLACE & | TS AFF LU E N T S Pl. X1 S ºz - ，s $ ( $ · Il， | | | º ! ſ . · SW . l - $ \ V $ \ : S | $ $\ \ $ $ | ºo N$ \ \N $ - « \ N 4 |4oº - - Engº by Erhard, alter the Map ot M Mieulet * GLACIERS' 60WWExITY. 179 perature, however, makes itself felt in the progress of the glacier, and al- though experiments do not all agree on this point, it is probable that at sunset the glacier slackens its course, and accelerates it again when the luminary reappears above the ridges of the mountains; in the depths, as on the surface, the sun imparts life and animation. As soon as the early Fays of day-break have lighted up the glacier, its very nature seems altered. Just as in the adjoining forest, the field of ice is harmonious with a thou- sand small yet joyous sounds; the little drops, falling on the projections in the crevasses, tinkle as they are broken up; the gradually-forming riv- ulet murmurs on its way; the slopes of gravel crumble down into the crevasses; and here and there some block, uncemented from its icy ped- estal, roars as it rolls down the incline. All these voices of the glacier gain strength as the sun gets higher in the horizon: but if a thick cloud suddenly interrupts the solar rays, silence is gradually re-established, and the glacier waits for the return of the sun ere it resumes its song. The enormous ice-river seems endowed with vitality; so much so that some enthusiastic Savants, as Hugi, have seriously asked the question—whether the monster did not possess a soul? Numbers of mountaineers, in all their simplicity of mind, fully believe it.* Just as in liquid rivers, a raising up of the central portion of the glacier corresponds in general to the highest rate of speed in the moving mass. The convexity of the surface of the icy stream must not be attributed to an afflux of the whole body toward the middle; the cause is, perhaps, the fact that the central parts, being animated by a more rapid motion, have not had sufficient time to evaporate and melt in as large quantities as those at the sides, which are slower in their progress, and more intersect- ed with crevasses. Sometimes, however, it is the case that the glacier ex- hibits an exactly contrary outline, and is hollowed out like a gutter in the central part. This happens when immense moraines cover a broad surface of the ice on each side, and hinder their melting. An instance of this fact is to be found in the glacier of Vernagt, in the CEtzthal.f Not only does the river of ice act exactly like a liquid water-course by its waves rolling on with much more rapidity in the central portion than at the edges, but, similarly to all other rivers, it assumes the greater amount of force in its current at the convex side of its successive wind- ings. Theory would have beforehand presumed this fact, which, however, the experiments of Tyndall in 1857 have indubitably established. His measurements, very carefully made across the various curves of the Mer- de-Glace, have proved that the thread of the current shifts its position al- ternately to the right and left of the medial line, and approaches each of the sides in turn, sometimes one, sometimes the other. Thus the axis of movement follows an undulating line, the windings of which are more de- cided even than those of the gorge of the glacier. The ideal progress of the frozen river is represented by the illustration on the following page, which would apply equally to the current of a liquid river. * De Charpentier, Essai sur les Glaciers. f Wide inserted Plate, XIV. 180 THI}{EARTH, # º Yºº gº §§ a …º.º. , * * º º jºy Jº .* - 35% º \ § G %) º §§ º \ & $º § N, *. º *. Fig. 47. Windings of a Glacier. The same cause which impedes the motion of a glacier at the edges— that is, the friction of the sliding mass against the rocks—equally dimin- ishes the rapidity of its current along its bed. In this point, also, the ac- tion of a glacier is perfectly analogous to that of a river moving at a slow pace. Forbes and M. Martins have proved this on the Mer-de-Glace and the Faulhorn, by experiments which Tyndall has since renewed at the risk of his life. Descending the sides of a precipice 137 feet in depth, opening between the rocks and the glaciers of the Tacul (Mont Blanc), he succeeded in fixing three pegs at the summit, at the middle, and at the base of the vertical wall of ice, so that he should be able to measure their respective rates of progress two days afterward. The upper peg had advanced 5% inches in the twen- ty-four hours; the middle one, fixed 36 feet above the bottom, had only moved onward 4 inches in the same space of time; lastly, the lower mark, fixed more than a yard above the rocky bed of the gla- cier, had only progressed at the rate of 2% inches a day.” Added to this, in certain places the cascades of surface-water cut out ledges resembling steps in the sides of the crevasses, which, as it were, bring before the eye the superior rapidity of the upper layers of the ice. The water falls, in the first place, on some projection, which it hollows out in the shape of a basin; but, in consequence of the on- ward motion of the glacier, the liquid column soon gets beyond the first projection, and drops down & upon a second, and then upon a third ; it thus forms the succession of steps resulting from the rapid advance of the ridge of ice from which the cascade descends. A comparison of the experiments—alas ! too few—which have been made up to the present time with regard to the speed of various glaciers warrants us also in thinking that the advance of the current is acceler- ated in proportion to the declivity of the slope; only, as M. Desor points out, the volume of the matter in motion being by far the principal ele- * Tyndall, Glaciers of the Alps. Fig. 48. Cascade of Glacier. RATE OF MOTION OF GLACTIſ/S. 181 ment in the increase of speed of the whole mass the result is that small glaciers at a very steep slope descend more slowly than larger ice-rivers on a slight decliwity. º Thus the advance of a glacier presents very considerable differences in the rate of progress, according to the importance of the total maSS in width and depth, its proximity either to the edges or the bottom, the winding of the sides, the degree of slope, the expansions and contractions of its bed of rocks, the state of the temperature, and the various seasons of the year. It is, therefore, impossible to estimate the mean rate of speed of a river of ice by taking as our basis a series of isolated observa- tions; we must, on the contrary, study the movement of the ice in every part of its bed, take account of every cause of acceleration and delay, and, if we may so speak, gauge the glacier as we should gauge a river of run- ning water. The movement of the ice, like that of rivers, takes place over slopes of 3f; wzºº-ºº:iif # Tig. 40. Slope of the Mer-dc-Glace. the most varied character. The Mer-de-Glace, at Chamounix, is inclined on the average 5 or 6 degrees, but at many points in its course it presents a much more considerable declivity. Some glaciers, half suspended on the mountain sides, have an inclination of 25, 30, and even 50 degrees, and yet it is but seldom that the masses lying on these formidable slopes take to sliding on their bases so as to fall down like avalanches into the val- ley beneath.* They descend gradually and slowly, like other glaciers which are almost horizontal in appearance, and run down gorges the slope of which does not attain to 3 degrees. The immense glacier of Aletsch is inclined only 4 degrees; those of the CEtzthal, on the average, 5 or 6 degrees; those of Monte Rosa and the northern sides of the Fin- steraarhorn group are much more sloping, and incline 10, 15, and 20 de- grees, or, as the upper glacier of Grindelwald, as much as 27 degrees. * De Charpentier, Essai sur les Glaciers. 182 THE EARTH. - *: CHAPTER XXXII. MARGINAL, TRANSWERSAL, AND LONGITUDINAL CREVASSES.–SfRACS.—MOU- LINS.-BRIDGES OF SNOW.-VEINS OF FRESH ICE.-SURFACE-STREAMS ON GLACTERS.-GOUILLES.–LAKES AND INUNDATIONS.—DISCHARGING CHAN- NELS. - THE whole mass of the glacier does not advance in a perfectly continu- ous Way as a stream of water would do; the layers of ice could not fol- low all the windings of the gorge and adapt themselves to all the ine- qualities of the bottom without some extent of fracture. Thus fissures, or crevasses, are produced in the thickness of the apparently motionless riv- er, and sometimes give to the latter a most uneven surface. - Most of the crevasses in a glacier are found near the sides, and princi- pally at the convexity of the bends, on account of the inequality of ten- sion to which the layers of moving ice are liable at these spots. The lay- ers which are the closest to the bank are retarded by the fiction of the RNºNºssºs s\º a-B7 gº-º-º: eº-> º-sº - W . , V, *,x* **, *, * : Y \, \ . ** : '." Vx N\, { NS *RRSN's . . \\ §§§e ===S £3 ES-e:&=Nºs=N:ES Šeš Nº. =SE=S <=NESSESSES EN # S==SE=SESE=SEN=Sã º - |% |||}| | | § %| } º / / Sºn ºf % %| R} s r * “I., Fig. 50. Marginal Crevasses in a Glacier. \ rocks, while farther into the stream the rapidity of the current of ice in- Creases with its distance from the edge. This difference in the rate of Speed results in a greater tension of the mass in the direction of the move- ment, and in consequence the ice on the edge has to resist a tractile force, acting, as M.M. Sonklar and Hopkins have proved, in a line inclined 45 de- grees to the bank. Finally, the ice gives way to the power which draws it; it is rent open; and, as the laws of mechanics dictate, the marginal crevasses are produced perpendicularly to the force of traction. The prin- cipal force of the movement being exerted in the direction of a line tend- ing up stream at an angle of 45 degrees to the bank, the fissures in general form at a similar angle to the bank, and also tend up stream; they are CIRE WASSES IN GLA CIERS. 1S3 consequently transverse to the course of the current; therefore, at first sight of these clefts, we should be inclined to say that the glacier advanced with more rapidity near its edges; indeed almost all the first observers were deceived on this point. The marginal crevasses, however, do not retain their early inclination of 45 degrees to the bank of the glacier, the motion of the current being more rapid toward the centre than near the edges; the fissure turns round slowly, like the spoke of a wheel, and becomes less and less obliquely sloped toward the bank; sooner or later it becomes perpendicular to it, and then inclines gradually in the direction of the descent, describing a more and more acute angle. But while this first crevasse is thus bend: ing round in a down-stream direction, first one and then another marginal cleft may be produced in the ice, subjected as it is to the tractile force of the moving mass; and these planes of rupture are at first likewise inclined at an angle of 45 degrees in an up-stream direction, and afterward bend S-SSºśSSSSSSSSSSSS SSSSSSSS$ $$$$.” S$$$$$$$$$$$. § - ***- NS$$ QN §§ N i f//// fllºtſ tººlſ # A fi : y : ; S Wºllſ/; f///f j%| |fft|||ſiſ, |||}||||WII; : % ft | % % |||}}}/ % }}}}/ſºft ///, /// //// ºf 1/??// III] ſ ſ /// f /// - sº § 26, 'Z !!!///#!/////////% / / jº *\s |% º/, - e * ...; Z. Ž. Zº: g g 2.2%; Fig. 51. Intersecting Crevasses. 2. round in the direction of the current. This sometimes results in an inter- section of cracks, which transform the lateral portions of the glacier into a perfect labyrinth of crevasses, in which it becomes difficult to recognize the regular order of the successive phenomena.” The crevasses which are formed from bank to bank across the field of the glacier are caused principally by the inequalities of its bed. In places where the declivity becomes more abrupt, the ice, being unable to accommodate itself to this fresh slope, cracks right across, and by a series of fissures spreads out its surface to form an inclination similar to that of the bed which it covers; the clefts, it must be understood, are all the more numerous and wider as the fall is more sudden. - Below rapids and cataracts, rivers spread out into large and smooth sheets of water; a similar phenomenon takes place in glaciers below any very steep slopes. When they reach these more level beds, the masses which have been separated by the fissures again come close together, and - - * W. Huber, Les Glaciers. 184 THE EARTH, pressing one against the other, resume the uniformity of surface. If a second sudden fall of the bed gives a more rapid movement to the river of ice, it will a second time descend in a cascade of crevasses, which will become obliterated on the mass reaching some less important declivity. issº §§§ Fig. 52. Transverse Crevasses, seen in Profile. The lower glacier of Grindelwald presents a striking instance (first point- ed out by Tyndall) of this succession of crevasses and level fields of ice. From the tops of a headland a clear idea may be formed of the general aspect of the glacier, and of its alternately dislocated and compressed masses. The kind of semicircular curve which the transversal crevasse produces by uniting with the marginal fissures very often deceives the sight, and would lead us to believe that the force of the current was more especially exerted at the edges, if reason and experience did not teach us precisely the contrary. It must also be added that these cross crevasses are generally slightly curved in the direction of the motion. In a similar way to the transversal clefts, those which extend in a lon- gitudinal direction are likewise owing to the direction of the bed. In { Fig. 53. Transverse Crevasses, seen in Plan. every part of the bed of the stream where the longitudinal risings, similar to the shallows of a river, force the ice to bend over laterally both right and left, the latter must form parallel crevasses, and these fissures can not CREVASSES IN GLACTERS. 185 close up until they have descended below the obstacle. Added to this, there are often abrupt rises and falls in the bed which are so constituted as to cause the simultaneous rupture of the ice in both a longitudinal and transverse direction, and, consequently, the field of ice is traversed by crevasses which are semicircular or bent round in various directions. In this way the appearance of the surface often reveals the irregularities of the bed. Lastly, glaciers also exhibit radiated crevasses, especially at their ex- tremities, when the base extends widely into the lower gorges. The pressure of the masses descending from the mountain heights compels the ſ:= £2. o: …” 222 ve:-- z 4. g: % *Sºs- % ***SE: 2 ºšš % 2 *Ss % * . NFS % *S.S % ... o. Sºº- *A • ‘S$ | % % * S; % ^, Ašš %3. *Z $SE %. S$$. Uſ? .S$ £, SS$ %. f SS % * FSSS: 2% • Sºsº |% * * * *--- \\ * : * > % - ... 6 S->- % Ž t 4 -º-º-º: e SS %2% SS % S$. % NS % Fig. 54. Longitudinal CrevaSSes, seen in Plan. ice down below to spread out laterally, and, in consequence, over the Wnole slope of the glacier there is a formation of radiating crevasses, sometimes exhibiting the regular arrangement of the ribs of a fan. According to various slopes and the inequalities in its bed, the ice presents the very greatest diversity in its lines of fracture. These clefts form a perfect lab- yrinth on the surface of all glaciers which possess numerous tributaries, and move along a winding and occasionally contracted bed. Any one who happens to be on a glacier at a time when a crevasse is =º: :#=< §§§§§ I'ig. 55. Longitudinal Crevasses, seen in Profile. developed can not possibly resist a certain feeling of dread. strous river suddenly takes to cracking and groaning; dull reports, caused by sudden ruptures, are every moment heard in the interior of the mass; and a prolonged whistling sound, like that made by glass when slit by a diamond, announces the gradual increase of the cleft. all the voices of the glacier are hushed, it is sometimes quite in vain that we seek for the crack, on account of its extreme fineness. widens very slowly, and it takes days, and sometimes even weeks, before º The mon- Nevertheless, when The crevasse 186 . TEIE EARTH, it becomes one of those formidable chasms which gash the surface of the glacier. - When the crevasses have arrived at their full development, they exhibit a most striking spectacle. The two bluish walls sink down into dark- ness which is unfathomable by the eye; stones, falling from the surface, bound over the projections, and awaken dull echoes as they are lost in the obscurity; a vague murmur of running water ascends from the depths; and sometimes sharp gusts of cold and biting air issue out from the mouth of the abyss. While leaning over the brink of the gaping chasm one feels a kind of dread, as if the noises and darkness of the gulf beneath belonged to some new world, full of mystery and horror. - Fig. 56. Frontal or Terminal Crevasses—after Tyndall. When the crevasses are numerous, and intersect one another in various directions, it often happens that masses which are thus isolated, and are also of a more compact nature, resist for a longer period the action of the sun and wind. In consequence of all these inequalities, and, doubtless, also on account of the difference in pressure operating at the base, the ice, in some spots, assumes the most picturesque and fantastic shapes. Some- times these blocks resemble knights clad in their armor, sometimes strange animals, broken statues, pointed clock-turrets, or ruined colon- nades. Tourists ask with astonishment how it is that nature, by nothing but the slow operations of the forces of gravity and pressure, the winds, and solar rays, is able to carve out the ice into groups so remarkable both for their regularity and grotesqueness. The tower-shaped forms which crown some of the abrupt falls of the glaciers have received from the Swiss mountaineers the name of séraes; a term which reminds one of the sérets—cheeses which split up into small cubical pieces. In the lower portion of the glacier surface the walls and pillars, which are divided from one another by fissures, seldom show perpendicular sides. Their faces which are turned toward the south become wasted and Worn away, and thus assume the appearance of enormous congealed Waves. When the great river has this furrowed surface, it really becomes a “sea of ice.” Owing to the more rapid motion of the upper layers, it general- ly happens that the ice-waves present their steepest face in a downward FEATURES IN GLA CIERS. 187 direction, and are less abrupt looking upward; when this latter side is also that which fronts the south, it ultimately becomes a more or less inclined slope. - In some places the fields of ice are also hollowed out into perpendicular wells, known under the name of moulins (mills), on account of the roar- ing noise of the water which is ingulfed in them. The formation of these abysses may be very simply explained. The drops of water melting on the surface combine into slender rivulets, which form tributaries of a more considerable stream, which winds along its bed of ice. When this surface-stream finds in its path some gaping crevasse, it sinks into it, and immediately disappears in the depths below; but it often meets with some crack crossing the field of ice which is almost invisible. The water makes its way into this crack like a blade of steel, and, gradually widen- ing it, is swallowed up between the separated sides of the crevice. Soon the incessant labor of the water succeeds in hollowing out a complete well, which sinks down to the stream hidden under the glacier. This moulin shifts its position with the whole mass surrounding it; but at the spot where it was formed a new cleft is produced in the glacier by the same causes as the first, and the little stream gradually bores out in it a second deep hole. Thus, on the same line, several circular wells are hollowed out, the most elevated of which is the funnel of a cataract, while each of the others has, in its turn, been deserted by the water that Fig, 57. Superficial Torrents of a Glacier—after Tyndall. formed it, Moulins, like crevasses, are sometimes made use of by ob. servers who wish to measure approximately the thickness of a glacier, either by noticing the duration of the fall of a stone, or by employing a sounding-line. In this way the thickness of some of the Alpine glaciers has been estimated at 800, 1000, and even 1650 feet. - . In winter both moulins and crevasses are either altogether or in part filled with snow, which makes its way into the interstices of the ice, and moulds itself to fit them just like lava flowing into the clefts of a rock. When the mass of snow does not descend right down into the depths of 188 THE EARTH. the crevassé, and only manages to unite the two edges of it, it forms over the chasm a kind of bridge, which a mere shaking of the glacier will Sometimes suffice to hurl down. These unsupported beds of snow consti- tute the greatest danger for travelers who venture on to glaciers. There is no visible indication to point out the vast gulf below, which descends perhaps to a depth of hundreds of yards. The field of snow is level, and seems to invite one to walk over it; but if an incautious traveler sets his foot upon the snow spread over the chasm before he has carefully sound. edit, the mass may suddenly give way, carrying with it the unfortunate individual whom it has failed to support. The greater part of the acci- dents which happen every year upon the mountains are owing to the fall of these snow-bridges across the chasms of the glaciers. Generally the snow in the crevasses is the first to melt and fall down in the hot season, on account of its position being exactly in the spot where the surface-water chiefly flows; but it often happens that, in consequence Fig. 58. Chasms in a Glacier filled with Snow—after Tyndall. of the motion of the glacier, some of these chasms filled with snow do not fall in the way of any of the rivulets running over the surface. In this case the Snow gradually hardens, and ultimately becomes changed into ice, under the pressure of the layers surrounding it. This recently-formed ice is at first distinguished by its whitish shade, its granular texture, and a great abundance of air-bubbles. Thanks to its color, it resists the melting influences longer than the surface round it, and may sometimes be distinguished from a considerable distance by a kind of cone which shows itself above the field of ice. It also sometimes happens that simi- lar white veins of transformed snow fill up all the windings of the beds of the temporary streams which are hollowed out in the thickness of the glaciers. In the tributaries of the Mer-de-Glace, Tyndall remarked sev- eral of these moulds of former streams. Lakes, as well as miniature rivers, fill up the depressions in some gla- ciers. Sometimes they are mere ponds, or gouilles, formed in some unfin- ished crevasse; in other cases they are like wells, and sink down to the rocks in the bed of the glacier. In some localities, the surface-water. GLACIERS AS BA RRIERS. 189 finding no outlet to the valley beneath through the solid mass which covers the ground, collects in a hollow between the field of ice and the sides of the rock. Cliffs of a deep blue tinge, with snow-capped summits, border the lake-like sheet of water, which is still bluer than the ice itself Sometimes blocks, separated by fissures from the masses above, break away with a crash, and, as they plunge into the water, raise high waves, which spread rapidly across the basin, and breaking on the opposite cliff like shore, describe on the surface of the lake a graceful network of in- terwoven ripples. Little islets of still unmelted ice float here and there under the impulse of the wind, which blows hard through the mountain gorges. There are few sights more charming among the lofty mountains than these little lakes surrounded by snow, like Sapphires set in silver. The greater part of these glacier lakes are formed by the waters of a lateral gorge which is penned up by a natural barrier of ice. This water, proceeding from the upper snows, or from secondary glaciers, which do not descend to any great distance from the summit, finds its passage ob: structed by the body of the principal glacier pushing on its way toward the plain, and, thus arrested in its course, forms elongated lakes, the lower extremity of which abuts on the barrier of ice. Some of these lakes are of a permanent character, and some merely temporary. The former, oc- cupying deep depressions hollowed out in the rock itself, can not possibly flow down into the valley; the latter, being only kept back by ramparts of ice, sometimes melt, and sometimes throw down the obstacle which opposes their outlet. As soon as the icy wall yields to the pressure of the water, the latter pours out in a sudden and mighty rush, the lake is changed into a torrent, or plunges in furious cataracts down into the gorges beneath, and in a few hours discharges the liquid mass which had been accumulating during a long period of years, or perhaps centuries. The history of Alpine inundations is full of incidents of this kind. Thus it was that the lake of Rofen, which had been forming for fourteen days by the encroachment of the glacier of Vernagt, in the CEtzthal, Sud- denly opened for itself a passage. Within an hour's time its basin was completely emptied, the valley of Sulden was devastated by blocks of rock and sand, and the Inn itself, swelled by the sudden flood, laid waste its banks as far as its confluence with the Danube. The temporary tor- rent which the inundation threw into the Inn was not less than three millions of cubic yards of water, at the rate of 953 yards a second. This, however, is a trifling matter compared with the mass of water that must have rolled down if the lake of Rofen had found no means of escape for several years. - The lower glacier of Giétroz, which flows, at a height of 6036 feet, into the valley of Bagnes, not far from the Monte Rosa group, had in the same way several times dammed up the passage of the stream of the Dranse, a tributary of the Rhone; but in a general way the barrier of ice melted at the beginning of spring, and no catastrophe had to be deplored. In 1818 the case was different; the mass of ice descending from the up. * 190 THE EARTH, Ae A º • . . e - - per névés was so considerable that the Dranse, being unable to flow through it, was driven back, and necessarily changed into a lake above the obstacle. At the beginning of May, the dam of ice, which was about º sº #: º § º: %ſ"; º wº º § F ºt º º º # g : g º º Wºlſº º §º § §§ §§ º §§§ Yº ſ \; Fig. 59. The Glacier of Giétroz in 1818. 660 feet in length between the two mountains, was not less than 420 feet high, and more than 30,000 feet in width at its base. The lake, more than half a mile in width, was incessantly increasing, and its depth, which in certain spots reached 260 feet, augmented, on the average, three feet a day. Its contents might be estimated at more than six millions and a half of cubic yards. The danger was a terrible one to the inhabitants of the valley below. Under the direction of Venetz, the engineer, they set to work to dig a draining channel across the rampart of ice, and suc- ceeded, in fact, in gradually lowering the level of the water of the lake. On the 16th of June, at four o'clock in the afternoon, the barrier gave way; the pent-up water, driving before it both ice and rocks, suddenly sprang into the valley with such rapidity that in twenty minutes the whole basin was empty. This formidable cataract swept away Woods and chálets, and laying bare the rocks, and carrying away the very mead- ows, emptied itself into the plain like a mingled avalanche of Water, trees, and débris, 300 feet in height, and preceded by a black and thick vapor, like the smoke of a conflagration. The havoc was very considerable, not DRAINING CHANNELS. 191 only in the valley of the Dranse, but also on the banks of the Rhone. In order to avoid the return of a similar disaster, the draining channel of the Dranse was cut out afresh every year beneath the glacier. This operation gave an opportunity of ascertaining the adhesion of the ice to the bed over which it flows,” even at an altitude comparatively not very considerable. The lake of Möril, which is penned up by the enormous barrier of the glacier of Aletsch, also communicates with the valley of the Rhone by a draining channel which carries off the overflow of its Water S. - * De Charpentier, Essai sur les Glaciers, f Wide p. 207. 192 THE EARTH, CHAPTER XXXIII. DfERIs LYING ON THE SURFACE OF THIE GLACIER.—HOLES IN THE SURFACE. —GLACIAL TABLES.–MORAINES; LATERAL, MEDIAL, AND FRONTAL-RIB- BONS OF MUD.—MEASUREMENT OF THE SPEED OF GLACIERs.-ABLATION, —SUIB-GILACIARY STREAMS. — TEIRMINAL ARCHIES.— CONTRAST BETWEEN THE GLACIER ICE AND THE SURROUNDING VEGETATION, IIRE all other rivers, the glacier bears along with it a certain quantity of alluvium, which it ultimately deposits at the end of its course, after a lapse of time which varies in length. The moving surface of the ice re- ceives all the débris which has been detached from the bare cliffs by the action of thaw, rain, wind, or other meteoric agents, all the avalanches of stones which come down with the Snow from the ravines above, all the fragments of those immense ruins which tower up in the form of needle- shaped peaks or jagged ridges. Glaciers which are shut in between schistose mountains, the sides of which easily crumble away, are often quite black with débris ; others, on the contrary, which are commanded by more compact rocks, or long, snow-clad slopes, retain partially the whiteness of their surface; but all carry with them along one or both of their banks a certain quantity of rocks and stones belonging to all the geological formations of the basin. Borne along by the ice, this rocky rubbish commences but slowly its journey toward the Sea, where it ar- rives, sooner or later, in the form of sand or mud. Some parts of the débris which fall from the cliffs into the bed of the glacier gradually make a hole for themselves and disappear in the depth below; others, on the contrary, seem to rise in consequence of the gradual sinking of the surrounding surface. In fact, if a small pebble of a dark color lies during the day on a bed of ice, it will rapidly absorb the solar rays, and, melting the particles on which it rests, will descend slowly into the little well which it bores by the action of its own heat; sometimes the disappearance of all the débris gives the surface of the glacier an appear- ance like an immense sieve. The result is, however, quite different when, instead of isolated stones, great masses of rock roll down upon the glacier in a body. These large heaps are, it is true, warmed on their surface by the solar rays, but at the same time they protect the space of ice that they cover against the heat. Therefore, all round them, the surface-layers of the glacier gradually melt and evaporate, while these Jumps retain their original height, and seem even to increase, like volcanic cones. Finally, however, the base of the cone of ice which bears up these heaps of rock gradually melts away, the débris slide down on the slope which has become too steep to keep them up, and soon after the hillock sinks and disappears. GLA CIER TA BLES. - 193 A phenomenon of the same nature takes place when a large block of stone—such as a slab of schist or granite—covers the ice and shelters it from the rays of the sun. The surrounding surface slowly sinks, leaving underneath the slab of stone a pillar like a marble column crowned with a heavy capital. However, on the glaciers of the Alps and other mount- aims of the temperate zone, these slabs of stone never lie horizontally on their pedestals; being shone upon obliquely by the southern Sun, they re- ceive the most heat from this quarter, and they warm the corresponding side of the pillar supporting them. Simultaneously the solar rays melt away some of the lower portion of the pillar of ice, so that the slab grad- ually bends over toward the south. As a matter of theory, as Tyndall º º % §º 's º #ffff: ſº º º Ts. | J. # | | § { ſ º | §|| ‘V j/##| || | § º | |||||ſſºl º 5 º ºf i º º ſº % \ Fig. 60. Glacier-table; after Tyndall. says,” these slabs ought to turn, like a kind of sun-dial, simultaneously with the sun, and thus mark every hour of the day; but this daily rotation is too slight to be perceptible, and the general result is all that can be ascer. tained—that is, the inclination of the stones toward the south. Ultimate- ly, the inclination becomes so rapid that the stone slab falls from the top of its column, and immediately after begins to form a second; thus pillar follows pillar under the rocky masses borne along by the ice. Some of these natural dolmens have been noticed having an area of twenty-four to thirty square yards. Among the variously-shaped rocks which are car- ried along by the glacier, some attain a bulk of thousands of cubic yards. The rock called Blaustein, which we now see in the valley of Saas, is a mass of serpentine more than 10,000 cubic yards in bulk, which, in iſ 40, was still upon the glacier of Mattmark.f It is perfectly natural that at first all the rocks and débris which have * Glaciers of the Alps. f De Charpentier, Essai sur les Glaciers. • . N 194 THE EARTHI. rolled down should lie at the foot of the high walls of rock which over. look the glacier. These heaps constitute the lateral moraines, or ranges of stones, running in a line on each side of the bed of ice like roughly- made ramparts, and participating in the movement of the frozen river. Sometimes, however, these broken rocks are buried in the hollows which * = I?ig. 61. Lateral Moraines. open either at the base of the mountain, or at a little distance from it in the heart of the glacier itself. The moraine is then concealed in the midst of the glacier, but, embraced as it is by the whole moving mass of ice, it does not fail to descend toward the valley; and often, when the up- per layers are melted, it again makes its appearance above the surface and overtops the level of the glacier. Some of these lateral moraines rise to a height of 70 or 80 feet above the current. On the Murzoll, in the Austrian Alps, there are several which are more than 100 feet high. Delow the confluence of two glaciers, the moraines which skirt both sides of the base of the central promontory unite like the solid waves which bear them along, and thus form in the middle of the river of ice a third moraine, running parallel to those on the edges. If a third tribu- tary glacier runs into the principal current, a second medial moraine is formed on the glacier, parallel to the first; finally, however great may be the number of the tributaries, each of them will unite one of its lateral moraines to that of the principal glacier, so as to form another medial ridge of débris. By examining the surface of a glacier of regular devel- opment, such as the Mer-de-Glace, or the glaciers of Geisberg or Roth- moos, the number of its tributaries may be reckoned by the number of walls of débris which extend along the line of its current. A number of these medial moraines disappear at their very source in the depths of the crevasses. They remain buried in the heart of the glacier until the layer above them is entirely melted, and then, after hay- ing traversed a greater or less distance, they reappear on the surface as if they had been upheaved by some great eruptive force. It is curious to notice how, at a distance of many hundreds of yards, or even some miles, the enormous alluvium of rocks retains its original diregtion. The rivers of ice poured out by the tributary into the common bed flow on side by side without mingling their masses; in the same way rivers, the Waters of which differ in color, like the Missouri and the Mississippi, roll on to- gether in the same channel for a long time without intermixing their GLAC, ERS of GEISBERG AND ROTH MOOS P1, X11 - t gº Yards - ºuld notº - ºl Engº by Erhard, 12 r Duguay Trouin HAR PER & BROTHER Nr. W YORK Drawn by AVuillemin after Sonklar TERMINAL MORAINES. 195 waves. The steep faces of the side glaciers sometimes exhibit most clear- ly the vertical line which separates the contiguous masses of two tribu- taries which have flowed in above. After a long course of years, or even centuries, the masses of the lateral and medial moraines reach the lower extremity of the glacier, and fall one over the other down the slope of the valley. During a succession of ages, the stones which are too heavy to be carried away by the action of water are collected together in enormous heaps below the river of ice. rtº º gºš º § º § §§ § RSSN N §§ § WNNNNY \ N NºN - *S* N 'N § N NN Nºvº- N Sºx § 6% § # - º S § y § WN * N § §§ Nº. § N § N § w §§§ w SN - N - § § §§§§ §§§ SS N § §§ §§ º § sº § º N S § º § SºMºMA'ſº wº flºº £º § aſſº, 2 &AºN Y N N § § § & § * sº Figs. 62, 63, 64, 65. Frontal or Terminal Moraines. These heaps constitute the great frontal moraines which obstruct the ap- proach to so many glaciers, as these formidable slopes are sometimes hundreds of feet in height. These moraines, consisting of a vast rough alluvium, pushed on by the ice, make their way for a greater or less dis- tance into the valleys, according to the pressure of the masses above. When the force of the latter increases, the accumulation of blocks moves onward, and, in its irresistible progress, overwhelms plains, rocks, and tor- rents. On the other hand, when the glacier recedes, the enormous barrier in front of it remains isolated, like a rampart built up across the valley, and, higher up, the glacier constructs another frontal moraine with the <ºarºº Jºh º % % % - * * % % º % º º % % % % a % º 325cket % % Fig. 66. Profile of the Valley of Avoca, New Zealand; aſter J ulius IIaast. débris it carries down with it. In several gorges, especially in that which extends below the glacier of the Rhone, and likewise in the New Zealand valley of Avoca, six or seven moraines in a line have thus been abandoned by the ice, the lower extremity of which has receded upward. But if the 196 THE EARTH. frozen river recommences its gradual advance, then these heaps will be added to the other débris, and all these old moraines will unite in one gi- gantic moving rampart. In a similar manner, glaciers which have dimin- ished in size, and have stranded their lateral moraines on the adjacent slopes, may, When they again increase, once more pick up these débris : like a flooded river carrying off the drifted wood left upon its banks, the river of ice may impel the mass of blocks a second stage toward the sea. In addition to these various kinds of lateral and medial moraines, the surface of some glaciers exhibits concentric bands of mud and rubbish, ar- ranged, in some cases, with the greatest regularity. The Mer-de-Glace, in the Mont Blanc group, is a remarkable instance of this singular distribu- tion of these layers of mud on the glacier field. The first bands of mud appear below the great cataract of séracs which are found between the névé of the Col-du-Géant and the glacier proper. During the heat of summer, when the renewed activity of the glacier communicates a more rapid impetus to all the layers in motion, the fallen rubbish accumulates in a circular rampart at the base of the escarpment, and then, carried away by the current of the river of ice, advances slowly in the rear of other ramparts which had fallen previously. Mud, dust, and fragments of every kind gradually fill up the furrows made between the raised bar- riers of ice; the latter gradually melt, and ultimately assume the same \| | |º // º |\\ º º ". # sºlſ|| §º §Wºº # * W %% | jºyº | | \\ § º º \\\\\\\\\\\\\\\\". ! Fig. 67. Ribbons of Mud, Mer-de-Glace; after Forbes. level as the general surface of the current, but the belts of brown or red- dish mud still retain their ribbon-like arrangement, and, like the concen- tric undulations which form in smooth water, present at first an almost perfect semicircular curve. But at the contraction of the ravine at Tré- laporte, where the whole river of ice is compressed and is compelled to pass through a narrow channel, the belts of mud are drawn out toward the centre on account of the increased rapidity of the movement which carries them along. These zones of mud, the curves of which are in a contrary direction to those of crevasses, may, therefore, be looked upon as regular floats indicating the direction and exact progress of the current of ice. Perhaps, also, in each interval between the ribbon-like belts we ought to see the precise measure of the annual growth of the glacier, and the belts would resemble the rings of wood which trees produce every ANNUAL MOTION OF GLA CIERS. 197 year, by which we are enabled to calculate the age of the trunks. If this were the case, the central part of the Mer-de-Glace would entirely pass away in about forty years, and the average rate of speed would be about 234 inches, a day, which agrees, in fact, with the actual measurements which have been made by various observers of the advance Of the glacier. - When several generations of Savants shall have followed up, one after the other, this kind of investigation, we shall perhaps learn the exact speed at which the stream of ice moves onward. This will be effected by drop- ping into the deep fractures on the highest point of the glacier various objects, which the mass will carry on with it down to the bottom of the gorge, and will ultimately leave bare at its terminal moraine. A ladder which Saussure left, in 1788, at the foot of the Aiguille-Noire, when he as- cended Mont Blanc, was found, in 1832, at a distance of 4757 yards below. The ladder had, therefore, descended during these forty-four years at an average annual speed of 108 yards, or nearly 11 inches a day. A knap- sack which, in 1836, fell into a crevasse of the glacier of Talèfre, traveled more rapidly than Saussure's ladder; it moved on at the rate of 140 yards a year, or nearly 14 inches in the twenty-four hours. But all these ob- servations fail in serving as exact measurements of the real speed of the mass of the glacier, for it would be necessary to know precisely if the foreign bodies which were carried along lay in the central part or on the edges of the icy current, in its very heart or in the vicinity of the bottom. However this may be, approximate calculations lead to the belief that the snow that falls on the Col-du-Géant takes about one hundred and twenty years ere it arrives, changed into ice, at the lower extremity of the Glacier des Bois.” Human remains, too, have unhappily served as means for estimating the rate of movement of the ice. In 1861, 1863, and 1865 the Glacier des Bossons has yielded up the relics of three guides who fell, in 1820, into the first crevasse opening at the foot of Mont Blanc. These buried remains had, therefore, during a period of more than forty years, passed over a space of about three miles and three quarters, descending at the rate of 160 to 170 yards eagh year. In the year 1860 a more slowly-moving glacier in the Austrián Alps, which flows in the Ahrenthal, threw out a well-preserved corpse, still clad in a dress the ancient fashion of which had been abandoned by the mountaineers for centuries.f Each glacier, taken as a whole, may be looked upon as forming two riv- ers, one of which takes years, or even a century, in descending from the summits into the valley, having assumed the shape of solid ice; the other flows down in a few days, and in the day-time assumes the appearance of a stream. In summer, the phenomenon, which has been designated by the name of ablation—that is, the surface-melting of the ice—takes place rather rapidly. In the month of August, on the glaciers of the Central * Helmholz, La Glace et les Glaciers. f Adamello-Gruppe; Mittheilungen von Petermann. 198 THE EARTEI. Alps,” the thickness of ice melted averages from one to 1% inch a day, and during a series of days which are favorable to the melting process the layer of ice which changes into water is still more considerable. Accord. ing to M. Desor, the mean ablation in a spot favorably situated in the middle of the Glacier de l'Unteraar rose to 23 inches a day during sev- eral months. On the Glacier du Gurgl (CEtzthal), not very far below the lower limit of the névé, Sonklar found, in the month of August, five sur. face-rivulets which together discharged 15% cubic yards of water a min- ute, 45 gallºns a second ; and on the great glaciers of the Swiss Alps tem- porary water-courses must doubtless be formed of much greater impor. tºnce. In autumn and winter the amount of ablation is diminished, but this phenomenon rarely ceases altogether, and in spots which receive the solar rays, or are touched by the warm mists of the plain, small rills of water hollow out a bed for themselves in the ice and among the débris of the moraines. M. Desor has estimated the mean ablation on the Swiss glaciers as amounting to 10 feet a year, or 0.3176 inch a day." The thawed water which trickles over the surface of a glacier sinks into the crevasses and the moulins, and makes its way from fissure to fissure to the deepest recesses of the gorge, now filled up by the frozen river. Owing to its temperature being somewhat above freezing-point, the water, when collected in this hidden bed, and here and there mingled with the flow from springs, thaws a certain quantity of ice above its course, and thus opens out a free passage toward the valley. The stream which gushes forth at the base of every glacier represents, in its annual discharge, the whole of the snow which falls in the gorges and on the trib- utary escarpments. All that has to be deducted is the moisture which has evaporated, and the water which is lost in the clefts and holes of th mountain. g Thus several of the rivers which spring from glaciers afford a very con- siderable flow of water. The discharge of the Aar, as it springs from the ice, fluctuates between 5 and 30 cubic yards of water a second. The Rhone, the Rhine, and the Arveiron also form considerable streams as they issue from their changeable grottoes. In summer, when torrents of water rush forth from the glacier, they bear with them masses of débris and excessively fine sand and mud, proceeding from the continual grind- ing of the rocks by the under-surface of the glacier. The water holding this matter in suspension is yellow, gray, or blackish, according to the nature of the rocks over which it flows in its sub-glacial course. During the cold season, when it is all frozen along its rocky bed, the stream usually becomes perfectly limpid; nevertheless, a certain number of mountain streams are mentioned, the color of which always resembles that of the ice itself; the quantity of small débris with which they are charged gives them a shade both turbid and bluish, as if they were mixed with milk. * * * See Agassiz, Martins, and Sonklar. # Eccursions et Séjours dans les Glaciers. f Dollfuss-Ausset, Matériaux pour servir à l'Etude des Glaciers. ICE-CA VEIPNS IN GLA CIE/ES. 199 An arcade of vast proportions generally rises over the source. Some of these open out with gigantic and almost regular portals with pointed arches, hollowed out of the ruin-like cliff which terminates the glacier. But each advance and each retreat of the mass of ice results in an altera- tion of the shape and appearance of the grotto out of which the stream flows. Sometimes the vault above partially gives way under the weight of the upper strata, and large sloping layers become detached from the sides or from the arch ; fissures and crevasses, like the clefts in cavernous rocks, cut through the walls of ice in every direction, and every now and then blocks break away and fall with a crash into the torrent. Visitors, therefore, who wish to admire closely the vault of crystal, and to contem- plate the lovely effects of light which are produced by the reflections of Sunshine passing through the transparent ridges at the edges, and falling on the blue-tinted walls, are not able at all times to venture without im- prudence into the depths of the cavern. Blocks of ice and rocks often #! jºiºſ]]|| º Šg - § * §: &=#3 N &S *†. Sºº }: #sº ;: §§§§§§§ Něš sº §§§ ŠešºšŠN º \\ º §§§ tº S. - * Nºs º §§ sº º: § 5. § § G º W N $ º - º A º bº g ś Nº \º A rºº §§§º º sing .#- §o, Sº f* ; &.2º º[-º Ż e g º º S § S * § 1 ©S/ O7 S. * º* ººÉ ſ Ž sº #. §§§§ 5 tº NSS sº ; §§ §§ § - §§ - º § lſº § & É º #S *is :;;: º3.:§º C.*i;#º* º4.}C;Eº § .º:& º § ; } º º à Fig. 6S. Sources of the Arveiron. obstruct the flow of the water, and it is but very rarely that these deep- ly-caverned water-courses preserve much regularity of form for any con- siderable time. Nevertheless, several instances are mentioned of men Who, having fallen into the bed of the stream through a crevasse in the upper part of the glacier, have been able to find their way again into the open air, by following the course of the water across the scattered débris and through the frightful darkness of these unknown gulfs. In the very 200 THE EARTH, depth of winter, the entrance to the terminal arches is sometimes entirely obstructed by snow and ice; the cold checks the torrent, and freezes it at the mouth of the glacier. This was the case in January, 1854, when the bed of the Landquart, which is generally fed by the two important gla- ciers of Sardasca and Silvretta, did not receive a single drop of water.” In 1839, the Arveiron itself was entirely dried up.f The mind is all the more vividly impressed with the majesty of these great rivers of ice when the vegetation surrounding them is green and luxuriant, and forms a more striking contrast with the white and blue- tinted cliffs. Some of the most beautiful glaciers in the Alps descend right down into the midst of forests of firs, beeches, and larches; and it is through the green foliage of the trees that we catch a glimpse of the white waves of the icy sea and the dark walls of the moraines. In other places, fields of corn, or even vineyards and gardens, extend to the very base of the solid river, and sometimes, it is said, they have to mount upon fallen blocks of ice in order to gather the fruit off the branches of the cherry-trees. Thus the cultivation of the temperate zone, and the ice- fields of the pole, which on the continent itself are separated from each other by thousands of miles, are here brought into close juxtaposition; man’s labor and Nature in her inviolable grandeur come in contact here without the least transition. This sudden passage into a virgin region, devoid of all activity, conveys an effect of grandeur which deeply im- presses the soul. It is difficult to restrain a species of dread at the sight of those enormous rivers of ice slowly marching on, from century to cen- tury, with their white or bluish layers, 300 feet high, descending gradu- ally, en masse, a few inches a day, carrying with them the fragments Of mountains, and grooving out in their course deep furrows in the bed of rock through which they flow. These glaciers seem as motionless as the peaks which tower over them, and yet they roll on as surely as the stream to which they give rise. The solid waves which roughen their surface rise amd fall, in the long run, just as those of the sea. They, too, have their eddies and their whirlpools; and the mighty moraines which they throw from them at the outlets of their gorges are as much an al- luvium as the mud or sand of a river or the deposits forming along the sea-shore. * William Huber, Les Glaciers. # De Charpentier, Essai sur les Glaciers. GLACI ERS OF LANGTHAL AND GURG L. PL., XIII I South º Querkoge * North Hochwildspitz 3 x º - coz de Gurya colºdeºartººnal 1. tº-doo scale in Yards - - — Yards º lood 1600 2000 Engº by Erhard, ºr Duguay Trouin. HAR PER & BROTHERS Drawn by AVuillemin atter Sonklar. NEW YORK A DVANCE AND RETIEEAT OF GLA CIE/ES. 201 CHAPTER XXXIV. PROGRESS AND RETIREMENT OF GLACIERS. — APPEARANCE OF THE BED wn BN ABANDONED BY THE ICE.-ROCHES MOUTONNíðBS.–PARALLEL FUR- FOWS. IN several parts of the Alps the mountaineers, influenced by the super- stitious ideas of former days, continue to believe that the base of a gla- cier advances and recedes alternately every seven years.” The fact is, that if the progress and retreat of the fields of ice take place under the influence of any regular law, this law, which, at any rate, must be dis- turbed by a host of special local phenomena, has not yet been discov- ered. Since the date when regular observations first began to be made on the forward motion of the Alpine glaciers, they have been subject to very considerable fluctuations in their movements. Sometimes they have advanced, sometimes they have receded, and sometimes, even, they have remained Stationary for several years together; but it appears that, on the whole, they have moved onward. Several of the Swiss glaciers— those of Zmutt, Aletsch, the Rhone, the Aar, and Grindenwald—have in- creased in length in their rocky beds. It appears to be certain that, in spite of temporary retirements, some fields of ice, even in the last century or two, have extended sufficiently to close mountain passes which were once practicable even for horses. Thus, several passes in the groups of Mont Blanc, Monte Tosa, and the Bernese Oberland, which still remained open in the fifteenth century, and were indeed used for troops, became more and more difficult to cross, and ultimately, during the course of the eighteenth century, have been ren- dered inaccessible, either for horsemen or pedestrians.# The Lötschen- pass, near the Gemmi, which was used less than a century back, is now closed up. Several facts of this kind are instanced in the Tyrol. One of the CEtzthal glaciers, that of Gurgl, has certainly advanced a mile and a quarter since the year 1717, for that was the date when it commenced to dam up the side valley of Langenthal, in which the stream has accumu- lated to form a lake. In like manner, in Asia, the glaciers of the Kara- korum seem to have uniformly advanced during the course of a century at least. The pass of Jusserpo was formerly accessible to horsemen; it can now only be crossed on foot. The glacier of Baltoro and the ancient pass of the Mustack have become impracticable.S. But this is not all, * William Huber, Les Glaciers. f Venetz, Denkschriften der Schweizerischen Gesellschaft, Part I., 1830. # Sonklar, CEtzthaler Gebirgsgruppe. § Godwin-Austen, Journal of the Geographical Society of London, 1846. 202 º THE EARTH, several Alpine glaciers are named as being of recent formation. Among these are the Dreckgletscherli (“little glacier of mud”) of the Fauldhorn, which was not in existence at the commencement of the century; the Rotheleh, a field of ice on the Simplon, dates from 1731; another, de- scending from the Galenhorn, in the valley of Saas, was formed in 1811; lastly, the fine Glacier de Rosenlaui itself is of modern origin.* Are the glacial encroachments which have taken place on various mountain chains to be attributed to some cause acting generally over the whole planetary surface 2 This is the idea which M. Adhémar asserted, which, too, is still maintained by his disciples. According to their view, the gradual cooling of the northern hemisphere during the present period is completely proved by the increase of the glaciers of Greenland, the Alps, and the IIimalaya; but the observations made up to the present time are neither numerous nor decisive enough to authorize any such con- clusion. And even if there was a uniform advance into the valleys on the part of glaciers every where, their progress might also be attributed to an increase of the humidity contained in the air, or to some change in the general direction of winds. Numerous instances may be mentioned of glaciers existing on the flanks of the same mountain, advancing with more or less rapidity according to the quantity of snow that falls directly, or is displaced after its fall by the atmospheric currents. Sometimes, even, a glacier has been noticed to increase in length, while near it, or on the opposite side of the mountain, another field of ice has diminished in size. Phenomena of this kind are evidently owing to the unequal distri- bution of snow on the various slopes. Very considerable falls of débris on the surface of a glacier will also result in the prolongation of the icy current into the valley, because the layer of rubbish causes the annual ablation to decrease to a very important extent. Perhaps, even, as Otto Volgar points out, the gradual upheaval of certain mountain groups is also one of the causes which contribute to the extension of rivers of ice. Nevertheless, if during modern times a certain number of glaciers have unquestionably advanced, others have certainly receded, and consequently their bulk has become lessened. Thus, in the Pelvoux group the two im- portant glaciers of Bonnepierre and Chardon have continued to decrease in length and thickness since the year 1850, and this movement of con- traction was still continuing in 1861. In like manner, in the Tyrolese Alps, all the glaciers of the Adamello group are diminishing regularly. The Mandron, the most important of all, has been retiring at least since 1825, and in the year 1864 especially had lost about 60 feet of its length. In the same year, the glacier of Fargorida lost nearly 100 feet, and the inhabitants of the country say that since the beginning of the last centu- ry it has continued to diminish in importance.S. It appears also that, in certain places, the fields of ice reposing on the summits have also disap- peared. * Tschudi, Le Monde des Alpes, vol. iii. + Vide above, p. 67. f Untersuchungen über das Phänomen der Erdbehen, vol. ii. § Payer, Adamello-Gruppe. MOTION OF THE ICE STREAM. 203 During the forty years which have elapsed from 1826 to 1866, the gla- ciers of Mont Blanc have also lost much both of their length and of their force, evidently because the snow in winter has been less abundant, and the summers on the average have been hotter. The Glacier du Tour, which once invaded the valley of Chamounix, has retreated, on the whole, 567 yards since 1854, and does not reach beyond one of the upper pas- sages, invisible from the road. A stone which marks the precise spot reached by the Glacier des Bois, or Mer-de-Glace, in 1826, stood, in 1865, at 424 yards from the arch of the Arveiron,” and at certain spots, accord- ing to the evidence of M. Bardin, the ice had decreased more that 100 yards. The Glaciers des Bossons and Argentière, the two other great glaciers of the valley, each of which used to threaten the village that was nearest to their frontal moraine, have receded 362 yards and 197 yards respectively during the period from 1854 to 1866. Although they have diminished in length more slowly than the Glacier du Tour, it is evi- dently because the basin which they occupy is much more considerable, and the névés above have never ceased to feed them. We must also add that, during these twelve years, the superficial ablation has in every case perfectly corresponded with the retirement of the ice. The Glacier des Bossons has lost about 88 yards in thickness. Previously to 1854, the lateral moraines lay much lower than the mass of the glacier; they now tower over it at a mean height of 82 feet.f The true system of action of glaciers seems to be pointed out by the alternations of progress and retreat, established both by official docu- ments and scientific observations with regard to the lower part of the Glacier de Vernagt, in the CEzthal group. The fluctuations of this river of ice have been noticed for nearly three centuries, and the chronicler who mentions them for the first time in 1599 adds that these motions to and fro are the “natural habit” of the glacier. The Vermagt descends rapidly toward the valley, and, striking against a wall of rock which rises up directly opposite to it, obstructs the passage of the Rosenthal waters, which there form a lake. Then the enormous obstacle gradually sinks, the glacier slowly recedes toward the steep slopes, until some fresh impulse of the névé again forces it on toward the bottom of the valley. Without reckoning the less important fluctuations, we find that the intervals between each great enlargement have been seventy-eight, ninety-three, and seventy-three years, which gives an average of eighty- four years. Like rivers of running water, the Glacier de Vernagt has its floods and low-water seasons. From 1843 to 1847, at the time of the last irruption of the ice, it advanced 1455 yards, and spread out in the valley over a width of 1382 yards. At the lower part the ice was not less than 518 feet above the stream, and, higher up, the glacier, at certain spots, attained a thickness even twice as great. The swiftness of progression of the front of the glacier was tuite unexampled. During the first two * Payot, Bibliothèque de Genève, September, 1866. f Martins, Bibliothèque de Genève, July, 1866. * 204 THE EA RTH, years it exceeded 63 feet a day; at the end of the month of May, 1845, it attained a rate of progress of 42 feet in the twenty-four hours. On the 1st of June the speed measured was not less than 6 feet 3 inches an hour, equal to about 150 feet in one day. The motion of the ice could be de- tected even with the naked eye. The thunder of the opening crevasses and of the séracs falling down was incessant. Finally, however, this ter. rible invasion, which threatened all the valleys below, was arrested, and the stream of ice receded, giving a passage to the lacustral waters which it had penned back. Since this epoch the lower portion of the Glacier de Vermagt has continued to decrease, but still here and there, on its former bed, it has left islands of ice protected against the heat of the sun by masses of débris. After resisting the elements for years, these isolated heaps sink and finally disappear.” By means of the temporary or permanent retirement of certain glaciers, we are enabled to ascertain the effect produced by the gradual flow of these enormous masses on the bottom and sides of their rocky beds. The numerous observations of M. Dollfuss - Ausset seem to have estab- lished the fact that above 8530 feet, that is, above the ideal line of per- petual Snow, the Alpine glaciers only rub away the stone in a quite im- perceptible degree, on account of the freezing which causes them to ad- here to the surface of their bed. But below this altitude the incessant friction of the ice and the gravel it carries with it gradually removes the most prominent roughness, and ultimately gives a rounded surface to all the projections. To use a congparison which is frequently applied, a glacier passes over the ground like a gigantic plane; it works over the bottom of its bed, and overriding all the projecting points, grinds them down, pulverizes them, and reduces them to the condition of sand. It subsequently makes use of this very débris for rubbing away and polish- ing the rocks in its bed; hence, therefore, arises that mammillated aspect of the old projections over which the heavy mass has glided for so many centuries. Clefts and fractures appear like dark lines of shade on these round, white, polished lumps, which sometimes have the appearance of heaps of wool placed upon the ground, or of flocks of sheep. They are thus known under the name of roches moutonnées, a name employed for the first time by De Saussure. In making its way toward the plain, the glacier does not confine itself to rubbing off the more prominent parts of the rock; it also scoops out the stone in certain places by means of the variously-shaped blocks of greater or less hardness with which it is armed on its lower face, which act as so many chisels on the rocks beneath them. The stones which are slowly impelled toward the bottom of the glacier are scratched as by stylets of stone, and the rocky bottom of the gorge itself is furrowed up and down as by a ploughshare. The walls of the bed of ice are likewise grooved by the rough edges of the blocks carried along on each side of ... the current. Nevertheless, wherever the bed of the glacier is narrowly * Sonklar, CEtzthaler Gebirgsgruppe. *. G. L. A. C. ER OF V E R N AGT in the Autumn of 1856 PI. XIV wº Wºº º º º | - º º - º º W. Zwerchwand - º Section taken at the line A B Eng” by Erhard 12 r Duguay Trouin- Drawn by A. Vuilleroin after Karl Sonklar. HARPER & BROTHERS NEW YORK - - º N º or " */cº ICE.PLANING AND GR00VING. 205 confined between two promontories, it is only the up-stream faces of the latter which present streaks, furrows, or other traces of rubbing, and the down-stream faces retain all their natural clefts and original projections. Sometimes, in portions of the bed abandoned by the ice, we may meet with circular cups or basins, like the holes which the sea or rivers hollow out on their shores. These glacier-cups originate in a similar way to those in river banks and cliffs: they are formed by stones incessantly turning round and round under the influence of sub-glacial torrents, or the cascades pouring down into the gulfs of the moulins. 206 THE EARTH. º CHAPTER XXXV. DISTRIBUTION OF GLACIERS OVER THE SURFACE OF THE EARTHI. MoUNTAIN Summits which rise above the limit of perpetual snow do not all give rise to rivers of ice; the concurrence of several meteorological and orographical conditions is necessary in order that the snow and mávé should be changed into glaciers. In the first place, it is requisite that the snow Zone of the mountain tops should be of some considerable breadth, and that vast beds of névé—those reservoirs for the supply of glaciers— should be formed in the mountain amphitheatres and in the upper pla- teaux. It also requires that the winds which blow against the mount- ains should be charged with an amount of humidity sufficient to leave immense beds of snow on the summits and the slopes. Added to all this, the gorges which open into the thickness of the chain must be of a gen- tle inclination, so that the Snow may not slide down immediately into the valleys below in the form of avalanches; and the mountains themselves must be grouped in such a way that their gorges unite to form a common basin, where the Snow may be finally elaborated in order to constitute genuine rivers of ice. Lastly, it is indispensable that the various seasons of the year should afford extremes of temperature sufficiently great to allow of the phenomena of thawing and regelation taking place in the masses of névé. It is owing to the great uniformity of climate that so little ice is seen on the sides of the lofty snow-clad peaks of the equato- rial Andes. The large number of different conditions which must all be combined as necessary to the formation of glaciers will readily show why these rivers of transformed snows are comparatively very rare in the regions of torrid and temperate zones. They are produced with a high degree of uniformity and grandeur only on the sides of lofty summits; while on mountains of less elevation, as those of the Vosges” and the Riesenge- birge, they are formed in very snowy years in the recesses of ravines shel- tered from the sun. It is, however, only in the vicinity of the poles that the ice-system manifests all its magnificence, and indeed constitutes the predominant feature of nature. In Europe, the Central Alps form the orographical system in which all the conditions necessary for the formation of glaciers are fulfilled at the greatest number of points. These mountains, too, will ever remain for savants the classical region of glaciers, for among them a De Saussure, a Charpentier, an Agassiz, a Rendu, a Forbes, and a Tyndall have gone on from discovery to discovery, and have ultimately brought to light the * Collomb, Comptes Rendus de l'Académie des Sciences, 1846, Vol. xxi. GLA CIEES OF THE ALPS. 207 true theory of the motion of ice. There are in the Alps nearly 1100 gla- ciers, a hundred of which may be looked upon as primary glaciers.” The total surface of the fields of snow, névé, and ice on the Alps is estimated by the brothers Schlagintweit at 1177 Square miles, or about one seventh . of the whole area of the great mountains from the Pelvoux to the Gross- Glockner. The glaciers of Mont Blanc alone, though inferior in extent to those of Monte Rosa, cover a surface of 109 square miles. According to M. Huber, their total mass amounts to nearly 1834 millions of cubic yards, and represents a body of water equal to the whole of the discharge of the Seine during nine years. º The glaciers of the Alps descend on the average to a point about 7414 feet above the level of the sea, that is, about 1650 to 2000 feet below the level of perpetual snow; but there are a great number of glaciers, and they are generally the most important, the base of which is below the JMłBlanc, [&Cervin MłRosa. Jungfrau Finsteraarhörn MłTödi 1578% 15774. * ač871 1,023, l686 - g g : 3 # .# $2 do Sº rº # § rº §§ 3 & §§ # * : - Þ *ś º z_º, NºS RSSS sºft º S$ sº sº. +; §§FFRFrº. >~~~~ºr, §§ Jiří Hºlläfli § $$$, RRRRNRyš Šiš º N.R.R º: ºiſºtºiºiº. * – * = …º.º.º. §ITS- tº S [...R. Monte Rosſ, Bernese Alps Alps of Glaris Fig. 69. Glaciers of the Alps—after A. and H. Schlagintweit. a, a, Lower limit of persistent snows. b, b, Lower limit of secondary Glaciers. mean altitude of about 7000 feet. The Mer-de-Glace, the receptacle of the greatest part of the snow of Mont Blanc, reached in 1862, at the Source of the Arveiron, a point which is only 3659 feet above the lovel of the sea. The Glacier des Bossons, fed by the snow of the same mount- ain group, descended to a level of 3605 feet; lastly, the lower glacier of Grindenwald, which of all the glaciers in the Alps pushes its way the far. thest into the valleys below, has its terminal grotto placed at only 3225 feet? above the sea-level. This fact must be attributed to the northern aspect of the glacier, to the narrow straits of rocks through which it has to flow, and its rapid declivity, exceeding 14 degrees. With regard to the Glacier d’Aletsch, which in its dimensions is the most important of all, and rolls down a wide current over a total length of 23,304 yards, it does not descend into the lower gorges, and in 1860 it stopped at an altitude of 5137 feet above the level of the sea. The Glacier d’Aletsch owes * The brothers Schlagintweit. The Bavarian savants have omitted in their list many gla- ciers both of the Western and even the Central Alps. The ice area in these mountains is probably somewhat larger than they have estimated it. f Studer, Bibliothèque de Genève, September, 1866. * º 208 THE EA RTH, its enormous development to the great body of névé collected in the high mountain hollows. 130,000,000 square yards. This glacier has a total area of no less than º * ºr. 3%Z ** º, & #3 g 24'. - *- //º/, jº § 22% §%; ºff - z. -i " . . §. --~~ / P. *%| wº àº; à G *** * *º º - { . 3. - - º º º ; | ... | } º * !) % % t --> º . . . $ r - * * º: ! * # % | ſº sº -- $: | (SS3 $ 2 / || ‘. . . \\ .. §§§ {\\\\| § Whº? - | ;; * . - - ** * -—- - - - ~…~ $º º º §§WA; º º: -Jº: :*- $ º-;§-§§§* ...:- sºwºº5¢%X.-|§ É&* º:à. si A:s- º º º ºi. sº- º} *ºiº iiigºº -i ::2. ~:º'º§v º:;ººº: ºc.§gº wº ºss -:w º º 3%ſº -º 3. Sº §§ § sº §§ § º | é # º % *.%% *£%º &* º% º º * †º ºf -4 i.i. % * s 2 3. * z º | | º: F-3 § ; & _*. %j ğ. 2% - 2. Nº % .” - º ‘. . $ºffº/ Ž. Sºlſº ºs- • * (3. º ^—- ‘… - º - * ſº % .* # sº º - º s: . : *\' º 2% ſ sº § ſºpº & º ::/ ſº # º wº § • . - & º × ... wº º º %. º º º º *s-s § : ºrs. r y; .*.*.* * § // ..., 2T. sº d ğ. * º Ú £2. 2% 22: 22% #) / º 2% \; %2. º º º &§º ſº º§§§ º º§ ººg #º º 2: 2. ſº 3.3% º §§ § t º ºS § § &º º W º sº º \\\\\\\\ §º sº ! š sº #. N NS ºš §§§ &M sº º §§ *-we-º: § º §§§ Sº 33% N § \\\\ *\Sºº N. Sº §§§ º W {S_º #: §§ §§ S. W $ §§ º Sº § º W §§ Q ºğ § § N § 3 § S: # § : § NS §§ § §§§ §§ §§ sº &\\ & §§§ \ § § § º § N}\ \\\\\º N § º º - º Sº & Fig. 70. The Glacier d'Aletsch. The glaciers of the Tyrol are numerous, since, in the CEtzthal and Stu- baier groups alone, Sonklar reckons 309 glaciers, 16 of which are of the GLACIERS OF THE ALPS. 209 first class. It is true that, in his enumeration, the learned explorer of the CEtzthal has not omitted a single one of the small glaciers lying on the sides of the mountains. Some of the rivers of ice, especially the Vernagt, the Gepaatch, the Murzoll, and the Gurgl, are important streams, and well known to savants through the investigations of the brothers Schlagint- weit, Simony, Sonklar, and other geologists; they are, however, inferior in extent to the principal Swiss glaciers. This minor importance of the Tyrolese ice-rivers, compared with those of the Western Alps, is principal- ly to be attributed to the unequal distribution of snow in the two coun- tries during the various seasons of the year. Not only does it rain and snow in larger quantities on the Swiss mountains than on those of the CEtzthal, but in the latter groups the Snow falls principally in summer, and consequently melts before it has a chance of increasing the mass of the glacier. The winter snows, which alone contribute to feed the ice- rivers, are more than twice as abundant on the lofty summits of Switzer- land as on those of the Tyrol.” The annual layer of névé which is formed on the Bernese Alps attains, according to Agassiz, a thickness of 2 to 24 yards, while on those of the CEtzthal it scarcely reaches a yard. Never- theless the latter group affords an area of 221 square miles of ice, equal to one seventh of its whole surface. The two other principal groups of the Eastern Alps are those of the Ortelspitze, south of the CEtzthal, and the Gross-Glockmer, very much more to the east. In the latter is situated the fine glacier of Pasterze, the dimensions of which, including the névé, are, according to the broth- ers Schlagintweit, 10,274 yards in length, 4494 yards in width, and 236 yards in depth. The rest of the Austrian Alps possess only two isolated glaciers, that of Dachstein, not far from Hallstadt, and that of Marmolata, above the plains of Venetia. In order again to meet with these mighty ice-rivers, we must turn to the other extremity of the Alpine system, to the south and southwest of the great central groups of Monte Rosa and Mont Blanc. There each of the great groups of Piedmont and Dauphiny, the Grand-Paradis, the Vanoise and Grande-Casse groups, the Grandes- Rousses, and especially the Oisans, afford glaciers of the highest im- portance. The mountains of Oisans, Pelvoux, the Ecrins, and Aiguille-de-Meije are almost as distinguished as Mont Blanc itself in the quantity of ice they bear on their slopes. There is no region in the Alps in which the phe- nomena of these vast ice-rivers can be better studied than in the upper valley of the Bane, situated at the point of junction between the Glacier. Noir and the Glacier-Blanc, at the foot of the pyramid of Pelvoux. Just at the spot where the lower extremities of these mighty masses, now con- fined between two vertical walls of ice, unite their lateral moraines, they present a most perfect and striking contrast. As viewed from the plain of débris lying between the two moraines, which is traversed by the * Sonklar, CEtzthaler Gebirgsgruppe. f Adolf Schmidt, Oesterreichische Waterlandskunde. O 210 THE EA RTET. stream of the Bane, the Glacier-Noir is so loaded with detritus of every kind that it looks like an immense flow of mud, such as those vomited out by the volcanoes of Java. The real nature of this mass could not be recognized, were it not for the gaping crevasses into which blocks of stone and trains of pebbles ceaselessly fall with a dull noise. At the foot of the glacier leans the frontal moraine, more than 300 feet high, with muddy rivulets trickling through its rocks and creeping away slowly among the scattered débris of the plain. On the other side the Glacier- I3]anc, almost entirely free from rubbish, is terminated by gigantic steps, themselves supported by vertical buttresses somewhat resembling a lion's paw. The beds are of a pure white, here and there streaked with red and gold color. From the middle arch, which is admirably curved and sup- ported by blue pilasters, flows the tributary of the Banc, with water of a milky white. To the east, on the other side of the valley, stands the Pel- voux, resembling a Gothic spire enriched with turrets; between each of its peaks there are small fields of ice, which look in the distance like slabs of white marble. To the south of the important Oisans group, the glaciers only appear singly in the upper gorges of the loftiest mountains. In no place do these small isolated streams combine to form an ice-river which, like those of the great Central Alps, pushes its way down into the valleys at the base of the mountains. The Viso, and some peaks of the Maritime Alps, present small ice-fields; the last in this part of the chain is that of Cla- pier-de-Pagarin, between Nice and Valdieri. If we comprehend in one glance the whole map of Central Europe, we shall see that the principal glacier groups are those which surround the rflountain summits of Mont Blanc, Monte Rosa, the Finsteraarhorn, Berni- na, and (Etzthal. The following table, from which we clearly see that Monte Tosa is the true centre of the region of ice, shows the comparative importance of each system of glaciers.” According to Studer, it is owing to the heightening of the temperature produced by the lofty plateaux of Engadine, that the fine group of the Bernina is distinguished from all the rest by the comparatively small quantity of ice which it possesses.f | Mont Planc. Monte Rosa. Finsternarhorn. Bernina. CEtzthal. | Yards. Yards. Yards. Yards. Yards. A Mer-de-Glace... 16,966 || Graener.... 16,732 Aletsch.... 26,246 Mortirat... 10,110 | Qepañtch. 1%; Argentière.... 10,607 | Ferpècle... 15,529 AViesch .... 16,185 Forno. . . . . 9,623 Gurgl ..... 10,936 Bionnassay.... 10,498 || Zinal. . . . . . 11,701 "tºternar. 15,638 II intereis... 10,061 ; Findclem ... 11,154 || Tschingel. 9,514 Murzoll ... 9,023 Zmutt. . . . . 9,404 Lötschen... 8,530 Mittelberg. 8,530 Turtſmann. S,311 || Oberaar... S,420 Vernagt... 8,311 Ried . . . . . . 8,311 * * The Pyrenees, which lie more to the south, are neither so high, nor So well arranged in groups as the Alps; they consequently afford a much less extent of snow-fields and glaciers. The area occupied by the latter * In this table, which is borrowed from Sonklar (OEtzthaler Gebirgsgruppe), glaciers less than eight thousand yards in length have been omitted. f Bibliothèque de Genève, September, 1866. - º º sº "ºº". - - - - º º º º º º ſº- º wº- º º (Mº)\º º º º - - º --- Wall, dige º Fºur Erhard - - - - - - - - - - GLA CIERS OF THE IIIMALAYAS. 211 has not at present been brought into comparison with the superficies of the whole chain, but it certainly does not reach a hundredth, and perhaps not even a thousandth, part of the total surface. The Pyrenean glaciers, which are about a hundred in number, are almost entirely sermeil/les, or summit-glaciers, and do not descend into the lower valleys. There is, perhaps, only one—the eastern glacier of Vignemale—which assumes the shape of an ice-river,” and the spot in the gorge where it stops is as much as 7208 feet above the level of the sea. Nevertheless, although the Pyre- nees can not be compared to the Alps either in the magnitude or the development of their glaciers, those that are found in the former chain are in no way less remarkable for their deep crevasses, their blue-tinted walls, their little lakes covered with thin ice, and all those other varied phenom- ena which confer such a charm on the study of the Swiss glaciers. The Carpathians are entirely devoid of glaciers. The mountains of the Caucasus, which, in the general configuration of Europe, may be considered as the chain corresponding to that of the Pyrenees, are much richer in ice- fields. One, the Desdaroki, descends as low as 6495 feet above the sea, which gives a vertical height of something less than 12,000 feet to the whole of the Caucasian snow and ice-fields, between the lowest moraine and the summit of Elburz, rising to an elevation of 18,405 feet. Never- theless, the glaciers of the Caucasus are not equal to those of the Central Alps, either in magnitude or beauty, which is, no doubt, caused by the comparatively small quantity of rain and snow which falls in this part of the Old Continent, and also by the large amount of summer heat which prevails there. The most important glaciers of the northern temporate zone are prob- ably the enormous ice-rivers of the Himalayas and the IXarakorum. In comparison with the immense flows of snow which descend from the prin- cipal summits of Asia, the largest glaciers of the Alps must be considered as belonging only to a secondary order. The largest glacier in the Indian mountains—that of Biafo, in the valley of Chiggar (Karakorum)—is not less than 36 miles in length, more than 21 miles longer than that of Aletsch, in Switzerland. The area that it occupies is several hundred square miles in extent, and in its vicinity there are other ice-fields, such as the IBaltoro and Mustack, which are but little inferior in magnitude. The quantity of ice which almost entirely fills up each of these important valleys of the Karakorum can not be estimated at less than ten times that which lies in the Mer-de-Glace and the Mer-d'Aletsch. It is a very re- markable fact, in regard both to these glaciers and those of the IIimalaya, that the ice-rivers are much longer and more abundant on the southern side of the mountain than on the colder slopes which are turned toward the north. This phenomenon must evidently be attributed to the larger * Russell-Killough, Les Grandes Ascensions des Pyrénées. + Behm, Geographisches Jahrbuch, 1866. # Montgomerie, Mittheilungen von Petermann, vol. ii., 1863. Godwin-Austen, Journal of the Geographical Society, London, 1864. * 212 * TEIE EARTH, quantity of snow brought by the south wind, and impeded in its course by the lofty summits.” The northern mountain chains of the Old World are of considerably less elevation than either the Alps or the Himalayas, and do not present any glaciers so remarkable for their extent as those of the great central groups of Europe and Asia. Nevertheless, the proximity to the pole com- pensates in part for the inferior altitude of the peaks. Thus, the high plateaux which terminate the Scandinavian mountains, exposed as they are to the winds from the west, so fully charged with aqueous vapor, pre- sent vast fields of snow, and the greater part of the ravines which sink down toward the fiords on the coast are filled up with glaciers descending as low as 1640 feet, or, as in the case of the Boudhusbraen, even to 967 feet above the Sea. Among the numerous ice-rivers, the most important is that of Lodal, which flows from the immense névé-fields of the Justedal; it is nearly five miles long and 880 yards broad, and descends to a point only 1320 feet above the level of the sea. The total area of this glacier is very inferior to that of some of the primary Alpine glaciers; it is esti- mated approximately as being about one seventh of that of the great ice- stream of Aletsch. - - Although the Ural Mountains, like the Scandinavian, are situated un- der a very high northern latitude, they do not possess a single glacier, and do not even reach the limit of perpetual snow. On their summits, the height of which varies from 4000 to 5000 feet, there are no continuous snow-fields to be noticed in the middle of Summer—no snow, in fact, but isolated drifts in the cavities of the rocks. The surprising contrast be- tween these mountains and those of Scandinavia may be explained by the inferior quantity of rain-fall which is discharged in the former region, and doubtless also by the comparative narrowness of the chain and its isola- tion in the midst of the towndrás, which, although traversed by cold winds in winter, in summer reflect the rays of a burning sun.f Neverthe- less the other mountain chains—much loftier, it is true—which surround the south of Siberia, have their fields of perpetual snow and their rivers of ice. In the Altai, the glacier of Katounia descends to a point which is 4068 feet above the level of the Sea. Even the plains of those desolate regions which stretch away to the north of the continent of Asia have glacier-like masses in which nothing is wanting but motion to make them resemble those of the Alps. The snow, driven by the eddies of the wind, is heaped up in the hollows of the ground, so as to form complete hillocks, which the heat ºn not entirely thaw during the short days of Summer; and after the middle of autumn these heaps again begin to increase. In consequence of the partial melt- ing and the successive freezings, the snow composing thºse hillocks is changed first into névé and then into ice, pure and blue, like that of the Alps. The mass presents some clefts, caused doubtless by the sudden change of temperature, but it does not shift its position on the surface of * Thomson, IIooker. # Hofmann, Der Nördliche Ural. THE ARCTIO IOE. FIELDS. - 213 the ground as glaciers do; only the thaw-water, produced by the Sun on the surface of the mound of Snow, flows down its sides and then freezes again, thus giving a wider base to the hillocks. Many of these patches of ice, which on sloping ground would serve as the beginning of a gla- cier, are some hundreds of yards in length. The countries of the Arctic zone—Spitzbergen, Jan-Mayen, and Green- land—are the domain par eacellence of névé and glaciers. In those re- gions the mountains are uniformly covered with Snow above an altitude varying from 900 feet to 1500 feet, and the fields of ice which flow down into the valleys reach very nearly to the sea-shore. The few travelers who have climbed a summit from the height of which a vast extent of country can be surveyed have seen, in that part of the horizon which is occupied by land, little clse than an immense white sheet, pierced here and there by black pointed rocks. The glaciers of these polar regions differ in no way from those of the Alps, except that, in consequence of the inferior altitude of the snow, the névé has a very considerable extent as compared with the glacier proper. Sometimes, even, it has been asserted that the lower portions of the ice- rivers of Spitzbergen present both the appearance and the structure of névé, this, however, is an error. In these polar countries the glaciers have also their crevasses and their mowlins, their stratification and their blue belts, their moraines and sub-glacial streams. Only, the thickness of the mantle of snow which covers the whole country, and the surface of the glacier itself, generally give it a considerable uniformity of aspect; the stones of the moraines appear on the surface in but few spots, and as to the mass of débris which ought to accumulate in front of each glacier, they must be sought for in the bed of the sea, into which the blocks are precipitated which break away from the principal mass. One of the largest ice-fields in Greenland, next to Humboldt's enormous glacier, which was no less than 69 miles wide at its lower extremity, and those still grander ones discovered by Hayes, the American, in his recent travels, is that of Eisblink, south of Goodhaab. The lower portion of the enormous mass pushes out into the midst of the sea, forming a cape, the length of which is more than 13 miles, and if a glance is thrown back to- ward the heights between the two walls which inclose the river of ice, the Eisblink may still be seen on the extreme horizon—that is, 35 to 40 miles away. The incline of this sea of ice is very gradual, and it blends insensibly with the horizontal surface of the icebergs on the shore. As the glacier does not terminate on the ocean coast in steep cliffs, it is im- possible to discover the point underneath the ice which forms the bound- ary between land and water. There is, however, a considerable mass of submarine débris—the Tallert Bank—which stretches around in a semi- circle in the sea, just off the end of the glacier. This is probably a kind of frontal moraine carried down by the stream which incessantly flows under the Eisblink. - The greater part of the streams which descend from the mountains 214 THE EARTH, in the interior of Greenland likewise remain hidden, during their whole course, under enormous moving ice-fields, and only betray their presence by bubbling up in different places, and by the muddy color and dimin- ished saltness they communicate to the sea-water with which they are mingled. Some streams which pour down a considerable quantity of water hollow out for themselves wide beds under arches of ice, which press with an enormous weight on the pillars that support them, and which are always tending to break down under the pressure of the masses above. At the same time, the waves of the sea, the temperature of which is much higher than that of the glacier, are melting away the base of the columns, and incessantly sapping them by their repeated shocks. This frequently results in the downfall of immense masses of ice, like whole sides of mountains, which give way suddenly with a crash. The downfall of one of these terminal cliffs of ice in Greenland and other Northern countries presents a magnificent spectacle—as in the gla- cier of Horn Sound, on the south of Spitzbergen, a prodigious mass, 150, 300, or even 400 feet high, rests entirely on the sea, which has gradually melted away the under portion of the ice with which the waves have come in contact. At low tide the enormous overhanging mass, under which it is quite possible to penetrate in a boat, hangs without support, and is only kept up by its cohesion with the rest of the ice and with the sides of the adjacent rocks. Still the mass continues to advance, and the numerous partial ruptures which take place in its bulk cause a noise sim- ilar to the crackling of the electric spark.” All of a sudden the great crash takes place; enormous sections of ice break away from the cliff with a roar like thunder, and sink down into the depths of the water; they soon, however, reappear on the surface of the waves, oscillating to and fro to find their equilibrium, and, impelled by the winds and cur- rents, float away on the undulating billows.f - In the continent of the New World, the glaciers on the mountains farthest to the north resemble those of Greenland and Spitzbergen in likewise reaching the sea-coast; but in the South the lower limit of gla- ciers rises rather rapidly. In a gorge at Mount Forbes, situated near the 52d degree of latitude, there is one which descends to the point of 4281 feet above the sea. Mount Renier, between the 46th and 47th degree, has on its sides small glaciers over which the burning lava sometimes flows. But farther to the south there are no other summits, either of the Rocky Mountains or the Sierra Nevada (not even those that rise more than 13,000 feet in height), which have on them fields of ice; all that is to be seen are the moraines and the furrows, telling the story of former glaciers now disappeared. Neither are the névés of the Rocky Mount- ains very extensive—a fact which may be explained by the dryness of the air, and by the rapid evaporation which results from it. In the tropical zone, the only mountains of America which exhibit small glaciers are the lofty summits which exceed 16,000 feet in height. * Wide the chapter on “Waters of the Sea.” - f Charles Martins, THE AMERICAN ICE-FIELDS. 215 Of this kind are Orizaba; some peaks of the Sierra Nevada, of Santa- Marta, and of the Sierra of Cocui, in New Granada; the Altar of Ecuador (the former crater of which is filled up with ice), and Illimani, in Bolivia.” Nevertheless, these small glaciers, as compared with the extent of the névé and the dimensions of the mountain chains themselves, have no geo- graphical importance. I may, therefore, be allowed to repeat, in common with most other authors, that the Andes are devoid of ice over an extent of more than 3000 miles, from the confines of Venezuela to the centre of Chili. The Descabezado de Maule, on the 35th degree of South latitude, is the first Chilian mountain on which we find an ice-field. But, south of the peak, glaciers become more and more numerous, and, according to Philippi, present in their structure and movement the same varied phe- nomena as the beautiful glaciers of the Alps. On the Patagonian coast, south of Chiloe, the terminal faces of the glaciers appear in all the val- leys in close proximity to the sea-shore. Even in the latitude of 46° 50', a position corresponding to that of the hills of Poitou, in the northern hemisphere, the ice-rivers make their way to the Sea, and the fragments which are detached from them go floating away to the north. The fact is, that the fall of rain and snow is very considerable on the western slopes of these mountains; added to this, it is a matter of certainty that the mean temperature is lower in the southern hemisphere than in the northern. Omitting any mention of the glaciers in the Antarctic regions, which have never been closely examined, the phenomena of which must exactly resemble those of the glaciers of the northern zone, there are still some very remarkable ice-rivers in the southern hemisphere which call for our notice. These glaciers flow down the sides of the Alps of New Zealand —the great southern island. The glaciers on the eastern side of the chain do not descend so low as those on the western slopes, because the quantity of rain and snow poured down on the former is much less con- siderable. The great glacier of Tasman, which flows toward the east, terminates at a point 2739 feet above the sea; while the glacier of Waiau, which fills a gorge tending toward the west, descends as low as 700 feet above the sea-level, and hurls its débris among the green ferns, pines, beeches, fuchsias, and other plants of the lowlands. The position of this glacier (43° 35') corresponds with the latitude of Cannes and An- tibes in the northern hemisphere. Now, in the Swiss Alps, the glacier which descends the lowest scarcely attains the point of 3300 feet above the sea. We must go twenty degrees farther north, to the coasts of Norway, to find the most southern glacier which has its terminal face so little above the sea as that of the glacier of Waiau.S * Behm, Geographisches Jahrbuch. f Mittheilungen von Petermann, vol. vii., 1863. f Wide the chapter on “Climates.” - § Julius Haast, Bulletin de la Société de Géographie, February and March, 1866. 216 THE EARTEI. * CHAPTER XXXVI. THE GLACIAL PERIOD.—ANCIENT GLACIERS OF EUROPE.-DISPERSION OF ROCICS AND BOULDERS FROM SCANDINAVIA AND IN NORTH AMERICA.— ANCIENT GLACIERS IN TROPICAL REGIONS. A STUDY of the existing phenomena which are presented to us in the Alpine glaciers has brought to light the unexpected fact that, at a com- paratively recent geological epoch, their dimensions were much more con- siderable than they now are. Under the influence of meteorological con- ditions which certainly differed from those of the present period, which conditions, however, are still the subject of somewhat animated discus- sion, the ice-rivers descended to great distances from the ridge, and reach- ed the extremity of some valleys which, during the present epoch, have become richly-cultivated tracts. This fact is evident from the striae run- ning along in parallel lines at great heights on the mountain sides, also from the gigantic moraines which in times gone by were pushed forward as far as the outlet of the valleys, and the rocks which were formerly transported by the ice from one chain of mountains and thrown upon the opposite slopes of another chain. Indications of a perfectly similar char- acter to those which mark the extent of the comparatively trifling fluc- tuations of the glaciers of our day serve also to measure the former de- velopment of the enormous ice-rivers of the past. One of these indisputable signs is the upper limit of the polis, that is, the traces of rubbing left by the ice in its course toward the valleys. It appears that on the sides of Monte Tosa, and the Bernese Alps, this limit does not exceed a height of 10,000 feet; but the slope of most of the ice- fields was then much less abrupt than it is at present; it did not exceed two degrees, and at some points on the banks of the former glacier of the Aar it was even less. The considerably larger quantity of the ice in mo- tion at that time allowed the whole mass to make its way over a Very slightly inclined bed. Fig. 71, borrowed from M. Desor's work,” will give some idea of the dimensions to which the glaciers of the Aar formerly attained. - In like manner, the glacier of the Rhone, which now occupies a mere gorge in the Valais Mountains, filled in those days the whole space in- cluded between the groups of the Finsteraarhorn and Monte Rosa, and from every lateral valley and every ravine which opens out right and left in the thickness of the chain it received a fresh addition of ice and m0- maines. The immense ice-river thus extended as far as the shöre of the Lake of Geneva; it even went beyond it, and spread over the plains of * Nouvelles Eccursions et Séjour dans les Glaciers des 4'pes. ANCIENT GLA CIEES OF EUROPE. 217 Switzerland up to the Jura, joining, at its lower extremity, the glaciers of the Isère and the Ain. A field of 1000 feet of ice stretched over the val- ley at the very spot where the Rhone and the Saone unite their waters, and where the city of Lyons has since been built. On the Italian slopes of the Alps, each of the great valleys, where, in the present day, nothing but a few fields of névé are to be found in some of the higher ravines, used Laatepaarhorn Mieselen Ilangendhorn ~~ Ritzlihorn ** ºf . Névé of Névé of Névé. Valley. Finsteraas Lautcraars of Gauli, of Gauli Fig. 71. Ancient Glaciers of the Aar. to serve as a bed for vast streams of ice, descending even to the plains of Piedmont and covering the great Alpine lakes. One of these streams, taking its rise in the upper ravines of Mont Genèvre, Chaberton, Mont Thabor, Mont Ambin, Mont Cenis, and Rochemelon, filled the whole of the Susa valley, extending even to Rivoli, at the outlet of the mountains. Another glacier filled the valleys of the Adige, and advanced beyond the Lac de Garde; these enormous Alpine glaciers were, in fact, twice or three times the size of the largest ice-rivers which are now to be found in the Karakorum and the Himalaya. s The former existence of these glaciers is proved not only by the pres- ence of the stria, and marks of rubbing on the rocks, but also by the front- al and lateral moraines which have been pushed forward in former days to the very outlet of the valleys, or which have crumbled down on the slopes. Thus, above the village of Monthey, in the valley of the Rhone, there may still be noticed a mass of stones of very considerable dimen- sions, forming a kind of rampart more than 3000 yards in length, and 200 yards in average breadth. This bank is formed of granite blocks, brought from the Val de Ferret by a former glacier, and must once have been a medial moraine, which, after the melting of the ice which carried it along, was stranded on this promontory. At one time a number of former mo- raines of this kind were found at various spots in Switzerland; but the harder rocks having been much used as stones for building, these remains are disappearing more and more every day. The question which has given rise to the most animated discussions among geologists is the problem how the moraines of the Alpine glaciers, and the great stones which in former times they drifted along in their course, managed to cross the great lakes of Switzerland and Lombardy. Thus the town of Lucerne is built upon the débris which was once borne 218 TEIF EARTH, along on the immense glacier of the Reuss, which, descending from the St. Gothard, crossed over the depths of the Lac des Quatre Cantons. In like -- ɺ =^ :Sºº-º-º-º: sº #ss Z --~~ §s; == :=2 º }: {} Fig. 72. Ancient Moraine falling down. manner, to the south of the Lake of Garda, the hills of Solferino, Cavriana, and San Martino, on which was fought the terrible battle of 1859, are noth- ing more than heaps of stones, which once served as an advanced guard to glaciers.” Added to this, erratic masses of stone, or boulders proceed- ing from the Alps—as is shown by the crystalline nature of these rocks —are found on the castern slopes of the Jura ; they are seen at various heights, and even at as much as 3300 feet above the level of the sea. Among these blocks—a few of which are from 5000 to 6000 cubic yards in bulk—there are some which the savants, from a study of their miner- alogical composition, can clearly specify as having come down from cer- tain mountains in the groups of the Finsteraarhorn, Monte Rosa, and Mont Blanc. Dy what means have these blocks of rock been able to ac- complish their journey before they became stranded on the mountain sides of the Jura 2 Was the Lake of Geneva much more elevated at a former epoch than it is at present, and did the enormous masses of ice, which fell into it from the glacier of the IRhone and ultimately floated to the oppo- site bank, inclose blocks of rocks and stones like the icebergs of the north- orn seasº Or was it the fact that the glaciers filled with their masses the deep cavities of all the lakes of Switzerland and Lombardy, and, like the IRhone, which continues its course after having so widely expanded in order to form the Lake of Geneva, crossed over these lakes, and flowed out far and wide into the plains of France and Italy 2 This last hypothe- sis appears probable, for on the sides of the mountains which overhang those lakes, and especially round the lakes Maggiore, Como, and Garda, the ancient striae of the glaciers are still to be perceived, and some of the insular rocks retain that moutonnéed appearance which bears witness to the fact that the ice had passed over them. Added to this, the protec- tion afforded by the masses of ice which filled them up have probably been the cause why the deep cavities of the lakes were not choked up by the débris which fell from the broken ridges above on to the moving bed of the glacier. Some geologists have put forward the hypothesis that the * Martins and Gastaldi. Murchison, Journal of the Geographical Society, 1864. # Martins, Bibliothèque de Genève, July, 1866. - FRRATIO BLOCKS AND BOULDERS. 219 beds of the Alpine lakes were hollowed out entirely by the Alpine gla- ciers. This view, so ably advocated by Professor Ramsay, the director of the geological survey of England and Wales, has lately received great support from Professor Newberry's investigation of the lake-system of North America. However this may be, the enormous extent of the old ice-rivers of Switz- erland is a fact henceforth unquestionable. Nor can it be doubted that the same thing was the case in all the rest of Europe. From one extremi- ty of the chain to the other the Pyrenees present unequivocal evidences of the glacial epoch, and in some valleys—those, for instance, of OO and Ar- gelez—the frontal moraines are still almost as distinctly visible as if the ancient glacier had melted only the day before. In like manner, to the west of Vosges, the natural banks of sand, gravel, and heaped-up rocks which pen in the water of the little lakes of Gérardmer, Longemer, and Frondomé, are nothing else but old moraines. Similar phenomena are found in the mountains of other countries—Wales, Scotland, and Ireland, in the Carpathians and the Riesengebirge. * Another proof of the enormous development of the ice system during a comparatively recent epoch may be derived from the dispersion of the er- ratic rocks or boulders, which are found in such great numbers in the countries of the north of Europe. It is now beyond all question that the numerous lines of rocks which are found here and there all over Northern Russia have proceeded from the granite mountains of Scandinavia. When an immense sea extended over Finland, between the Baltic and the Polar Ocean, the blocks of ice which fell into the water that washed the base of the Scandinavian mountains drifted away in flotillas toward the south- east to the shores of the continent opposite. The prominent angles of the granite blocks contained in the masses of floating ice have traced out long furrows over all the points and projections of the rocks in Finland, which was then only a marine shoal. M. Nordenskiöld has ascertained that al- most all these lines of erosion tend from the northwest to the southeast, and that all the rocks with which the icebergs have come into contact are polished on the side which faces toward Scandinavia, while on the other side they have in every case fetained their uneven surfacés, their projec- tions, and their clefts. With regard to the boulders themselves, they are all more rounded by friction the more distant they are from the Swedish mountains of which they once formed a part. All the phenomena which once were effected on so vast a scale round the shores of the Baltic are, however, still taking place. During the winter of 1862–3, immense mass- es of ice, coming from Finland, were cast upon the southern coast of the gulf, and thrown up on the land to a distance of more than 300 yards from the shore, and to a height of 30 feet above the level of the sea. The ice, which was 40 to 50 feet deep, overwhelmed many dwellings and whole forests; in the latter large quantities of stones were subsequently found, which the ice left behind when it thawed.* * Keyserling and Von Baer, Bull. de l'Acad. de St. Pétersbourg, vol. v., April, 1863. 220 * , THE EARTH, These boulders are scattered in considerable numbers over the towndras and plains of Northern Russia; they are also found in Prussia and Poland as far as the slopes of the Carpathian Mountains. They are seen round the North Sea, on the coasts of Friesland, England, and Scotland. The investigations also of M. Böhtlingk have shown that erratic rocks, or boulders, have made their way, borne on masses of ice, from the fiords of Lapland toward the Northern Ocean. Thus the great island of the Nor- wegian mountains was once a centre of dispersion from which the rocks, instead of merely rolling to the bottom of the slopes, were distributed in various directions over the immense space included between the British Isles, Spitzbergen, the Ural Mountains, Valdai, and the Carpathians. Strange to tell, numbers of these Scandinavian rocks, thus stranded be- yond the sea, are still overgrown with lichens and other plants belonging to Norwegian families. They might be compared to colonies of poor ship- wrecked creatures cast upon a foreign shore.* In the gentle undulating plains of North America, boulders and other débris brought by floating ice are likewise found scattered over wide tracts of country. The vegetable soil of some of the most fertile districts, such as Illinois, Indiana, and Michigan, is in great part composed of earth brought by stranded icebergs, and here and there may be found in the mass of this transported soil enormous blocks of granite which one belong- ed to the Laurentian Mountains, or to some other rocky chain in Canada. Thus the effects of the ancient glacial period are still perfectly visible in the plains of the New, as well as of the - Old World. These are, in fact, the spots where we should expect to find the traces of former glaciers; but even warmer coun- tries exhibit on their mountain sides and in their gorges most distinct traces of an- cient ice-currents. Thus Hooker, the bot- anist, noticed at the base of the Himalayas the remains of old moraines forming actual barriers across the valleys; in Syria, too, he felt justified in stating that the cele- brated cedars of Lebanon grow on masses of débris of the same nature. At the foot of the Sierra Nevada, of Santa-Marta, on the coast of Columbia, where the mean ITW § --§º's§ $**- S. - temperature is 80° (Fahr.), masses of débris º =º e º - *S R º E ** º º ºf:5 are also found that the ice, which then de- * §º jº scended 1300 feet lower than it now does, jºšº pushed in front of it to the very sea. Last- Fig. 73. Ancient Glaciº.gººgºna, in the * º tº e Himalayas; after Hooker. ly, Agassiz has likewise recognized the - y track of ancient glaciers in Brazil, not far from Rio de Janeiro, and even under the equator, at the mouth of the Amazon. In fact, the reef of Per- * Christ, Alpenflora, in vol. ii. of the Schweizer Alpen-Club. ALTERNATION OF GLA CIAL PERIODS. 221 nambuco and the whole of the adjacent coast are nothing but a long Se- ries of moraines beaten and consolidated by the waves. Every region of the globe has therefore had its glacial period. But was this period coin- cident in all the various regions of the globe, or did it fluctuate from one hemisphere to the other, prevailing at one time on the north, and at anoth- er time south of the equator? We can not tell; it is, however, probable that a rhythmical fluctuation of temperature took place during the lapse of centuries from one pole to the other, and that consequently the glacial periods have alternated in Europe and Africa, and in North and South America. According to Hochstetter, New Zealand and Patagonia, where the ice descends so low, are now passing through their glacial period. There are, however, hypotheses in abundance in respect to the extension of the ancient glaciers, and on this point generally geologists are still very far from agreeing on any common theory. 222 TEIE EARTH, CHAPTER XXXVII. SECON DARY PART TAKEN BY GLACIERS IN THE CIRCULATION OF WATER.— MOUNTAIN FLOOD-WATERS.—AIBSOIRIPTION OF RAIN AND MELTED SNOW BY TIIE EARTII, PEAT-MOSSES, AND ROCKS.—SPRINGS AND THEIR NYMPIIs. ExCEPT in the polar regions, only a very small portion of the atmos- pheric waters become fixed in glaciers, to remain lying on the mountain sides for years or even centuries. The proportion of water which falls from the clouds in a liquid form is much more considerable, and conse- quently plays comparatively a much more important part in the economy of the globe. Tain and melted Snow, being incomparably more active than ice in its circulatory movement, either flow away at once on the sur- face as rivers, or disappear into the depths of the rocks, whence they will gush out at some distant spot in the form of springs, or will perhaps con- tinue their subterranean course as far as the abysses of the ocean. In mountain gorges where the ground or bare rock will not allow the rain and snow-water to sink in, the stream runs down rapidly toward the plain, carrying with it along the bottom of its bed the débris which is washed away from the slopes. After an exceptionally heavy rainfall, it is often difficult to form any clear distinction between one of these tempo- rary torrents, a fall of rubbish and mud, or an avalanche. In this case, the masses of half-melted snow, mixed with liquid mud, are hurried on by their own weight, and slide down the slopes, driving before them heaps of loose stones and rubbish. The whole semi-liquid body very soon sinks down into the ravine which forms the channel of descent. The water and dirty snow are mingled in one dark and miry mass, in the midst of which rocks and stones bound about as they roll along; in this moving chaos the fragments of débris are constantly coming into collision with a crash that shakes the rocky banks, while the flow of the torrent tears away their base. In many places these enormous masses totter in their turn, and soon participate in the immense downfall. A noise like thunder is the harbinger of the avalanche, and announces it from afar to any persons that may happen to be in its line; but these phenomena, which are at the same time both earthfalls and avalanches, last but for a very few instants. The torrent carries away with it and tosses about like pebbles enormous rocks thirty feet square, and when it has passed away it leaves nothing behind but thick layers of mud. These semi-liquid avalanches are, fortunately, not very frequent, at least in Europe; but all the heavy rains which fall on the mountain slopes, and even on the more or less inclined soil of the low-lying lands, cause the for- mation of torrents and temporary streams. These constitute flood-waters. Dashing down all the defiles, ravines, and depressions of the ground, they % A BSORPTION OF MOISTURE. 223 wash away all the débris which is accumulated in them, clearing off the vegetable soil, plants, and brushwood, and plowing up their beds when the rock is not of too compact a character; when they reach the river flowing through the plain, they pour into it masses of mud and heaps of pebbles carried away from the hills. They are, in fact, real geological agents, and their operations during a day, or perhaps only an hour, contribute no mean share in the modification of the earth's surface. If all soils were absolutely impervious, there would be no springs, and the whole of the liquid mass furnished by rain and snow would flow away over the surface of the ground like the torrents and flood-waters of the mountains. The greater part, however, of the water which falls upon the ground sinks in the first place into the depths of the earth. There it be- comes more or less perfectly purified from the foreign bodies with which it was charged, gradually rising to the temperature of the strata through which it passes, and becoming impregnated with the soluble salts which it meets with. Ultimately, when the water, in sinking down, encounters im- pervious beds, it can penetrate no farther, and, flowing laterally to the out- crop of the beds, makes its escape in the form of Springs. The absorption of the rain and melted snow takes place in various ways, according to the nature of the soil. Ordinary vegetable earth only allows the water to penetrate to a very slight depth, especially when the rain falls in showers and the slope of the ground is favorable for drainage. As mould is capable of absorbing a very large quantity—indeed, more than half its own weight, it prevents the strata beneath from receiving its due share of moisture, retaining almost the whole of it for the use of the vege- tation which it mourishes. In fact, it requires an altogether exceptional rainfall to saturate any ordinary arable soil to the extent of a yard below the surface. Water passes with much more facility through sandy and gravelly beds; but compact loams and clay will not allow it to penetrate through them, retaining it in the form of pools or ponds on the surface of the ground. The action of vegetation is not confined merely to imbibing the water falling from the clouds; it often, also, assists the superabundant moisture in penetrating the interior of the ground. Trees, after they have received the water upon their foliage, let it trickle down drop by drop on the gradually softened earth, and thus facilitate the gentle permeation of the moisture into the substratum; another part of the rain-water, running down the trunk and along the roots, at once finds its way to the lower strata. On mountain slopes, the mosses and the freshly-growing carpet of Alpine plants swell like sponges when they are watered with rain or melted snow, and retain the moisture in the interstices of their leaves and stalks until the vegetable mass is thoroughly saturated and the liquid surplus flows away. Peat-mosses especially absorb a very considerable quantity of water, and form great feeding reservoirs for the springs which gush out at a lower level. The immense fields of peat which cover hun- dreds and thousands of acres on the mountain slopes of Ireland and Scot- *~ 224 THE EARTH, & land may, notwithstanding their elevation and inclined position, be con- sidered as actual lacustrine basins containing millions of tons of water dispersed among their innumerable leaflets.” The superabundant water of these tracts of peat-mosses issues forth in springs in the plains below. Rocks, like vegetable earth, also absorb water in greater or less quanti- ties, according to their fissures and the density of their particles. If the soil is formed of volcanic scoriae, or porous beds of pebbles, gravel, or sand, the water rapidly descends toward the underlying strata. Some of the harder rocks, especially certain kinds of granite, absorb but a very small quantity of water, on account of the small number of their clefts; others, on the contrary, as most of the calcareous masses, imbibe every drop of water which falls on their surface. There are some rocks which have their layers broken and cracked to such an extent that they resem- ble enormous walls of rubble-work; the rain instantly disappears on them as if it had fallen into a sieve. But the greater part of the calcareous rocks belonging to various geological periods are formed of thick and reg- ular strata, cleft at intervals by long vertical crevices. Below the sur- face-beds, perhaps, are layers of soft marl, which the water penetrates with difficulty, although it can soften and carry away its particles. Here are formed, rill by rill, the subterranean rivulets which ultimately spread all over the substratum of marl, following the general slope of the bed. After a more or less considerable lapse of time, the stratum of marl ulti- mately becomes saturated, and the water then flows out through caverns which are variously modified by subsidences—faults in the strata and the perpetual action of the streams. The springs which proceed from calca- reous rocks of this nature are in general the most abundant, owing to the length of their subterranean course. The water which falls on vast areas on the surface of plateaux is ultimately united in one bed. A liquid mass of this kind, which springs up suddenly into sight, just as if it merely is- sued from the soil, drains perhaps an extent of country of many hundreds or thousands of square miles. Thus, according to the nature of the rock on which the rain falls, the latter finds its way again to the surface, either at a considerable distance from the spot where it fell, or else springs out in little rivulets immedi- ately below the place where its drops were first gathered. On a great many mountains we are surprised to meet with springs gushing out at a few yards from the summit. These jets have, indeed, often been consid- ered as the evidence of some miraculous intervention. Among others, we may mention the “Sorcerers' Spring,” which gushes out on one of the highest points of the Brocken, the culminating peak in the Hartz Moun- tains. The position of this spring is, in reality, 19 feet lower than the highest part of the terminal plateau, and it has been calculated that if it served as the drainage outlet for all the rain falling on the top of the mountain, it might well supply rather more than a gallon and a half a minute. Now, as a matter of fact, it scarcely furnishes a third of this quantity. It is, however, but very rarely that it altogether fails, and in- * Wide the chapter on “Lakes.” SPRINGS AWD THEIR NYMT’HS. 225 stances of this have been seldom recorded.* In the principal islet of the Chausey group, which is only 770 yards long by 275 broad, there is also a constant spring, and the question is whether the rain which falls on this rock is sufficient to supply the fountain, or whether it is fed by the filtra- tion of water from the neighboring continent. The valleys which lie at the mountain foot, or even the plains that border on less important heights, are, however, the principal spots where springs gush forth in the greatest number. Springs form a special charm in those unassuming landscapes in which nature develops all its beauties within a restricted space. Stand- ing on the bank of some little brook which bubbles as it glides along, lending, as it were, to nature an almost articulate voice of kindness, the eye embraces a graceful ensemble which can hardly fail both to charm and soothe. Almost involuntarily a feeling seems awakened within us of liv- ing sympathy with the objects around, all of which appear as if made to harmonize with man's condition. The spectator feels softened, and is not oppressed and bewildered with admiration as when surveying a mighty cataract, a glacier, or the waves of the sea. Besides, can we look upon even a tiny spring without an instinctive feeling being stirred up within us that in it we see the real fountain-head of all civilization ? In this lit- tle corner of the earth every thing is arranged as heart could wish for the needs of the first husbandman. There are overhanging trees to shade him, a hillock to shelter him from the rude wind, pure water for his gar- den, and stones to build his hut. What more could he require ere he commenced those great labors in the improvement of the earth which have made us, his descendants, what we now are 2 If a blasé inhabitant of our cities is unable to contemplate a spring with- out some degree of poetic feeling, how much more vivid must this senti- ment have been among our ancestors, who lived in the very bosom of na- ture | Some ancient nations, indeed, worshiped fountains as if they were divinities. The Greeks, who knew so well how to ascribe even to inani- mate objects a fellow-feeling both in their passions and in their joys, have given a personality to each of their fountains, transforming them into some graceful nymph or some glorious demigod. Travelers can not refrain from astonishment when they perceive the humble springs of Hippocrene or Castalia, and the mere rivulets of the Scamander, the Alpheus, the Ilyssus, or the Eurotas, on which the poets of Greece have conferred such imperishable glory. What ' they cry, are these miserable streams the fountains and rivers that the Hellenes honored with statues and temples? Are these slender crystal rivulets, gliding among the rocks, the objects which were invoked as patrons for powerful cities, and were sung of in their poetry in almost divine rhapsodies? These springs seem very trifling things to us—to us barbarians of the North, who only know how to appre- ciate the colossal, and reserve all our admiration for great rivers, such as the Mississippi or the Amazon. Yet who can ever adequately describe * Von Klöden, Handbuch der Erdkunde. f Audoin and Milne-Edwards, Le Littoral de la France. P 226 THE EARTH, the ineffable beauty of the smallest spring, no matter whether it flow be- tween two flowery banks under the mysterious shade of overhanging trees, or slowly trickles from a dark grotto under white chalky rocks, or jet up in glittering pearls from a pebbly bed, dancing the grains of sand on its tremulous drops—each fountain has its own special character of grace or stern beauty. One is the charming Acis, escaping from the laya rocks under which the Cyclops wished to overwhelm him; another is the nymph Arethusa, swimming under the sea so as not to mingle her blue water with the troubled wave; another, again, is the virgin Cyane, bath- ing the flowers which she once gathered to weave a coronet for Proserpine. It is easy to understand the veneration which is felt for springs by the inhabitants of tropical countries, who live on an arid soil and under a burning sky. Even on the borders of deserts and on the oases, water- sources are rare, and their inestimable value is all the more appreciated. That slender spring, which trickles from the cleft of some rock, is the agent which nourishes the grass, the grain, and the fruit which are neces- sary for the subsistence of a whole tribe. Should its water happen to fail, the whole population is obliged to migrate immediately, or else die of hunger or thirst. The inhabitant, therefore, of the oasis professes a kind of worship for the bounteous element which is to him the source of life. In climates more favored in their rainfall, man's love for water- springs naturally lessens in proportion to their abundance; but some relics of this sentiment may be found in the hearts of every nation—those even that inhabit the best-watered countries. This instinctive veneration for rising springs is probably the cause of the Swiss mountaineers not con- sidering the torrents of muddy water issuing from the terminal arch of a glacier as the real source of rivers; this honor they award to the little unassuming rills which trickle out at the foot of the rocks. In their idea the true Rhone is not the furious water-course which dashes out of the glacier; it is a slightly thermal spring which glides among the rocks some hundreds of yards below the frontal moraine. This spring-water, which—differing from the ice-torrent—never fails in winter, is ferruginous in its nature, and stains the snows in its bed with a reddish hue; hence, they say, the name of Rhone (Röthen).” Neither the charm nor even the utility of springs are the sole causes why they are so much beloved; the mystery of their origin also promotes this feeling. We are fond of inquiring as to the origin of these jets of pure water, and of tracing out the paths that they have followed through the bowels of the earth before they emerged into the light of day. From what mountain summit has this charming fountain nymph descended, and in what grotto has she made her abode 2 Such are the inquiries which the uninitiated might make at the sight of a spring—inquiries, too, which Savants are yet far from having answered. What a multiplicity of studies and investigations have yet to be made ere we can trace out, without fear of error, the circuit accomplished by a drop of water through the rocks, rivers, and clouds ! * H. de Saussure, Voyages dans les Alpes, vol. iii, WALRIATION IN SPRINGS, 227 CHAPTER, XXXVIII. VARIATION IN THE DISCHARGE OF SPRINGS. — ESTAVELLES. — EQUALIZA- TION OF THE SUPPLY IN SPRINGS WITH DEEP SOURCES.—INTERMITTENT SPIRINGS. IT may be stated generally that the discharge of a spring varies accord- ing to the quantity of rain. After an extraordinary rainfall, all springs have a tendency to increase and overflow, with the exception of those which, owing to the form of their subterranean bed, are unable to yield any more considerable body of water. It sometimes happens that, during exceptionally rainy seasons, springs gush out from rock-crevices which are almost always dry, and form temporary rivulets. These are called fon- taines de disette (scarcity springs), fonts famineuses (famine springs), or bramafans (hunger cries). The farmers very justly look upon their ap- pearance as the formidable foreboding of a year much too wet for their crops. With regard to springs of a permanent character, there are a consider- able number which, issuing from a rock which is split and rent in every direction, form supplementary orifices after any great amount of rain. Among the mountains we may often notice that walls of rock, which in ordinary seasons have little rivulets of water trickling along their base, will, in a rainy season, be enlivened by cascades dashing down from vari- ous heights of the jointed face. In gorges, and on gently inclined slopes, phenomena of the same nature are developed; but in some cases it is dif. ficult to recognize the intimate connection which exists between the va- rious springs which rise at different intervals of space along the same val- ley. In fact, at first sight, one can hardly understand how a temporary flow of water, gushing out a mile or two above a constant spring, can nevertheless be connected with the same subterranean stream, and so form a kind of waste-valve for the lower orifice. In Languedoc these supple- mentary flows are called estavelles, a term which has been recently intro- duced by M. Fournet into scientific language. The calcareous slopes of the Jura present some remarkable instances of estavelles, among which those in the environs of Porrentruy are specially worthy of notice. Four copious springs, which rise in the town itself, are the outlets of a subterranean water-course fed by the mountains rising to the southwest. Owing to certain depressions in the ground, and to the sound of underground currents which are here and there heard, the con- cealed stream may be easily traced as far as the well, or crew (hollow), of Gena, about two miles and a half from the town, situated at the foot of a hill. In a general way, all that can be seen at the bottom of the hole is a 228 THE EARTH, little stream of water making its way down toward the valley; but after heavy rain or a rapid thaw of snow, the water bursts up with a roaring noise from the subterranean cavities, and, pouring furiously into the meadows, spreads over the surface of the ground, and ultimately runs down to the town of Porrentruy. Beyond this estavelle, where several subterranean water-courses unite, the slope of the valley becomes more and more steep, and other wells or crew of the same kind are seen, from Which the overflowing water of the stream beneath temporarily issues. ; i | i # i º eves §º Fig. 74. “Estavelles” of Porrentruy. N N S S > 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 Saône, which receives the surplus of the sudden overflow. The Frais-Puits, in conjunction with another estavelle, 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, Erdbeben in der Schweiz, vol. iii. 230 TIIE EARTH, ſº. ...º.º. jº in - !" .** ~.4%. , , º, turnºullº \ *"N ºšiº 2. º rº º % lººr-º º W... §§ ^ ' ſº Q. W jº. i. - W. #...:” º § º ſº ;" § § #. : §º:...; tººlſ. j...'...}} º , &, nºnh" {\º ºf Sºudº" : ºùWº: º;" º SY) §.º.º. º "...r.º.º. r * \" - ... wis's , ill. ºffer:* w ="..' . , NY,\\ :* - wars #7. ." . . . .” - §§ \"", Wºr * ...; * * t .A -----------" " ". - §º, , , , , , ...."...º.Bº-E e º ***-s . •.º.” . . . " sº * § § \\ Y- º % } ! **:: T. –4 “. . ... ." ": w º º “º \\ ºve/ A) Tº lf; * * * ~ * * * .2" . . . . . . . * * * * * * *, *NSW $ºfº” . .22 ſº *ſº " * - - < º ñºz - Stºłº - 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 chters 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 Kloeden, Handbuch der Erdkunde. ASCENDING SPRINGS. 231 CHAPTER XXXIX. ASCENDING SPRINGS. — ARTESIAN WELLS. — TEMPERATURE OF JETTING SPRINGS. THERE are many of these subterranean streams which, before they break forth in springs, do not flow over beds continuously sloping in the 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 itselfin a po- sition of cquilibrium 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 nover fail to dart 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 Châtagna, in the department of the Jura, where a natural jet d'eau springs up to a height of 10 or 12 feet. In the grotto of Male-Mort, near Saint-Etienne, in Dauphiné, 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 (Ain Musa), 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 débris 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, Hydrologie Souterraine. 232 - TEIE 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 Egypt 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 Afghanistan 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. Dy 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 Alger 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 every 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 & * Mittheilungen von Petermann, 1861. ARTESIAN WELLS.–TEMPERATURE. 233 waterg 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 débris which the rains had probably carried away some weeks previously into the depths of the earth. At Elboeuf 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 Oued 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. # 3 : : à tºo #3 ă § # Flap, of e • ** s & * y {r. Qulaia. —t- zº-Yº" jºr- *~ºSS --~~~~~~~ *- Šºš º - --- w Nº Sº º N mºnºs §§§ Ş 310 t—l—1—t 1 |--|- 1–1 620 miles. Fig. 76. 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, 1° (Fahr.) to 36 feet of depth. * Buff, Physik der Erde. t Wide above, p. 30, 31. 234 THE EARTH, CHAPTER XL. COLD ANID THEIRMAL SPIRINGS. 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 froczing-point up to the boiling-point. A spring which flows from the side of the IIangerer, 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- * Somklar, CEtzthaler Gebirgsgruppe. THERMAL SPRINGS, z 235 ber 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- onal 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- bières, 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.); 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.} 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 * Wide the chapter on “Volcanoes.” f Humboldt, Cosmos, 1st Part. f 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 Bagnères 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 Bagnères de Digorre suddenly be- came cool at the time of the great carthquake 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 Tyrenees, 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 excrcised by the cold waters sat- urating the soil and forcing back all the small scattered rills toward the central spring. ISut 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 to 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 Plombières, which do not even contain gºrm of salts; also that of Gastein, Pfeffers, Wildbad, and Baden- weiler. The springs of Chaudes-Aigues—those in France which have the highest temperature, 158° to 176° (Fahr.)—contain only a small amount of mineral substances. The inhabitants of Chaudes-Aigues use the Water 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 * Lycll, IBritish Association at Bath, 1864. f Filhol, Eaux des Pyrénées. f Buff, Physik der Erde. THERMAL SPRINGS.–IIEAT UTILIZED. 237 sluices, placed at the entrance of each conducting tube, stop the warm water and throw it back into the rivulet which flows at the bottom of the town. M. Berthier, 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. * Allard and Boucomont, Eaux. Thermo-minérales d'Auvergne. 238 THE EARTH, CHAPTER XLI. MINERAL SPRINGS.-INCRUSTING SPIRINGS.—METALLIC WEINS.—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 magnesian salts. The purest water that the French chemists have yet found is that of the Dorne, a small river of Ardèche, 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. Pſence 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. 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 sur les Eaux Potables. f Lyell, Principles of Geology. INCA USTING SPIRINGS. 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 orifice, 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 of 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 is composed. On reaching this spot from Smyrna, something like an immense cataract may be seen in the dis- tance, 328 feet high and 24 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 2 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, Les Dépôts Calcaires de Hammam-Mes-Khoutine. f Tchihatchef, Le Bosphore et Constantinople. 240 THE EARTH, Sº ſº * : ſº º Fig. 77. Natural Bridge of Panbouk-Kelessi—after Tchihatcheſ. 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. Daubrée has seen these phenomena in action at the springs of Plombières. 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 * Wide chapter on “Volcanoes.” MINERAL VEIWS. 241 the fissures of Plombières 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 Ročhes, 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. Weins 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- bières and Chaude-Fontaine. In Tuscany sulphureous fumaroles proceed from the veins of antimony. In France and Algeria the waters of Syl- vanés and Hammam R'ira issue forth from beds of copper. Lastly, near Freyberg, a voluminous thermal spring has been discovered in a vein of silver. w 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. * Daubrée, Bulletin de la Société de Géologie, 1859. + Lyell, British Association at Bath, 1864. f Daubrée, Bulletin de la Société de Géologie, 1859. * Q 242 THE EARTLI. 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 which numerous liquid veins issue forth which are impregnated with salt. Lastly, the United States have the celebrated Springs of Syracuse. 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 cliffs 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. - 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. # Tchihatchef, Le Bosphore et Constantinople. IIOT AND SA LINE SIP/EINGS, 243 pears that a simple movement of the liquid is sufficient to alter the con- stituents of the water as regards its gaseous clements; 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- Fig. 78. Saline Spring * S 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 sº 244 - THE EARTH, hot baths in 53 localities, the principal of which are Bagnères 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 them 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 Louëche, 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, 1864. # Otto Volger, Ueber das Phänomen der Erdbeben, vol. ii. SUBTERPANEAN WATER-COURSE'S. - 245 CHAPTER XLII. SUBTERRANEAN RIVERS.—THE SPRING OF WAUCLUSE, 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- ſº Q]] % Žižj. cººfy. *ºffs º * R 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 TEIE 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 % Nº º º ... 'S # % Nº $% NIS: Esº º º º ...A.” # | | º T \ly RSX. : § º **- º §ſº t s N ɺl\t Ziſſº, sº. " 'hitº is -- *_º Z. Sº § º w º | ſº § wº 3. $º º:2:. -- º --- Sº .* º' Sº 2.sºss - -: º Zºº & §§§º:3# flºº - **** g * º, 2Sº *ſj//:/9. Nº #1 & sº # #ns § º ſº # *ś%2% "…º-ºº: 253 §§ %3::s ޺A: §§§ º § §§ r **ś ºšº : ſººn Sº ſº §§§ § % §lºß §§§ : 49 sº.g. ºffs šāºšič $º. Nº. - ºš Y' a * - - * * Sºğ - N s sºlº º - Fºº &#ºo? - "º 42 #ſº wº- $# N. *"S Sº fed #. ſº ... ºv- Şe Žº Bº sº ſº : ... ຠ㺠fºº; : .* - y t" > ºf: ºf . - z- 7. : -º-º-º: . … .sº - & *NChºente” f § ºš §§ i tºº-ºº: º º § º £º' jºšº Fig. S0. Course of the Touvre. N ;3?º ~ - r. - \|| Ż. Tºrº #N \\ &\º &2 “&ºx. *.x- barrier of rocky débris which 9bstructs the entrance; at that time it is quite possible to penetrate j. 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 Angoulême, 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 immediately 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 Angoulême. 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 Nîmes, 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 Vénéran, 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 may be 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.; * Wide the chapter on “Lakes.” f Marsigli, Histoire Physique de la Mer. # Villeneuve-Flayosc, Description Géologique du Var. 248 THE EARTH, The coasts of Algeria, Istria, Dalmatia, and the Herzogovina 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 Key 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 surface 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 l'Hydrologie. 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.f 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 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 |ffl|| §§§e=º; Aº -:#E 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 supposéd. 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 Abbotſ think that this power consists in the dis. * Wide chapter xliii. f Arthur Schott, Mittheilungen von Petermann, 1866. f Report on the Mississippi River. 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 which 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- tiºS L Xº. **ś *Sº -- ..~ - iº ge . ** * - w § j - |* { ſº Fº º % §§§ \ 4. }ſ & º º g sº * . .” sº º: : rººt --→ Tºjºs- a /2 rv\; - - ºffº'ºrº ºtſºlº \{ \$ºlº º Gºś º §§§ º * * * * *-* f : Bººrºº Zºº łºśº-ºº: º ºº ########## : # - Bºlſ: º º #EEEEEEEE|3:#E EEE 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 come 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- orable 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. * * Géologie de la Louisiane. Essai sur l'Hydrologie. SYSTEM OF UNDERGROUND RIVERS. 251 CHAPTER XLIII. SYSTEM OF SUBTERRANIEAN 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 débris 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; ſpots, enton/voirs, and crewa, in the Jura; embues, embucs, goules, gouilles, gourgs, gourgues, bétoirs, boit tout, anselmoirs, emposiew, avens, scialets, ra- gagés, garagaš, 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, t * Fournet, Hydrologie Souterraine. 252 TIIE EARTEI. 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 Trobich 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 casier 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. Put the water which drops from the stalac- tites has not yet lost all the lime which it held its solution; it still retains sufficient 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 and 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. ISut yet how large is the number of those vulgar admirers who, under the pretense of loving nature, seek only to profane horſ tº, When the action of the water is not disturbed, the needles and other deposits of the calcareous sediment continue to increase with considerable STALA CTITES.–FLOIRA AND IFA UNA OF CA VES, 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,f 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 - * Kuhlmann, Presse Scientifique, 1865. f Perrot, L'Ile de Crète. f Miniopterus Schreibersii. - 254 THE EARTEI. —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 blends 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 S-> antennae. course by means of enormous One of these Rentucky 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 4 o' §ºlºmº ºr º §º º ºlº º £ºr: }; §§ & ſ NºWiś; ºf M ... š Šlsº % a' ..,’ zº * Ż #!º-Eºm-sº à-dº §: 2. % § ~ º º à\} %/,\% & '%) £º t”, % lsº % X& f z %2, º, - - % º ºS 4% º ZX2 §§ % º % %; % § A & r º & P § 4. #ſº f |-Sºº 2:32, ºù º § #'ſ. § (£ §§ - #3 Nº & | º § § º % % ºf 'F, º' "…? ºwns ~. º, Yºº tºº, }} ºš % **}} *ś% º ×é; ºù \ sº % §§ %/ſº tºllſ|| %|} #}},Nº.4 %. § | % g £º §§ A tº gº * Yºr. º m %(ſ) ºffſ) º ºğ $o'; §§% % $º § jº ºš ºff.; Sºlºš ***{{ g º §º 3% º **.ſ.º.º. Jo’ r - %22 & º, ! | WIWA * - º - §§ & º º º º w ºſº"; SW & §§§ §3%. º: º ºº: * * * *::::: 3. º § & SNMN §N §§§ {lſful...! º ſº w ºv, #3 $. Vo f § ºx. St. *... ººº- \ º --- - º ***Alºys/º. * Wº - ºšŠºš’: §ºž. WR \ º ºº::S %iºW 8 * §§. sº: - * : & A Vill) Nº. %; % ºſſº, “ t liº ſ º Ø. - R * 3. . Nº & *z, * }, z S*SNū f w º *.. Sy sº w *** % :2 r". Sº § w £º ºft { % º º $33. NWºr §Mºſſl/4%%. § jºy ºf W §º sº w §§ º/lſº à §§ .4% - -, * * W.A" ºth ºlliſº th." § ſº sº º ºº::\ºlſº ... tº %tº ºl: tº § ſº R § * - º: §§ % º º *** - º sº e Fº @º º N-Z ;R2 §§ scº. In 2ſ2 ºść º § % % - ; }: Nº. % º 3. !'}ſ § |Nº. Wº sº - 3 %\º. !!!!Nº. º º #º W |/|| º º &t. º - º §§§ Wºź : †S º - º &º 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 CA VERNS OF CARWIOLA AND IST/RIA. 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 moth- ing more than an accumulation of cells. On one steep cliffside 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 cliff, 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- wants, 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. Tig. 84. Grotto of Lueg, Illyria. One of the Istrian rivers, the subterranean course of 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 Trieste. Virgil's description* no longer applies to the mouths *k “Fontem superare Timavi Unde per ora novem vasto cum murmure montis It mare praeruptum, 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 cleven 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 untoward 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 G ROTTO OF A DELSEERG. 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 C3, Vé divides; on the north the stream, the depth of which varies, according to º S º 6SN § N º ; Fig. S5. 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 débris 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 holes 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 débris is to be descended to reach the edge of the stream. It can only loe 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 boatºto 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 sieve), 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, $the water of a stream which is swallowed up in the rocks a little above º 259 ch of these wells. Torrents es- THE LAKE OF JESSERO. with a roaring noise in ea the plain rises ter. This is the lake of Jessero S-> “cribles” form in the wide space hemmed in by z, the lacus Lugens of the Romans. The surface of the sheet of d trans caping from all these open sea of blue an the cliffs a da- parent wa ‘knit or Zil §.§3€.2á№ÈS，¿? șśź%ģØ &= zº%} ØS Ģșš% Zğ`š Z，Ž§§ ??§§ś 、 ©į، ، ، ğ。 .%% ¿? %2wº … ·· - ºwº Źź@~Ø• • ſ^@^ %@Ø %@Ø∞ Ø2ØØØ@źž ſúģ% №gæ：№2%、。 ·źØŽ！*®§§§ź§ È\;Źź%šźșš%Øķ%}șš% REĢ\\2$ģ�žģ@%@ś }}}}}}}}}Ķ%ŹźØž%% | ģ%，2%%§§§•、 J~~~$：-Ķ 。§§§§5?Š%@Š§§%。 ■ºØÈ%…’%% •@šź% Ø%§éź=∞% ØZae �% 2% º'|| | || | 2 - ; at the time of great inun y lake, thus vomited out by the under- xtraordinary temporal area of 14,826 acres º ſă gh S away throu The water run 4,711 acres. than 2 less 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 Copais, in Boeotia, may likewise be compared to the Zirknitz lake, at least as regards certain por- tions of its basin. g AWAMES OF WATER-COURSE'S. - 261 CHAPTER XLIV. RIVERS.—VARIOUS DENOMINATIONS OF WATER-COURSES.-DETERMINATION OF THE PRINCIPAL BRANCH AMONG THE AFFLUENTS OF A RIVER,-RIVER IBASINS AND WATERSHEDS.—FORES OF CIERTAIN 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 2 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 (rivière) to mere affluents which are themselves fed by tributaries of the second order, or rivulets. In virtue of this purely scho- lastic distinction, the Argens, 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 Rhône, the Arno, the Orne, and the Arnon. 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. In 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 Marañon 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 Saône and the Rhône are only tributaries of the Doubs, which has a total development, from Mont Rizoux to the Gulf of Lyons, exceeding that of the Rhône 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 to 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 2 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 Rhône and the Seine are nothing but seconda- ry water-courses in comparison with the Saône 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 share 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- ORIGIN OF WAMES OF RIVERS.—ſº IVE/2 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 Solimočs 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 Alps, 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. ISut 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 IRepublic—where, however, the annual rainfall is greater than that of France—the prairies are dotted over with lagumes 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 crosion 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, Confédération 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 lever 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 . Riñihue, situated in the Chilian Andes, near the fortieth degree of latitude. 7 W º £ c...we, \\\\\\\\! ºr § tº \º º \\\\\ wº § Å łºśSº §§ §§§ cyº, §º: §§§ -ºº º \\ \ i \ r \ \ & * . . . . \º. +. * .5 N iº º sº \\ } º º (ſğ . § #f. ºy" . W. $º º sº r sº gf tº * º: ; {{!!. º de Panokavullº, *::::://ſº t ... * º t º Fig. 87. Cut of Rihihue, in the Chilian Andes. According to the unanimous evidence of the aborigines and the Chilian peasants of the country, the stream of Huahuum, 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 ls known under the name of the Caillitue. It is certain that further down it is replenished BIFUPCATION OF BITVER-COURSE'S. 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 Riñihue, which is a tributary 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 Riñihue. 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 : ~! %, - */ š. { & Nº. ~ §ºn 4 3. & s 7 º, :*º w wwiil. Wº% - ºw ź.ºš .* "º. & ºff, ***, V F, ºº: ºb", * All r 4\º: *… f º º sº-Jº * > º: . § }, *. † =: º § ſº %tº º -- º * : *% *... Kº **i........." - ** º &º *Lºkºuliº f º * K *ś º ^ 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 than 3300 feet at the foot of the lofty mountain of Sneehättan, 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. 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- ously into an affluent of the Têt du Roussillon and into the rivulet of An- goustrine, a tributary of the Sègre 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. 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 streams, 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; * Wide the chapter on “The Labors of Man.” f Fritsch, Mittheilungen von Petermann, vol. xi., 1866. | Salvagnoli Marchetti. § Simonin, L'Etrurie et les Etrusques. IRIVER-BASINS AND WATERSIIEDS. 267 the double communication of the water only takes place in an artificial way by means of a dam.” tº º º 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 3TE.Tof Paſs º *...*. º º §§ º º §§ #º º º ºº §§ A tº - º º, 3 - - * . .* g º g º º, º, ęż Sºssº º º * - . --- Fig. 89. Bifurcation of the Valleys of the Rhine. º sº º : º 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 des Plateaux et des Vallées 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 SSS §º Rºj ºšWNSºft|$ Žº º º | % § # :-ºº-ººººs º | º º % 3 Gº Mººrººz. ### |º º l gº à º º º % * º º § % £º gº |% A §º Al | § § §§ - f : •' º 2 : º, .º ſ §º º - - gº º # § *Nº. s tº: º ſſ # º NSA *. §º º Nº.u.,. 3: |\}\R} * - §§ º º-. . º § s. Şſ, § C • *: 27/ Wººl!' WNS - Tºº 4. Nº. 4 % % º § § ºllſ/ šº § 㺠- ſº #. W. º S =s: - º % º غ º 1. º º º :Eº º ºnwºo 4% § ¥= % 2. ' §º % º * 2: 3: -3S %3:; tº ź º º §§ 3233 wº % º š 3. ºğ: %\\ º % % a.º. WN %\ 2:3 wº (MVN W £32% E- º % !º º %. º % ãº. º * * º Žiš '** * - ** Fig. 90. Threshold of Sargans. probable that this mass of pebbles is a portion of a slope of débris brought down by the torrent of Seez from the recesses of the gorge of Weiss-tan- men (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, 1866. CHANGES IN THE COURSE OF Jeſſ/EIRS. 269 between the two basins, which were, indeed, once united in one and the S8,1116 OCé3D. º Zo E. of París º r- 3, 2. 52 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 commenced, 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 Pyrénées, the Gave d'Ossau forms a fork at the foot of the high hill of the Sévignac. 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 IIaute-Vézère 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. ORDERL Y DISTRIBUTION OF Jºſ/E/ES. 271 CHAPTER XLV. TIII, IIYDROGRAPHICAL SYSTEMS OF WARIOUS IPARTS OF 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, bo. 272 TIIE EARTH. 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 Marañon. In a hydrographical point of view, the continent of Asia may be di- vided into three entirely distinct 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 IIoang-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 cast 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 I3engal, to the cast 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 IIindostan 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: same 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 ach 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 1)TVERSITY 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 IIindostan. 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 Rhône, 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 Rhône and the Rhine, present some remarkable peculiarities. These two great riv- ers, nearly equal in volume, flow each in a diametrically opposite direc- 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. IIuber, Bulletin de la Société de Géographie, 1866. S 274 THE EARTH, and the Levanna, near Mont Cenis, 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 # Sº, - . S * g. 3. g © Jº º 3 ; 3 $ Asasy” .8 § § -3 à Ø- º # § 3. Nº - v) Hy w J ;3 § º º 3 YS NSubterrane- {\ll COll TSG N of the Ga- TO]]]] e. N join the Vistula.” In like manner, the Garonne rises in the glaciers of the 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 Ritter. . . .''. NORTH AMERICAN RITVERS. 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- molds has given the name of “Union 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 Saskatchewan. 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 great 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 [Jpper 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 less 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 eaccellence the country of rivers. There roll down * Humphreys and Abbott, Antisell, etc. 276 THE EARTH. 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, all the 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 Marañon in the Andes, the Parana and the greater part of its tributaries spring from the high plateaux 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 Rio Guaporé, 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 Marmoré 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- Ta. 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 Binué—a tributary of the Niger—various streams falling into the Congo, and some important affluents of the Nile. Still, the pºincipal branches of the large rivers take their rise at enormous .*. 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 ramifica- 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 l'Hydrologie du Nil. º st § %. THE RIVER AMAZON. 279 CHAPTER XLVI. 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. 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 Rhône 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.* • s 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 Boué. 280 THE EARTH, . ing fresh-water sea, which takes its rise at a short distance from the Pa. ºffic, 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 'garapés, 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. Avé-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. f Bates, The Naturalist on the River Amazon. § A CTION OF RIVERS ON THE LAND. 281 the surface of continents, to convey the life and the alluvium of lofty mountains down to the 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. In 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 eaccellence, 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. e 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 282 THE EARTH. cliffs. The projections are broken down, the fissures are filled up, a gracefully curved slope of débris abuts against the vertical 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 $ § § } i i.º.º. is ill ill- # # #: # - i i ; : i ! *S ſ |||s # §§ #: § §§§ §§ § # *-āº isjº 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. '. E. £; º: -Q SJ 3 QR º : º tº £- § § †: ;3 ;: §: £; .9 o CNº. {- As. *: ā... : 33 § 3 ; Ś ‘º # T : É 'T' & 3 3 : ă ă 3 # ‘s 3 ºf % º ‘3 # = 3 O © f O '82 # # ‘ºp ă ă # # § ; :- *-* H § 1-4 ſº Pig, 96. Slope of the Pó, the Tessin, the Oglio, and the Mincio. 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 estal 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 and 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 Ritter, Europa. 284 THE EARTH, CHAPTER XLVII. MOUNTAIN TORRENTS.—INEQUALITIES OF THEIR BEDS AND OF THEIR DIS- CHARGE OF WATER.—TEMPORARY STRIEAMS.–FILLING UP OF LAIKES.— 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 débris. 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 débris 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 mented 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 débris 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, 6ioules 2^ º 2.2%. 3’. Vº | º º º ºf , º Aft *. Ž. º •: º: º ºil - - w * : º f - - -- } º % % º % 3:3. 㺠-, * > º . . * - 2. *&ºº | º * º . \ º/ . _^. ºš * … wº §§§ 2 ->2/2 ºft:%2% >º * 2. % #. %% fºr-Tº:// § 2.3% S. • * % % % % %22 - º 2. g #. 3% *:::: º º - - 22.ſ: … - > sº 2… -- • * ...~ * * g Fig. 97. Circle of the Valley of Lys. The War 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 Tinée and the Vésubie.* 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 War. In great rivers, such as the Mississippi, the difference between high and low water is as I 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; and doubtless a comparative study of the inun- dations of all the water-courses in France would disclose still greater * Villeneuve Flayosc. f Belgrand, Anwales des Ponts et Chaussées, 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 to 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 the 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 water-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 wo have said, in modifying the relief of the terrestrial surface; but these 288 THE EARTII. 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 :---- £- d / sº .** | .*.* ~...º. Yºr: •º-, ** ..." . § tº 2::::::::::); * - w ***** * , * ^: **Tº - Jºy! ...; sºº -,-7, - §§ % ////' Wilſº. ~#4%. ---- Fig. 08. The Igharghar. débris fallen from the heights above. All the meteoric phenomen” of the atmosphero—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 débris, which accumu- late at the foot of the rocks in more or less inclined slopes. The torrent JºſèOSIVE ACTION OF TORRENTS. 289 into which this débris 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 bank of a flooded torrent 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 after year and century after century, the torrent clears away whole mountain sides which have crumbled down into it rock by ÉÉ £º Wiſºft|º]}\º º º % sº% % % º . §º § §% § § % º W % % ºf % É. à ſº % Wº º ź - ſº # - º %. º W - ; W N § § §§ § % \Ríº #}}|\ ſ % * ~~ à : | 3.3–1. ! N- - % W Z | i. º à. 7. %|\%. # d & \ %; º º |||| */ % - º/r º º/º Aft}; %| % §§ WR'ſ i. w º % º *SSS ſº º -Fº º % º2^ 3 sº Ø Ø % Ø - 2 º W */ §§§ §ft\}% §§§ Ö/XS tºº º yº \ - Wº% à §: º-º-º-º: §§§ sº ſº % º : º É §§ Š: § § (vº § º * º º º ſ/ ſº §§ § §ºś \ſº ºº:: | Wº º §§§§ º % §);} º sº-º-º-º: tºº 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 º-º-º-º- 3. base a small triangular valley, whence the Fig. 100. Quaºn of water leaps down into the lower gorge. In º 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 rosion ; Q 290 THE EARTH, of erosion which is found at their confluence generally assumes a quad. langular 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 ai. 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 fail 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 débris torn away from the sides of the mountain. The tooth of the 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 Ribbe. JEROSIVE ACTION OF TORRENTS. 291. kind are being formed every year. In some localities there is not a sin- gle green bush over a space of several leagues in extent; the scanty gray- 2° ro" FºssWºº [. ==TºššŠV º º º º sº \ \º sº, ºft 2-44. . 4. 2. * º }%|\Sºff - | | § % "N sº t 2, ---, º% º º º % ºft #S$ 2. %=\ #!/? % #ºft\; 4.3% º N % sº º §º º % sº § ſºº ... 71,... . § §§§§||\}=\!º: % § {{!!}}º. '' º: *ś%lº %2% \\ º %2% º #: sº § §3% \ º |ſº º Šć ºS- tººk li Laº alſº A$ yº ſº Čšiščğ. º §% ºff ſº §º º º / S %| ! \ s flºwſ: . º º *S § ºf \\\\"...º.º. º 㺠§: ºr º | §lliºğ §§ fºss NS §§ & a- - **A.Q N.** > \º- º : § §’” SºśWiśSN §§ º: - s: §: • §§ * * * ~s º ſº §º #º º | § [. \ { \ º % % º, a, , º, . %%% 5%; {{{{{{{ \ s W fºr: § ~~ %% º tº ſº # 2 WºmºN= | º & 3: % §% |º º | § ×2 º ..º º _----- M f --- § º hº ". . ! § 2% 㺚 § º %; W ſº º 22% §§§ "º. # **śćW!!}=#3% - g §§."ºs sº º 2.2 : º, ĺ ºś º *ſº hºº ſº sºgº : º ſº * > E: 2, %. , 'N v (; 1 % $º %iº ºr a § Nº. º § % § §§ § s Nú § §. º º sº º - * ** º **. % % § - % 62. % º, % # º w % º a º ºz º:3% #2% §: ſ %| % º N % %|\}=3%lſ's 3. º º º º % 2. % \ * % º e---. £: º Sºs *. ---, -- * a- s' à 5. - §§ Q - e. º: 3.3 - : º : à 2. º ſy º £º %; tº; % \ : %22% ºf . º; *-jºº %|}}}| º § ^ Bºº º & % º #4% t (7 Fig. 101. Valleys 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 employés 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 offir-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- TALLI. *. 293 den check in its progress, it deposits over a long extent of descent all the débris 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- § 3. 36% ºftº: § & & & § º § º º ºx & º & 2\{{{2} % ºMº ſ ? § & º ºš º § ºś % §§ § º -3 º º * (, §º sº Fig. 102. Talus of Débris 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 débris. 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 CEtzthal 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 débris 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 débris 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 and 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 - Fº §§ - º: º º §§ º §§§º: §§ § º º V § 2, "...,' º, º #. º & º * º § &º - d t : N *ś §§§ 49. złº **.* # º º #% wº §§§ §§ § ºš sº () º P § º §§ § §§§ ºš a 8 *-*. F º: $º. tº: - | º º |||}; ſº º t jº º ºf ºil Fig. 105. Lakes of Thun and Brienz. FLUTVIATILE 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 EAIRTH. CHAPTER XLVIII. EROSION OF LACUSTRINE DIRES.—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 SC3b. 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 *º-ºº: §§§§ §§ N - - … ... 2% tºſiſ”:4::::::::::tºs Ž&º § Š 22 & §§ º § §N §§§ Fig. 106. IFilling 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, 11% miles from the end of the lake; it also extended down the stream in nar- row basins as far as Ecluse, 94 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 débris below the gulf that the furious shock of the torrent has hollowed out at * Wide the chapter on “Lakes.” N Nº. § §§§ §§ § § FILLING UP OF LAKES. 297 Fig. 107. Alluvial Deposits of the Rhone and the Dranse. 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 fall, 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 and volcanic eruptions. Of the former, there are some in Europe which are very remarkable: such as the falls of the Rhine at Schaffhausen; the four cataracts of the Gotha-Elf at Trollhäta (dwell- ing of sorcerers); the IIjommel-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 Mjösvand 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 1300 to 1400 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 º 298 THE EA RTH, • 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 e 295 yards wide—take their final Vz, leap, and describe their vast para- tºl bola, 147 feet and 160 feet in height. tº tº Ej \" • ** ** } \'. § sº §Wº | §ſ! NW | º t N liftſ: % 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 as 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 Afonso. 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 90 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 $ * % - r: i- ºf I- º -º-, --~~~.--- NºS$ - Nº. - Rºgºź º º Wººlºº £º: : & º §º - º gº == à º Tº &\Nº. 㺠aggºgºź §§§ ſ(3. rerºgºś --- .* : * Sºº Lºg. 㺠º jº. ‘…**_-, 4---- ºf: à § §: #######38: º º º! º Z. - º www. : Ynº. " - iº § jºr- - #34}\ #3; º : tº t º **** - º § - º º W vº º wº §§ tº W §. Nº. §: º 2 mºtº sº;º * * * *.*.*. º º º -Eas: Sº K w *W** y º:Es: QWYA § Wº º § ğ. % tº § º - º * º --~~~ º n N - Sºº º º § Š. | WNº. W %; §§§º º º := \º &% º §§3 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 th. 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 * * Avé-Lallemant, 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-od-Townya, or “Thunder- ing Smoke.” With regard to rapids, we find them on most rivers at different points | * §s Sºsº %5C޺ *~~ SS- § 32 ºfflºº Sºº ##$# %: º - - % $4 º X) - sº §§ º *Nº º f |% WS; % ºft - É i s:º:.” ſº § : à 333 gº & É ** º ºw. - gº º: § tgº # º : w % 3. 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 dé- bris, and pile them up like dikes across the current. The American rivers * Baines, Exploration in Southwest Africa. SA FALLS AND RAIPIDS. - 301 are the principal localities where these rapids may be contemplated in their full beauty. Humboldt was the first to describe the rawdales 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 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 raudal 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 Rhine. 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, Voyage aur Régions Equinoriales. 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- & ** -ºu () v-H i * ~ * ~ *, *...* g “ (, , ~ §W /2\ºss' sºnſ • . . . " QSYWilſº \ , ºf 8 ŠS ºil ‘. . . . . **ś §§ %22S$W//.3% .* %.º ºš * *ś * \!/ % §Wºź. % 222 stº S-. Jº A \ * * ~~~\ … §§§ • sº. 3. SSS N SSS) # $SRYS Ş/ſºs." sº NS/šš # - - \ 23 Y : | É % -* § ś 2. 9:…]" - - ºš 2% ~ Ž % º ść 22% ſ ŠàºSN ...” 22. ~ : - Ø º # - *~ $N sº 22 *AS'. šč ; [..."; %%% ººš% % § §§º %•', 2-3-2-222 - * > § % - w -*. **T. §§ºś Žºššºšº § £2. § º: 㺠* º SS-3 -º- §º Nº. º ‘. 㺠4 §ºšč A & º: }% º I &| | > Zºº N § #. N\, * * . £3: º, -8.3 #4 É$$. tº . ." § ºš rººt:SE gº ºr S. . *3%||\!/? Rººs º § • * 2. {\! | § º 'º';. § º àQ º : º-2 lºssº § CUIP º | }º y * • ? / Wº: \{!/2 㺠\,\w 3...? º 4. à-3 Q & # Sº ‘. . . . . º WNºş%|\ N º // \\ º ºS § \ §§ ſº * *ś §: WN; § - rº; Sºº- º $S – T. * * tº :*: ...” % | SS -: , , º % Ž%ff | W Fig. 111. Cataract of Felou, Senegal. % 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 - º - Yx ſ *sº 0. B-FEE-ºr-N - - $EEE sº- \ - Nº. E- - C & ;=º §: - - à §= % ɺle d *-** §I===EEEEze= G º ź * - a. Niagara Limestone. c. Niagara Marl. b. Clinton Group. d. Medina Sandstone. Tig. 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 gººd 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 ; Goat Island will become united to the main-land, and the River Niagara, constantly receding toward Lake Erie, will pour down the whole of its water in one formidable fall. It may likewise be presumed that the height of the cataract will tend to increase; for the calcareous strata which gave way under the weight of the water gradually augment in thickness in the up-stream direction.} But we are scarcely warranted in estimating, even approximately, the time which the Niagara will take in receding to Lake Erie; for, as M. Marcou remarks, the prodigious manufacturing activity of the Americans may much modify matters in this respect. A canal, which is, in fact, a * According to Lyell. Mr. Bakewell says that the annual retrogression of the falls has been nearly a yard since 1790. # Marcou, Bull. Soc. Géol. de France, 2d Series, vol. xxii. 304 THE EARTH. perfect river, already turns a large number of mills on the American side; and if the river is tapped by thirty or forty conduits of this importance, the mighty Niagara will become nothing but a humble rivulet. “Arts and manufactures will have disarmed the thundering Jupiter.” But Lake Erie itself, which, actording to Ellet, contains at present more water than the fall could run off in six or eight years, will be perhaps filled up with alluvium before Niagara has been able to wear away the lower ledge of rocks which prevents the lake froßh rushing down bodily into the basin of Ontario. - That which the future will perhaps accomplish as regards Niagara has already taken place in the Mississippi. Nearly half way between St. Louis and Cairo, the river penetrates a defile which cuts through the chain of the Ozark Mountains; rocks 300 feet in height rise between the two banks, and on their perpendicular sides may be clearly distinguished the lines of erosion which were once traced out by the current of the Mississippi. In former days these rocks formed a barrier over which fell a cataract like that of Niagara, which, too, like the former falls, constant- ly wore away the strata which served as its bed. Above this barrier of hills the water of all the upper tributaries united in a vast lake, which extended north as far as the mouth of the Wisconsin, and, joining Lake Michigan on the east, covered all the immense prairies of the intervening peninsulas.” In like manner, the Rhine, the Danube, and a great many other rivers, the course of which at the present day is tolerably uniform, presented a succession of lacustrine ponds, placed in gradation one above another, and united by cascades. The rocky barriers situated between the ponds have been gradually demolished and washed away by the wa- ter; some of them have even been pierced through at their base, and this is the origin of the natural bridges which throw their arches above a great number of streams and rivulets. The Pont-de-l'Arc, which the was ter of the Ardèche has slowly bored out during the course of geological ages, has a span of not less than 177 feet. The famous natural bridge Of Virginia is only 111 feet in width. - By operations of this kind, rivers gradually regulate their slope and effect a communication between plateaux of different height, which sink in successive gradations from the base of the mountains to the sea-coast. Whatever may be the irregularities of the continental surface, running waters cut out their beds in the form of inclined planes, and give them a more or less regular slope, which is followed by merchandise, travelers, and even civilization itself, in order to penetrate into the separate basins of the river-system. Every cut made by a river across a chain of hills or the side of a plateau may be considered as a gate opened through a wall dividing two distinct regions. Thus, in studying the monography of each river, it is necessary to study specially the apertures which the wa- ter has made through the barriers which once opposed its free course. By a succession of victories obtained over enormous masses of rock, the * Humphreys and Abbot, Report on the Mississippi River. º THE “GREAT TOWER,” - 305 river has succeeded in emerging from the lacustrine reservoirs where its waters once lay dead, and has gradually constituted itself as a living in- diyiduality ever at work shaping anew with its waves, its alluvium, and the bars at its mouth. The Danube obtained its hydrological impor- tance from the time when its waters ceased to be lost in the former lakes which have now become the plains of Hungary, Austria, and Wallachia. Oftentimes, when the river thus cuts away a passage through a rocky barrier, it leaves standing erect, as an evidence of the former state of things, an islet of hard stone which it has failed in washing away. In the most picturesque parts of their course, almost all large rivers exhibit some of these solid masses which continue to resist the pressure of the water some centuries after the destruction of the surrounding strata. Thus, on the Danube, we find those proud rocks, with their perpendicular sides towering up, like enormous pillars, as high as the level of the rising ground by the river-side, and crowned on their summits, some with a feu- dal fortress, some with a hermitage, and some with nothing but a clump of bushes or brush-wood. Thus, too, in the Mississippi, not far from the spot where the whole body of its water once poured over a precipice in a mighty cataract, we notice the fine rock which, from its form and majestic aspect, has obtained the name of the “Great Tower.” This rock still bears, at a height of 132 feet, the circular line of erosion which was once traced out by the current. But although we still find a pretty consider- able number of these natural water-girt “towers,” the greater part of those which once existed have gradually disappeared under the action of the elements, and their place is now marked only by hidden reefs or rocks on a level with the stream. * . TT 306 - THE EARTEI. CHAPTER XLIX. FORMATION OF ISLANDS.—RECIPROCITY OF CURVES.—WINDINGS AND CUT- TINGs.—SIIIFTING OF THE COURSES OF AFFLUENTs. IT is therefore a fact that rivers, like all other natural agents, never cease in their work of destruction, but they destroy only to reconstruct in another place. They are continually eating away rocky islets, and em- ploying the débris in the formation of islands of sand. Wherever some obstacle exists in mid-current, such as a bank of rock, the trunk of a fallen tree, or some construction of human industry, the water, arrested suddenly in its course, divides into two flows as if before the cut-water of a ship, which, gliding round the opposite sides of the obstacle, rush, one on the right and the other on the left, either against the remainder of the water flowing regularly down the current, or in small streams against the banks themselves. From this results a double encounter; the two-curved flows, being more or less inflected and retarded by a thousand local circumstan- ces, are thrown back toward the middle of the river, where they meet, each having described its parabola. There, one portion of each of these flows continues to descend, describing a more elongated parabola, while another portion flows into the comparatively tranquil space which lies be- low the obstacle, and gradually deposits on the bottom the sediment with which it is charged. Thus is formed the first islet, which is destined to increase by degrees, and to serve as a starting-point for a series of other islands and sand-banks which make their appearance in turn in the extent of tranquil water embraced between the parabolas of the two curved flows. The Germans give these islands the name of “Werder” (from werden, “to grow” [?]), to point out their slow and gradual mode of for- mation. In conformity to this same law of the seriation of islands, banks of al- luvium ought likewise to emerge regularly at the confluence of two riv- ers; for there, too, the masses of water come in collision, and, being mutu- ally repelled, again approach one another in elongated curves. In fact, the tongue of land which separates the two water-courses is often contin- ued by a series of islets below the confluence; but the force of the current being considerably increased by the doubling of the liquid volume, and the joint bed being always much less in width than the sum of the two beds together, the stream must naturally gain in depth all that it loses in sur- face. The water, being confined in a narrower channel, hollows out the bed with increased energy, and thus tends to prevent the formation of sand-banks.” The alluvium is deposited in the interval between the two * Won IIoff, Veránderungen der Erdoberfläche, vol. iii. FORMATION OF ISLANDS. 3{}7 - e - - º - ..?? º currents, and helps to lengthen, in a down-stream direction, the “bec” ol tongue of land which separates the two streams. º Ho 5 * º * º * r a º - ſ %2 º % — As 45" w Fig. 113. Series of Islands in the Western Scheldt. These chains of sandy islets would always be deposited with the great- est regularity if the river descended to the sea in a straight line. It is true that every water-course, in obedience to the law of gravity, seeks to scoop out for itself a rectilinear channel, so as to gain the ocean by the most rapid incline. But the irregularities of its bottom and banks consid- erably modify the direction of the river, and cause it to describe a series of curves or windings, thus lengthening the total extent of its course. Thus another law, that of the reciprocity of curves, is combined with the succession of islands in beautifying the surface and contour of a river, and in causing it to incessantly remodel the ground of the valley through which it flows by hollowing away the ground, sometimes on one side, and some- times on the other. Some lateral impulse communicated to the liquid mass is all that is re- quired to throw the current of the river either to the right or to the left. If the water strikes against a wall of rock, or any other obstacle placed across the regular direction of the stream, the latter rebounds so as to form an angle of reflection equal to the angle of incidence, and, induced both by its impelling force and the general slope of the bed, it becomes more and more inflected, and describes a parabolic curve toward the opposite bank. There its current is again turned back, and again takes an oblique course across the bed of the river. When the first seriation is once brought. about, the current must necessarily form a succession of windings, in con- formity with the law of the reciprocity of curves, which is, in fact, nothing more than the law of the pendulum. Each oscillation calls forth an equal 308 THE EARTH, and isochronous oscillation in a contrary direction; each curve calls forth another curve of an equal radius and equal velocity. If the fluviatile econ- omy was not constantly modified by the varied composition of the soil and §§ E: 22. ... (2 - 2 •., * Sºº 2: 2.É.332.21.3. ‘," A., !"Vº2% § Šs= - - --- ; £3. ~: * - >N S - - - - - - * * Sº SS + . . - º * ! \ Y, Y §§ 3 Wºlff ſºlº § #: - .:23 a ſº," " a 4° #F#: º - § Šºš ::::::::::Fººt-º; SN'S WVVV-V sºs ><ºº. == Å2 \ AºS § § w ŠEŠ N º , W. . . . . º, º ºxy: :". *:::: { 'Sº Yº - § Š== Nº àº, , ...Wºlfº: ; ; ; §§§ \ % --> S >SS §§ N Š -- sº .;4 l' º:::::::::::::...; º \ W \ \\ \ . . .'; ; ; | \ . . . . . ;-º-º: \\ §4/º Wº W.W.1% ºf jºyº,SX//Z24 SSS R \\ # §§§ Nº p. R. M §§lſº y §§ º ºš); sº | \ º N/S #y \ % \\\\\\|\;\|/ N º º * º ºº %iº Nº Ş. §§ º | ** S | \\ Nº. §N\, - § §§ sº º Sº º º []§ ºº Ø\ Q 32 t º º : & e s & - . * * . . .”. Fº t Ø \\ Ø 23 &\; §º % Ş - & ºš. / ſº W & º º º \ º | º | % | ſ/ % | º §: *ś % Z * % 22:3- sº- ſº - --> ſ *º £, %iº fº º N º * º 2:2-º %. Á #$ §§=; º #E: §º & \\ ñºs § ; §º £4 § § §§|ſº º §§§ º º º f § :- 3&º º º § § **. § - Š §ºžeššš Š &º j à 㺠% ſ §§ ź|\º ~~~~ - § : º tº ||f|5:# § &N º º jº 4||N * £ * f 5: ..º & ** * Sº .*.*& Ç º-> \\ W Sºº-º-º-º: N §§ º % § S. º é Žes § % Wºº Sº Fig. 114. Meandering of the Meuse, at Fumay. the immense diversity of the obstacles of every kind which it meets with, the river would flow down toward the sea, always forming a series of zig- Zags as regular as the oscillations of a pendulum. TWINDINGS OF RIVERS. 309 But the mass of the current does not confine itself to merely striking against the two banks in turn; it also continually wears them away, and modifies their outline. When the water dashes against the bank with all the impetus which is communicated to it by the current and the action of centrifugal force, it tears away the earth, dissolves some of the solid par- ticles, washes away the sand, and has a constant tendency to penetrate farther. Being then driven back toward the opposite side, there, too, it destroys and washes away the soil before it is repelled afresh to continue on each shore alternately its work of destruction. Thus, by a law of equi- librium, the current undermines each bank in turn, while its alluvium is de- posited at the points of the two bends. In consequence of the succession of bends and points, the windings are sometimes almost perfectly annu- lar. A boat leaving the upper bend describes a long curve in following the river, and when it arrives at last at the lower bend it is sometimes ac- tually in sight of the starting-point that it quitted long before. In the greater part of its middle course the Mississippi forms a series of windings so exactly like one another that the Red Skin Indians and the earliest Eu- ropean colonists were in the habit of estimating distances by the number of curves which the river described. These windings, however, in a cer- tain point of view, are of the very greatest utility for navigation. Every bend has the effect of moderating the slope, and, thus retarding the veloc- ity of the current, proportionately augments the mass and the depth of the Water. # s\!!!, º <3 º, , 2 § tº WNº - r- & º * - Jo’ Rig. 115. Meanderings of the Seine. By dint of gradually washing away both the upper and the lower bend in a contrary direction to one another, the river constantly tends to dimin- ish the isthmus of necks which still connects the little peninsula with the surrounding plains; thus the time will ultimately come when, the isthmus having disappeared, the two bends will be united, and the winding of the 310 - THE EARTH, stream will be converted into a perfect ellipse. Then, unless the labor of man offers any opposition, the whole liquid mass will flow on in a straight line along the rapid slope formed by the junction of the two bends, while the water still remaining in the old beds will become sluggish and dead on account of the slight slope which is afforded to it by the enormous curve of the circuit in comparison to the newly-formed passage. The rapid wa- ters of the upper bed striking against the still water in the former winding are suddenly arrested in their course, or even driven back; they then de- posit the earthy débris that they hold in suspension, and thus gradually form natural embankments of sand and mud between the two old beds of the river. It is not long before a similar embankment likewise separates the two beds of the lower bend, so that the forsaken winding is ultimately left without any communication with the new current of the river; its water becomes stagnant, and it is, in fact, converted into a lake. In the basins of the Mississippi, the Amazons, the Ganges, the Rhone, and the Po, there are a considerable number of these circular lakes. We may trace ~ Z 3. S\},*º º § § ºSS § §|- .*^.SS-SSl§ \\* —St.§ S - *-*. %/ | sº ſ sº tº=== # % =#% S$ Āš / º É *IFEMA == s-> - SE: PºS £: S; § ſº. Fº §§ ſº &AW = 㺠Fig. 116. Meandering at Luzech. M|DDLE COURSE OF THE MISSISSIPPI PL, XVI 9- West nº lºans, º w Enº by Erhard - Drawn in AWullmun alter A Humphreysst Abbot. HAR PER & BROTHERS NEW YORK wº XVINDINGS Oſſ' ſº I VIJ/ºS. 311 out with the eye, as it were, three rivers, one of which, active and living, flows without interruption from its source to the sea, while the two others on either side are become “dead waters.” The remains of them, scattered : sº ºğ &rº ºSN: ; § §§§ *~~ º y Nº N N s ‘... * % º N. 3: 34 tº º º ºan D-GULF º PORT CIBSON oº: 2, ; : & % º 2. gº X* º Bruinsbury * gº; 2. - -- º,50 aſ sº Fig. 117. Old Channels of the Mississippi. all along the existing river, still point out the Spots where once extended its ring-like windings. In Consequence of these alternate shiftings of po- sition, the valley is always much wider than its river, and along its cir- 312 * THE EARTH, Quitous path winds the continually changing bed of the existing stream. In some parts of its course the Po onl and destroying each of its meanders.” y takes about thirty years in forming w * …W. ...].`WA'º & §º §§ & Aş º ºnſºri, '… º ſº ** º $rs N-is .5’ © SS w p "TS §" *A* y * º * s ** v vºw # , c\}'t o Pi º, ºr • * * Wrº.§ . x.} ; o *ſºn i º º $ :2. § § : © # $3 sº º- #. § |% ..o”. § ºr..." •'t * x,y'ſ *W.2. ; :- 7. §§§ §º * Lºs 4.3% ºS3.2× É lº ARLSRUHE * gº Fig. 118. Old Meanderings of the Rhine. The perforation of these river isthmuses is not always brought about by the sole action of nature; many channels uniting two river-beds have been dug out by the hand of man, and, thanks to the currents which have * Elia Lombardini, Dei Cangiamenti del Po. OUTTING OF CHANNELS. 313 deepened them, they have ultimately replaced the former beds. Some en- gineers have gone so far as to propose to carry out a systematic series of operations as regards the whole line of the Mississippi, and thus to rectify the bed of the river from Cairo to New Orleans. Since the colonization of Louisiana, the labor of man, assisting the action of the currents, has al- ready rectified several beds; in this way have been formed the “cuts-off.” of Bunch, Needham, Shrieve, Point Coupée, and Fer-à-Cheval. Above these different points the isthmuses are much more difficult to cut through, on account of the strata of compact and hard clay which extend immedi- ately below the superficial bed of the modern alluvium, and are not easily washed away by the water. Thus it was that in front of Vicksburg a por- tion of General Grant’s army worked in vain for several months endeav- *oring to cause the current of the Mississippi to pass through a channel cut across the narrow isthmus of the right bank. Nevertheless, all these “cuts off” dug out by the hand of man can not fail ultimately to become obliterated; for, in conformity with the law of the reciprocity of bends, a river, when deprived of its windings, is not long before it forms new ones. This was the case above Compiègne, where it was vainly attempted to straighten the course of the Oise. In a very short time the river made fresh windings, the development of which was found exactly to equal those which had been done away with. It was managed better in fixing the course of the Midouze, in the Landes, for there the ingenious idea was adopted—and followed by success—of giv- ing to the river a series of meanders of perfect regularity. When man attempts to meddle with nature, he can only succeed in permanently mod- ifying its aspect by studying the constant laws of its phenomena, and by making his work conform to these. - The idea of digging out and maintaining a straight channel between two parabolic bends of the Mississippi is in no way more absurd than the idea of constructing piles perpendicular to the current of the stream, in order to limit the bed of the river, and to throw the waters into a regular channel. By operations of this kind, contrary to every principle of hy- draulics, our French engineers have entirely ruined the system of the Loire, the Garonne, and several other water-courses. The Loire—a river which is the despair of engineers, and still more of boatmen—is distin- guished above all the streams in France by the inconstancy of its current, and the continual shifting of its navigable channels. There is a very great difference between the mass of water which a river rolls down in flood- time, and the slender rivulets which slowly make their way through the sand in the dry season. Now, as a lateral shifting of the current takes place at the time of every fluctuation in the level, the result is that sever- al temporary channels are formed, and obliterated in turn. Some mouiſ- les, or comparatively deep holes, are certainly to be met with almost con- stantly at the concave extremity of the bends, where the partial currents unite; but every where else the bed rises more or less over its whole ex- tent, so as to form ridges (rácles), and navigation becomes impossible dur- 314 TIIF EARTH, Fig. 119. Channel of Vicksburg. ing a great part of the year. This fatal interruption to commerce, repre- senting an annual loss of many thousands of pounds, would not take place if it was decided to adopt the system of “guiding banks” proposed by M. Edmond Laporte,” and subsequently by M. de Vézian. Instead of recti- linear rows of piles constructed across the bed of the river, embankments should be raised formed with a parabolic curve, against which the princi- pal current might strike at all seasons, so as to describe unhindered its regular series of serpentine curves; this is the only plan for insuring the greatest possible depth to the channel for navigation. The annexed plate, \ borrowed from M. de Vézian's work, points out the position which the em- * Gironde, September, 1864. f Annales du Génie Civil, May, 1863. NAVIGATION CIMANNELS. 315 bankments ought to occupy, and the direction that they would communi- cate to the current of the river. Even if the mass of water were to remain the same º year to year and from century to century, it is certain that the mere fiction of the cur- rent, striking each bank in turn, would in the long run be sufficient to alter the curves of the river, and gradually to remodel the ground in the valley. But the liquid mass of every stream is incessantly varying from the com- mencement of spring until the end of winter. It increases during the rainy season and when the snow melts; it diminishes, on the contrary, when the supply from the clouds, the snow, and the glaciers is not equiv- alent to the water which is absorbed by the innumerable rootlets of the vegetation by the river-side, and by the continual evaporation caused by wind and heat. Under the influence of these various phenomena which either increase or abate, the level of every river constantly fluctuates be- tween flood and low-water. The current of the stream is consequently shifted, first to one side and then to the other, and thus every day con- tributes in a different way to the erosion or consolidation of each of its banks. The quantity discharged by the river during flood-times being five, ten, fifty, or even a hundred times as much as at low-water seasons, it is hardly to be wondered at that the erosion accomplished by the cur- rent should also vary in very considerable proportions. By dint of manipulating the small particles which it has itself been the means of conveying to the alluvial plains, the river ultimately succeeds in completely altering the direction of its own tributaries. The short prom- ontories which are situated at the confluence of the principal river and the streams which run into it are constantly lengthened in a down-stream di- rection by all the sandy or muddy débris which is deposited by the two currents. The two masses of water, which are ultimately to encounter one another, tend to take a direction more and more parallel on each side of this increasing promontory, and, developing their windings on both sides of their axis of descent, thus make their way side by side through the plains. A magnificent example of this inflection of river-beds may be noticed in the valley of the Rhine between Basle and Mayence. All the affluents that the Vosges and Black Forest send down to the great river bend to the north as soon as they have emerged from their natal valley, and wind through the plain, tending in the same direction as the current of the 316 - * THE EARTEI. Rhine. Above and below this wide plain of alluvium, in which nature has afforded no obstacle to the free passage of the water, the lateral rivers do not double round in this way before they join the Rhine. Being kept $4. r º s F tººk 4: ºz Tºº - * . >\" º: / *ś §. *S - § ºzzº, 6. º º § Gº X: §§§º º §. | º º . º &# º t § f ſ % **, *, -ºš, - *—º - wºujyº. 3. !. ºw.… § §§ ; * º-3 º, e - “. Nº § ſº §: ; Tijº. Kº *4& A.H.'s : ºğ jºº Ş. º *'. *$ º % º: § & ºš. * sº º § %; § sº * *h rº Nºtes º - W N º: * * lººp ºffiºſºſº.'"º º Fig. 121. Middle Course of the Rhine. back by the mountains or hills which command them, they fall directly into the river nearly at a right angle to it. FLUCTUATIONS IN RIVE/3 LEVELS. 317 CHAPTER T. PERIODICAL RISING OF STREAMS.–“ EMBARRAs.” OF FLOATING TREES.–ICE- FLOODS IN THE NOIRTEIERN RIVERS.–INUNDATIONS. A LARGE supply of rain-water being the principal cause of the swelling of rivers, the rainy seasons must necessarily be the times when floods are generally produced. In tropical regions, where the zones of clouds and showers shift regularly from north to south and from South to north dur- ing the course of the year, the fluctuations in river-levels can be calcu- lated and predicted beforehand, just as the seasons themselves, according to the passage of the sun over the ecliptic.” When the luminary shines above the northern hemisphere, and dry seasons prevail on the north of the equator, the water-courses in the northern tropical zone become low, and many are completely dried up. During the winter season, on the contrary, when the sun has brought back to the north the rain-clouds and tempests, then the rivulets, streams, and rivers again swell and flow brim- ful of water. The same phenomena take place in a contrary order in the southern hemisphere. Thus the level of running waters on the north and on the south of the equator fluctuates in turn, so as to form a kind of annual tide, which in its regularity may be compared to the daily tides. of the ocean. We must, however, add that in all tropical regions the periodicity of the annual floods is variously modified both by the relief of the ground and also by ačrial eddies and other phenomena which have an influence on the falls of rain. Among all the rivers of the intertropical zone, the floods of the Nile have obtained the most world-wide celebrity. Herodotus and other his- torians of Greek antiquity have told, with a sort of religious astonish- ment, of this periodical swelling of the sacred river which conveys to Lower Egypt the soil which nourishes it. To the agriculturists by the river-side this beneficent flood seemed like a miracle, and their priests never failed to take advantage of it, so as to increase their power among the people. So long as the valleys of the Upper Nile and its tributaries were unknown, it was really difficult, when surveying the annual inunda- tions of the river, not to consider it as a prodigy. The course of the Lower Nile is not fed by a single tributary; it traverses an arid country rarely watered by the rain of heaven; a burning sun evaporates its wa- ter, and yet, all of a sudden, about the beginning of July, the river-level rises, without any apparent cause, in its wide isle-studded bed. The wa- ter rises, and goes on rising, and from August to October it covers the sand-banks, flows over its brink, and, inundating the banks, pours itself * Vide the chapter on “Clouds and Rain.” 318 . . . . THE EARTH, out in strata no less regular than the annual rings in the trunks of trees. At the very highest flood the river often contains a mass of water twenty times” as great as that which it conveys to the sea when at its very low- est, and yet perhaps the Egyptian sky has not for several months yield- ed a single drop of rain. This prodigy, incomprehensible enough to our ancestors, may nowadays be easily explained. The enormous mass of water, which serves to irrigate the cultivated districts of the delta, pro- ceeds from the snow and rain which the clouds so abundantly shed on the mountains of Ethiopia and on the other countries of equatorial Africa. There are many water-courses in the intertropical zone which afford the phenomenon of periodical floods with as much regularity as those of the Nile; but there are none which are more curious in this respect than the great river of the Amazon basin. This “Father of Waters” flows: nearly under the equator, and receives simultaneously the affluents of two hemispheres. Owing to this arrangement of its river system, the floods of the northern rivers take place in summer and autumn, while the southern tributaries overflow during the winter. The principal river and the Madeira are mostly swelled by the equinoctial rains, and their floods take place in spring and summer. An actual system of compen- sation is thus established in the lower bed of the Amazon between the tributaries flowing in on the right bank and those on the left. When the Pastaza, the Japura, and the Rio Negro are at low water, the Ucay- ali, the Madeira, and the Tapajoz are running brimful; when the latter begin to get low, the northern affluents increase their mass of water. Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. Tapajoz. Madeira. Japura. : Rio Negro. Amazon. 1. Rio Branco. -*— Fig. 122. Compensation of Floods in the Basin of the Amazon. Beyond the tropical zone, rivers must necessarily manifest less regu- larity in their annual floods, the rains themselves being more irregularly distributed among the various seasons. Nevertheless, an unquestionable. system of order never fails to show itself each year in the fall of atmos- pheric moisture, and this system is again met with in the corresponding fluctuation of the river-levels. This is a fact which may be proved by the study of various water-courses. In regions like the north of France, which are favored with rains in winter, spring, and summer, the floods, * Elia Lombardini, Essai sur l'Hydrologie du Nil. J2ERIODICALL FLOODS. 319 generally take place between the 15th of October and the 15th of May, and it is only due to the rapid evaporation which takes effect during the hot weather that summer floods are so very rare.” In the Mediterranean districts, where 'autumn rains predominate, the water-courses begin to swell toward the end of the year. In those river-basins which, from the vastness of their area, extend into several meteorological regions, the fluctuations of level, which succeed one another with more or less regu- larity in each of the different affluents, are combined so as to form a fresh series of floods as regards the principal artery, and the general course of these floods may be easily foreseen. The most striking exam- ple which can be mentioned is that of the Mississippi, a river which unites in its vast bed the water coming from the great western deserts and the streams which flow down the pleasant valleys of the Alleghanies. At New Orleans the river commences to rise about the 1st of December, and its mass of water increases until about the middle of January, which is the time of the first flood. Then the level slowly sinks, and afterward remains nearly stationary during the months of February and March. In April and May the river swells afresh, and in the course of the month of June it forms the great flood so dreaded by the planters. Immediately after it sinks rapidly until the end of September, and its lowest level coincides very generally with the commencement of November. Several water-courses in the temperate zone exhibit, in the fluctuations of their level, a phenomenon of compensation similar to that of the Ama- zon. These are rivers which are replenished simultaneously by streams fed by rain-water, and also by torrents increased by the melting of snow and glaciers. The variations of lowland streams being, as regards the seasons, precisely contrary to the variations to which mountain tributa- ries are subject, the level of the main river remains at a nearly regular height. The rain-water tributaries diminish in bulk at the very time when the affluents, which have come down from the glaciers, are increas- ing—that is to say, in summer; in winter and spring, on the contrary, the glaciers supply very little water, while the plains are inundated with rain, and their streams are filled to the brink. Thus the abundance of one affluent balances the poverty of another. As an instance of this, the Rhone and the Saone have often been brought forward. During the heat of summer the latter brings down only one fifth of its winter dis- charge. On the other hand, the Upper Rhone rises much higher during the same Season; but below its junction with the Saone the average height of its water is nearly the same during every season of the year. A compensation of a similar kind likewise takes place between streams of surface-water and those which are fed by springs. The rivulets which traverse the subterranean passages of rocks can not descend into the plain so rapidly as the water-courses which flow on the surface of the ground. - - - The grandeur of the geological operations accomplished by flood-wa. * Delgrand. .. * 320 & TEIF EARTH, ters are best to be appreciated on the banks of rivers which have been placed by the labor of man in a state of defense against the watery ene- my. When the River Amazon overflows, it forms in some places, with the marshes on its banks, a perfect sea of 100 or even 200 miles in width. The animals seek a refuge in the tree-tops, and the Indians who live by the sides of the river make a kind of encampment on rafts. About the 8th of July, when the river begins to sink, the water, returning to its original bed, undermines the thoroughly soaked banks and slowly washes them away. A sudden fall then takes place, and masses of earth, amount- ing to hundreds or thousands of cubic yards in bulk, sink down into the water, carrying with them the trees and animals existing upon them. The very islands are exposed to sudden destruction: when the entangled masses of fallen trees, which serve as a breakwater to them, give way be- fore the violence of the current, a few hours, or even a few minutes, are quite sufficient for their disappearance; they are literally washed away by the flood. They may be observed visibly melting away; and the In- dians, who are quietly at work upon them collecting turtle-eggs or dry- ing the produce of their fisheries, are suddenly compelled to fly for their lives. Then it is that the current of the stream is encumbered with long floating piles of entangled trees, which hitch together only to break away again, and, accumulating round some headland, are heaped up one above another all along the banks. All round these immense trains of trees, which roll and plunge heavily under the impetus of the current like great marine monsters or drifting wrecks, great masses of the plant Can- na rand float on the surface of the water, giving to some parts of it a resemblance to broad meadows.” We may thus readily comprehend the almost religious awe which has been experienced by travelers who have made their way up the river of the Amazons, and viewing these whirl- pools yellow with sand, have been eye-witnesses of their destructive operations in tearing away the river-banks, throwing down trees, wash- ing away islands in one place to form them again in another, and drifting down the current long trains of trunks and branches. “The great river was terrible to look on,” says Herndon, the American traveler, “as it rolled through the solitudes with a solemn and majestic air. Its waters seemed to wear a wrathful, malevolent, and pitiless aspect. The entire landscape had the effect of stirring up in the mind a feeling of horror and dread similar to that produced by the imposing solemnities of a funeral at sea, by the minute-gun firing at intervals, the howling of the tempest, and the wild uproar of the waves, when the crew assemble on the deck to bury their dead in the bosom of a troubled sea.” The Mississippi presents a remarkable instance of a great water-course which man has recently annexed to his domain, and has succeeded in modifying considerably, as regards its geological action, during the course of a few years. In 1782, and even at the time of the great inundation of 1828, the whole of the region embraced between the left bank of the Mis- * Avé Lallemant, Reise in Nord-Brasilien. TOIſ, FLOODS. 321 sissippi and the course of the Yazoo—that is, an area of more than 30 miles in width on the average—was completely covered with water, as is proved by the bones of wild animals which have subsequently been found on the artificial mounds raised by the red-skin Indians. At the present day the river is confined on both sides by lateral embankments, and no longer floods the whole basin of the Yazoo. Now it only tears away narrow strips of the vast forests by the river-side; and even in the very highest floods, the masses of trees which drift down the current do not form, as before, long floating trains. Even at the beginning of the present century, these floating trains, or embarras, rendered the navigation almost impossible in some reaches of the Mississippi and its tributaries. A great portion of the courses of the Atchafalaya and the Ouachita were completely choked up by heaps of trees. In many places a person might cross them without any idea that he was going over a river. Bushes and even large trees grew upon some of these floating masses.” One of these entanglements of drift-wood, known by the Americans under the name of the “Great Raft,” always ob- structs the bed of the Red River. This immense agglomeration of trees, under which the water disappears in a mass as if under a movable arch, gradually gets higher up the course of the river as the trees at the lower end break away, and the annual floods bring down fresh drift-wood to the upper extremity. The obstruction was probably first formed at the confluence of the Red River and the Mississippi, and has since gradually advanced 391 miles from the mouth, gaining a mile or two every year. In 1833 the Federal Government undertook some important operations for the removal of the obstruction, which had then attained a length of 124 miles; but while a flotilla of boats was occupied in pulling out the trees which formed the lower extremity of the “raft,” the upper end was constantly increasing by means of the fresh drift. In 1855, after twenty- two years devoted to this “labor of Sisyphus,” the question was raised whether it was not better worth while to abandon this ungrateful labor, and to apply the funds at disposal to the improvement of the bayous, or lateral channels. “The Great Raft,” being thus abandoned in the marshes, which formed the old bed of the river, will be gradually con- verted into a great peat-bed, destined perhaps to become coal at some future geological period, unless human ingenuity should otherwise dis- pose of it. - In cold countries, such as British America, Russia, or Siberia, the wa- ter-courses carry down to the sea a far less quantity of vegetable débris than the rivers in tropical countries; but, to make up for it, they are loaded with enormous blocks of ice at the time of thaw, a period which often coincides with the highest floods. It is a wonderful sight, especial- ly in rivers adorned with cataracts like the Niagara, when the rocks of ice, dashing against one another, and breaking up in the midst of the watery columns, give one the idea of a cataclysm, in which lakes and . * Lyell, Second Visit to the United States. X 322 THE EARTH. continent were all being simultaneously swallowed up in the abyss. The icy sheet which extends over the surface is shattered with a sharp, grind- ing noise, and the broken fragments are caught by the current, and dashed violently against each other; their sharp angles are broken off in the collisions, and they are whirled round and round in long eddies. In the curves of the headlands, at the points of the islands and sand-banks, and also in those portions of the river where the icy barrier still remains firm, the broken masses gradually accumulate, and, mounting up one upon another, owing to the force of their impetus, butt against the banks like battering-rams, and thus often clear away an outlet into the plains for the flood-water. Sometimes they rear themselves up like dams, and drive back the body of the river up-stream again. For this reason, dikes, embankments, and other hydraulic ramparts, built along the course of a river subject to these annual breakings-up of the ice, must be construct- ed with the utmost solidity. Among other constructions of this kind, we may mention the enormous buttresses with which the piles are fur- nished to support the bridge of Montreal on the St. Lawrence, and the defensive ice-breakers built in the Vistula on the up-stream side of each pier of the bridge of Dirschau. At St. Petersburg the granite quays and the edifices they protect would be all carried away by the ice-flood, if at the same time violent tempests from the west were to drive the waves of the gulf into the mouth of the Neva. In temperate Europe the breaking up of the river-ice is attended by little or no danger; but the mere inundations are very much dreaded on account of the towns, villages, and richly-cultivated districts with which the banks are covered. The inhabitants on the edges of the Loire still recall to mind with horror the disasters which have been caused by the great though exceptional floods which in one year only (1856) carried away roads and defensive embankments, causing damage to a most enor- mous amount. In the same year the calamity was but little less disas- trous in the valley of the Rhone, which was covered in some places, es- pecially the Camargue, by an inundation almost like one of the floods of the Amazon. The inhabitants of the banks of the rivers are now Worse off in this respect than their ancestors. The extraordinary rains caused by atmospheric changes are not all they have to dread. They have now to look for greater irregularity in the action of the streams and still more Sud- den inundations, in consequence of so many of the marshes and pools being drained dry, and the mountain slopes being cleared of wood by the axe of the woodman, or laid bare by the feeding of the goats. They also have to fear the immediate effects of the drainage channels which pour down the rain-water so rapidly into the streams. Lastly, the surface-water is every year precipitated into the plains more and more suddenly on account of the increasing number of ditches, which are carefully kept up along the roads and paths, into which the boundary trenches of the various proper- ties all empty.* On the other hand, the extension of cultivation on the * Becquerel, Comptes Rendus de l'Académie des Sciences, November, 1866. IN UNDATIONS, 32 3 § ºzzº Bºž º :==-|-- ÉÉ7. Aation Fig. 123. Limits of the Inundation of the Rhone in 1840. edge of a river, without the application of drainage, enables the earth to absorb the water to a lower depth in the soil, and thus diminishes the height of the floods. This fact is proved by the example of the Lake of Aragua, in Venezuela. At the commencement of the century, when the greater part of the neighboring plains were under cultivation, the level of its water was comparatively low; but during the War of Independence it gradually rose, owing to the devastation of the country by the con- tending armies, and the consequent return of the plains to their original condition of virgin forest. Latterly, fresh clearings have for the second time sunk the water of the lake. - Under the action of all the causes which so variously influence the flu- viatile economy, some rivers, such as the Oder, since i778, and the Elbe, since 1828, have diminished in volume, although it is certain, from the meteorological registers, that the amount of rain falling into their basins has not lessened. Other rivers, as the Rhone and the Loire, do not ap- pear to have at all decreased in the quantity of their water; but, on the other hand, their inundations are much more dangerous than formerly. The Seine, which, according to the testimony of the Emperor J ulian, poured through Paris, some fifteen hundred years ago, nearly the same quantity of water in every season of the year, shows, at the present time, a difference of about 33 feet between the high and low water levels. Some rivers, indeed, such as the Garonne, appear to have been more for- midable in days gone by than they now are. The highest inundation of the Garonne which is on record is that of April, 1770. *At Castets, the point at which the tide stops, the flood-level attained a height of 423 feet above the low-water mark. This is 63 feet more than in the largest floods of the present century.* - * Raulin, Géographie Girondine. { 324 THE EARTH, However this may be, some of these inundations assume such propor- tions that they become perfect cataclysms for all the river-side districts. The example of three little streams, the Doux, the Erieux, and the Ar- dèche, all three confined to the limits of a single department, may give an idea of the rapid swellings of these high floods. On the 10th ºf September, 1857, the three water-courses, which usually flow peaceably enough over their rocky and pebbly beds, poured down into the Rhone a combined mass of more than 18,000 cubic yards of water, instead of the 20 to 25 yards which was their ordinary discharge in the same time. This flood was equivalent to the body of water which the Euphrates and Ganges together pour into the sea. Spreading over their respect- ive valleys to a height of 50 to 60 feet above their low-water mark, the flooded rivers overthrew the houses, washed away the cultivated ground, and uprooted the trees. So many thousand trunks of trees were carried away in one day that, below the Erieux and the Doux, the whole surface of the Rhone seemed nothing but a train of drift-wood, over which, as it appeared, a bold man might well have ventured to cross the river. Still, even these inundations have been exceeded, for, on the 9th of October, 1837, the Ardèche rose, at the bridge of Gournier, to a height of 70 feet above low-water mark, at least 10 feet higher than in 1857.* Above the Iron Gates some of the floods of the Danube have caused the river to swell to a height of more than 60 feet above low-water mark. It is a fortunate thing that, in most river-basins, it is very seldom the case that the floods of the various affluents exactly coincide, and that all the tributaries are seen to swell at the same time. In fact, whenever a rain-cloud passes through a valley, it discharges its moisture sometimes on one side and sometimes on the other, and the various water-courses which it swells overflow in turn after the rain-cloud has passed over. Thus, in the valley of the Rhone, when the damp winds encounter the Cevennes, the slopes of the Alps which are turned toward the river are sheltered from the storm, and it is only gradually that the series of showers makes its way from the Cevennes toward the mountains of Annonay. If all the tributaries of the Rhone were to swell at one time, it would roll down a most formidabe mass of water, amounting to more than 180,000 cubic yards a second. It would be another Amazon. Even when the Rhone discharges into the sea only 16,000 to 20,000 yards a second, the havoc which it makes upon its banks is most frightful. * Marchegay, Annales des Ponts et Chaussées, vol. i., p. 861. 3 2 5 MEANS OF PREVENTING FLOODS. CHAPTER LI. MEANS OF PREVENTING FILOODS.—NATURAL AND ARTIFICIAL RESERVOIRS.- IRRIGATION CHANNELS.—EMBANKMENTS, AND CRACKS IN THEM. IT is evident that it would not do for man to remain constantly under the apprehension of these inundations, and that it was necessary to find some means of preventing them. For hundreds and thousands of years, and especially during this century of industrial activity, plenty of plans of protection against river-floods have been both projected and put into execution; but too often these works have remained useless, or have even produced entirely contrary effects to those which were expected by the engineers and the inhabitants. The fact is, that in going to work they did not always pay sufficient attention to the laws of hydrology. If man wishes to become master of the forces of nature, and to make them work to his advantage, the first condition is, that he shall thoroughly under- stand them. It must be remarked, in the first place, that the mass of surplus water forming a flood is not actuated with the same speed over all its width. The nearer the liquid particles are to the bank, the slower they move. This phenomenon, caused by the friction of the fluid against its banks and the bottom of its bed, may, it is true, be observed to some extent at Iow-water seasons as well; but it is when the level of the river is at the highest that the various portions of the liquid mass present the greatest differences in speed. The thread of the current, the mathematical line of the greatest rapidity, which varies every day and in every stream, ac- cording to the quantity of water and the section of its bed, exceeds by about a fifth the average speed of the river.” In flood-times this line gradually rises above the bottom, and by thus ascending toward the sur- face of the river, so as to keep—according to the direction or forces of the wind—sometimes on the surface of the river, sometimes a few feet be- low, it leaves the solid walls which constitute the sides of the river, and the medial part of the water, of which it is the ideal axis, and moves con- sequently with greater facility. In great rivers, such as the Amazon, the Mississippi, or the Rhone, the current sometimes descends with the speed of seven or eight miles an hour. While the central part of the current. thus hastens down toward the sea, the water at the side, kept back by the irregularity of the bed, remains behind, and flows more slowly along the banks. Thanks to this difference in speed, which increases accord- ing to the height of the river, floods are sometimes lessened or even en- tirely prevented. In fact, when mighty masses of water, descending ei- * According to M. de Prony, it is 0°1835. 326 THE EARTH. ther from the clouds or the mountains, fall simultaneously into the basin of a stream, these liquid avalanches would certainly produce formidable inundations if they were not immediately carried away by the centre of the current, and did not distribute in succession a portion of their bulk over all the points that they traverse. Forming, so to speak, a river in the middle of a river, this rapid flow weakens the flood by dividing it over a vast length of bank. In the river of the Ohio the mid-flow has rolled down for a distance of five miles, when, at a spot two miles and a half from the very place where the rain fell, the high banks are scarcely touched by the rising water. - In consequence of the speed communicated to the mid-flow of the flood, the liquid mass that it carries along is perceptibly higher than the mean level of the river. It forms a kind of convexity, from the top of which the water spreads out in light sheets toward the two banks; but, on the other hand, when the flood-wave has disappeared, the middle of the river exhibits a considerable depression, and the water which has gradually ac- cumulated near the two edges has to flow back toward the centre of the current, so as to re-establish by degrees the fluviatile level. It has been % +: ; Fig. 124. Growth by Floods. Fig. 125. Subsidences of the Waters. ascertained that on the Mississippi the central convexity of the flood-wave is on the average about three feet. When the river sinks, almost as con- siderable alteration of the level takes place in a contrary direction. The wood-cutters of Maine and Canada are not ignorant of this hydrological fact. They are well aware that logs of timber thrown into the river in flood-time are thrown up on the banks, while they float regularly down the middle of the current when the river-level sinks.” - The depression which is formed in the middle of the river during the period of subsidence is, however, obliterated as soon as the liquid mass ceases to diminish; the water then commences to bulge up again in the axis of the current, owing to the greater facility of movement possessed by it in that part. The surface of those great Russian rivers which are covered with ice for several months of the year exhibits a remarkable in- stance of the bulging up of the liquid mass in the central line of the cur- rent. At the conclusion of the winter, when the water from the melting snow runs down off the banks toward the bed of the river, and the sheet of ice stretched over the river is not yet broken, it is ascertained that the surface-water collects in elongated pools on those portions of the field of ice which are nearest to the edges, while the medial part bulges "P in an arch above the current, and remains constantly dry. On the Volga, the - + Marsh, Mo, and Nature, JRESULTS OF FLOODS. 327 difference of the level between the edges and the middle of the ice amounts sometimes to more than three feet.* The current is not the only regulating force which weakens the action of floods, and gives more certainty to the height of the water. There are other agents which assist in equalizing the discharge of a river by receiv- ing the overflow during the rainy seasons, and afterward emptying it into the principal current. These regulating agents are the surface or un- der-ground reservoirs which exist on each side of water-courses which are still left in a state of nature. Thus, according to IIumboldt, the Upper Maranon pours into the caverns of the pongo of Manseriche a portion of its waters, and also all the drift-wood which it brings down from the higher valleys. Many streams lose a considerable quantity of water by the mere process of filtration, through the spongy soil of their valleys. It is stated that in some places the water of the Nile penetrates laterally as far as fifty miles from the bed of the river. In like manner, during floods, the Seine feeds the land-springs which extend under Paris, and all the wells are then filled by the water of the river. Next to lakes, which are the chief regulators of running waters, $ the marshes lying close to the edges of a river take the principal share in modifying its discharge. During inundations the lagoon and swamps on both sides temporarily store up a large quantity of flood-water, which is only set free after the sinking of the river. The marshy regions through which the Mississippi runs in its middle course affords a remarkable in- stance of this fact. Thus, in 1858, the great American river, which be- low the mouth of the Ohio sent down 52,039 cubic yards of water, only discharged 45,915 yards at Baton Rouge, after it had received the con- tents of the Arkansas, the Yazoo, and other less important rivers. A mass of water, amounting to 6124 cubic yards a second—equivalent to nineteen times the bulk of the Seine—must, therefore, have been lost on the way. || Just in the same way, the Rhone, in its great inundations, makes its way over the side embankments opposite Culoz, and, covering the whole of the vast marsh of the Chautagna, pours its surplus waters into the Lake of Bourget. It has been calculated that during the flood of 1863 this reservoir absorbed from the Rhone a mass which altogether amounted to 71,900,000 cubic yards of water, the effects of which would have been most disastrous on the plains below." In places where the marshes beside a river have been drained by the operations of man, the water-level of the stream rises to a much more con- siderable height in flood-time, and the plains around are inundated. But the inundations themselves become new regulators of the discharge of the water, and that, indeed, by means of their very irregularity, The liquid * De Baer, Bulletin de l'Académie de St. Pétersbourg, vol. vii., No. 4. f Marsh, Man and Nature. - - t Delesse, Carte Hydrologique. § Wide the chapter on “Lakes.” || Humphreys and Abbot, Report on the Mississippi River. ‘ſ Gobin, Commission Hydrométrique de Lyon, 1862. § 328 THE EARTH, sheet which covers the fields is hindered in its flow by the inequalities of the ground and by clumps of trees. Being unable to follow the river in its impetuous course, it remains behind, like a temporary lake, until the river is low enough for it to return into its natural bed. Thus the flow of an inundation always decreases in height as it gets nearer to the sea, and ultimately it completely disappears. The inundation of the Nile diminishes as it flows on from Assouan, where it is from 53 to 56 feet in height, to Rosetta and Damietta, where it is not more than three feet in height. A similar decrease in the flood-wave may be observed on all other rivers. We must not, however, lose sight of the fact that this gradual waste of the water proceeds partly from several other causes, such as the porous nature of the ground bathed by the river, the activity of the vegetation growing by its side, and the amount of evaporation. This last cause of the exhaustion of the water is probably the most im- portant in all hot countries like Egypt and Guinea. It should be man’s part to complete the work of Nature by imitating in his operations some of those means which she employs for storing up sur- plus waters, and afterward distributing them equally over vast areas, thus insuring a regular discharge. Man should make it his task to watch the drop of rain as it falls from the sky, to follow it in its course, to arrest it in its progress when it would help to swell a dreaded flood, and to em- ploy it for the benefit of agriculture, navigation, and manufactures. On every mountain-side and elevated plateau he may avail himself of a pow- erful remedy for the prevention of floods, by replanting them with trees; for, as M. Becquerel's experiments have proved, the quantity of water which drops during heavy rain on wooded ground is only six tenths of that which falls on the bare soil.” In a great number of the upper Val- leys reservoirs might be constructed, where the liquid mass would accu- mulate in times of rain, and be subsequently emptied over the slopes in innumerable irrigating conduits. On cultivated declivities, as Provence and the Maritime Alps, man should enlarge and consolidate the flat stages which rise one above another along the mountain-sides, forming, as it were, so many staircases, each step of which should keep back its share of rain-water. In the valleys he should tap the river in order to feed ir- rigation ditches and mill streams. Finally, in the lowland plains, it would be easy to line each side of the river with reservoirs, where the stream might deposit the sediment with which it is charged. • The streams, on the sides of which water-mills and manufactorias have been established, are, as it were, disciplined by means of the Waste Water channels and the reservoirs where the water is stored up, and especially through the mill-dams and other obstacles which convert the river or stream into a regular canal, with its dammed-up levels. Inundations are, therefore, very rare, or even quite unknown, in a great number of the manufacturing valleys of England, Scotland, and the United States. Still, the gratuitous power afforded by water is not by any means geneº " * Comptes Rendus de l'Académie des Sciences, November 5, 1866. LAKE MOERIS. 829 ally utilized at present; and even the inhabitants of manufacturing coun- tries allow a very considerable quantity of available water-power to run away to waste. Thus—to select an instance among the French streams which turn the greatest number of mill-wheels—the Doubs itself, flowing through the manufacturing districts par eacellence, scarcely does one quar- ter of the work which might be obtained from it. From Vougeaucourt to Besançon, a distance of 43 miles, the total fall being 248 feet, only 900,000 horse-power was utilized in 1860, out of the total amount of 3,400,000 horse-power which might have been employed. gº Although manufacturing operations can only assist exceptionally in moderating and gradually doing away with floods, the agricultural proc- esses which are going on in all the valleys inhabited by man ought to exercise a direct and decisive influence in regulating the flow of streams and rivulets. The husbandman ought not to allow the waste of a single drop of the beneficent water, which, by a widely-extended system of irri- gation, might double, or even increase tenfold, his crops, and convert a wilderness into a garden. In the intelligent employment of running wa- ter in the fertilization of a district, our agriculturists have much to learn from the example of the ancients. As far back as the time of the early Egyptians, works of irrigation of really colossal dimensions had been ac- complished; and perhaps, among all the undertakings of this kind due to modern industry, there is not one which, in boldness of plan or practical utility, can be said to surpass the meri (basin), or Lake Moeris, which was opened to the waters of the Nile in the reign of Pharaoh Amenemha III., more than 4500 years ago, according to the chronology of M. Brugsch. From the topographical details which have been left by ancient authors as to this wonder of the world, we know that the site of Lake Moeris must be looked for in the present province of Fayoum, the name of which is de- rived from the Coptic, and signifies Sea. Now, a considerable lake exists at the present time—the Birket el Keyroun—in the lowest part of the province; and so long as the geography of this part of Egypt was but partially known, it was very natural to look upon this lake as the ancient excavation of the Pharaohs. A study of the localities has proved that this is not the case. In fact, the Birket el Keyroun is situated in a deep depression, nearly on the level with the sea, and 53 feet below the aver- age waters of the Nile. This basin, therefore, can not be the one which alternately received the surplus flood-water of the river and emptied it out again through two wide gates, as Strabo tells us, into the plains by the side of the Nile. Besides, the position of this lake differs much from that which the ancient geographers assigned to the Moeris. According to the discoveries of M. Linant de Bellefonds, the engineer, the site of the great reservoir was just in the very highest part of Fayoum, to the west of the rocky gorge of Illaoun, through which flows a natural side-chan- nel of the Bahr Yousef, which probably, at some former geological period, was the principal current of the Nile. Fragments of a long dike, which in some places is not less than 30 feet high and 200 feet wide, may still be 330 THE EARTH. met with in the eastern part of Fayoum. It must once have constituted a semi-circular rampart, spreading round the outlet of the great basin of the Fayoum plains, and have penned back the water brought by the Bahr Yousef. M. Linant has calculated that, during the hundred days of flood, this branch of the river, which represents on an average about the twenty- eighth part of the Nile, emptied into the basin a quantity of water equal to 466 cubic yards a second, and that the total mass of water contained in this gigantic reservoir, even after making allowance for evaporation, could not have been less than 3,694,000,000 cubic yards. This was suf. ficient to diminish very considerably the dangers resulting from the in- undations of the Nile, and subsequently to afford all the water that was &** s % &§§ .* % § N.' º * SW Aş wº - % - te - - - - sº SS º {{}}| ºxagºlåſ"ſº # § º *A*. • eN ºš" % Wii §§§ſº 2: Nº ãº". º • 2.2× 23:2 - º :3 - Šºš2:3:33 ºfflº-. - * }\ - yº º § W =Area: \ sº *illinº" & ‘’NN 23 º **ºs º h - É % N § º ſº & º Fig. 126. Map of Fayoum. requisite for the irrigation of 444,000 acres. According to the statement of Herodotus, the surplus waters spread out to the west toward the Syrtes of Libya; that is to say, after crossing the lake, which is called Birket el Keyroun, it filled the bed of a channel now dried up, which car- ried the waters of the Nile into the western deserts. At the present day, Fayoum still possesses a magnificent system of irrigation, which may be compared to the ramifications of the arteries and blood-vessels of a liv- ing being; but forty-five centuries ago, Lake Moeris, which constantly changed its level according to the needs of agriculture, was like a heart from which the flow of life was shed out to nourish the great body of Egypt as far as distant Memphis. Nothing now remains of Meris but the broken-down dikes, a few fragments of the two pyramids which Were IRRIGATION CHANNELS. 331 built up in its waters to the glory of Amenemha, and a thick layer of al- luvium deposited on its basis by the troubled waters of the Bahr Yousef.” Among European rivers, the Po is that which may be best compared to the Nile of the ancients, as regards the care with which its Waters have been utilized for the fertilization of the soil. So far back as 1863, the Lombard agriculturists required for the watering of their crops 59,000,000 of cubic yards of water a day, equal to 681 yards a second; that is, a liquid mass equivalent to the average discharge of the Seine during the same period. Since the above date, the great Cavour canal has been opened—a perfect artificial river—which requires for itself alone 144 cubic yards of water a second. Starting from Chivasso, below Turin, this river, which is not less than 55 yards wide at its commencement, spreads its fertilizing water on both sides in the already fertile plains of sººr -z-z-z-rº-rº- Fig. 127. Section across Fayoum. Lomellina; it receives, en route, numerous streams—the Elvo, the Sesia, the Agogna, the Terdoppio — and at Turbigo empties into the Tesino all that remains of its liquid mass, after having irrigated more than 494,000 acres. Next to the great canal of the Ganges, in Hindostan, it is the most important operation of this kind accomplished in modern times. There can be no doubt that the Po, once so dreaded on account of its sudden floods, will ultimately become, in conjunction with the other water-courses of Lombardy, a scientifically arranged system of agricul- tural canals. : - Agriculturists should not only employ the water of torrents and stream for increasing their crops and nourishing the soil, but they should also make use of the sediment and débris of all kinds which are washed away by the water from their up-stream banks. As an instance, let us take the Durance, a French river, which has been thoroughly surveyed and studied to ascertain the plan for utilizing its water and mud for the irrigation and manuring of the plains by the river-side. The eighteen channels which are fed by this stream can draw from it as much as 90 cubic yards a second; so that at any time when the whole of this liquid mass is being * Linant de Bellefonds, Mémoire sur le Lac Maris. f Elia Lombardini, Politecnico, January, 1863, quoted by Marsh. 332 º THE EARTH. taken away at once, only 30 cubic yards remain in the bed of the Du- rance in low water seasons, or about a quarter of its regular discharge. According to the observations of M. Hervé-Mangon, which lasted from the 1st of November, 1859, to the 31st of October, 1860, the mass of mud brought down by the stream during the whole year represents a quan- tity of near 18,000,000 tons. Some idea may be formed of the enormous bulk of the mud which is washed away every year by the Durance from the upper portion of its basin, by picturing this mass in the form of a cube 242 yards on each side; if spread out uniformly on the ground this allu- vium would cover in a year more than 108,000 acres, with a layer an inch thick, containing in a form of combination most suitable to the plants more azote than 100,000 tons of guano, and more carbon than 121,000 acres of forests (?). Unfortunately, as these canals are constructed with a view to irrigation only, nine tenths of the mud is lost for manuring pur- poses; and the farmers purchase, at the cost of many thousand pounds a year, the very elements of fertilization which their stream washes down into the Mediterranean, although they might so easily avail themselves of them. As every river possesses its own special peculiarities, the regulating works which the engineers have to undertake for the purpose of doing away with floods and distributing the water discharge, must be contrived in different ways, according to the form and capacity of the upper mount- ain hollows, the rapidity of the current, the suddenness of the floods, the porosity of the ground by the river-side, and the extent of the forests which clothe the hill-sides. The operation of regulating the discharge of a water-course is certainly very difficult to accomplish; in some river- basins it would require the labor of several generations; but suffice it to say, it is, not impossible, and that it has already been successfully carried out in many parts of the globe. Although the greater part of the rivers, in both Europe and the civilized portion of America, have up to the pres- ent time remained free from man’s guidance, and still occasionally devas- tate the cities and cultivated districts which lie upon their edges, there are at least a few of which the floods have been rendered harmless, thanks to the labor of the frightened inhabitants. Among the rivers which were once most dangerous, and are now almost entirely subdued, we may mention the Arno, which has been looked after for centuries by the skillful Tuscan engineers. At one time this river was most formida- ble, on account of its periodical inundations. From the year 1400 to 1761, no less than thirty-one disasters of this kind are recorded. Since 1761–the date when the improvements of the river were carried out- until 1835, there has not been a single serious flood.* The Po itself—the river which in flood-time hangs suspended, so to speak, over the surround- ing plains—is now much less to be dreaded than heretofore, thanks to the irrigating channels which tap it, and also to the lateral embankments which border the whole of its lower course below Cremona.f * Marsh, Man and Nature. f Wide p. 335. JEMBA WKMEWTS. 333 In this stream, as in a great many others, the surplus Waters Of the high floods come down too rapidly, and in masses too considerable, to afford any possibility of storing them up, or of turning them off in a lateral direction without devastating the plains. It is necessary that the inhabitants should protect themselves by well-planned constructions §ſºx wº wº §§ º * Wºw NY §.sº | s ſ º S lf'...''''', "||\ i SSR. S |MN sº // #if: ...S. $ 7, 11 § * * *;&#}_º *: Ottersdorf * tºº, *# Fig. 128. Dikes along the Rhine near Seltz. - Q against the threatening pressure of the water. The Egyptians dwelling in the Delta built their cities on artificial hillocks above the level of the annual floods. The inhabitants of some parts of Holland, wishing to fa- cilitate the “warping” of the fields, elevate their habitations above the ground, and the houses become so many islands in the midst of the floods. In recently colonized countries, where man's first care is to protect his habitation, all he does at first is to construct a circular embankment 334 THE EARTH - round the town or village. This was the procedure of the French colo- nists after they had planted the first pile-work of New Orleans. The Americans, too, adopted this plan of protection for the Californian city, Sacramento, and the warehouses at Cairo, situated at the confluence of the Ohio and the Mississippi. In like manner, the towns on the banks of the Loire are protected against the flood-wave by walls. Added to this, when the banks of a water-course are covered by cultivated fields, and the inundation would prove fatal to them—as in Louisiana, Lombardy, China, and many other countries in the temperate zone—it is necessary to raise longitudinal dikes on the edges of the streams which at flood- time are higher in their level than the surrounding plains. Thus shut in between their dikes, rivers are compelled to give up their wandering course, and to flow down to the sea through the channel which has been traced out for them. These longitudinal embankments, which, at any rate, are no ornament to nature, are sometimes a matter of absolute ne- cessity; but if the constructors wish to prevent their dikes being broken through, and to avert the disasters which are the certain consequence of cracks, they must calculate beforehand the force of the liquid mass with which they will have to contend during extraordinary floods; and they must build their ramparts of materials sufficiently solid to resist without difficulty the lateral pressure of the water. They must likewise carefully protect their dikes against burrowing animals, for the embankments of the Po have several times been perforated by moles, and those of the Missis- sippi by musk-rats. It is necessary, also, to give the embankments a gen- tle bend, and to leave a sufficient width for the penned-in river. The Loire, in front of Orleans, was once 3827 yards wide, but has been re- duced by the embankments to a bed of 306 yards. At Jargeau, it is only 273 yards wide at a place where it once had a lateral spread of 7650 yards. In 1856 the Loire burst twenty-three breaches through these banks, which were said to be impenetrable;" as soon as the height of the flood rose in the river to more than 16% feet, cracks became inevitable. The losses occasioned by the breaking down of these too feeble ramparts, over which the flood-water rushed like a deluge, were so considerable that the question was often asked whether it would not be better to throw the dikes down entirely and to replace them with plantations of trees. The water, flowing without difficulty through the open barrier of the crowded trunks, would be distributed equally over the plains by the river-side, and would consequently never rise to the formidable height whióh it reached between the dikes. Added to this, its annual ravages would be in great part compensated for by the fertile alluvium which would be deposited by the sediment with which the water is charged. It has been calculated that if the vast basin of the Saone, situated above the gorge of Pierre-Encise, were protected against the inundations of the river by means of dikes, confining the water to a bed 273 yards wide, the same as at Lyons, a liquid mass of 1,869,000,000 cubic yards, which, during * . * Champion, Inondations de la France. JEMBANKMENTS OF THE PO. 335 inundations like those of 1840, now spreads over the plains, would then rush down upon the town in the space of a few days. On the other side of Lyons the Rhone affords a remarkable instance of the influence which the dimensions of the bed exercise on the height of the flood. In 1856, in the wide plain of Miribel, seven miles and a half above Lyons, the flood-wa- ter rose only nine feet and a half; but it rose to 20 feet—that is, more than double—in the narrow bed contained between Lyons and the Brot- teaux.” In the valley of the Isere, the mean height of the flood-waters has undoubtedly risen since the construction of the side embankments, which were, in fact, placed too close to one another. This has been proved by the very exact observations of M. Dausse. The embankments of the Po, more scientifically constructed than those of the Isere, were commenced many centuries ago, when the long night of the Middle Ages still darkened the rest of Europe. At a point below Cremona, where the continuous line of dikes commences, they are very wide apart, but the space through which the flood-waters can flow is gradually narrowed in down to the mouth of the river; from 6564 yards Febr. March April June October November Décember. Fig. 129. Mean Heights of the Isere, it diminishes to 3000, 2000, and even 1000 yards. Ultimately each of the branches of the delta is not more than 300 to 500 yards wide be- tween the inclosing embankments. The fact is, that a great portion of the mass of water, finding between its upper dikes so considerable a space over which it is able to spread freely, remains stored in the plains above, and thus the flood-water tends constantly to diminish in a down- stream direction. The flat districts that lie between the dikes are called golemas. Each land-holder may cultivate them and embank them as he likes; but on the condition that his dikes shall be always nearly six feet lower than the principal embankments, so as not to offer any serious ob- * Gobin; L'Eveillé, Commission Hydrométrique de Lyon, 1863. 336 THE EARTH. stacles to high inundations. These golemas, therefore, with their dikes all round them, form so many settling reservoirs where the alluvium ac- cumulates after each fresh flood, and their level is much higher than the plains outside the dikes.* Owing to the care with which these embank- ments are kept up by the syndicate of the river-side proprietors, cracks in them are very rare. Since 1705, the date at which a breach of more than 50 miles took place below Cremona, the reconstructed portion of this enormous rampart has not yielded at any point. Although lower :- ** 2- - * * * vº º Nº ºr - ~". . . w > . SNSS- 7 [] >,'... * * º º - . . 3-2:º : . * ! | y * - * - f | :- iſ: º ºs º - - ------- ===ſ===#: - - =2<===#EEEE:::::::::Hº::::::::FE:::::::: Fºº % W' (Rºſvoſanº -: - - -------- ==== <=º: ##########". % -- ". % [l]ºº 6 Fig. 130. Dikes by the Po, from Cremona to the Sea. down the river extraordinary inundations still occasionally break through the lateral embankments in some few places, any great disaster is in a measure prevented by the side channels, opened on both sides of the river, in the delta of the Po. Nevertheless, the system is not yet perfect. M. Lombardini thinks it very important that in the lower part of the river a considerable space should be left open to the flood-waters, so that the alluvium might be distributed on the plains on each side, instead of throwing out a promontory into the Adriatic Sea, and consequently rais- ing the bed of the river. Next to the embankments on the Dutch rivers, those of the Po form the most remarkable system of protection against inundations that has been devised in Europe; but they are inferior in importance to the em- bankments which run along a great portion of the Mississippi, and which, from their enormous size and length, form a source of admiration to overy traveler. On the right bank of the river, from Cape Girardeau (Missouri) to the Pointe-à-la-IIache, situated below New Orleans, the em- bankments form a wall of 1125 miles in length, only interrupted by the mouths of rivers and a few spots of rising ground. On the left bank, the * Elia Lombardini, Dei Cangiamenti del Po. Y EMBANKMENTS OF THE MISSISSIPPI. 337 base of the plateau, which the Mississippi here and there touches, has enabled the inhabitants to dispense with constructing any continuous dike; but they have been compelled to resort to embankments for pro- tecting all the plains which extend from Memphis to Vicksburg, and from Baton Rouge to New Orleans. The ramparts that have been raised on the eastern bank are altogether more than 625 miles in length, and some of them are of very considerable dimensions; that which has been constructed at Yazoo-gate, in order to close a bayo” of the Mississippi, is no less than 42 feet in height, 42 feet in width at the top, and 817 feet broad at the base. To these immense constructions we must add all the embankments formed along the tributaries of the Mississippi and the bayous of its delta; we must likewise take account of all the double and triple parallel dikes which have been raised in some of the spots which are most exposed to the action of the river. The whole of the embank- ments of the Mississippi must altogether reach a total length of at least 2500 miles. It is true that in many of these imposing ramparts there is still much to be wished for in respect to solidity. Every great flood on the Mississippi which has been recorded has formed one or more breaches in the embankments above New Orleans. The water then rushes like a cataract into the plains which extend below its level to a depth of 10, 12, and even 15 feet. It rapidly enlarges the opening by washing down the dikes for an extent of one or more miles, and then, digging deep into the soil, hollows out for itself a new bed across the plantations. One of these temporary beds which the river made in 1850, 1859, and 1862, near the hamlet of Bonnet-Carré, dis- charged no less than 3930 cubic yards of water a second—that is, a sixth Wide foot-note, p. 347. Y 338 THE EARTH, of the average liquid mass of the Mississippi. If the inhabitants had not succeeded in Stöpping it up on each occasion, the new river would, with- out doubt, have gradually become one of the branches of the delta of the Mississippi. In like manner the Hoang-Ho, having burst through its em- bankments, emptied itself into the sea, partly to the north and partly to The Mississipi R #============= *:::::===S:#E:::::::: N. - * :----> --~~~~ Lisa:s:=== -- -- ºs-i: …-- - 3:25.5ºEF. --> :: ^ - rt: II-C.I.I.I.ICETCL.III-CIOCººrºººººººººººººº-ººrºº º 3.2׺ siz::::=--...º. º. 33. . . …...:R=== ::::::: º: 1) [w- w §§§§ N §N * * N § N N Fig. 132. Gap formed near New Orleans. the south of the peninsula of Chantoung, leaving a distance of 217 miles between its two mouths. The territory exposed to its ravages was not less in extent than the whole area of England. According to a tradition related by Ritter, which, however, is doubtless exaggerated, 200,000 in- dividuals of the province of Honan were drowned during a civil War in consequence of the dikes being cut through. - DISAPPEARANCE OF RIVERS. 3 3 9 CHAPTER LII. TIII, MOUTHS OF RIVERS.—ESTUARIES.—LONG BANKS OF SAND.-DELTAS. —NET-WORE OF BRANCHES OF RIVERS IN ALLUVIAL PLAINS. BELow its confluence with its last tributary a river can not fail to di- minish in volume, on account of the evaporation of its water, and also of infiltration into the earth. There are, indeed, some streams which, as We have seen, gradually waste away without receiving any compensation from tributaries to make up for their liquid loss, and ultimately entirely dry up. Not only in the burning regions of the torrid zone, where rains are rare, but also in the great plains of the temperate zone, wherever the surface of the ground is too level to afford an incline for the running away of the water, we find many rivers flowing down from the mountains, and then, failing to make their way to the ocean or any inland sea, they disappear among the sands of the level country. Thus the Rio Dulce, the rivers Primo, Segundo, Quinto, and several other water-courses in the Argentine Republic, come to an end amid the pampas in a series of lagoons, which rise or fall, advance or retire, in the desert, according to the Seasons of the year or the quantity of water. Farther up-stream these rivers are navi- gable for boats, and sometimes cover the country round with their floods; but below their current becomes weakened, they break up into pools, and at last, becoming little more than liquid mud, they fail even in moistening the soil of the prairie. In a similar way the branch of the delta of the Rhine, which retains the name of the river, disappeared amid the sand- banks previously to 1806, the date at which a canal was dug through the dunes, and was protected against the sea by efficient flood-gates. A river, however, can scarcely be considered to be worthy of its name, and can play no important part in history, if it fails to send down its wa- ter to the ocean in a constant and regular way. Only under these condi- tions is it accessible to ships, and in a position to connect the inland dis- tricts with those of the sea-coast. Just as a tree, the trunk of which, formed by the union of all its branches, brings into communication the at- mosphere and the bowels of the earth, so the chief trunk of the river, in which all its affluents combine their liquid mass, links the sea to the moun- tains and to the plains. By its ever-moving flow, by the junctions of its own current of fresh water with the salt waves of the rising tide, it brings together all parts of its basin, and gives life and energy to the earth, as the blood quickens the flesh which it moistens. - The oceanic portion of a river is characterized by the tides which twice every twenty-four hours change the direction of its current, and cause the water to flow back up-stream. In this small portion of its development, * 340 THE EARTH, the action of a stream is completely modified; it is no longer a water. course, nor is it the ocean. It is, in fact, a common bed where the two elements meet and unite. The river-mouth is not only an entrance to a continent through which navigators may pass; it also opens an outlet to the sea-water, and enables it to ascend far inland, and to mingle with tho liquid mass brought down by the river. That portion, therefore, of the channel where the junction takes place between the salt and fresh water constitutes a geographical division which is perfectly distinct from all the rest of the basin. - Most water-courses, however winding their course may have been, straighten as they approach the sea, and descend toward the shore by the shortest line possible, so as to form a right angle with the coast. This tendency may be partially explained by the fact that the steepest slope of the ground is generally inclined in this direction; but another cause, also, is the alternate action of the tide-wave, which takes place perpendic. ularly to the shore, the to-and-fro motion of which ultimately governs that of the river. Added to this, a large number of rivers, when they reach the maritime portion of their course, spread out their banks very widely so as to form real gulfs, in which it would be impossible to trace out the precise limit which marks the river-mouth. When these bays are not original indenta- tions of the coast, they owe their existence to the combined action of the river and the sea, which gradually cuts away the banks, and ultimately deposits them on some distant shore. Thus fluviatile estuaries are gen- erally found on those parts of the coast which are directly exposed to the force of the tides and storms. Estuaries are very numerous on the coasts of the open sea where the tide rises to a great height, but they are com- paratively less frequent in land-locked seas, which preserve an almost un- altered level, such as the Mediterranean, the Baltic, and the Caribbean Sea. Nevertheless, the shores of several inland seas—among others, the Euxine, so formidable for its winds—present river-estuaries similar to those On the Oceanic coasts; the most remarkable are the limans of the Dniester and the Bug. *g. Almost all the rivers of Western Europe spread out into estuaries in the lower portion of their course. There are some among the number, as the Thames, the Severn, and other rivers of Great Britain, which are streams of no great importance above the gulfs at their outlets, and owe all their consequence to the powerful tide-waves of the Atlantic. In France, the Seine, the Loire, and the two combined rivers of the Garonne and the Dor- dogne, water basins which are better proportioned in their area to the di- mensions of their estuaries; nevertheless, the quantity of fresh water sent down into these advanced bays of the ocean forms but a very small por- tion of the liquid mass which they contain. In the Gironde, which may be taken as a type of a marine estuary, the salt water generally ascends as far as Pauillac, 31 miles from the outlet; any one sailing on the river may readily notice the shifting line where the various liquid masses, some ESTUARIES. 341 green and transparent, and others yellow and muddy, mingle with one anº other in long eddies. At a point more than 10 miles from the sea-coast, the saltness Of the Gironde is scarcely diminished by the admixture of fresh water. At one time, the low ground by the river-side was intersected by salt mºshes, and the creek of Méchers, on the north bank, has been utilized for"Some years in the cultivation of oysters. The depth of the estuary is also very considerable. At Méchers, the Gironde, which at that place is 7% miles wide, is from 50 to 100 feet deep even at low tide. At the outlet properly so called, the estuary contracts, and is only 34 miles wide; but in mid- channel, the sounding-line finds no bottom at 100 feet. This enormous basin does not look like a river. If a spectator contemplates it, not from the point of a headland, but merely from the edge of the shore, at St. George or Royan, he can not distinguish the whole extent of the opposite bank; all that is visible is a few clumps of pines, separated by the White line of the distant water, and these isolated clumps seem to form an archi- pelago; the Gironde appears like a sea dotted over with isles and islets. The color and the appearance of the water are continually changing; it is as if several rivers, crossing one another in every direction, were flowing in one and the same bed. Sand-banks which show their white masses in- distinctly under the green waves, the marine currents which meet and mingle with the turbid water of the ebbing tide, the gusts of wind which raise on the estuary a perfect net-work of winding ripples, the long trains of foam which incessantly shift their place; lastly, the submarine counter- currents which flow up to the surface and there spread out in sheets per- fectly smooth—all these ever-changing phenomena are always modifying the magnificent spectacle afforded by the Bay of Gironde. But what, after all, is this beautiful estuary of the French coast when compared with the grand outlets of some of the American rivers, such as the St. Lawrence, the current of the Amazons, and the Rio de la Plata ? This last estuary, into which pour the gigantic Parana and Uruguay, more than six miles in width, is at the outlet no less than 155 miles across, and occupies a space of more than 15,400 square miles. Within a recent geo- logical period it stretched over a still wider area. At that time the Pa- , rana had not filled up with its alluvium all the higher portion of the estu- ary, and probably, also, the surface of the pampas was covered by the sea- water. Even in the present day, the now diminished gulf is nothing less than a real sea. Its bed, which prolongs in a gentle slope the surface of the Argentine plain, is hollowed out 66 to 100 feet below the level of the ocean. Currents and counter-currents, like those in the open sea, travése the gulf in every direction. Furious winds, which seem to upheave the whole liquid mass, give rise to tempests which are more dreaded than those of the ocean, on account of the sand-banks and rocks which hem in the channels. The highest floods of the Uruguay and the Parana have no perceptible influence on the level of the Rio de la Plata, and seem lost like rivulets in the enormous estuary. 342 TEIE EARTH. , Although the winds and tide have such an effect in increasing the mouths of rivers, into which the waves enter in a direct line, their mode of action is very different when they are diffused along a sandy shore, which they meet at a very acute angle. In this case, the waves from the open sea, being driven obliquely against the coast, wash away from it ** quantities of débris, which they deposit in front of the mouth of the adjacent river. Under the enormous pressure of the ocean, the current of the river bends and gradually doubles round in the same direction as the marine current, allowing a tongue of sand to form across its former bed. In the course of time, a narrow peninsula, having a sea-shore on one side and a river-bank on the other, divides the fresh water from the salt water for a distance of several miles, sometimes breaking up into islands, accord- ing to the various changes of the atmosphere, the current, and the tides. Thus, on the coast of New Granada, extending from the Cape de la Vela to the foot of the snow-clad mountains of Santa Marta, all the river outlets are pushed toward the west by the current which runs along the shore to. J2 *- Fig. 133. Belts of the Senegal. MOUTH OF THE SENEGAL.-J.A.N.D.E.S. 343 ward the Gulf of Darion; mere embankments, ornamented here and there with green vine-branches, and the violet corollas of a kind of bindweed, protect the still waters against the onset of the breakers. * The River Senegal exhibits one of the most remarkable examples of these belts, formed along the shore by the marine currents, and running across the outlet of a river. For a distance of more than 180 miles, the great water-course follows a direction perpendicular to the coast. In this way it reaches a point 15 miles from the sea, at which its course is arrest- ed by a chain of dunes, and it is compelled to find an outlet through some other part of the sea-shore. At one time the river, or at least one of its branches, continued in its direct path to the ocean, and on the spot where its-former bed may still be traced there is a narrow marshy flow, known under the name of the Marigot of N'diadier. Being thus driven in a southwest direction, the Senegal is compelled to approach the sea oblique- ly. Above St. Louis the river is separated from the line of breakers by nothing but the narrow bank of the Guet-N’dar, on which the blacks have built their faubourg. Farther down the coast, the embankment of sand thrown up by the marine current running from the north continues for a considerable length, altering its position every year, owing to the double action of the river-floods and the sea-waves. At the present time the mouth of the Senegal opens 2% miles south of St. Louis, and is ascending slowly toward the town. In 1849 it was 9 miles farther to the south, but in 1825 it was near Gandiole, a little farther up the stream. This sandy rampart, which extends its graceful curve from north to south for more than 24 miles, is cut through by the current of the river, sometimes at one spot and sometimes at another, but it never fails to form again, owing to the action of the sea-waves. Until the operations of man have fixed the place of the mouth of the Senegal, it will continue to shift its po- sition along the Sandy dike. * In a similar way, all the various streams which cmpty into the sea along the low coasts of the French Landes bend round toward the south as soon as they reach a point at a short distance from the sea-shore. There is, in fact, a current produced by the swell which runs parallel to the shore of the Landes, a matter which is easily proved by noticing the drifting of any floating substance, or the bearing of shipwrecked vessels, which al- ways point their sterns to the south. This current pushes before it mass- es of sand, which are mixed with the breakers, and thrown up upon the beach. The sandy points, which are constantly augmented by the addi- tions brought by the waves, are thus elongated toward the south, and would ultimately reach the bases of the Pyrenean promontories if it were not for the tendency of the streams to rise, so as to increase their slopes, and thus to press with increasing weight on the sands which obstruct them. Formerly the waste channels, or “courants,” of the Lakes of Sous- tons and St. Julian flowed parallel to the sea for a length of several miles above their outlet, and fears were entertained that, in consequence of the lengthening of these streams, and the rise in their level, the lakesłabove 344 THE EARTH, would spread over the surrounding country. In order to avert this disas- ter, the inhabitants undertook to rectify the course of the wasté channels, and thus to lower the level of the lacustral waters. This plan succeeded perfectly as regards the Soustons Lake. Its level was sunk 10 feet, to the great advantage of the village near, which was enriched with a tract of fertile alluvium. The Lake of St. Julian was likewise lowered several feet by the alterations made in the “courant” of Contis; but the engineers met with considerable difficulty in mastering this water-course, and in pre- venting it from flowing in a southerly direction parallel with the coast. They were several times compelled to lengthen the barrier which forced it to flow in a straight line down to the sea. As regards the more im- portant stream of Mimizan, which serves as a waste-channel for several considerable lakes, an attempt was often made to dig out for it a regular bed in the direction of the coast, and to retain the flow of water in it; but the river would not be subdued, and, throwing down the barrier of piles and fagots which was opposed to it, continued to run toward the south and southeast. Miles of basket-work dikes, which were set up to guide its waters, now lie buried under the dunes. º During the course of the Middle Ages, and probably also in the previous historical era, the Lower Adour, which is now perpendicular to the coast, extended in a line parallel to the chain of dunes and the sea-shore for a length of about 12% miles. The river then fell into the sea at a short dis- tance from the spot where the town of Cape Breton now stands. Toward the end of the fourteenth century a violent tempest obstructed this outlet, and the Adour, thrown back farther to the north, found no place of issue nearer than a point 22 miles from Bayonne; a village called Vieux Boucau (old mouth) marks the banks of the former river. At first sight it seems as if this ancient course of the Adour is to be explained in a similar way as the curves described toward the south by the streams of the Landes; but, if this were the case, the current of the sea-swell in this part of the Gulf of Gascony ought to tend in a northerly direction. Now the action of the waves points, on the contrary, from north to south, as far as the mouth of the Bidassoa, and consequently the Sandy points are lengthened with a southerly bearing. The belt of banks across the course of the Adour was turned toward the north ; it is therefore necessary to look for the cause of this in the existence of a chain of dunes solidly based on the nearest Pyrenean rocks, which presented an insuperable barrier to the river on the western side. In 1578 this chain was broken through at a point three miles and three quarters below Bayonne, by means of a trench cut by Louis de Foix, the engineer, and still more by a formidable flood, which threatened to carry away the city. Since this date, the mouth of the Adour, yielding to the coast-current, constantly tends to bend round toward the south, and on this side the piers formed to maintain the river are carried the farthest. At the end of the seventeenth century—at a date when these latter works had not been commenced—the river, bend- ing gradually toward the south; emptied itself into the sea at the foot of CLIANGES IN RIVER-MOUTIIS. 345 4° W. of rarig &o % / 7/ #o' º z - --~~~~ * 3. 3. Č, s º: . .2-- **): ja : ºx*. QºS Zºº” ¥ \\ /* *, *. 3. Yº N. ** * - sº wº i. …” *...*&s - }\\ i & & } ..I.'s "I ...tº, *:: * ... * 3. * * • ** • NA & *** *. A. • *, I * º “º • ‘s ºt.-l..." **** *** 4. A. §: * -r-, -a-. a ... * * ***... • “.. ... v. º º * t . . ºf !, º, S.J., * Yº...” sº - - rt, t *... . . ." *** * \ •res ** - =. Sºº, ‘ ~/ - s" sº * : g: r < º, ..ºy” % Nº ** *"...” * [[: *.* * - * ...t. Fig. 134. Old Course of the Adour. the rocks of Chambre d’Amour, about two miles from Boucau Neuf (new mouth). If the river had not been repelled on the right by the dikes con- structed by Louis de Foix, it is very possible that it would again have turned toward the north.* One of the most wonderful phenomena on the face of the earth is the formation of those long banks of alluvium which affect a considerable number of streams, and, for a distance of hundreds of miles, protect a multitude of river outlets against the waves of the sea. A magnificent example of this formation exists on the coasts of Virginia and North Car- olina. The rivers there, which flow on the surface of the ground, counter- poising the pressure of the ocean in the same way as the subterranean waters of Yucatan, have formed out at sea an immense breakwater. This sandy dike—which is not less than 186 miles in length, bends round the continent in gracefully-winding curves, and incloses within its limits per- fect seas, with their bays, archipelagoes, and currents; behind this, the Tar, the Alligator, the Neuse, and several rivers run into the sea. An idea may be formed of the peculiarities presented by these long banks, com- * Vionnois, Annales des Ponts et Chaussées, vol. xvi. * Wide above, p. 248,249. 346 THE EARTII. mon to several rivers, by comparing this dike with the altogether regu- larly formed littoral bank which lies in front of the River Cape Fear, in- mediately to the south. A third arrangement of the mouths of rivers is that which the ancient Greeks designated under the name of delta (A), on account of the triangu- lar form so often assumed by the alluvial plain embraced between the branches of a river. This plain, which projects beyond the regular line of the coast, is nothing but a former estuary, which has gradually been filled up with mud and sediment of every kind. This alluvial plain can not be formed to any great extent in places where the swell, the currents, and the tides are constantly disturbing the outlets of the rivers. It is necessary that the stream should be subject to conditions somewhat simi- lar to those existing in still lakes, where deltas form without the least ob- stacle. These conditions are found in almost inland seas, with a scarcely berceptible current—such as the Mediterranean and the Baltic—which al- low river-mouths to gradually fill up with mud. The alluvium which is brought down by the river is certainly soft, and has but little solidity; it is often roughly handled by the water at flood-times, and fails in pre- venting the liquid mass from forming forks, or even from dividing into numerous branches. But the sea, which assails these deposits, being con- stantly at about the same level, ultimately has the effect of consolidating them by dashing against them with its waves. On the contrary, when a river falls into a sea where the tides rise to a great height, and where the coast is alternately traversed by the rapid currents of the ebb and flow, mo time is left for the deposit of the river alluvium. This matter is first pushed back into the river by the flow of the tide, and then, being seized by the ebb, is carried out to great depths in the open sea. In this contest between the river and the ocean, the latter gets the advantage on account of the enormous mass of its waves, which, by their fluctuating movement of rising and falling, are incessantly scouring out the estuary through which the fresh water flows. Among those rivers the deltas of which are incessantly gaining on the sea, we may mention, as belonging to the first class in this respect, the great affluents of the Mediterranean, the Danube, the Nile, the Po, and the Rhone; also, in the Caspian, the Terek, the Kouban, and the Volga. Other rivers possessing deltas fall into the sea at the extremity of Some gulf well sheltered by a barrier of isles, and visited only by scanty tides. Of this kind are the IIoang-ho, the Yang-tse-kiang, and other water-courses, the alluvial shores of which continue to project more and more into the shallow Chinese Sea and the Gulf Pe-tchi-li. The delta of the Mississippi, which may serve as a type to all other formations of the same nature, pushes its way into an almost closed gulf, where the height of the regular tide never exceeds three feet. The only instance which can be mentioned of a great river delta existing at the extremity of a gulf widely open to the ocean, is that of the Ganges and the Brahmapootra. But it must not be forgotten that at the outlets of these rivers, the tide, fluctuating be- DELTA.S. 347 tween 1 foot and 164 feet, never exceeds, on the average, 10 feet in height;" added to this, the delta, instead of pushing its Way far into the sea, pre- sents a flattened shape, and extends its low shores from east to west, giv- ing a width of at least 186 miles. There is no doubt that in a more pro- tracted sea, the delta of these two combined rivers of IIindostan, which bring down in their turbid waters so large a quantity of alluvium, would have thrown out a long promontory of delta exhibiting very different pro- portions. In a cursory and rapid examination of a map, it would, however, be easy to fall into error as to the real character of certain river-outlets, and to look upon them as actual deltas, thrown out by the action of the river itself, instead of collections of soil deposited under the shelter of isles Of marine formation. Thus Holland, which is placed at the angle of the continent of Europe, appears at first sight to be the combined 'delta of the Scheldt, the Meuse, and the Rhine; but the outer shore is, in fact, an ancient coast cut through by the waves of the ocean, and is composed of a vast semicircle of dunes, stretching from the mouths of the Scheldt to those of the Ems and the Weser. Far from having gone beyond this original coast-belt, the greater part of the Dutch rivers have formed estū- aries, and the wide sheets of the Bies-bosch, the Zuyder Zee, and the Dol- lart constitute unquestionable testimony of the invasion of the Sea-Water. The alluvial tracts of Holland do not, therefore, present the character of a delta properly so called. Deltas are not formed solely on the lower portion of a river's course; they also exist at all the points of the river where former lacustrine basins have been filled up by one or more several affluents. At these spots, the principal water-course and its tributaries divide into several branches, radiating in a fan-like shape across the alluvial plain; sometimes they even cross one another so as to form a complete net-work. About the middle of its course, the Mississippi receives two considerable affluents from the west, the Arkansas and the White River. The principal river and its two tributaries are united by a net-work of innumerable bayous,f which at every inundation change their course and their depth, falling alternately into one or the other of the three currents, according to the respective height of their waters. When the Mississippi is very high, it disgorges its surplus water into the system of bayous, and the latter empty into the Arkansas and the White River. During the low-water season, on the contrary, when the water poured by the Mississippi into the marshes above has had sufficient time to flow from lagoon to lagoon down to the White River, the latter feeds the net-work of bayous which connects it with the Mississippi and the Arkansas. When the latter river is swollen more than usual after heavy rains in the Western prairies, then the pressure of its water drives back that of the Mississippi, and for a * Beardmore, Manual of Hydrology. f Derived from the French word baie. The Spaniards of La Plata give the name of bahia to natural channels of the same description. 348 THE EARTH, time the Arkansas takes possession of the common delta. On the banks of the Amazon River all these phenomena take place with much more grandeur; at the mouth of the Japura especially, the principal current forms with its affluent an inextricable net-work of false rivers, which seem to flow indifferently in any direction, and, for a space of several thousand square miles, direct their surplus waters from marsh to marsh through the virgin forests. This system of furos, as they are called in South America, resembles those congestions in the human body when the too great abun- dance of blood gives rise to a system of false arteries and veins. CHANNELS OF THE MISSISSIPPI. 349 CHAPTER LIII. THE CHANNELS OF THE MISSISSIPPI.-“WORKING RIVERS.”—SHIFTING OF TIIE, POINT OF BIFURCATION.—RAISING OF TIIF RIVER-BED ABOVE TIII. DELTA.—ALTERATION IN TIII, SITUATION OF MOUTIIS OF RIVERS. IN a geographical point of view, it is important not to confound appa- rent deltas with the real deltas of alluvial earth. Thus the basin of the Mississippi, in which there is opportunity for studying so many other hy- drological phenomena, exhibits several instances of emissaries which must not be looked upon as branches of the delta. The Atchafalaya, in fact, is not a branch of the Mississippi, as it is not fed by the latter; it is, on the contrary, a continuation of the Red River, which sends down to the Atcha- falaya a portion of its water directly, and another portion indirectly, by using for nearly a mile the bed of the Mississippi itself. The Plaquemine and Lafourche bayous, which, during floods, receive a small portion of the water of the Mississippi, are not regular fluviatile beds, like the branches of the Rhone, the Nile, and the Po; they are mere channels communica- ting between the inland lakes and marshes, and have become united to the Mississippi by an erosion of the banks of the river. It is, indeed, owing to the labor of man—that is, to the side embankments and the drainage of the marshes near it—that the Lafourche bayou has assumed the aspect of a river for so large a portion of its course, and now no longer disap- pears, as it once did, in a labyrinth of pools and marshes. The Manchac, or Iberville bayou, which used to reach the sea through the Amite River and the Lake Maurepas, is now completely obliterated by the alluvium and masses of entangled trees; but it has always been a mere flow of no great importance.* Thus the delta proper only commences at the “Iſead of the Passes,” and this sheath-like bed, through which the Mississippi rolls” between two narrow banks of alluvium, one side of which is sea-shore and the other river-bank, is, geologically speaking, the sole bed of the river. Projecting from the continent like an arm, it pushes out for 62 miles into the sea, and spreads over the water the branches of its delta, like the fin- gers of a gigantic hand. A Hindoo might well compare the extension of the mouths of the river to an immense flower opening over the ocean its serrated corolla. These narrow embankments of mud, brought down into the open sea by the fresh water, present a striking spectacle. In several places these banks are only a few yards thick, and during storms the waves of the sea curl over the narrow belt of shore and mingle with the river. The soil of the banks becomes perfectly spongy; it is not firm enough to allow * Humphreys and Abbot, Report on the Mississippi River, 1861. 350 TEIE EARTH, even willows to take root, and the only vegetation is a species of tall reed (Mºegea macrosperma), the fibrous roots of which give a little cohesion to the ooze, and prevent its being dissolved and washed away by the succes- sion of tides. Farther down the reeds disappear, and the banks of mud * Wes. š Jo §3. ºl. § º §§ §§§ §º w sº º § ſº # º s sº º | § N §§ ºt : § §: º § Š: § [. 3. º & º º - z … - | } sº # § - §§ § § sº - §3.4.xºfºº *f;: º ..º. M ! ..º.º. ** 3: - . . . s.* iſofº Šišº S Jº- % Øs= Ss Sºłą ...” SS-S-SS S-Tº- . 22. ºr: # = * 4o’ Fig. 135. Mouths of the Mississippi. form, are washed away, and form again, wandering, so to speak, between the river and the sca, at the will of the winds and tide. On the left bank of the southwest passage, which is used for the largest ships, the plank- built huts of a small pilots’ village have been fixed as delicately as possi- ble. These constructions are so light, and the ground that carries them is so unstable, that they have been compelled to anchor them like ships, fear- ing that a hurricane might blow them away; still, the force of the wind often makes them drag on their anchors. Below, the banks of the Missis- sippi are reduced to a mere belt of reddish mud, cut through at intervals by wide cross streams; still farther down even this narrow belt comes to an end, and the banks of the river are indicated by nothing but islets, which rise at increasing distances from one another, like the crests of sub- marine dunes. Soon the summits of these islets assume the appearance of a thin yellow palm floating on the surface of the water. Then all is mud; the land is so inundated with water that it resembles the sea, and 1A YERS OF WATER, 351 the sea is so saturated with mud that it resembles the land. Finally, all trace of the banks disappears, and the thick water spreads freely over the ocean. After getting clear of the bar, the sheet of water which was the Mississippi preserves, during floods, the yellowish color by which it can be distinguished for about twenty miles, but it loses in depth all that it gains in extent, and, gradually depositing the earthy matters which it holds in suspension, becomes ultimately perfectly mingled with the sea. 'Nº,' §§ 2. jº N - Ž º %% #Sy: §º Z # ! | * % §§ # ſ - Fig. 136. Channel of Loutre. In calm weather, the union of the fresh and salt water presents an in- teresting spectacle, affording some similarity to the meeting of the tide and the river-current in an estuary. Gliding in layers of increasing thin- ness over the weightier masses of the ocean, the muddy water, on escaping from the mouths of the delta, swims like oil on the surface of the Waves, and the sailors are able to collect it without difficulty by skimming the surface. Ships, as they pass, break through this light yellowish sheet, and leave behind them a long track formed by the blue and transparent water of the sea. A contrast of the same nature is produced at the spot where the Gulf Stream causes the belt of the water of the Mississippi to swerve to the east; one might fancy that a straight line traced out by a ruler 352 THE EARTH. separated the two diversely-colored waters as far as the horizon. Finally, the sheet of fresh water, becoming very thin, is broken up into little tur. bid islets, surrounded with salt water. They are often full of vegetable dé0,78–they are then edged with breakers in miniature, which give them a border of foam.* The sounding-line let down to the bottom of the sea off the mouth of the river finds the mud of the Mississippi as far as the coral banks of the Florida coast. The accompanying plates show the dif. ference in the depth of the sea between the axis of the Mississippi and those portions of the gulf which are situated immediately to the south. * CŞı İ-> <-> r- CN *H co ºr-i E # c c Cº. C/3 <-- º Fig. 137. Depths of the Gulf of Mexico in the Axis of the Mississippi Current. The fluviatile tracts of alluvium which are constantly forming before our eyes may be classed among the most important geological phenomena in the history of the globe. Owing to the quantity of mud which the masses of running water bring down to their outlets, the shore-line is in- cessantly changing, and continents are increased in area. Carl Ritter has given the name of “working rivers” (fleuves travailleurs) to those water- courses which deposit a large quantity of alluvium in deltas, and push their shores farther and farther into the midst of the sea. Every river, indeed, takes its share in this labor, but in great deltas the earth quite visibly encroaches upon the ocean. At the mouths of several rivers the lifetime of a man would be a period long enough for the salt bay to be converted into a plain, and the floating sea-weed beds to become a magnificent forest. #. .g- ă și $2 # 3 # # 3 g g g g g = % # * a # :3 º CN § 3 * as QN #: Aro E. º : i. : º % º % % ! ! º º ºs J / º * Fig. 138. Depths of the Gulf of Mexico South of the Mississippi Current. The deltas themselves, the vast plains which, as Herodotus says, are the “gifts of rivers,” bear witness to the geological importance of running wa- ters in the formation of continents. But the investigations which have been made up to the present day enable us to estimate the progressive course of these alluvial formations in but a Small number of rivers. In fact, the problem which has to be resolved is a very complex one. In the first place, it would be indispensable to prepare at intervals exact charts * Kohl, Zeitschrift für allgemeine Erdkunde, September, 1864. DELTA OF THE GANCES - PI, XVll 86 & - - - - ..” *"----------- I º º'. Aº - º, Vs., . wrºt ...Aº ‘ ** 86 East of Paris 3, 88 - Drawn by A Vuillemin after Tassin. Rºngd by Erhard H.A.R.P.F. R. & B R ()'ſ H F S, NEW YU RI'ſ A LLU WIUM OF RIVERS. 353 of the sea-coast and the depths of the sea in the vicinity; next, it would be requisite to strictly apportion the quantity of sediment brought down in each season of the year by the water of the river, and to ascertain the amount of alluvium which is lost along the coast. Lastly, in the beds of the delta itself, it would be necessary to distinguish between the déðr's washed away from the adjacent coast and the matter which is brought down by the river; for when a muddy point is formed, the currents along the shore always drive upon it a constantly increasing bank of sand. Some day, doubtless, more exact observations will enable us to trace out the journey of the alluvium down the river that carries it along; we shall ascertain the average time that elapses before the rock rolled down by the torrent is broken up into pebbles, and then in succession reduced to grav- el, sand, and impalpable mud; we shall learn the number of resting-places. that the débris avail themselves of in bend after bend from the river's source to the sea. Perhaps, even by the mere observation of the alluvial layers, we shall be able to discover the age of the bed, as we ascertain the age of a tree by its concentric rings. We must, however, confess that this class of geographical observations is scarcely inaugurated, and that it would require an enormous staff of savants, which does not at present ex- ist. We are therefore compelled to form rather rough estimations as to the results of the labor of rivers; this is the case as regards the Hoang- ho, which is probably more loaded with alluvium than any river in the Old World. *~ This river owes its name, Hoang (yellow), to its muddy sediment, which, far out at sea, soils the purity of the sea-water, and is carried by the cur- rents as far as the coasts of Corea. The delta which it has formed during the present period extends over at least 96,000 square miles, and consti- tutes one of the most important provinces in China. The tracts of allu- vium have joined to the main land the mountainous mass of Chantung, which once stood alone in the midst of the sea. Fresh islets have slowly risen from the bed of the sea, and the detritus is deposited in quantities so great that, according to a calculation made by Staunton at the end of the last century, they would be sufficient in the course of sixty-six days to form an isle a square mile in extent and 118 feet in depth. According to the calculations of the same author, the whole of the Yellow Sea is des- tined to disappear entirely in about 24,000 years; but this period should be at least doubled, for the waters of this sea are much deeper than Staun- ton stated. - The English authors who have written on the subject of the lower re- gions of the Sunderbunds—that prodigious mass of alluvium brought, down by the Ganges and the Brahmapootra, the terrible “son of the Brah- mah”—afford us but uncertain information as to the lengthening of the mouths of the rivers. According to Rennell, the Ganges alone sends down in its water from five to six cubic yards of mud a second; nevertheless, the line of shore extending from the mouth of the Hoogly to the estuary of Huringota, which consequently limits the Gangetic portion of the delta, 354 THE EARTH, appears to have been subject to but very slight modifications during his- toric times. The promontories and the islets of the eastern portion of the delta encroach much more rapidly on the sea; for on this side the waters of the Brahmapootra, which on the average are charged with twice as much mud as those of the Ganges, pour into the Bay of Bengal.” A great quantity of the alluvium which is brought down by the two rivers is lost in the immense depths of the marine depression, which lies about 31 miles from the mouth of the Ganges, which is called the “Great Swatch.” The Nile—that typical river which was the subject of study to the Egyptian hierophants thousands of years ago—which spreads out the graceful delta formed of its own alluvium, is incomparably better known as regards its lower course than any river of Asia. This great water- course, which may be compared in the length of its bed to the Mississippi *3 º * 3. 1...excº cº-ZKºrn/ º *; 3. gºſº Fig. 139. Delta of the Nile. and the Amazon, Scarcely surpasses rivers of the third class, such as the Rhone or the Po, in the importance of its liquid mass, and is much inferior to them in the quantity of its alluvium. It has been calculated that if all the mud brought down by the mouths of the Nile was thrown up uni- formly on the coast, the latter would advance about 13 feet a year. The low points of alluvium which are deposited near the Rosetta and Damietta mouths increase on the average—the one 34 acres, and the other 39 acres, × Forguson, Zeitschriſt für Erdkunde, 1804. e DELTA OF THE PO, 355 every year, which gives only three feet of annual progress for the front of the delta, the convexity of which is 186 miles in length. If the advance of the alluvial deposits was not more rapid during past ages than it is at present, it must have taken the Nile no less than 74,253 years to deposit, grain by grain, the triangular plain of the delta, comprising an area of 8610 square miles.* The fact is, that the Nile leaves the greater part of its alluvium on the plains by the river-side; added to this, the extension of the water over the two banks, and the diminution of the current which results, necessarily cause the fall of a certain quantity of sediment on the bottom of the river- bed. The French savants of the Egyptian expedition found that the rise in the bottom averaged 4:960 inches a century. This gradual elevation of the bed doubtless corresponds with a similar change in the level of the two banks of the river. By measuring the bed of alluvium in which the statue of Remeses II. is buried at Memphis, Mr. Horner came to the con- clusion that dºuring the last 3215 years the soil of Egypt had risen 3-043 inches in each century. It is probable that in future the soil will be raised more and more rapidly every year, owing to the “warpings” which are incessantly carried on by the agricultural inhabitants on each side of the river. Now that a vast system of skillful cultivation has appropriated the banks of the Nile, and that steam-pumps are drawing off the water of the river in every season, the liquid discharge and the mass of sediment must diminish at the mouth; and if this impoverishment of the Nile con- tinues to go on in the same proportion, we might perhaps calculate the future date when the Nile, being exhausted by the irrigation canals, will no longer send down to the Mediterranean either a drop of water or a grain of sand. It may be readily understood that the best known river-delta must be looked for in Europe, and in that country of Europe which, for so many centuries, has devoted itself most earnestly to all questions relating to hy- draulics and irrigation. The delta we speak of is that of the Po. Owing to the testimony afforded by history, the monuments left by the ancients, and the operations of the engineers of the Middle Ages, we are enabled to follow with the mind's eye the progress made by the alluvium of the river during the last twenty centuries. In some spots, especially round the la- goon of Comacchio, there are secondary deltas, the encroachments of which may be measured with mathematical exactitude, for these tracts are, so to speak, of human creation, and have been altogether deposited since the opening of artificial channels and sluices. Notwithstanding the shortness of its course, the Po is one of the most remarkable “working rivers” in the whole world. The gradual subsidence of the shores of the Adriatic, which is estimated by Donati at six feet at least since the foundation of Venice, does not prevent the river encroach- ing without intermission on the domain of the sea. Ravenna, which once, like another Venice, stood in the midst of lagoons, its outer rampart being * Eli Lombardini, Essai sur l'Hydrologie du Nil. 356 THE EARTH. o "E, of Paris - | Fig. 140. Mouths of the Po. bathed by the Adriatic, is now situated far from the gulf, in a plain filled with the alluvium of the Po. We also know that the town of Adria, the ancient emporium of the Adriatic, to which, indeed, it gave its name, is now 21 miles from the extreme point of the shore. This is a proof that in two thousand years the annual average progress of the delta has been 55 feet; but at the present day the advance of the alluvial tracts is much more rapid. The patient investigations of M. Lombardini have established the fact that the river brings down every year 15,015,600 cubic yards of mud and ooze"—that is, about 1.781 cubic yards a second, and enlarges the shore of its delta 76 yards. A chain of dunes, now left inland by the encroachments of the alluvial deposit, still points out the direction of the former sea-coast. The enormous amount of increase in the deposit at its mouth, which is thus accomplished by a river of the third class, is readily explained by the embankments, which compel the Po to carry down to the sea the whole of its alluvium, whilst the Nile and the Ganges, during each period of flood, spread over a great area of land, the level of which they raise by their deposits. The Rhone is the most active among the French rivers in the forma- tion of a delta. The promontory deposited by its current in the open Sea projects much more decidedly beyond the regular line of coast than the delta of the Nile, and advances every year with a rapidity which may al- * According to M. Ch. Hartley, the Danube, which discharges five times as much water as the Po, brings down to the sea only 46,500,000 cubic yards a year. ALLU VIUM OF THE RHONE. 357 §§ º §/. 2.2× N.Y. 2:3 jºr -*. L. A C R.A. "º =s= = Fig. 141. Delta of the Rhone in the Fourth Century and at the Present Time. most be compared to that of the Po. In the fourth century the town of Arles was only 16 miles from the sea, while at the present day it is 29 miles removed from it. The advance of the alluvium has, therefore, been 13 miles during the space of fourteen centuries, or about 52 feet a year.” The annual average elongation of the shores of the principal branch of the river is, therefore, about 164 feet. But this does not prove that the débris brought down by the river are increased threefold, in consequence of the embankment of the land by the river-side; for the Rhone has frequently shifted the position of its outlets by opening them alternately on both sides of the banks of mud caused by its own deposits. In this way the increase of the delta takes place at several points in succession; on one side the alluvium encroaches rapidly, and in other places it remains almost & stationary. - In the Rhone, as in the Po, an endeavor has been made to estimate, by means of the annual discharge, the quantity of matter deposited by the river. This mass is about 22,000,000 cubic yards every year. It certain- ly is a fact that, by direct measurements of the increase of the delta, and by soundings made on the bar, M. Reybert found that the total quantity of matter brought down from 1841 to 1858 amounted to 419,000,000 of cubic yards, which would be equivalent to an annual increase of 25,000,000 a year; but this difference may be explained by taking into account the enormous quantity of infusoria and small shell-fish which exist in all the newly-formed soft banks. Some specimens of the mud taken from the mouth of the Rhone contain, as M. Delesse has ascertained, as much as 30 * E. Desjardins, Aperçu Historique sur les Embouchures du Rhône. 358 TEIE EARTH, per cent of carbonate of lime, proceeding, no doubt, from the remains of the shell-fish. It also appears that the proportion of the alluvium of the Rhone which is brought down to the sea, and afterward carried away by the currents to distant shores, is very slight. Almost all the mud is ab- sorbed in the construction of the delta, and forms the teys or muddy islets which make their appearance on each side of the mouth. The soil which is thus brought down by the river is generally very fertile. The mud of the Rhone is no less productive than that of the Nile, and sanitary and irrigatory operations would soon render La Camargue another Egypt. In this respect France has much to learn from the ancient land of the Pha- raohs. The delta of the Mississippi advances even more rapidly than that of the Po. Among all the questions in respect to the great river of the New World, the yearly prolongation of its alluvium has most of all excited the curiosity of science. How many yards does the Mississippi advance into the sea during the course of each year? How many square miles does it add to the main land in a century 2 How many thousands of years must it have been at work in forming its delta, and depositing its enormous burden of alluvium ? Many geologists have, each in their turn, endeavored to an- swer these questions by basing on data which are sometimes only hypo- thetical the very different results at which they have arrived. Thus M. Elie de Beaumont, who at that time had not the necessary elements at his disposal, estimated the progress of the delta at 382 yards a year. M. Thomassy, comparing the ancient French charts with the American sur- veys, has felt warranted in fixing the annual conquest effected by the Mis- sissippi at about 110 yards. Messrs. Humphreys and Abbot, looking upon the old chart as being too incorrect to serve as the base of a serious calcu- lation, are satisfied with comparing the charts of Talcott and of the Coast Survey, and judge the annual prolongation of the delta to be 86 yards. M. Ellet, one of the most conscientious investigators of the action of the river, reduces the probable elongation of the delta to 22 feet, so as to make allowance for the crosion exercised by the sea. Lastly, M. Kohl, whose hypotheses it is very difficult to understand, even if you have the maps before you, maintains that the delta of the Mississippi remains nearly sta- tionary.* It must be confessed that the differences on the point would be serious enough to render doubt “the best pillow for the wise man” if it were not that the calculations of M. Thomassy and the learned explorers, Humphreys and Abbot, undoubtedly surpass all the others in scientific value. The average advance of the delta during the two last centuries must therefore be estimated at from 86 to 110 yards. This rapid progress in the alluvium is perhaps very much owing to the cutting down of the forests, which has rendered the soil of the banks much more movable.} To this cause for the growth of the delta must be added the construction of high embankments on the banks of the Mississippi and * Zeitschrift für Erdkunde, September, 1862. # Marcou, Bulletin de la Société de Géographie, July, 1865. DELTAS. 359 its tributaries; for, as only a small portion of the mud is able to settle at the sides, a much more considerable mass is carried down to the mouth; nevertheless, the delta is not increased in proportion. The more the points of alluvium gain on the water, the deeper is the spot in the gulf in which the matter (estimated at Seven cubic yards a second) is deposited. At the lower extremity of the delta of the Mississippi, the thickness of the bed of sediment is not less than 98 feet; and soundings have shown that the river will soon reach the edge of the deep abyss through which the Gulf Stream flows. At 11 miles from the southwest channel, the bottom of the Sea is 885 feet from the surface, and this depth rapidly increases to more than 5000 feet. Being, of course, unable to fill up these gulfs where the rapid currents would carry the alluvium into the open sea, the Mississippi must be content with obstructing the lateral bays, or with extending to- ward the east, in the direction of Florida. Some day the delta of this river will be bounded on the southern side by a rapid slope, like that which is formed by the Rhone in the Lake of Geneva, and by the Congo in the Gulf of Guinea. At the mouth of this latter water-course the sounding- lead falls rapidly from 30 to 1600 or 2000 feet. - When the river-outlets are left to themselves, the spot in the river where the bifurcation takes place gradually shifts its position in a down-stream direction in proportion as the mouths advance toward the sea. In fact, Fig. 142. Height of the Layers in the Delta. the current striking against the upper point of the delta must necessarily wash away the two banks of the island which it has itself formed by the deposit of its alluvium. A remarkable instance of this alteration in the place of bifurcation of the river-outlet may be noticed in the Egyptian delta. At the time of Herodotus, Memphis was the spot where the Nile divided into two branches; it now forms its fork at Cairo, more than 18 miles from the spot where it took place 2400 years ago. The upper point of the delta will henceforth remain stationary, owing to the barriers con- structed just at the beginning of the two principal branches of the river. The elongation of the delta has a proportionate and constant tendency to raise the bed of the river above the mouth. The calm and immense river which empties itself into the sea obeys the very same laws as the boisterous torrent pouring into a lake. In proportion as it pushes its branches farther into the sea, it must form a slope considerable enough to insure the discharge of the mass of water. This slope can only be pro- duced by the gradual raising of the river-bed. It is evident that this rise will be the more rapid the better the shores are protected by embank- ments against inundations; for the alluvium must, in this case, all descend to the Sea, and lengthen the extreme points of the delta. The results produced on the action of rivers by lateral embankments 360 THE EARTH, have, however, been singularly exaggerated. Pessimists have often point- ed to the example of the Po as a proof of the rapid heightening of the riv- er-level which is brought about by the construction of embankments; “but this oft-repeated assertion is not based on any real fact. Cuvier was entirely mistaken in stating, according to a communication from M. de Prony, that the surface of the water of the Po is now higher than the roofs of the houses in Ferrara.” This, unfortunately, is one of those accredited errors which it is difficult to dispel, on account of the great names which countenance them. Elia Lombardini has proved, by strict measurements, that the mean level of the Po exceeds in but very few spots the level of the ground in the adjacent country. In 1830, at the time of one of the highest floods of the century, the surface of the Po was scarcely ten feet above the level of the pavement in front of the palace at Ferrara. The mean height of the water over the whole course of the river is considera- bly below that of the neighboring plains. To make up for this, the streams of the Reno, the Adige, and the Brenta, which empty into the delta of the Po, have certain portions of their beds higher than the adjacent country. The fact is, that, having so lately left the mountain gorges, they still retain their characteristics as torrents, and, like all mountain streams, raise a bank of débris below the ravines of erosion. The exceptional height of the Adige, the Reno, and the Brenta must not, therefore, be attributed to the dikes which border the lower portion of the course of these streams, but to the impetuosity of the water above. The calculations of MM. IIumphreys and Abbot prove that the mouths of the Mississippi must project 24 miles farther into the sea for the river to rise only one foot under the ramparts of Fort St. Philip, 31 miles above the southwest chan- nel. If, however, rivers which are subject to high floods, such as the Nile, the Po, and the Mississippi, are, during inundations, higher in level than the plains by the river-side, this fact is owing to the lining of alluvium which is gradually formed on the banks. During the period of flood, the waters which pour over the banks are retarded by a thousand various obstacles —trunks of trees, bunches of plants, mounds, palisades, buildings—and con- sequently they deposit on the ground much of the sediment which they contain; before they leave the banks and flow far and wide into the plains they are comparatively purified. The effect of this is a gradual elevation of the banks and the ground near them to a level somewhat above that of the country generally. Above New Orleans the natural inclination of the soil is very marked; from the shores of the Mississippi to the marshes in the interior the difference in level is not less than 13 to 16 feet, and at some points even this considerable slope is exceeded. The banks of the islands scattered about in the lower courses of rivers are likewise raised by inundations to a point above the level of the surrounding country. The Lower Parana, the Volga,s and a number of other large water-courses * Discours sur les I?évolutions du Globe. f Wide above, p. 298. - f Martin de Moussy, Confédération Argentine. , § De Baer, Kaspische Studien, JLEVATION OF RIVER ABOVE ALL UVIUM. 361 present, near their mouths, multitudes of islands, the raised banks of which circle round pools or marshes. The elevation of the lower course of a river above the surface of the surrounding plains explains in the most simple way the continual shift- N& Fig. 143. Section of the Mississippi at Pla ing of the outlets of the delta. As soon as a breach is made in the lining of the bank, a considerable portion of the running water immediately escapes through this opening, and descends to the sea over a new bed which it hollows out for itself across the low-lying tracts, marshes, and lagoons; these are natural crevices, similar to those which occur in cm- bankments raised by man's labor. Thus, when the economy of a river has not been modified by human agency, its outlets are of a changing character, and move across-the delta, depositing their sediment in the la- goons, so as gradually to clevate the soil, and to bring it every where to the level of the high floods. Every delta becomes modified, even during the historical period, in the number, direction, and importance of its branches. Of the seven famous mouths of the Nile, five have now ceased to exist except during floods; the two which still remain open—those of Rosetta and Damietta—appear, according to Herodotus's statement, to have been dug out by the labor of man. During the last 3000 years, the branches of the Lower Hoang-ho have undergone similar modifications in their course, which are more remarkable on account of the immense ex- tent of ground over which they have constantly wandered.* Still more strangely, the Amou-Daria in Tartary, which nqw falls into the sea of . Aral, was in former days a tributary of another sea, and flowed into the Caspian; the traces of its abandoned bed may still be seen here and there in the desert. In consequence of the incessant modifications to which the lower por- tions of rivers are subject, it often occurs that two water-courses, which were once perfectly distinct and independent of one another, become united in their deltas and principal outlets. We may mention the in- stance of the Shat-el-Arab. In like manner, the Adige and the Po, which communicate with one another by lateral branches, have a tendency to join one another completely in a common bed, and nothing but extensive operations has prevented, up to the present time, the perfect junction of these two rivers. The Mississippi, so remarkable in all other respects, presents, according to Ellet, the phenomenon of three former rivers united in one. At one time the River Ouachita ran down to the sea throughthe Atchafalaya, which is now an overflow-channel of the Mississippi, but was then a distinct river. The Red River, too, flowed in the valley of the Tèche, where it has left numerous traces of its passage. The opposite windings of the Red River and the Mississippi gradually approached one - * Wide above, p. 353. 262 THE EARTH, A. 53 §º; i. S.S. % º 3& * lº -- - - w . . - sº ------ - '. º - - - 2.: ºf . - * Nº. ŽS$º {Wºr:%2. 7- - **** t :% ºf 3 sº - ** t |º]}; ! 3 º •º *2. at- f . . * º | ºf ſº - ºWWJM w * MW); !"thunwº, º, ºf ſº ** .. {A, ** 11W º º { ºr ºt. º Wººyºſº, * * * * * º ºº:: §º §§ağlſº - .." º *** w § * -n- *i- Fig. 144. Ancient Course of the Amou-Daria. another and then united; the Ouachita-Atchafalaya has been, as it were, cut into two parts, one of which, the northern portion, is become an afflu- ent, and the other, the southern portion, an effluent of the Mississippi. Similar phenomena are observed in the delta common to the Ganges and the IBrahmapootra. There seems to be a real conflict between the branch- cs of these two rivers; they first come together and are then mutually re- pelled; they sever one another and fill each other up.” Thus, while in some cases distinct rivers unite, others, on the contrary, which were once combined, are now separate, and take contrary direc- tions. As a striking instance of this double series of hydrological phe- nomena, we may mention the two rivers of Cilicia, once called the Sarus and the Pyramus, now known as the Seihoun and the Djihoun. These streams, which project their alluvial deposits more than six miles beyond the outline of the former coast, fall into the sea sometimes through two distinct mouths, sometimes through one outlet common to the two rivers. Since the days of Xenophon, the two streams, which then flowed in beds some distance from one another, have united three times, and three times have again separated. In the space of twenty-three centuries, says M. Langlois, six complete revolutions have taken place in succession in the course of action of the Sarus and the Pyramus. * Ferguson, Zeitschrift für Erdkunde, 1864. JBAL/PS OF RIVERS. 363 CHAPTER LIV. BARS OF RIVERS.—OPERATIONS UNDERTAIKEN FOR DEEPENING THE TMOUTHS OF TRIVERS. NOTHING is more variable than the channels at the mouth of a river. Thus—only to mention the Mississippi—this river has now five channels, the southwest, the south, the southeast, the north, and the Loutre, which is a ramification of the one preceding. Sometimes one, and sometimes another of these outlets becomes the real mouth of the river, and the stream takes to them and abandons them in turn. The fact is, that the Mississippi, having considerably elongated its principal outlet by the al- luvium it has brought down, is compelled to seek sºme bed which is short- er, and consequently more inclined, in order to pour down its mass of water; when this fresh outlet is likewise pushed out too far into the sea to afford the requisite slope, the river turns either to the right or left to clear for itself a third place of issue. At the time of the first attempts at colonization in Louisiana, the Southeast channel was the principal one; but this gradually became obstructed, and the northeast mouth was next the most important. The mass of water in this channel diminished every year; and in 1853 there was not more than 8 feet of water on the bar, and small coasters were the only vessels which ventured over it. Since 1843, the southwest channel has become the real mouth of the river, through which almost all large ships try to enter. In 1853 there were 163 feet of water; but constant labor was necessary to maintain even this depth, for the quantity of water constantly tends to diminish, while in the Loutre Channel it is gradually increasing. Some hydrographers think that this latter mouth will ultimately become the true Mississippi; it al- ready has 13 feet of water on the bar; and, in order to avoid a considera- ble circuit, nearly all the steamers running between Cuba, Mobile, and New Orleans now attempt to pass through it. However much they may shift their course, still most rivers are ob- structed by a bar of sand or mud, to which mariners have given the name of “bar.” These banks of alluvium are, for the most part, deposited in the form of a crescent, off the mouth of the river, and, turning their con- vex sides toward the open sea, mark the precise spot of the line of break- ers which rise in rough weather. They may be deposited in different modes, according to the quantity and impetus of the river-water, the mass of sediment which the latter holds in suspension, the configuration of the coast, and the general direction of the winds and currents out at sea. There are, however, a few hydrological problems which have given rise to lively discussions among geographers and engineers, for which, too, many 364 THE EARTH, various or contradictory solutions have been propounded. The fact is, that the question is altogether a complex one, and presents itself under a new aspect at the mouth of each particular river. It certainly is the case that, as regards all rivers, the collision of the two liquid masses flowing in Waves of the Scº. Fig. 145. Longitudinal Section of the Bar of the Mississippi. contrary directions is the primary cause of the formation of bars, bu the materials which are employed and the progress of the work vary singu- larly. e --- At first sight, the origin of a bar seems a matter easily to be under- stood, especially in the case of rivers with waters much charged with mud. It is thought that the current of fresh water, being suddenly arrested in its career by the sea water, immediately lets drop on the bottom the mat- ter which it held in suspension, and thus gradually forms the kind of sill which rises between the bed of the river and the ocean. This, however, is not the exact mode of formation. The flow of fresh water, being but lit- tle retarded, continues its movement above the salt water coming in a contrary direction. The sediment which is let fall by the current of the river is taken hold of by the counter-current and borne up stream. At the same time, the heavier alluvium, which makes its way to the sea by gliding over the bottom of the river-bed, is arrested in its progress, and is mingled with the sand and the innumerable organic remains driven in by the waves. Thus an increasing cushion of mud is formed in front of the rising tide flowing to meet the river, and in this way the heaps of débris which constitute the bar are gradually accumulated. This obstacle, being produced by the shock of two opposing currents, shifts coincidently with the scene of the conflict. During floods, the impetus of the mass of fresh water becomes sufficiently strong to remove the whole bar and to carry it farther in advance; but, on the other hand, when the water of the river is low, the tide resumes the preponderance, and the bar is again driven back. The barrier shifts its place, sometimes in one direction, sometimes in an- other, and is incessantly seeking to preserve its equilibrium between the two opposed forces which impel it. - The bars of the delta of the Mississippi may be quoted as an instance of this mode of formation. Over the bar which obstructs the entry of the principal channel, and the most practicable of all those on the coast of the Gulf, there is an average depth of 16% feet. The alluvium of the bed, being kept in constant motion by the waves and the current of the river, BARS OF RIVERS. 365 is in an almost liquid state. Vessels have been known to cross the bar without any other assistance than thet sails, although their hulls were, for more than half a mile, buried in the mud to a depth of six feet. Not- withstanding the soft nature of the ooze, vessels may still incur consider- able danger in crossing the bar. Those that do not avail themselves of a steam-tug are sometimes taken athwart by the wind and driven irretriev- ably upon the banks. It is often impossible to get them off again; the motion of the keel stirs up and sends into the current the smaller particles of the mud, but the heavy sand remains, and ultimately becomes cemented round the bottom of the ship. There are some bars which are almost entirely the work of the sea; these are banks of sand or shingle which the waves throw up across the outlet of a river, thus continuing the line of shore. Barriers of this kind form in front of water-courses running into a sea agitated by violent storms, or raised every day by a very strong tide. The flow coming from outside ascends far into the river-mouth, and forces the current meeting it to deposit its heavier alluvium at some considerable distance above the bar properly so called. The earthy particles held in suspension by the current of the river can not be precipitated on account of the continual agitation which is kept up at the entry by the breakers and the swell; they remain mixed with the masses of water, and are driven up stream by the flow, or carried out to sea by the ebbing tide. Even the fine sand which the waves throw up on the bar is not allowed to remain there for long; it is again stirred up by the water which brought it, and it finds a resting-place only in those spots where the motion of the waves ceases. The heavy sand, the shingle, and the stones which the waves drive before them without carrying them along in eddies, are the only materials which constitute the bar. Like the banks of mud in river-deltas, this line of dé- bris is incessantly shifting its place, sometimes up stream and sometimes down stream, seeking the exact line where an equilibrium exists between the ebb and the flow. When the river is flooded, the force of the water running down carries the bar farther out to sea; on the contrary, when the river is low, the tide gains the ascendency, and pushes the sand up into the mouth of the stream. In France, these phenomena have been best studied at the formidable bar of the Adour. Thanks to the submarine charts which the engineers prepare twice every month, we may trace out, so to speak, by the eye, all the fluctuations of the bank of débris, and all the causes of its movements can readily be taken into account. In this bar, however, there is every evidence to show that the materials forming it are brought up by the waves. The soundings that have been made in the bed of the Adour, as far up as 15% miles above Bayonne, uniformly show a bottom of mud or fine sand; but it is ascertained that the bank at the mouth is composed of heavier sand and shingle, proceeding, no doubt, from the cliffs of the Spanish coast.* t * Vionnois, Annales des Ponts et Chaussées, 3d series, vol. xvi. 366 THE EARTH, The bars of rivers, which have always been an obstacle and a source of danger, are at the present time mºre troublesome to deep navigation than they have ever before been. It certainly is the case that, thanks to the steam-tugs, vessels with a light draught of water are able to follow the direct channel, and can cross the difficult part in the space of a few min- utes; but, nowadays, commerce is no longer contented to employ the small vessels of former times; it requires ships of heavy burden, carrying large quantities of merchandise, and drawing a considerable depth of water. Many a river-port, once the resort of whole navies, is now aban- doned on account of the bar which cuts it off from the ocean, and is fre- quented only by coasting vessels; commercial vitality has gradually left it. Thus the deepening of their river-mouths is become a most important question in some sea-coast towns. If they could only succeed in doing away with the bar, these towns would increase suddenly in wealth, popu- lation, and importance. If the bank of sand must remain fixed across the outlet of the river, the city is on its way to certain ruin. Every engineer recommends his own special plan as being adapted to avert the danger; each promises that he will correct those river-outlets which Vauban char- acterized as “incorrigible.” But only too frequently, operations are un- dertaken without taking account of the numerous causes which determine the formation and fluctuations of the bar. Amongst all the immense works which have been carried out at the mouths of rivers, many have become useless, or even absolutely injurious to navigation. Millions and millions of money have been thus cast into the ocean and purely wasted. The most simple means, and that, indeed, which is always resorted to in the first place, is dredging ; but this plan is evidently merely provi- sional, and in the present state of science can scarcely be considered as a remedy of a lasting character. Moving an obstacle is not doing away with it; besides, the flotilla of dredgers which can be employed on a bar in removing the alluvium is always insufficient in number. Even if they were constantly at work, there would be little or no result, for the inex- haustible ocean would take up the task of providing the alluvium and raising the bar; the obstacle would be merely shifted in place. Instead of moving the mud, the more simple plan has often been tried of sending it into the current by keeping the water in a constant state of agitation. For a length of time it has been a recognized fact that, after the passage of several ships, there is an increased depth of water on bars composed of mud and fine sand; the particles stirred up by the keels are carried away by the current. This phenomenon may readily be produced by artificial means. More than a century back a French company ap- plied this remedy in the principal channel of the Mississippi, by causing heavy iron harrows to be dragged over the shifting bed of the river. Re- cently, in 1852, the same plan was applied, and the federal government employed on the bar a certain number of steam-boats, which kept the mud on the bottom incessantly in motion by means of drags or harrows, and thus prevented its precipitation. According to a popular tradition, JBA ES OF RIVERS. 367 mentioned by M. Engelhardt, a Turkish pacha formed the same idea as the American engineers. He obliged every vessel which left the Danube to drag astern, while crossing the bar, a harrow attached to a heavy chain. In both cases the agitation of the water seems to have produced a favor- able result. The pacha succeeded in maintaining a channel of about 13 feet deep through the Soulina bar, where formerly it was not above half this depth. By the same plan the American engineers obtained nearly 20 feet of water in the southwest channel. In a similar way, in Order to force the torrents to deepen their beds, the inhabitants of the Piedmontese Alps used to plow up the tracts of pebbles which were brought down by the floods.” Unfortunately, this simple method of improving the condition of the bar produces no lasting result, and the work always has to be begun over again; for the bank forms again whenever the drags allow a moment's res- pite to the sediment held in suspension by the water. Besides, when the water is low in the river, the operations must be suspended, or the sea would drive back all the sediment in an up-stream direction, and thus contribute to the silting up of the river-bed. It must also be remarked that measures of this kind are only practicable in rivers where the bar is composed of small particles, and is not subject to all the fury of the wind and the billows. At the mouth of the Adour, for instance, what immense harrows it would be necessary to use to move the beds of shingle driven up by the storms A system of moles and jetties is, therefore, the plan that has generally been resorted to by engineers in the improvement of the mouths of riv- ers. This plan is somewhat similar to that of the embankments which have been employed, with various degrees of success, on the middle courses of rivers; but the marine dikes have not always produced favor. able results, and a great many experiments which seemed to offer good chances of success have entirely failed. Among the undertakings of this kind which have been the most costly and the most useless, we may men- tion those which have been carried out in the delta of the Rhone. It was hoped that, by confining the mass of water in a narrower channel, and compelling it to run into the sea through a single outlet, a current would be produced which would be strong enough to clear out the passage to a considerable depth, and thus to allow ships of a deep draught of water to enter the river. In 1852, Surell, the engineer, closed up the various grants through which the water of the Rhone found lateral Outlets, and lengthened the two banks of the principal mouth by means of dikes con- Verging one upon another, thus doubling the force of the current. The water of the river did, in fact, accomplish the work of erosion, and cleared out the channel; but fresh alluvium being incessantly brought down by the flow of the Rhone, and thrown up by the waves of the sea, a new bar * Chabrol, Statistique du Département de Montenotte. f From the Latin gradus, a step, passage. In the south of France this name is given to the outlets of rivers, which connect the shore lakes with the sea and the mountain defiles. 368 THE FAIRTH. formed across the mouth outside. Before the operations of banking were begun, the average depth of the channel was 5 feet 10 inches; at the pres- ent time it is the same, after having varied from 13 feet to 64 feet, and 3 feet 8 inches, according to the quantity of water sent down by the current.” s - A similar undertaking, attempted in 1857, in the southwest channel of the Mississippi, had not a more favorable result, a curvilineal jetty 1849 yards in length having been carried away by a tempest. However, the commissioner appointed by the federal government to study the course of action of the delta of the Mississippi recommended the reconstruction of convergent jetties as being a plan which was likely to keep the chan- nel clear. Looking forward to the constant increase of the alluvium of the river in the now contracted channel, they advised, besides, as an indis- pensable matter, that the jetties should be lengthened about 245 yards every year, leaving it open to abandon a channel and choose a fresh one when the dikes of the first outlet should have attained any immoderate length. These operations would be enormous in their character; but if, as was hoped, they would result in maintaining a depth of more than 19 feet in the channel, a tax might be imposed every year on the immense commerce of the Lower Mississippi which would be amply sufficient to de- fray the costs of construction. tº The Adour, which does not carry down to its mouth such large quanti- ties of alluvium as the Rhone and the Mississippi, is one of those few riv- ers where engineers have obtained, at least temporarily, favorable results. I3esides, it must be confessed that the works undertaken for the improve- ment of the bar have lasted for a good many years; for it was in 1694 that Ferry, the engineer, constructed at the southern point a jetty which was to fix and deepen the channel, and since this date there has been no cessation in this interminable labor. The lateral dikes have been carried on to the sea, either in rock-work or by means of piles, and tending in va- rious directions, which were adopted, in despair, after each successive fail- ure. Finally, from 1855 to 1860, the jetties of the two points were slight- ly bent round to the north, and continued, to an equal distance into the sea, to a point 550 yards from the shore. The northern jetty, resting upon a base of rocks hidden under the water, is constructed with openings along all its length, and allows the current to flow between the piles. The southern jetty, which was to prevent the mouth from bending round to the south, is solid for a length of 220 yards, and keeps the bar tending in a direction leading to the coast. Since these operations were finished, the condition of the river-mouth has been subject to much change. In Febru- ary, 1862, when the level of the water was very low, a bank of sand form- ed exactly across the mouth, and compelled the water of the Adour to es: cape laterally through the openings between the dikes. Nevertheless, the general state of the channel exhibits a considerable improvement. The * Minard, Des Embouchures des Rivières Navigables. # IIumphreys and Abbot, Report on the Mississippi River. IBARS OF RIVERS. 369 channel has taken a fixed direction toward the west, and no longer spreads out to the south; the bar has been driven far out to sea, but the average depth of water on it is greater. Before the improvements were begun, at low water it was covered with only 5 feet to 5 feet 10 inches of water; the depth is now as much as 10% feet. This is an immense result, which, according to the calculations of an author who is sufficiently skeptical in matters of this kind,” represents a clear annual gain of forty thousand pounds for the commerce of Bayonne. If, in the future, the bank of shin- gle should attain to the same height as before, it would be necessary to again lengthen the jetties of the Adour for several hundred yards into the gulf, and, by means of the experience already acquired, the engineering operations would again produce a considerable temporary improvement. According to M. Bouquet de la Grye, whose opinion is a very valuable one, it would be a very useful measure if the barriers were curved round in a southwesterly direction, so that the waves from the offing should not beat directly in front of the current and ebbing tide. But the chances in favor of any decisive amelioration of the bar must be much increased in proportion as the jettics are lengthened. When these artificial promon- tories, like headlands, are surrounded by a deep sea, the débris which the currents and waves deposit at their base will be no longer incessantly agi- tated by the breakers, and thus raised into the form of a bar; they will accumulate but slowly, and a long series of years, or even centuries, must elapse ere they could seriously modify the submarine features.f The operations undertaken at Soulina—one of the mouths of the Dan- ube—appear to have met with great success, but through an entirely special cause. Mr. Charles Hartley, the skillful constructor of the Soulina jetties, has taken care to push them out more than a hundred yards into the sea, as far as a point where a current generally passes along the shore tending from north to south. This current catches hold of all the alluvi- um which glides down over the bottom of the bed of the river, and thus hinders the formation of a fresh bar. The average depth of the channel, which was only 9 feet before the commencement of the works, is now not less than 16% feet since the dikes have been constructed. It is cer- tainly a fact that the gradual encroachments of the whole delta of the Danube will have the effect of pushing the current itself farther out to Sea, and Sooner or later a second mound of sand will obstruct the mouth of the Soulina. According to an approximate calculation, based, howev- er, on plenty of hypotheses, the works finished in 1860 will not become completely useless until the year 1916.; There are other mouths of rivers, especially those of the Oder in Prus- sia, and the Meuse in IIolland, which have been permanently improved by engineering operations; we are not, therefore, entirely warranted in * Minard, Des Embouchures des Rivières Navigables. f Mongel-Bey, Percement de l’Isthme de Suez. f Zeitschrift für Allgemeine Erdkunde. § Engelhardt, Etudes sur les Embouchures du Danube. A A 3 7 0 THE EARTH, ** ~ * ~~~~ , , -º-, *r-º----ºr-º- ºr * * . . . . . & Tºº. . . ...~~~...sºs. - - - - * * * * - -- - **- - a • ... --rrºwere:- Kil i} . —e crº-ºs----' º'-- zº +: , , * * * * e ~ - * * -- * - a "w * .*, * * * - tº sº...º.º.º. 2 e- **** ** -L" sº AA- - - - - - * * * * * * * ~- - - :* - , “H” cº-ºrtz. z.-- " -- ~~~…~~~~----- , , -º ń y º ... ... . . . . . . **** * * * * *** *- : ---~ ''' ' -– woºerrºr---º-º: 3: & " ' sº º, ºë',” • * ~~~~~ *-* * *rrit:-3 4. . . . * * a • * * *-* * ". . . . . . . a tº t-sº- we sº- a * ...tº, §º * - * --- * * *** - - -- ~~~~~ - --~~~< * * * * * ~ * * * * * ~ * % ºr." "...º. - * } * * * ~ * * . . . . ; ; , s , , § t *...* \, arº ' ' * ~~ ... º.’ ‘’” - s' -->s-se: - - --> Aºa º Sº ‘..….ſ. . . .” ----------- . • - * - -- ~, * : * ºw w K. . " * -- * * * ~ ********Tº ſº.-- -- ". . . . ..~A. ººr, a . w ... -->~. . . . .” **-*.*.*.*. ...: --- tº:- - ww.t. - . . . " : : - - --> •- * * * *s •r 1 - - , , , , , , , . . . " * -e - . r \f º ~~~~ * y Agº ***.- *w-** * ... •,• * * • * * , • A * * * * sº a * * * * * * * * * * * . . * * * **rº -- ... --~, rr-— - _-ax.-- nº 'vº - . . . . . . . . . . v. ºxº~ “ . . . . . . . . . .” --- * : *-* : * '''' * * , *** * * * - v \ ea • A. . * *.*.*.*.x --~ * & r - - - - - - ***** - - * * * • . --- * * ~ * * * * * ~< * *** * .-- * > ..' * * s - a x * * * * * - * t $. -*. * * * * º -- * * * ~ * * * , , ... -- - ...i ~ *-** ~~~~ * * * * * * *-*. - • & . . . . . A ~ * º ! - - *** * ~ * . . . . . ~ * .* -- ºr------v- w . - . ... zºº. • * * * * * gº--- # , i. • * * * 'º. º -* *...* * * - - - - - , jº ... -- * * * . . . . . . '' " Yºr, ** * * * * * '-º'----- , * * * * * * * *-*. }*N " ' " , is", , ... --- “” <.…ºrº -: * . Nº • Jºe-s, “ , ” ------ *** * * * .. . *A*-r-sa-...":''''. " .*r-º.” , a * * * , - ºr a 3 s , , a * * : - r < 1 A-.' ' ' --- *** t *A *-*...* “t ºv... " * * * ** . . . . . . . * * * * , 3- " * * * * * * * - - * * * - - - * : *% - tºº … , 2-T---. * º es-º- p = ~. * - ~ * * * º e * * * Mr T- t * } & - te , - -- **-º-º:2 . º. º.º.º. * * – g * !". * * * * - - * : * * * *-* - •=< * * ***** * * * * *- t wº .*... . , *-a-ºr-r vºrt " ; , ; 2:..", ºr -, *, *; * ** - r : - , X- ** * - ---- 2- ------>'', 4 Ja- * --~~~~~~. * * * • *4 *** * * * *-*. Fig. 146. Mouths of the Danube. Arms of IXilia and Soulina. repeating the words of Vauban, and characterizing all the bars of naviga- ble rivers as “incorrigible.” The results obtained on the Clyde, in Scot- land, may especially be classed among the most important triumphs of engineering art. The water of that river was once so very shallow that ships of a deep draught of water were compelled to stop 15% miles below Glasgow, and the merchandise had to be reshipped in barges; at the pres: ent time great three-masters easily come up close to the quays. Resides, in a great many cases it might, perhaps, be possible to divert the mouth of a river in places where it was not possible to force a Passage, and thus, by indirect means, to obtain the depth of water necessary for large ships. I3ARS OF RIVE/2.S. 3.71 º * * . - - wº- - - - º:34: --- - - - - -- wº -as-rºº --- - º: w ----- 4 a. * * •r-- - Fºrº ºº: - - -- * * ***** - ** * * * * : *.*. • ºrwº --- 38: “. . ºf º: :-ºr- ** *Xº, § jº - --- S.- ~ W- º:-ºº: - tº ...ºh.Sººº. §º: º º º “Fs—a,” **. Tº-º-º-º-º-º-º-l. -33. rºº? #; º ~ w --> --~~~~} : - * T. - . º,--tº-3-ºxº; •º. 2: -ºſiliº3:::::::::::::::::::: º - * ..., --> .**---- 3 tº . . . . ... ºr - *_ rºl: *... . - . - “wr. "' -- eyew tºf #3 "... *...* -ºš. * Hºº º: - - * - ...--, *-> > * > *- -- - - - •- -- ... --4*****- --~~~, “T- "...º- 3: • ** Jº — v-". , fº. Yo". •. “... .4'-- **** *... • ' --- *ſ, *. ..T. - . : : - - - - • . . ." - * . - **** , - - - - . ****- -- - - * * ... tº: -------ºutº- ** -****!!!… - * -- 4 º' ºr "ºº-J •- * — s \"." "º-Nui. - • * - - ** º * : * • *** **!!º wºrea-- * 4 *** * * * * * * * * . *- : * \ - - --- * - - - f alºv ---ºf-º'-- ** tent, * - • * * * * * * * “..., , , --~~~~9ta-----. ... ... • * * *** X' * * * - - " - - , “ . –º - • “ſºlº - ". ~ſº-º,-r". * -º,- , ºr " -'l'-." ' " .. , “ . . . . . . º. --AM- -- . . ...” *u-šuſu- -vºlii~Tº . . . r * - ** * * * ****, *. - “c---~~~~-º"…” :*- : •-l. -- - - - - - , , , , , , • * t. “”-º'-- - ** -- --~~~~ ...T.” “ - *-*.* -- -- :- in "**"...º. -- a tº ***** -- ~ : ** ...:*** **-- “...--sºlº- -- - - * e- ** * 2'---ºut-rº-º-º-exi". , , º ºr-º- * * * ~ * *** * ~ º * A • * ... - • * ''. - ***** - " ... - . . . . . . ºff. Rig. 147. Jettics of Soulina. A deep canal, protected against alluvium by a system of sluices, would then replace the natural channel. This plan, according to M. Desjardins, is that which was adopted by the ancients in the case of the Tiber and the Western branch of the Nile, which was diverted toward Alexandria. This plan, too, has been proposed by several American engineers for insur- ing to New Orleans a magnificent port worthy of the river which bathes its quays. Moreover, a work of this kind is being carried out at the mouth of the Rhone by the digging out of the canal of St. Louis. This navigable channel is 2% miles long and 66 yards wide, and is intended to connect the river with the Gulf of Fos—so called from a former navigable canal dug out by Marius (fossae mariana). Vessels drawing 24 feet of water will thus be able to ascend as far as the port of Arles, which at the present day has been almost abandoned by commerce, on account of the deficiency of water in the channels of the Rhone. If the excavation of the canal of St. Louis meets with success—which scarcely seems a doubt. ful point—this great undertaking will serve as a model for the subjection of other mouths of rivers, which, up to the present time, have continued rebellious to the operations of engineers. 372 THE EAJRTII. CIIAPTER IV. A LTERATION IN THE POSITION OF WATER - COURSES IN CONSEQUENCE OF TII E IROTATION OF THE ICAIRTII.—MASSIES OF WATER IBROUGIIT DOWN TO TII E SIA I} Y I&IVERS.—GICNEIRAL CONSIDEIRATIONS. TILE sudden changes in river-beds produced by the rupture of their (likes, as well as the movements, and even obliterations of their mouths, constitute, generally speaking, catastrophes of a serious character, and it may readily be conceived that the imagination of man has looked upon these incidents as among the most important facts in the history of rivers. Yet this is not the case. However great may be the influence of these sudden modifications in the action of water-courses, they are but phenom- ena of a secondary class in comparison with those more durable changes which the rotation of the earth brings into the economy of every river and the general physiognomy of its basin. The fact is, that the water of rivers, like that of the ocean and the aërial waves, is subject to the influ- ence of all the great astronomical laws. Tivers, as well as the winds, have a natural tendency to shift their course, so as to effect an arc of rev- olution round the planet. - In fact, the running water which the carth carries round in its diurnal movement is affected differently from the solid bodies which lie upon the ground. While the latter, just as the mere incolualities in the terrestrial surface, describe their daily orbit round the central axis, the fluid parti- cles which glide over the rotundity of the globe traverse in succession various latitudes, and their movement consequently varies. The speed of rotation being completely nullified at the mathematical points which act as poles, and increasing gradually as far as the equatorial regions, where it exceeds 1470 feet a second, every thing movable which tends from one of the poles to the equator must necessarily remain in the rear of the in- creasingly rapid terrestrial movement which carries it round, and must consequently deviate toward the west—that is, to the right hand in the northern hemisphere, and to the left in the southern. In like manner, any movable body which takes its course from the equator to one of the poles exceeds—owing to its acquired speed—the angular movement of the globe, and inevitably deviates to the cast; that is, to the right in the northern hemisphere, and to the left in the southern. These facts have been ren- dered perceptible by the celebrated experiments of M. Foucault on the pendulum of the Pantheon; and they can easily be verified by every one by causing the rotation of two suspended globes, and by allowing some colored liquid to glide over their surfaces.” The trade winds and all at- * A. IIerschel, Intellectual Observer, November, 1865. DIRECTION OF RIVER-COURSE'S. 373 mospheric currents obey this law of deviation, as well as the Gulf Stream and the other flows of the ocean. Even balls rushing from the mouth of a cannon are subject to this law; and sometimes the locomotives on our railroads, when they run off the lines. This law applies equally to all water-courses, and—provided that the configuration of the ground allows it, and that the oscillations of the terrestrial surface do not hinder it—it causes running water to deviate regularly to the right in the northern hemisphere, and to the left in the southern. With regard to those rivers which flow in a line parallel to the equator, there is no force which com- pels them to eat away either one or the other of their banks; but they are retarded in their course if they flow to the east, and are, on the con- trary, accelerated if they run toward the west. This is the law which, for some time past, several geographers have pointed out; which, however, M. de Baer has had the honor of completely bringing to light. The only difficulty is to make a choice among the mu- merous rivers which may be mentioned as examples of water-courses mod- ifying their course in the direction presupposed by this theory. South of the equator there are the affluents of the gigantic Rio de la Plata, which, after having watered on the west the extent of the pampas, are incessantly wearing away their left banks. In the northern hemisphere there is the Euphrates, which endeavors to pour itself bodily into the bed of the IIin- diah, to the right of its own course;” there is also the Ganges, which aban- dons the town of Gour, in the midst of the jungles, and shifts in its delta four or five miles to the west. There is the Indus, wearing away the Stony hills of its western bank, so as to move its delta for more than 600 miles in that direction. There is the Nile, leaving its ancient bed in the Libyan desert, in order to carry its waters by the side of the Arabian chain of mountains. In like manner, in Europe, the Gironde, the Loire, and the Elbe wear away the escarpments of their right bank; and the Vistula deepens its eastern mouth at the expense of that to the loſt. The Rhine, in the plains of Alsace, is gradually increasing its distance from the base of the Vosges, and is approaching the mountains of the Black Forest; and so long as its course was not fixed by the continuous rampart of its embankments, it constantly gained on the territory of Baden, and bent round to the west of the hills, along the foot of which it had previously flowed. A still more remarkable fact is exemplified by the Danube, which passes in succession through a series of dofiles, and always develops its windings toward the right below each gate of rocks through which it has to pass. The river shifts its place under the influence of the move. ment of terrestrial rotation in the same way that a cord fastened at cer. tain points would bend under the influence of a currents Thus, when entering the plains of Hungary, which were once a vast lake, the Danube, * Mittheilungen von Petermann, vol. xi., 1862. f Ferguson, Zeitschrift für Jºrdkunde, April, 1864. f Bourlot, Variations de Latitude et de Climat. § Von Süss, Der Boden der Stadt Wien. 374 THE EARTH, instead or crossing diagonally the level tract bathed by its waters, bends suddenly to the South, and then to the east, so as to take the course of the great central depression round the high ground on its right. In European and Asiatic Russia the normal displacement of rivers affords an especial opportunity for most interesting studies. In these countries, &z & ** &G y S &r ſ', ; ź3 * * *\ Å ºv 62- . * Tig. 148. Middle Course of the Volga. in fact, all those conditions are united which are most favorable to the gradual encroachment of the rivers on their right banks; they have 4 very considerable length of course, and the liquid masses are powerful cnough to readily clear away any obstacles; there are enormous floods which periodically increase the force of erosion in the currents, and the JDIRECTION OF RIVER-COURSJS. 375 cliffs are composed of friable rocks; lastly, the sharp curvature of the globe is the cause of a rapid change in the speed of rotation in the vari- ous latitudes. Two centuries ago, the principal mouth of the Volga flowed directly to the east of Astrakhan; since that time the great current has successively hollowed out for itself fresh beds, tending more and more to the right; and at the present day the branch navigated by vessels turns to the south-southwest. Above the delta the river has every where shifted its bed toward the west, and opposite Tchernoî-Iar, the Achtouba, the former bed of the Volga, now lies 12% miles from the principal current. The twenty-three towns which have been built on the western bank, also called the upper bank on account of its high cliffs, have been almost all demolished in detail, house by house, and street by street, and, being thus undermined on one side, they have been compelled to advance on the other into steppe-land. On the east, the plains once washed by the river are scarcely raised above the average level of the water: during inundations they are converted into perfect seas; therefore the people have not been able to build more than three towns on the eastern bank. One of these towns—Kasan—was once situated at the confluence of the Kasanka and the Volga, but is now two miles from the latter river; it has, so to speak, traveled to the east. In Siberia the water-courses move to the right still more rapidly. The modern towns of Yakutsk, Tobolsk, Semipalatinsk, and Narym have already been partially rebuilt. Along these water- courses, the right bank, which is undermined by the current, is almost in- variably higher than the left bank bordering on the towndras, which once served as the bed of the river. This is a fact of such a general mature that map-designers admit it as an axiom, and never fail to draw the right bank as being the highest and the most escarped. A large number of rapids and cataracts—among others, the magnificent falls of Trolhäta—also afford examples of a continuous displacement pro- duced by the rotation of the globe. Similar phenomena are likewise ob- served in those river-like arms of the sea which are formed by the sea- Water passing through a narrow channel; thus the force of the current is exercised mostly on the right-hand side in, the Straits of Kerteh and - º: ===tºg: S N Fig. 149. Left and Right River-banks. the Bosphorus, and the greatest amount of erosion takes place on this side. The law is of general effect, and applies to all the rivers which flow on the surface of the earth. The great rushes of water in former geolog- ical periods have likewise in their flow worn away the ground on the 376 - THE EARTH, right-hand side. In the north of the Pyrenees, the gaves, which radiate so remarkably round the plateaux of Lourdes and Lannemezan, all flow through valleys of erosion, commanded on the east by high cliffs worn away at their base, and on the west by long slopes of easy access, on which the débris are deposited.* ...Nºw 2. Jºãº º ºr - stºº, J - .. • G. pº ºv : & S. is '• *.ſº *- &: §§§ rve. & W *** 3. Sºlº Fig. 150. Radiation of the “Gaves,” North Pyrenees. Among the important rivers which, in consequence of local circum- stances, seem to contradict this law of the displacement of running water, we may mention the Mississippi and the Rhone. Instead of gaining on its right bank, and eroding the base of the heights which rise on the west, the great American river impinges in fifteen places against the cliffs of the eastern plateau, and, throughout the whole of its course, constantly tends toward the left. As soon as it enters the marshy plain of its delta at a point below Baton Rouge, it flows almost in a straight line toward the Southeast, to form the remarkable peninsula of mud through which it falls into the sea. It must be remarked that the direction taken by the water of the current of the Mississippi is exactly the same as that of all the rivers which run into the Gulf of Mexico—the Rio Grande and its af. fluents, the Rio Pecos, the Nucces, the Colorado of Texas, the Brazos, the - * Leymerie. DIRECTION OF RIVER-COURSE'S. 377 Trinity, the Neches: these rivers, which uniformly tend toward the south- east, are parallel to the ridges of the Rocky Mountains. If it is a fact, as many geologists seem to have established, that the western chains Of North America are undergoing a movement of upheaval, while the Caro- linas, Georgia, and other neighboring regions are gradually subsiding, it might very well be the case that the lower course of the Mississippi and all the Texan rivers tends to the east, in consequence of the slow move- ments of elevation and depression to which the North American continent is subjected.* - With regard to the Rhone, the mouth of which likewise flows in a south- east direction, instead of tending to the right, as it once did, and follow- ing the vast bed now adopted by the smaller Rhone, it is possible that its course may have been modified during historic periods by the impetuosity of the Mistral. However strange an assertion of this kind may appear at first sight, it perhaps merits the attention of geographers. In fact, it seems a matter beyond all doubt that, in consequence of the gradual cut- ting down of the woods of the Cevennes and the central plateau of France, the Mistral has continued to increase in violence since the ages of the Ro- man occupation. If this be so, this turbulent wind must necessarily impel the waters of the Rhone toward the left bank in the direction they are taking at the present day. The aërial current beating down from the Cevennes on the marshes of the Camargue must necessarily have pressed upon the current of the river, and marked out for it the line which it had to follow in hollowing out for itself a fresh bed. Every thing in nature takes its share in effecting modifications; every feature in the planet owes its form to the breath of the winds, the currents of the waters, and the movements of the soil, quite as much as to the motion of the globe in space. Tivers, taken as a whole, being merely the arterial system of continents, renewing the liquid mass of the seas, whence the waters return again to the interior of the land in the form of clouds and rain, it is important to know, at least approximately, the quantity of river-water which is flowing on the surface of the globe. For many years back, various hypotheses have been regarded on this point; but any very precise data are still wanting, and nothing but observations taken for a series of years will render it possible to arrive at any accurate knowledge of this hydrologic- al fact, so important in the economy of the globe. Buffon supposed that the mass of water emptied out by the whole of the rivers running into the sea would represent, in 812 years, a quantity of water equal to that of the ocean; but the data on which he based his supposition are not of sufficient authority to render it of much use to discuss his opinion at the present day. Among the most important calculations which have been recently made, taking as their starting-point the quantity of rain falling annually on the earth, we must mention that of Metcalfe. He estimates the total mass of water brought down by the rivers at 176,000,000,000 of cubic yards of water every day. Keith Johnston considers that the daily average dis. * Wide the chapter on “Upheavals and Depressions.” 378 - THE EARTH, charge of the rivers of the earth is 229,000,000,000 of cubic more than 2,620,000 cubic yards a second. This estimate is certainly much too high, for, by adopting another meth- od, more in conformity to the rules of direct observation, and consequently more scientific—that is, by adding up the masses of water rolled down by the rivers which have been already gauged in various parts of the world by engineers and geographers—we find that the total discharge of a col- lection of river-basins comprehending an area of 4,246,000 square miles does not exceed a little more than 72,000 cubic yards a second. Now these basins, which are those of the principal rivers of Western Europe, including the Danube,” as well as those of the Nile, the Chat-el-Arab, the Ganges, the Hoangho, the Mississippi, and the Atrato, form a tenth part yards, Of § # Co. . \ & rif I \ . *H #| \ # 3 # . # , , ; ; ă \# 3 g # 3 # 3 # #| \; ; ; ; ; ; ă ă ă ă ă : ; ; ; ; ; # 3 i ; ; : ... à 3 & É • . . . is . . . º ; : : : Fig. 151. Diagram showing the Comparative Discharge of Rivers, in Cubic Yards. of the terrestrial surface, the waters of which flow down to the ocean. If, therefore, the proportion of water which runs from the surface of the ground into the Sea were every where the same, the liquid mass of fresh water combining with the salt waves would not be more than 850,000 cubic yards a second. We must, however, take into account the enor- mous quantity of water discharged by certain rivers in the tropical zone, and especially the Amazon, the delivery of which is probably 100,000 to 130,000 cubic yards. If, therefore, we add a third to the total river-dis- charge obtained by the previous calculations, we shall have for the whole mass a maximum of over 1,100,000 cubic yards a second. This is a quanti- ty which represents an average fall of about 11 inches of rain over the en- tire surface of each basin, an average much larger than that of most of the rivers which have been studied up to the present time. If we admit that the average depth of the seas is 5400 yards, the quantity of water which flows down the surface rivers of the Continent would not equal that which fills up the abysses of the ocean until after a lapse of fifty millions of years. This is evidently nothing but a provisional calculation, which will be gradually rectified as the facts relative to the hydrology of the globe be- * The discharge attributed to the Danube is probably too great; according to M. Hartley, the real discharge is only 11,123 cubic yards a Second. t • f At the defile of Obydos, the section of water which flows every second to the sea is, aº- cording to Spix and Martius, 23,113 cubic yards at low-water time; in floods, says Avé-Lal- lemant, it is 310,476 yards at the same spot. &EDIMENT OF RIVERS. - 379 come better known. When the mean discharge of all visible water- courses is accurately gauged, when the force of subterranean streams has been disclosed by the investigations of meteorologists as to the fall and evaporation of rain, then it will be more easy to calculate, within a few millions, the total mass of liquid which is annually poured into the sea by the rivers of the continents. No doubt, within a period not very distant, the measures which have been adopted with so much precision as regards the Mississippi, the Po, the Rhone, and the Nile, will be applied with equal care to the other river-mouths. The investigations which have been simultaneously made as to the pro- portion of sediment which exists in suspension in rivers will enable us also to resolve the often-discussed question as to the actual importance of the alluvium of rivers. Without mentioning here the streams which are lit- erally liquid mud, or sometimes even avalanches of mud, there are some rivers, like the Missouri, the waters of which are so charged with sediment that the drift-wood, being completely penetrated with muddy particles, is ultimately entirely submerged, and covers the bottom of the river.” There are, on the contrary, other rivers, such as the St. Lawrence, which send down to the ocean water which is generally pure and transparent. Dur- ing floods the Durance holds in suspension as much as 21 thousandths of mud;f the Garonne sometimes contains 10 thousandths; the Rhine 6 thousandths only. § It will be readily understood that the quantity of alluvium held in suspension must Iaecessarily vary in different rivers, ac- cording to the more or less compact nature of the soils through which they * pass; thus observations made on any particular water-course have noth- ing more than a local value. The estimations made by various geogra- phers as to the average quantity of alluvium contained in running water differ prodigiously one from another. In the last century, Eustache Man- fredi, who, taking account of the enormous deposits produced by the Po, exaggerated the work of this kind accomplished by other rivers, and esti- mated the average proportion of muddy matter at r}+ of the liquid mass of rivers. But in this estimate he doubtless included the sand and mud which are impelled by the current along the bottom of the bed, the bulk of which is probably twice as large as that of the floating matter. Hart- soeker, in his Traité de Physique, admitted that the proportion of alluvi- um was rºw; while another author of the same epoch, the writer of the Jęecherches Philosophiques sur les Américains, was led by his observations and calculations to fix the amounts of débris existing in the water of riv- ers at arºsa." The differences between the various estimates are naturally quite as great when an endeavor is made to reckon approximately the time that it * Continental Monthly, June, 1864. f Payen. The average for the whole of the year is not more than one thousandth. f Baumgarten. § Payen. | This question is treated on in detail in Von Hoff's work, Veránderungen der Erdobeftāche, WOl. 1, 380 THE EARTH, would take for the alluvium emptied out at the mouths of rivers to raise the level of the ocean to a given point. Manfredi supposes that the de- tritus carried down to the sea would be sufficient to raise its bed a yard in 3300 years. Tyler thinks himself warranted, by his calculations as to the alluvium of the Mississippi, in asserting that the deposits of rivers would elevate the level of the ocean only two inches in 10,000 years, or about a yard in 180,000 years. These are estimates of a very different character; but when one reflects on the greatness of the sea, and on the lit- tleness of rivers compared with the immense reservoir, even the last-named estimate seems too high. If we admit that the average proportion of the earthy matter carried down into the sea is about stºrm of the entire liquid mass of rivers, and if we adopt, as the total discharge of running water, the approximate quantity to which the critical examination of the known facts of fluviatile hydrography has led us, we shall find that the mass of allu- vium deposited every second at the mouths of rivers would be equivalent in bulk to 436 cubic yards, or every year a body of matter equal to 4000 Square miles in area, and a yard thick. This, however, would be an al- most infinitesimal quantity in comparison with the enormous abysses of the Ocean. ; - Yet the earth belongs to all time, and during the course of ages any geological work must ultimately be accomplished. These rivers, almost imperceptible, so to speak, in comparison with the ocean, are gradually eating away mountains and plateaux, and filling up the abysses of the sea with their accumulated débris. These deposits have the effect of raising the average level of the waters of the ocean, and of causing them to cover low shores. There is, therefore, a double cause operating in the modifica- tion of the relief and outline of continental masses. If the only force in action on the surface of the globe was that of running waters, the elevated parts of the earth would be constantly becoming lower, the sea would in- cessantly encroach on the coasts, and, sooner or later, the planet would become an immense globe, covered with a thin sheet of water. Owing, however, to the geological movements of the earth's strata, a transforma- tion of this kind is not to be dreaded ; but still, from the action of the was ter of rivers, continents and seas are undergoing changes of the very high- est geographical importance. The Baltic Sea has already become some- thing between an inland sea and a chain of fresh-water lakes. The liquid mass poured into it by rivers continues always the same, while the area and depth of its basin are constantly diminishing. In the long course of ages, its water will ultimately become perfectly fresh, and the straits of the Sound will be only the European St. Lawrence. Some day, Bory de Saint Vincent tells us, the Mediterranean itself will become nothing more than a chain of lakes, and then a gigantic river. The Sea of Azofis already being gradually converted into a stream, as its shores are getting nearer and nearer together, while its bed remains per- ceptibly the same.* The tracts of water which extend from the mouth * Zeitschrift für Erdkunde, May, 1862. VALUE OF RIVERS. 381 of the Don to the Straits of the Dardanelles might be compared to the Lakes Superior, Huron, and Michigan; the isles of the Archipelago will some day overlook a labyrinth of lagoons similar to those which border the Baltic Sea; the Gulf of Venice will be only an elongation of the val- ley of the Po; and the two great basins of the Mediterranean, separated by the Siculo-African bar, will become two lakes of increasingly contract- ed dimensions, the waters of which will feed the greatest river in the world. Then the Dnieper, the Danube, and the Po will be but mere trib- utaries. Perhaps even the Nile, which is now of no great size at its mouth, may lose all its water by means of evaporation before it reaches the Med- iterranean Sea, and will become nothing but a water-course of an entirely continental character, such as the Chary, the Houach, and the Jordan. Certainly it would be difficult to exaggerate the importance of the part played by rivers in the history both of the earth and mankind. They dis- tribute uniformly the snow and rain which fall at the various points of their basins, and fertilize the whole territories by their innumerable rami- fications. They powder up the rocks of the mountains, and spread the matter which results in fertile alluvium over the plains, forming also new tracts of land at their mouths. They equalize climates. Rivers coming from the south warm with their vapor northern districts, while rivers flowing in a contrary direction moderate the heat in more southern lati- tudes. Added to this, water-courses, those powerful workers, do not limit themselves to carrying down water, alluvium, and climate; they also roll down in their flow the history and life of nations. The course of the riv- er’s current is the path down which descended the canoe of the savage warrior, and is now the highway for the fleets of commerce bearing peace and comfort. Steam has converted rivers into roads, which can be trav- ersed both in a downward and upward direction, and a floating popula- tion is constantly pervading their surface. Far from forming a barrier to nations, rivers are the means of mobilizing them : they are continents set in motion. Aided by rivers, the mountaineers of the Alps and Pyrenees make their way to the Atlantic and the Mediterranean, while the inhab- itants of the sea-coast ascend to the elevated districts in the interior of the continent. In the present, day water-courses no longer assume, in the history of civ- ilization, the high importance they once possessed, for now they are not the only ways of communication between nations. No river can now be all that the Nile was to the Egyptians, at once their father and their god, the cause from which sprung both a race of husbandmen and also the harvests which they gathered on the river-mud, warmed by the rays of the sun. Another Ganges, with its sacred waves, will never again flow over the surface of the earth, for man is no longer the slave of nature. He can now develop artificial roads, which are shorter and more speedy than the roads formed by nature; and this second, and even more vital nature, which he has created by the labor of his own hands, supersedes his adoration of that first nature which he has succeeded in regulating. 382 - THE EARTH, Nevertheless, rivers will be more important as servants than they have ever been as gods. They bear upon their waters ships, and the products with which they are freighted, and serve as arteries to vast organisms of mountains, valleys, and plains, which are sprinkled over with thousands of towns and millions of inhabitants. They vivify the earth by their mo- tion, carve it out afresh by their erosions, and add to it by their ever-in- creasing deltas. Some day, when the hand of man will be enabled to guide rivers and to trace out for them their beds, he will employ these potent workmen to carve out a nature in harmony with his own will; wa- ter-courses will wear away the hills, fill up lakes, and throw out promon- tories into the sea in obedience to his orders: their eternal and mighty vitality will become the complement of ours. 3 8 3 FORMATION OF LAKES. CHAPTER LVI. LAKES. — FORMATION OF LAKES. — THEIR INCREASE AND DIMINUTION. T. THEIR FORM AND THEIR DEPTH.—LAKES LYING IN SUCCESSIVE GRADA." TIONS OF ELEVATION. CoLLECTIONs of water—ponds, pools, lakes, or inland seas—are formed in every depression of the ground which receives a larger quantity of liq- uid, either from rivers or directly from the clouds, than it can get rid of through its affluents, or transfer to the atmosphere in the form of Vapor. Hence arises that infinite variety of lacustrine sheets of water which gives so much grace or grandeur to landscapes, and exercises such a considera- ble influence on the action of rivers, on climates, on the productions of the soil, and consequently on the development of mankind. The liquid mass contained in any basin on the surface of the earth does not increase to an indefinite extent, even when considerable quantities of water are constantly being poured into it by its tributaries. Either the basin completely fills up, and the overflow is emptied out through the low- est depression in its rim, or the lacustrine sheet, gradually enlarging in area, ultimately presents a surface sufficiently extensive for evaporation to establish an equipoise to the supply of water. : Perfect equality between the mass of water received and that which es- capes does not, however, exist in any lake, and, consequently, the level never ceases to fluctuate; sometimes it rises and sometimes it sinks, accord- ing to the various seasons and years. After heavy falls of rain, or at the time of the melting of the Snow, some pools are changed into perfect lakes, in the same way as, during long periods of drought, some lacustrine basins entirely dry up. The great phenomena of the vitality of the globe—such as the upheavals and sinkings of the ground, the growth of mountain-ridg- es, the encroachments or retirement of the shores of continents, the alter- nations of the winds and rains, land-slips, and the rupture of natural dikes —all have the effect of either giving rise to and increasing, or of doing away with or diminishing, the masses of water which are collected in the interior of continents. Like every thing else which exists on the surface of the globe, lakes have their periods of increase and decrease, and even within the limited period during which man has begun to record the an- mals of his planet numbers of fresh lakes have made their appearance, while many others have entirely dried up, or have considerably dimin- ished in extent. In mountainous regions it is a well-known fact that the fall of rocks and the advance of glaciers have often caused the formation of considerable lakes. In like manner, some of the large lakes of the Landes have appear- 384 TIII, EARTII. cd since the Middle Ages, owing to the cutting down of the trees upon the dunes, and the shifting of the latter toward the cast.” On the other hand, instances of lakes which have disappeared owing to natural causes, with- out being subjected to any human labor in the process of their exhaustion, are likewise very numerous. Thus the plain of Oisans, in the Alps of Dauphiny, having been sudden- ly closed up in 1181 by a downfall of rocks which came from the sides of the Voudène, the waters of the Romanche, the Olle, and the Vénéon accu- mulated above the obstacle, and spread out into a lake of 64 miles in length. Villages, vast plains, and whole forests were swallowed up under a liquid sheet of an average depth of 33 feet, and the local employment gradually became that of fishing. The lake existed for thirty-eight years, and then the barrier of débris suddenly yielded under the pressure of the water, and the body of liquid rushed like a deluge over Grenoble, and all the towns and plains on the banks of the Isère. At the commencement of the fourteenth century, the former lake, which had received the name of the Lake of St. Laurent, was completely dried up. The formation of lakes of this kind above some dam of rubbish, and their disappearance when these dams are broken down, may, however, be con- sidered as accidental phenomena, and not dependent directly upon climate. In this latter respect, the changes in level which are exhibited by some great lacustral sheets, such as the lakes of Titicaca and Van, are much more remarkable facts. Travelers assert that the area of the immense Bolivian lake has always been diminishing since the commencement of the historical period. Its water once bathed the walls of Tia-Huanacu, one of the principal cities of the Incas; but this locality is now situated 12% miles from the lake, and more than 130 fect above the level of its water. This would be a remarkable proof of the increase of dryness on the high pla- teaux of Bolivia. On the other hand, the height of the Lake of Van con- tinues to increase—a fact which is confirmed by travelers every year. The inhabitants on its shores are frequently obliged to turn the Sea-shore roads farther inland; ancient villages have been swallowed up, and in some spots the ruins buried by the water are still visible. Finally, the town of Erdjisch, which was once separated from the lake by a great plain, is nowadays invaded by the water, and the city of Van itself, which was once far from the shore, is now quite close to it. A legend, which ex- plains in its own way the constant swelling of the water, relates that some capricious nomads, having obstructed an outflow of the lake, afterward made useless efforts to re-establish the former outlet; but, since this date, the irritated lake has never left off covering a fresh extent of plain every year.] As a simple process of reasoning must point out, lakes are most numer- ous and most extensive in those countries where rain falls in considerable quantities, and the surface of which, although but slightly undulated, is * Wide the chapter on “Dunes.” + Pentland; Bollaert, Antiquilies. f Oſto Blau, Millheilungen von Petermann, vol. vii., 1863. FORMATION OF LAKES. 385 nevertheless formed of compact rocks which do not allow the water to flow away into the depths below, and retain it as if in natural basins. Of this kind are the regions of North America, in which lies the fresh-water Med- iterranean crossed by the St. Lawrence, the Winnipeg, Winnipegoos, Bear and Slave Lakes, and several other sheets of water of less extent. In these districts there is certainly less rain than in the tropical zone, and even than in most of the countries of the temperate zone; for the depth of rain and snow water does not attain to more than three feet in a year. But the granitic soil retains in the shallower depressions the moisture which falls from the atmosphere; evaporation does not take place actively, and the slopes toward the different seas are not sufficiently inclined for the numer- ous rivers to be able to pour down to the ocean all the surplus Waters. The island of Newfoundland is also in great part granitie, and is like- wise covered by lakes maintained by the constant humidity which pre- vails in those parts of the sea. In like manner, in Europe, the eastern Val- leys of the Scandinavian mountains and the plains of Sweden exhibit a perfect labyrinth of lakes, some of which are very small, while others stretch away and are lost on the distant horizon, save where they are dot- ted over with archipelagoes, rocks, and islets, like the Lake of Mälar, which º Of F IW L A.Y D º © SR # § tº #~~~. gº: Fig. 152. Lakes of Finland. contains no less than 1260 islands. On the other side of the Gulf of Both- nia, the granite plains of Finland are sprinkled still thicker with lakes than IB B $ 386 TEIF EARTEI. those of Scandinavia itself, so that the whole country may be considered as an immense sheet of water intersected by innumerable isthmuses cross- ing one another in every direction. Labyrinths of lakes of an altogether similar character are also found in countrics where the soil, although not rocky, lies on a clayey or ochreous subsoil, which is entirely impervious to water. Thus there used to exist in the French landes a great number of pools which the bed of allos re- tained on the surface;" these are at the present time mostly dried up. In the same way Sologne, Drenne, and some other solitudes in central France were dotted over with shallow pieces of water. La Dombes, a plateau of 36 -a- S"/ §§ g- & ºil, J W s %iº &. º *=es* * *W". * : s” ºa º 'º), \! i. Å. # §§ § .9°NS NA OUI *Nº ºxº AA º * % i % s & § G © (f * \ - º2.4&. | & %"S" º'e iſ...}, \º º **, - º < \! f $ } 0 z .2: - Nº S$ w W º * is t gº Q ºil; ^% ëº, - a PS lºſſ." "Mºšº jº) ºft # * 'lºº & "...? & ºa-ºt sy.º. Ży j.--"º 1. Nº º tºº º wº §§§"% ſ/sý $9 º ŞūM % } •Nº. 9& W PQ ". 49 - # É # = ºf "º sº 'º •ºn Sºs & ºp *33& |º. 7 ºs” ſº a jº.º. Sºº (; ºš & Wºn', º, .º.º. º. É º sº º 6 º' as N* % % |\º § cºs W s ÉN. • ?: %) 3.36 ° W. tº f(N \\ {}. º % § 9 @ 9 º º $ >. &\"." ºf $ "sº jºb ºf ºoº. § ...nº.ºOº. f ...º.º.º. ºf ºoº; W gº : 6 ** a S” º, . : §º yº, § NM % So sº %.sº Ş. *f; 5 * %. 69.2 º' 50- 9 º' s & Wº, Qº t § º 7/*2 Ö &S Q- © º # ". Wi. §3. ce.8°sº . º ** Y # 'Z' Sº o 6.6 Sºś &e º; ºº is , ; ;Sº ºl.", a.º. Tº º §º & &? & *º A---> $ Q A. gº?014,22' cº \, ºne º #59 \ º tº, Q.g. Jºš .. 9, Vy. º º”: ©** : & ** () Á # \ § 4.º | % * % 5 º attr© º s 69 s : § ! .** N ſº | § f t ºr. §§ . * SYN - * * - §§ſº ºff sº sº." Žº º s § N £: º º w º • ? §\% § \ -- & . | SES Avº • § hº : % . # º º łº §º & | s: Z ! * º sº * ...ºf º ^ºa” ſº § “... "I ºž º t )|) §§: §: §§ f** ‘.…W. º º §. $ºne º º º & % º f 7 º § * ºgºsº ſº"; Nº|| t * , º § - % 㺠¥º º § º: §y” iºnºv § AW/ as: y w & % % sº f §º. - nº "...W)/\ §§§ {: S㺠ź. §§§37* \t sºe sº ſº gº %.) / §lſh, Will sº §. $º º, éſ NW wº," i. W - 2 |N 2% ~ W w º É A * - &ºff'....”- sº sº lºº % ºſſº sº. º # º- \ | º§ Illinº 3 j, ". haë § Núžº."; N IIIM i–tº–4–4–3 §§§j}\º Fig. 153. The Dombes. - about 300 feet in height, which extends to the northeast of Lyons, botWoon the IRhone, the Saone, the Weyle, and the Ain, is also covered with a mul- titude of pools, occupying altogether an area of more than 47,000 acres. It is a fact that in this part of France man has unfortunately lent his aid * Wide above, p. 83. DIMENSIONS OF LAKES. . 387 to the work of nature. Most of the pools of the Dombes are of artificial origin, and their being laid dry would cost even less than their construg- tion. They serve as fish-ponds for the wretched inhabitants of the neigh- boring villages, and then, being emptied and cultivated for cereals, they are again filled up and stocked with fish. The form of a lake always bears some relation to the general relief of the ground in the depression of which its water is contained; its outline and the profile of its bed harmonize perfectly with the continental archi. tecture. The water of alluvial, oozy soil is spread out in vast marshes, in which it is difficult to point out the precise spot where the dry ground ends and the water begins. The liquid sheets of low plains, deserts, and level plateaux present generally more sharply-defined outlines; but their depth is but slight in comparison to their extent, and the least fluctuation in level considerably modifies the line of their banks. The lakes of more undulating regions are in general tolerably deep in proportion to their ex- tent, and present bays and promontories of a more varied and picturesque 165b. 132 o *T6 1247%. 1230 º sº tir ºr: & #. sº #. ess: Iseo § & % E. & gº . 5. # # * * * , E% ŻE %=% %H% (r. --Ta N 30 E 3- E% %=% 213. Gar EZ. E% E %5 غccasiº * %H% %F E% %E4% %%:#ff rest Lowd of the Sea %= ## ## à. *#3 O F *}=% * #=# E% Øe=% E #Eff %=% #% 2So Fett, Eğ ºf .º à ſ §=% *E* slé ãº. 060, %=% #E ** #4 #Eğ Q Ot #Eff 㺠-99 Eá # 1320 # º 1513% 1650 ###, . #. tº 986 ‘. %tà g . - * (sº % Lz316 & Fig. 154. Altitudes and Depths of Lakes in Italy and Savoy. character than the sheets of water in the plains. But the place where lakes exhibit all their beauty is round the bases of lofty mountains. There torrents run down into them, falling over in rapids and cascades; green glens slope down to their very margin; the spurs of the mountain plunge straight down into their waters, and the shores between the headlands are traced out in gracefully-curved bays. Py the harmony and variety of lines presented by their outline, these lakes seem almost a necessary feature of the landscape, and their horizontal surface, by the contrast which it affords, gives a more noble appearance to the surrounding moun- tains. Lakes, like seas, are in general all the deeper as the cliffs which over- hang them are the more steeply escarped; indeed the cavities which are ‘ulamA-oquoo op unmy on tº ‘uo's 10:11007/2S ‘losoCI sp.tvijo.1 Sv topio uſuntoo u uſ poinqū’īsſp out Hoxſuſ oil ºutſ, luffs 18.III qu 5uppituiol proAt on oſqissoduſ sſ ºf ‘sdiv ou'l Jo duur U qu juſoutſi:) '0.101.jju IN ox{u"I '09L ‘jſſ ‘t’.In ſº on III donu A Jo lootis It!dſo -upid oun “longtſono N Jo ox!t!"I ou" Jo put ‘stl|V out uſ suſst:q Itaúsuouſ ot." III; Jo sodoop ou', ‘ololáju IV oxiuſ I Jo uoissolidop ouſ, Jo ouſſºno It:n101; ou" odou xotium; on A.lussooou si q; ‘Soxſul outdIV oil) Jo odults oil, Jo poultoſ og Autu topſ it:0ſo tº quun dopio III Ulptoid ou" (ITIA (IOSI.It dutoo III pio)-poll) -uniſt populošāuxo uooq Sull Indopoun sould osolſ, Jo iſoto uſ 'soul ºut." -Ioduſ "soul out Jo outos uſ opuu (tooq JoA you o Auu Suoſitºlodo 5uipumos ontº.Inoot: “uouſ ogluoros Kuliuſ os Ko populs put: po) ISIA ‘SSOIOU1.10Aou ‘oil; UoTIA ‘80ſ V of uſ io) : on UA optiuſ Xolddu ut: Åluo Aſoluunllojun ‘ioAo -Aoû ‘o Aull Sonu!d osotſ] uſ polodop Sºluso.1 ou.J., 'uos ouſ, Jo [o Aoi otſ) (ITIA uosſaudutoo III SqLV Italytto() ou'l Jo Hoxt:I Iudiouſld ou" Jo Sopn]]][u o AI]oods -0.1 ou'l Quoso.idol soluld boxouttu oA) ou I, ºu dop uſ 100) 896 L SI iſ quil) ‘S’llossu olussut's St. ‘on.In oq 11 J1 ‘Zuoſi. I Jo Tuul solutilod sº toºl:A-tos ouſ) Jo IOMOI ou AOIoq poq u Suu (IoIIIA oxſul Kluo ouſ ‘SolIV ouſ, Jo opis loulo où" to ‘oſt|A : Indop uſ 100) 03W put ‘SIg ‘s 18 I ‘GWIZ AIoAIloodso.1 od III's pInow oosſ put: “upitº) ‘oluo() ‘oloſºju INJo Soxuſ I out uſ loſt;A olinJo SoSSAql, où" ‘uos ou') Jo IoAOI ou" on UAop ºno SdRW ou" Jo Kpoq olou A oil, osod -dus pluoo ow. JI 'uos ou" Jo IoMoI ou Aoſoq Itſ pubosop on 15nouo (loop III's Qud ‘doop os jou out oosſ put up.Itº) Jo Sox|UT ou.J., usud Shi Jo nud N cººd "sowo oil itſ doop 100 1861 SI outoo ox!t"I ot) : Indop uſ nooſ oosa utºp Sºol on slºoſºtºpy out oAoqu looſ ago sº Hou A Jo IoMoI on ‘olor:#5up ourſ 'Sodols "sodoons (Ioun quosoid opps spun uo Tom A ‘sdiv ou" Jo ost:q IIIo "Iºnos out it pumoſ out sox{tº osotinjo sodoop oun “soul oudly onjo osotin tº sooutºsuſ toūno ou pit. Aloj 5uſiq on ‘snuſ, sossutu powwouldn oun Jo "TºoHoº, on Suosuoup IIoun uſ puodso.Itoo on uloos Iowa, oùn Aq du poſtg II/37 VI ſ/III, S89 LA K E GARDA PL. XVIII. º/MMW, º | W º º º º º º CAST to Lº Drawn by A Vuillemm after Schºla Enº º E ºn?" by Erhard ºlº ºr BROTHERS, Nºw York f.A.R.ES OF THE ALPS AND JURA. 389 the great groups of mountains. Thus the Maritime Alps, those of Viso, Provence, and Dauphiny, and also the Mont-Blanc group, have but a very small number of lakes, and even these better deserve the name of ponds. On the east of Switzerland the various ranges of the Alps, which extend as far as Turkey, are likewise almost devoid of lakes, except in Southern Bavaria and the districts of Salzburg, where several masses of water fill up some narrow valleys which open nearly uniformly from south to north between parallel chains of mountains. The noble lakes which form the Fig. 157. Lake of Neuchâtel. glory of the Alps are all situated round the central group (of which the Saint Gothard occupies the middle), and in the valleys and plains which, under various names, form the western limit of the parallel ridges of the Jura. These lakes, which evidently owe their origin to the star-like form of the chains which radiate round the Saint Gothard, and to the intersection of the Alpine system by that of the Jura, have in general elongated ba- sins, tending either from southwest to northwest, or, perpendicularly to this direction, from southeast to northwest. The waters of the valleys of the Jura—for instance, the Lakes of Joux and Saint Point—lie in the for- mer direction, likewise the great bodies of water situated at the base of the limestone mountains—the Lakes of Neuchâtel, Bienne, and Morat. The Alpine lakes of Brienz, Sarnen, and those of Engadine also lie in this di- rection; and even the lakes on the Italian side, Maggiore and Garde, are nearly parallel to the lacustral basins and mountainous ridges of the Jura. On the other hand, the great Alpine lakes of Constance, Zurich, Sempach, Zug, and Thun all stretch in a contrary direction to those above named. With regard to the two magnificent inland seas of Switzerland, the lakes of Geneva and Lucerne, they owe their admirable shape to a combination of the two types. The Leman is a lake of the Jura in its lower part, and an Alpine lake in its upper part; toward the middle the two sheets meet and cross one another. In the Lake of Lucerne the two basins cross one another at right angles, and thus give to the whole body of water the shape of a cross. It must likewise be remarked that the largest lakes are found on the courses of the most plentiful rivers, which goes to prove that the same ge- ological laws have presided in the formation of the valleys and in hollow- ing out the lacustral basins. The Lake of Constance, the largest of all, receives the Rhine, the largest river in Switzerland. The Leman is cross- ed by the Rhone; the Aar flows into the two lakes of Brienz and Thun; the Reuss enters the Lake of Lucerne, the Linth that of Zurich. An ar- rangement of this kind can hardly be fortuitous, but must depend on the general structure of the great groups of the Alps. 390 THE EARTH, In those mountains which possess an architecture of almost perfect reg- ularity, as, for instance, those of the Jura, it is easy to classify the various lakes according to the form of the depression which is filled by their wa- ters. Thus the lacustral sheets which spread out in a valley between two |Parallel ridges of mountains generally exhibit outlines which are Scarcely at all broken and disposed in a regular oval; the slopes of the bed are gently inclined toward the central part, the average depth of which is not, however, very great. Here and there, and especially at the two ends, the banks are marshy, and it is difficult to determine the exact Spot at which the firm ground begins. Among these valley lakes we may mention those of Joux, Saint Point, and Bourget. * % Fig. 158. Valley. Fig. 159. Cluse. Fig. 160. Combe. In a similar way, the combes and cluses which serve as reservoirs to the lakes confer on the water which they contain special characteristics very different from those of the lacustrine basins in valleys. Thus the lakes in cluses, lying crosswise to a chain of limestone mountains, are generally narrow, and the escarpments of the high cliffs which command them de- scend to a great depth below the surface of the water. With regard to the lakes in combes, the amphitheatre-like reservoirs which contain them give to the surroundings of each basin a magnificent aspect of grandeur and majesty. The water in them is deeper than that of the valley lakes, but not so deep as that of the lakes in cluses ; and it is just in the lower portion of the lacustrine cavity that the section of water presents the greatest thickness. It is, however, but seldom that—in the Swiss Alps and other moun- tainous countries with a deeply indented vertical outline—we do not find lakes which present characteristics of all the different types. In some parts of their basins they are lakes of the valley, and in others they are lakes like those contained in cluses or combes. For this reason, what a di- versity of appearance they present in their shores, what picturesque beau- ty in the windings of their bays and the succession of their headlands ! Between mountain ridges which are not arranged in long parallel lines like those of the Jura, valley lakes are not mere oval sheets of water; they extend in long windings like the Lakes Maggiore, Como, and Lugano; or in those valleys in which basins and contractions alternate in succession, the lakes spread out and become narrow alternately. Numerous instances of this may be seen in the Scandinavian mountains. In a general Way, however, these lakes are cut up into several pieces of water lying in gra- dation, one above the other, as if on enormous steps, and are connected by A'ORMS OF DAYES. & 391 narrow defiles, down which the water of a torrent pours in cascades. These lakes, lying on graduated levels, are found in the high valleys of almost every mountainous country. In Switzerland, the three lakes of sºsºsº. SSSSSSSºßSNūgūſīyſ/2/22:3# §§§ >:3:Sc §§§ §§§ }º Sº §§§ Nº. ######$ºj º 3%;= § : 3 º º - Rººſ º º à % gº º ºs--- 3% 5% % º *3 §§ % ſº §::=; $ º N §§ tº $ ºš §§§º: º § % *...*& tº S. º Q §º sº º X; %; - ſº sº ºr - - %:--> šNº. w º 2. % %gºš º - fº % £º º º : #2.É%. §§ º º - w ſº ſº tº: & Exºs §§ §§ º - Sº 㺠º: : w % ſº §§ ºfºº º ſº §* Nº. |\}{N º §4% 3 3. * §§ º \º º: º iº à §% º - Sºś 2: # ºà §º % §§ ſº º % º ſº * N # § [. | º & /º/? Wºš § Żºłż/ſº ###$g: *}[º §§ % %)/º º: ğlºlºss ſº | ºſſº's S. #. 23% - º Š &º > §§ N/ 3Ryº # ; j}\ É%N % $º r º % º/22.3% ºf 2:Hº: % ºSW % º: & 㺠&Z2; º: º % ØØ2: Ä% ÉÉÉ; § º … º º š% ſº - º: - ºº: ºº & § º Sº !% żºłºś. sº w sº § º º ſº % % §§ § sº º º - w - º º § § s § ſ ſº º g º º º * * *º ºğ ſº | º º º % º º: % § \ :-º ºšš - § É º § ºf;2) ºf: § § # §§ }º:33; §§§ Fº gº § §§§ W º .*s º \;\º ºś §§§ º SN § §§ § §§ § º § #º § d § % º § 㺠ºś iº §§§ºś ºš. ~~~~ Nº. º º ºriºſ ºiſº º, # $º 'º § tº & tº: § \º & Sº § Kºº. º’ vº tº 3 ſº º º- § § sº Y. N. |ſº * * ----- Sºº Wºº } ſº ś § ź. º º: < - Nººses ~ tºº 3. Kºš }))))/2}}\\ § | / &lºſſ §§ Šºš ſº Z %:#; $º º %2% §§ §º t ; º º º ſ º 2. º % º º sº § yº ºš ºr Yº: §§ §; º º *Sº £2:Sº -ss Sºº 2:=$º: §§ º - §º *—Sº \ \ º f jº • , \ =S S Žºs & sº º sº $ º *SNN. ) t §3%; º º º; \\ 'Sº 3’. sº- J §§§§ “NS$ 3 SS º: º §º Nº. § 2. 2. Mº-º-> § āş §§ §§ §: Nº § <<=~. S # % §§ %; §§ §§§º) ºfts & Hºt § ſ ºaºğ º -. w º ~, ~~~~ * * §º/, 2 § §§) Bºž ~ jº % § %| M § *U. 㺠§§27;N § º §% - - - * : g º ºffiliºğ §§ §§§2tº SSSº A zºº & iſº § § % ºś § §%zº - l * § º §§§ §§§ Nº (t §: º YººHºº §§§º jº - jº * Sº, sº | ſ ** §§3% %. % | §§§º 3% & g Fig. 161. Stages of Lakes in the Valley of Oo. Tungern, Sarnen, and Alpnach, which are traversed by the River Aar, may be mentioned; in the Pyrenees, the mountain lakes of Oo and La Têt, 392 - THE EARTH, t * and the lakes of the valleys of Couplan, Aygues-Cluses, and Estom Sou- biran, belong to the same class of lacustrine basins. In the Carpathians they form those charming little pools of water to which the name of 310 I -5 **** º . 7 N. º ºlllll: º SLo l'ig. 102. Iakos of Norh Elſ. f e ‘mcørtºffen” (eyes of the sea) has been given; lastly, in Scandinavia, lakes situated on graduated levels may be reckoned by hundreds. FORMATION OF LA/OES. t 393 Lacs d'Estom Soubiran | Fig. 163. Lake-stages of Estom Soubiran and Estom. ſ º There, all the rivers, almost without exception, are, from their source to their mouth, nothing but chains of lakes connected with one another by rapids and cascades. They are, in fact, water-courses in process of formation, which have not as yet hollowed out for themselves regular beds, but flow in all the natural depressions of the soil through narrow channels which have been opened since the ground itself has risen above the level of the sea. The land of Scandinavia having risen only at a re- cent epoch by a gradual movement of emergence, which at the present time is still continuing, the rivers have not yet had time either to fill up with débris the lakes that they meet with in their course, or to pierce wide valleys through the rocks.” * Wide the chapter on “Upheavals and Depressions.” 394 - THE EARTH, CHAPTER LVII. VARIOUS PHENOMENA IN LAKES.—COLOR OF THEIR WATERS.—SEICHES.— CURRENTS AND TIDIES.–FORMATION OF ICE IN LAKES. LAKES are not only distinguished from each other by their shape and the depth of their basin, they also vary in the appearance of their water, and even in this respect the diversity of the matters held in suspension or solution in the liquid mass is not always sufficient to explain the remark- able contrast presented by adjacent sheets of water. The color and trans- parency of the liquid differ astonishingly in most mountain lakes. Some are of an emerald green, others of a sapphire blue, a few even have a milky shade. There are some, indeed, the water of which is transparent, that have a brown or yellowish color. In every case, whatever may be the natural hue of each of these lakes, they incessantly vary on account of the reflection of the rays of the sun, the clouds, or the color of the sky and the refraction of the light. One lake, the water of which, not far from the bank, is of a yellowish-green, owing to the rocky bottom just visible below the undulations of the surface, is of a deep blue above the invisible abysses of its central portion. Another lake presents a well-defined if ference of color between the tranquil water of its basin and that which is brought in by the rapid current of the river which crosses it. In other places, again, the eddies light up the surface with reflections of a bronzed or greenish hue; even the particles of sand or ooze, as well as the chem- ical substances dissolved in the water, must necessarily, however infinites- imal their tenuity may be, tinge the liquid sheet with various shades. Vegetable mould gives to lakes a color more or less shaded with red or brown; clay gives them a yellowish tinge. As to the débris of rocks and pebbles, these, according to Tyndall, are the agents which confer on the fake of Geneva and other mountain lakes their lovely azure color. The most wonderfully transparent water, which, too, is the most devoid of all impurity, is in general a sea-green hue. It is said that objects are some- times visible in it at a depth of 80 and even 100 feet. - All long and narrow lakes, over which atmospheric variations often take effect in a sudden and violent manner, frequently exhibit abrupt oscilla- tions of level, which can only be explained by a difference in the pressure of the air. Such are the seiches of the Lake of Geneva and the Rºssé" of the Lake of Constance, which are noticed sometimes at one point, someº times at another. In these purely local swellings of the water, the latter may rise all at once some inches or even a yard above the level of the sur- rounding surface. The outbreak of subterranean tributaries can not be taken as an explanation of the cause of this sudden rise, for it takes place ASEICHES AND LAITES. - 395 at the foot of mountains of a compact formation, which certainly do not conceal any considerable streams in the depths of their rocks. Added to this, on the surface of many lakes and inland seas the phenomena of Sečc/es have been observed around islets and mere rocks. Schulten has proved that the Seiches of the Baltic, which are in every respect similar to those of the Lake of Geneva, are in direct connection with the height of the barometrical column. When the pressure of the air diminishes the water begins to swell, and when the barometer again rises up the surface of the sea sinks, only the movements of the water are always a few minutes earlier than those of the instrument, on account of the greater mobility of the aqueous particles. Now, as the total varia- tion between the different heights of the barometrical column at the level of the Sea corresponds to a variation of about a yard in a column of water, it follows that the most considerable seiches can not exceed this height. This has, in fact, been verified by observations in the Baltic as well as in the Lake of Geneva, and in the great lakes of North America. In the midst of the open sea seiches would likewise be produced, especially during hurricanes; but the liquid mass being at full liberty, and able to spread out freely all round the rising of the wave, the phenomena is there more difficult to notice than in narrower lakes.” It is probable that the phe- momenon known by the Sicilians by the name of marubia (from mare ebº- aco, “drunken sea”) is also a swelling of the water accompanied by the barometrical depression. It is observed on all the coasts of Sicily, but especially off Mazzara, at the precise spot where the Mediterranean, con- tracting into the form of a strait, is severed into two basins by a subma- rine ledge which approaches the surface. Daubeny considers that these movements of water are a sign of some volcanic vibration of the soil; yet the description which he himself gives of the movements seems to indi- cate that they are Seiches similar to those in the Lake of Geneva and the Baltic. When the marubia occurs the air is calm and the horizon misty; suddenly the water, stirred up in short waves, raises its lovel about 23 inches, and then, after an interval of from half an hour to two hours, the south wind begins to blow, and a heavy storm rises. Lakes, moreover, which are, indeed, inland seas of fresh or salt Water, must exhibit phenomena similar to those of the ocean. Lacustrine shoots of Water have also their tempests, their swells, their breakers, and their bores; and certain bays of Lakes Superior, Ladoga, and Baikal are not less dangerous than the Black Sea and the Bay of Biscay. The waves raised by the wind in the more confined areas of lakes are neither so high nor so rapid as those of the sea, because they have not so vast a field on which they can spread out, and because they do not move over a suffi- ciently great depth of water. They are short, compact, and “ chopping,” and from this very fact they are more formidable to any ship against which they incessantly dash. Added to this, the water of most lakes being fresh, and in consequence lighter than that of the ocean, it is also more * Anton von Etzel, Die Ostsee. 396 THE FAIRTH. readily stirred up, and the wind has scarcely commenced to blow before the surface of the lake is roughened with foaming billows. With regard to the currents, it is evident that in lakes they can not be developed with the same regularity as in great seas which lie open and exposed from the poles to the equator; but currents are nevertheless pro- duced in every spot where any perceptible difference in temperature exists between two adjacent regions on the surface of the sea. There is, of ne- cessity, a flow of cold water toward the sides of the lake whenever the superficial liquid layers, heated by one cause or another, are comparatively lighter, and suffer a greater loss from evaporation. Besides these lateral currents, which are sometimes difficult to be certain about, there are also, in lakes as in the sea, interchanging currents flowing between the upper sheet of water and the masses underneath. Moreover, all the rivers which cross an open lake or fall into a closed-up lake, like the Rhone, the Rhine, the Reuss, and the Jordan, determine the formation of local currents, from each side of which the water of the basin flows back in a contrary direc- tion. Lastly, lacustrine basins also have their tides, although these phe- nomena are generally nearly imperceptible, and are only discovered by a long and attentive series of observations of the oscillations of the level. In Lake Michigan the height of the tide reaches to about 3 inches. One of the most curious phenomena in the lakes of the northern tem- perate and polar zones is that of the formation of ice. In winter, when the sheet of water is perfectly still, needles of ice, radiating one from the other at angles of from 60 to 120 degrees, appear on the surface; then, joining their net-work together, they soon form a level sheet of ice. On the contrary, when the water is violently agitated by a storm, the first needles of ice, being incessantly bruised and rubbed against each other, agglomerate in disks rounded by the friction, and the whole of the con- gealed mass ultimately presents an uneven surface like that of rivers with a rapid and violent current. The ice of lakes is generally much more reg- ular and transparent than that of water-courses, in which the process of crystallization is nearly always being disturbed. When a prism of this pure ice is exposed to the influence of a ray of the sun concentrated upon it by a lens, a multitude of little corollas, with six sepals arranged round a glittering point, suddenly appear in the thickness of the prism. This is one of the most charming sights which the beauties of nature can present to the eyes of an observer.” - - When the whole extent of the covering of ice is solidified over the water, it does not remain immovable until the thaw ; on the contrary, it is constantly agitated by various movements, according to the state of the atmosphere and the phenomena which are going on in the liquid mass be. neath. If the temperature diminish, the lower side of the frozen crust is immediately increased by a fresh layer of ice more expanded than the water; the sheet must therefore necessarily rise and form a somewhat curved surface. If the cold become less intense, the solid mass conse: * Tyndall, Glaciers of the Alps. THE ICE OF LAKES, - 397 quently grows thinner, and forms hollows in some places. "When the level of the lake rises, owing to any larger quantity of water being poured into it by its affluents, the arch of ice is upheaved unequally by the liquid sheets which flow beneath it. If the supply of water diminish, and the level of the lake consequently sinks, the solid cover simultaneously gives way, owing to its own weight, and splits up so as to follow the downward movement of the water. Lastly, the long undulations which are produced in the liquid mass by shocks received on the surface, the large quantity of air which makes its way under the sheet of ice either in considerable bodies or isolated bubbles, even the gas incessantly being evolved by the respiration of the fish, all combine in producing the same result—that is, the upheaval of the ice. The comparatively thin crust which separates the hidden water from the great atmospheric ocean is constantly being drawn sometimes in one direction, sometimes in another. Enormous crew- ices, generally tending in the direction of the greatest length of the lake, open suddenly with a terrible crash; the roaring of the air which penetrates under the icy layer, or which escapes from it, is mingled with the crack- ling of the breaking crystals; we have simultaneously noises like the roll- ing of thunder and the rattling of musketry. On that part of the Lake of Constance which is called the Untersee, M. Deiche has noticed cracks in the ice which were six miles long and 13 to 16 feet wide. In the great lakes of North America, and also in those of Siberia, espe- cially in Lake Baikal, the phenomenon of the formation of ice takes place in the most magnificent way. During three months of winter, the mighty Baikal, the inland sea in which seals live and coral-stems grow as in the ocean, is covered by a field of ice, presenting in some places a thickness of 6 to 9 feet. The vast sheet of water, extending over an area of more than 1400 square miles, and surrounded by mountains as high as the Alps, and glittering with glaciers, is nothing but a solid mass, on which caravans of travelers venture without fear. Sometimes, when the ice begins to form, a sudden tempest reduces it to fragments, which, under the pressure of fresh pieces of ice, brought by the waves and currents, are piled up one on the other, intermingling in a kind of chaos which calls to mind the séracs of the Alpine glaciers. Subsequently, when the water is entirely covered with its heavy shell, the latter is occasionally rent asunder, and , shrill whistlings, dull cracking noises, prolonged thunder-like rumblings, mingled with innumerable partial crepitations, are heard while the ice is bending and breaking. The water springs out from the fissure in vertical sheets, and, falling down again on the surface, forms risings on each side of the crack which is sometimes more than a yard wide. Sometimes a fragment of the broken layer of ice sinks below the general level; anoth- er piece, being pressed on in every direction by the frozen masses, curves perceptibly in the middle. All these movements of the solid crust pro- duce long undulations in the water beneath. Travelers, borne along rap- idly in their sledges over the ice of the lake, feel distinctly the shock of the waves breaking against the lower side of the trembling floor beneath 398 THE EARTH, them. On the sides of the cliffs which border on the lake may be noticed heaps of solidified flakes, sometimes resembling a cascade; this is the foam which is jetted out at the time of the violent rupture of the ice, and has hardened upon the rocks before it had time to fall.” In a general way, Lake Baikal freezes so rapidly that, according to the statement of the na- tives, the ice begins by adhering to the bottom of the lake, from which it afterward becomes detached with a terrible noise, and rises to the surface.f But this fact, which could not take place unless the temperature of the deep water was much lower than that of the surface which is traversed by freezing winds, has not yet been scientifically verified. It is, on the con- trary, very probable that the water on the bottom remains constantly liq- uid. At the temperature of 39°Fahr. the aqueous particles acquire their greatest density, and consequently their heaviest specific gravity. In obe- dience to the law of gravity, the layers which are at 39°Fahr. of temper- ature are those which must lie upon the bottom of the lake, and therefore ice can only be formed on the surface. The direct observations which have been made as to the temperature of the Swiss lakes confirm this the- ory. In the Lake of Geneva, the effects of meteorological variations are not felt below a depth of 236 feet, and deeper still the constant temper- ature is 42° Fahr. In the Lake of Constance the temperature is lower; there it is only 39°Fahr., and in the Lake of Lausanne 39°12' Fahr. ; this comparatively slight excess of heat is probably owing to the natural warmth of the ground. Added to this, in the environs of Boston, where all the small lakes are regularly worked during winter, and furnish for the demands of commerce more than 200,000 tons of ice a year, the solid layer of ice has never been noticed to form in the first place at the bottom of the basin. * Russell-Killough, Seize Mille Lieues. f Carl Ritter, Erdkunde. f Buff, Physik der Erde. - REGULATING ACTION OF LAKES. 399 CHAPTER LVIII. LAIKES ACTING AS REGULATOR'S OF THE RIVERS WHICHI IPASS THIROUGH THEM.—FRIESEI-WATER AND SALT-WATER LAIKES.—THE CASPIAN SEA. THOSE lakes which receive a superabundant quantity of water—and these constitute the most numerous class—give rise to a river which car- ries off the surplus of the liquid mass poured into the basin by the upper affluents. These lacustrine reservoirs may then be considered as expan- sions, to some extent, of the fluviatile valley; in this point of view, the Lake of Geneva would be the Rhone, and become a hundred times wider and deeper. The Lake of Constance would be an immense hollow of the Rhine, containing in its reservoir nearly a hundred times as much water as all the rest of the river. In like manner, the great inland lakes of North America—Superior, Michigan, Huron, Erie, and Ontario—form the first part of the course of the St. Lawrence, a river of such slight importance in comparison to the vast basins which feed it. The large basins in which the water of a river is spread out before it again takes its course down to the ocean, regulate the discharge of their out-flows all the more efficiently the more extensive the area over which they extend. Very considerable inundations in a stream produce com- paratively but a slight rise in the level of a lake, because the water has to be diffused over the whole surface of the basin, and loses in depth all that it gains in breadth. During the season when the ice is melting—that is, in spring and summer—the Lake of Geneva rises on the average six feet above the low-water of winter, and consequently contains a surplus mass of 1,572,000,000 cubic yards of water. The gauges used at Geneva estab- lish the fact that the discharge of the Rhone at its issue from the lake is at its maximum 753 cubic yards; now, as the various affluents of the lake supply more than 1400 cubic yards during their highest floods, it is evi- dent that the Lake of Geneva acts as a complete regulator. It keeps back at least one half of the inundation-water, which it subsequently emp- ties down gradually when its tributaries have retired to their usual level. It is certain that, owing to the regulating action exercised over the dis- charge of the river, the plains on the banks of the middle course of the Rhone, from Geneva to Lyons, are comparatively protected against floods. The equilibrium in the action of the river would be still more complete if a dam were constructed at Geneva, with flood-gates to regulate at will the discharge of the water.” Lakes which are crossed by rivers must be, almost without exception, fresh-water basins, as the Saline particles which are carried into the basin * L. L. and E. Vallée, Du Barrage de Genève. 400 THE EAZRTH, by one or more affluents are conveyed out of it with the surplus water. Still, lakes of no great area, which are mostly fed by salt springs, discharge brackish water through their out-flows. As regards lakes without any outlet, it is evident that the saline particles brought into them by tribu- taries can not make their escape, and must consequently be deposited on the edges, or must more and more saturate the liquid mass. Except they are fed by affluents entirely devoid of saline matter, lakes which are with- out any communication with the sea must therefore more or less resem- ble the ocean in the composition of their waters. Almost all the lakes without outlet are filled with water more or less saline. It must, how- ever, be understood that the proportion of salt varies in all inland basins, and the transition is most gradual between the condition of water called fresh, and that of brackish or salt water. The largest inland sea devoid of any outlet—the Caspian—is the re- mains of that great central Sea which once extended from the Euxine to the Frozen Ocean. It is probable that the slow upheaval of Siberia and Tartary has gradually separated the Caspian from the Gulf of Obi and the Sea of Aral, and that subsequently the rupture of the Bosphorus, by low- cring the level of the water of the Black Sea, has laid dry the Ponto-Cas- pian isthmus, which is now traversed by the waters of the Manytch. Be that as it may, it is certain that by remaining isolated in the middle of the land, the Caspian has lost by evaporation a larger quantity of water than is supplied to it by its tributary rivers; for it has gradually dimin- ished in extent, and its level has sunk more than 80 feet below that of the Black Sea. If the Caspian was again to fill up the whole concavity of its basin to a height corresponding to that of the adjacent open seas, it womld inundate the whole plain of the Volga below Saratov, and would cover the surface of the steppes for an area of several hundred thousand square miles. The Caspian Sea is divided into three distinct parts. The northern por- tion—the bottom of which continues the almost imperceptible slope of the steppe—is a vast marsh, which is nowhere more than 48 to 50 feet deep, which, too, several rivers are constantly engaged in filling up with their alluvium. In the southern part of this sea of steppes lies the central ba- sin of the Caspian, which is bounded on the south by the promontory of Apcheron, a prolongation of the Caucasus. The southern basin, mostly surrounded by high mountains, the escarpments of which extend beneath the water, is also the deepest. In some spots soundings have been made of 1772 and 2953 fect. The saltness of the water is very unequal in different parts of the Cas- pian. On the north, the Terek, the Oural, and especially the Volga, bring down to the sea an enormous liquid mass, so much so that the total salt- ness is only from 15 to 16 ten thousandths, and at many of the post sta- tions, where there is a deficiency of springs, they drink the Sea-Water with- out either dislike or danger. The central and southern basins, on the COn- trary, contain water which is completely salt. It is proved by the exper- iments of M. de Baer that the average saltness is about nine thousandths: CASPIAN SEA. * 401 this is a degree of saltness about one third of that of the waters of the At- lantic Ocean. - % Tº -º- —%– , ſºo m f —w- -z - s § - £ ..º. 2.-- § * Q2 - F & º * . . - f • - - - ST%2A - - = . £8. + - == . } - - == - *3 - tº --- * * #### Žs tº º *s- - # --- - *A - #º. * - 22 ºr - cº e ~$2,. - * 44 isº, -y", —ll l Eºs 2 - 2. É **. © Tº Pri -E s - Ro - *3 62 - Berben sº wº - £2 - § | t ES |S Bakoya º º gºš 3% it㺠4. *. : =º. 1–- -- —º Fº ºr= >= { > - É == - =AGT Reshdº - É ##### o *=== #~\ * Astrabad ti- £6 —#— w & - 62 Fig. 164. Caspian Sea. Is the saturation of the Caspian diminishing during the course of ages, or is it, on the contrary, in process of increase? At first sight one is C C 402 - THE EARTEI. tempted to admit the fact of the increase of the saltness as an evident matter, since the soil of the surrounding steppes is gradually yielding up to the sea the salt which it contains. The rain and snow Water, when penetrating through the surface layer of sand, carry with them the saline particles, and concentrate them in the clayey subsoil. In every place Where the ground is hollowed out by the ravines, so numerous on the steppes, the Saline clay is washed away by the water, and carries the mat- ter with which it is charged into the Caspian Sea, either directly or through the bed of a river. It appears, then, that the waters of the Caspian ought to present an increasingly large proportion of salt. Yet M. de Baer, who has devoted more study to this inland sea than any other Savant, does not believe in any increase in the degree of Saltness in the Waters of the Caspian; and, in his idea, if the proportion of salt be un- dergoing any change at all, it is diminution. In fact, in the plains aban- doned by the sea, banks of shells are here and there to be met with which are identically similar to those of the shell-fish which now inhabit the Cas- pian. . The dimensions of these shells, being always proportional to the quantity of Salt contained in the water, ought to indicate the degree of Saltness of the former sea, and thus give a point of comparison. Now the shells which are picked up in the vicinity of the Lake of Elton, more than 200 miles from the present sea-shore, are as large as those of the molluscs which now inhabit the open Caspian at a point 60 miles from the mouth of the Volga. Near Astrakhan, where the sea-water, being mingled with that of the river, must be comparatively fresh, the shells left by the retire- ment of the Sea indicate a degree of Saltness equivalent to that of the wa- ter in the central basin. Moreover, in the environs of Baku, on the sides of the hills which overlook the water, amid the rocks, shells of molluscs are found which are much larger than those of the same species now swim- ming in the sea some yards lower down. This fact alone is sufficient to afford considerable probability to M. de Baer's hypothesis as to the de- crease of Saltness in the waters of the Caspian. The Black Sea, however, with which the great inland sea of Russia formerly communicated, con- tains proportionately twice the amount of salt. How can this decrease be possible 2 How is it that the salt brought down by the rivers and rivulets is able to escape from the vast basin which has received it, and to separate itself from the sea-water with which it is mingled? Nothing can be more simple; by the regular movements of its waves, the Caspian—the same as all other seas—throws up banks of sand in front of the shallow bays of its shores, and thus converts gulfs and creeks into lagoons, into which the sea-water runs only through a narrow channel. Evaporation, which is very active in these regions bordering on the burning desert, is constantly tending to sink the level of these basins, while the sea-water, charged with salt, flows in without intermission to maintain the equilibrium; in this way are formed perfect magazines of salt, which are incessantly being increased. When, after heavy storms or a long continuation of dry weather, the channel which communicates be: CASPIAN SEA. 403 tween the sea and the lagoon ultimately becomes dried up, the sheet of water, now completely isolated, diminishes rapidly in area, or is even com. pletely absorbed by the atmosphere, nothing being left of it but a layer of salt of variable thickness, which is formed at the expense of the sea. Thus it is that the lagoons recover from the Caspian the salt which the rivers of the steppes carry down to it. The only question is to know if equality exists between the incomings and the outgoings, or if, in conformity to M. de Baer's theory, the loss of salt is more considerable than the gain. A long series of accurate observations could alone solve this problem. The formation of these saline reservoirs may be studied all round the circumference of the Caspian Sea. A former bay, situated not far from Novo-Petrosk, on the eastern coast, is nowadays divided into a large num- ber of basins, which present overy degree of saline concentration. One basin still occasionally receives water from the sea, and has deposited on its banks only a very thin layer of salt. A second, likewise full of water, has its bottom hidden by a thick crust of rose-colored crystals like a pave- ment of marble. A third exhibits a compact mass of salt, in which glitter here and there pools of water, situated more than a yard below the level of the sea. Lastly, another has lost by means of evaporation all the water which once filled it, and the strata of salt which carpet its bed are partly covered by sand. The same facts are found existing farther to the south, in the environs of the Bay of Alexander, and also quite at the extremity of the northern basin, at the point where the arm of the sea lies, which is known under the name of Karasu (black water). The Saltness of the Ka- rasu exceeds that of the Gulf of Suez, the saltest of all the seas which com- municate with the ocean; in this part of the Caspian the proportion of marine salt rises to nearly 4 hundredths, and all the salts combined form 57 thousandths of the water; animal life, therefore, must there be almost, if not entirely suppressed. Among the thousands of bays and lagoons in which the 'salts of the Caspian are stored up, none is more remarkable than the ICaraboghaz, a kind of inland sea which probably connected the Hyrcanian Sea with the Lake of Aral, and into which perhaps the Oxus emptied itself when this river was still a tributary of the Caspian. This vast gulf communicates with the sea by a narrow mouth, which, in its most contracted part, is from 150 to 160 yards wide; the bar will not allow vessels to enter which draw more than 5 feet of water. A current coming from the open sea is always running through the strait with a speed of three knots an hour. The west winds accelerate it, and the winds which blow in an opposite direction re- tard it, but it never flows with less rapidity than a knot and a half. All the navigators of the Caspian, and all the Turkoman nomads who wander on its shores, have been struck with the unswerving, inexorable advance of this river of salt water, rolling over the shoals toward a gulf which even recently none had ever ventured to navigate. In the view of the natives this inland sea could be nothing but an abyss, a “black gulf,” as is express. ed by the name Karaboghaz, into which the waters of the Caspian dive 404 * THE EARTH, down in order to flow through subterranean channels into the Persian Gulf or the Black Sea. It is, perhaps, to some vague rumors as to the ex- istence of the Karaboghaz that we must attribute the statements of Aris- totle about the strange gulfs in the Euxine, in which the waters of the Hyrcanian Sea bubble up after having flowed hundreds of miles through the realms of Pluto. - - The existence of this current, which conveys the salt waves of the Cas- pian into the vast Gulf of Karaboghaz, is nowadays most satisfactorily explained. In this basin, exposed as it is to every wind and the most in- tense summer heat, the evaporation is considerable; the water is there- fore constantly diminishing, and the deficit can only be supplied by a continual fresh flow. Investigations, which can readily be made in the narrow and shallow channel of the Karaboghaz, have failed to ascertain the existence of a submarine counter-current conveying back to the Cas- pian the salter water of the gulf. It is therefore very probable that it is the atmosphere only which absorbs the water brought by the Caspian current; but, though deprived of its water by evaporation, the immense marsh retains the salt; the saline matter is more concentrated in it, and the water is more and more saturated with it every day. Already, it is said, no animal can live in it; seals which used to frequent it are no longer found there, and even its banks are devoid of all agitation. Tayers of salt begin to be deposited on the mud at the bottom, and the sounding- line, when scarcely out of the water, is covered with saline crystals. M. de Baer has made the attempt to calculate approximately the quantity of salt of which the Caspian is every day deprived for the benefit of the “black gulf.” Taking only the lowest estimates of the degree of Saltness of the Caspian water, the width and depth of the channel, and the speed of the current, he has proved that the Karaboghaz receives daily 350,000 tons of salt—that is, as much as is consumed in the whole Russian empire during a period of six months. If, in consequence of violent storms, or the slow action of the sea, the bar should close up between the Caspian and the Karaboghaz, the latter would quickly diminish in extent; its banks would be converted into immense fields of salt, and the sheet of water which might remain in the centre of the basin would become only a marsh. Perhaps, indeed, it would disappear altogether, like that sea which used to lie between Lake Elton and the River Oural, the former existence of which is made known only by a depression in the ground of about 79 feet below the level of the Caspian, and 151 feet below that of the Black Sea. Like a tree letting fall its fruit upon the ground, the Rus- sian Mediterranean detaches from its bosom the bays and gulfs on its coasts, and scatters them over the steppe in the form of lakes and pools. The comparative observations which have been made as to the average lovel of the Caspian Sea are not yet numerous enough to warrant us in admitting, with certain geographers, as a proved fact, that there is a con- stant diminution of the water in this inland sea. We are likewise ignorant what foundation there may be for the opinion of some of the inhabitants THE BUGORS OF THE CASPIAN SEA lºf," …,ast of Parna I 45%– k- º - * * A % . * | *5° l *Go HARPER & BROTHERS, NEW YORK, after Bergsträsser. CASPIAN SEA. 405 of the coasts, mentioned by Humboldt in his Asie Centrale, according to which the Caspian Sea experiences a succession of rises and falls every twenty-five to forty-five years. It seems, however, probable that the oscillations in its level are of no great importance, and that the quantity of water removed by evaporation is on the average exactly replaced by the liquid mass accruing from rivers and rain. An equilibrium is nearly established between the supply and the loss. There is one point which is certain, that at the epoch when the Caspian Sea was separated from the Euxine, its level sank in a comparatively rapid way on account of the excess of the evaporation. A proof of this fact may be seen on the sides of the rocks which were once washed by the waves of the Caspian. At the height of 65 to 80 feet above the present level of the water, these former shoal-rocks have been furrowed out into tooth-shaped points and needles; lower down, on the contrary, the rocks bear no trace of the erosive action of the water, evidently because the level of the sea sank too rapidly to allow the waves sufficient time to at- tack successfully the cliff walls. The innumerable indentations which cut into the shore between the mouths of the Kouma and those of the Oural, and principally south of the Volga, constitute another striking instance of the rapidity with which the level of the Caspian must have sunk after the sill of the Isthmus of Manytch emerged from the water. For a space of more than 248 miles the shore is gashed with very long and narrow channels, twelve, twenty, and even thirty miles in length, and throws out into the sea a multitude of peninsulas, which are prolonged for a great distance into the water by isles likewise disposed in parallel ranges and separated by long channels. These tongues of land form a kind of chain, which is interrupted here and there by the sea-water, and sink by successive falls from isle to islet, and from islet to marsh. The thousands of channels which separate these narrow embankments of land are an immense labyrinth, unexplored even by fishermen; it requires a map of the most detailed character to give any idea of this strange swarm of isles, islets, channels, and bays. The bugors, or chains of hillocks which run between the parallel bays, and farther inland, are connected with the level ground of the steppes, are in general very narrow, their length varying from a hundred yards to three or even four miles. They usually rise to the unpretending eleva- tion of 26 to 30 feet; but some attain double this height. Seen from a balloon, the ensemble of the bugors would resemble a tract of marshy land turned up by a gigantic plowshare. Immediately to the west of the Volga, the limans, or furrows which separate the bugors, are always changed into rivers. During the inundation of the river, the current pours into these channels the overflow of its waters charged with mud; then, after the flood is over, the sea again penetrates them, and there is thus produced in these channels a constant backward and forward motion between the sea and the Volga. Farther to the south, the narrow valleys of the limans, not being so often filled up by the flood-waters, do not, in 406 THE EARTH, general, present a continuous sheet of water, but only a chain of lakes, separated from each other by sandy isthmuses. w If we compare the whole of these ranges of hillocks to a border of fringe attached to the continent, we shall observe that these fringes spread out somewhat like a fan, on one side toward the north, on the other toward the south. They are like the extremities of radii diverging from a com- mon centre which would lie in the depression of Manytch, on the ledge which separates the slopes of the two seas. How can this arrangement be explained except by the fact of the rapid sinking of the level of the Caspian waters hollowing out in the soft soil the narrow furrows which so astonish us? Thus, on the muddy banks of a reservoir when the sluice- gate is opened, small limans are formed, separated by bugors in miniature. A very remarkable fact, which again tends to confirm the result of M. de Baer's investigations, is that all the bugors of the Caspian shore are strati- fied, and the superimposed beds assume the form of concentric arches. The strata of the strongest clay are, as it were, the nuclei round which are deposited the earth that is more mingled with sand. This distribu- tion of the strata is owing to the action of the currents of water which gave to the bugors their present appearance. It may, in fact, be readily understood that the strata of clay and sand, being undermined laterally by the water running down the channels, bent over on both sides toward the currents which washed their bases; hence arise these stratifications in the form of an arch. DEAD SAEA. 407 CHAPTER LIX. THE DEAD SEA.—TIIE SALT LAKES OF ASIA MINOR AND THE RUSSIAN STEPPEs.—TIKE GREAT SALT LAKE-THE MELR'IR. ALTHOUGH the Caspian is the largest of all the inland seas, the Asphal- titº Lake is in some respects the most curious on account of its position in a deep fissure of the earth, many hundreds of feet below the level of the Mediterranean. Since Schubert discovered, at the beginning of the cen- tury, this single instance of a similar depression, it has been ascertained by exact measurements that, over an area of nearly 186 miles, the whole val- ley ascending toward the base of Lebanon and lying parallel to the sea- shore of Palestine is lower than the ocean. Below the small Lake of Houleh, the River Jordan, which traverses the valley, flows into a cavity which deepens by quickly recurring steps below the ideal sea-line. The level of Lake Asphaltites, in which the waters of the river are lost, is 1286 feet lower than that of the sea. The greatest depth reached by the sounding-line exceeds 984 feet, and is, therefore, 2270 feet below the level of the Mediterranean. Thus the depression into which the Jordan falls is deeper than the whole extent of the Adriatic and several other marine basins in communication with the ocean. Lake Asphaltites, however, does not merit the name of sea from its depth and its intense Saltness only; it also possesses its principal current, flowing from north to south, and continuing the course of the Jordan, and its counter-currents flowing on both sides parallel to the shore.* The surface of the Dead Sea exceeds 460 square miles; but, as is proved by the horizontal layers of gypseous marl and the beds of salt deposited in stages on the slopes of the sur- rounding mountains, the level of the lake was formerly much higher than it is at present;f and probably the water filled all the elongated space comprehended between the foot of Lebanon and the entrance to Arabah at the north of the Red Sea. The drying up of the ancient sea of the Sa- hara, and the consequent diminution of rains and increase of evaporation is, perhaps, the cause which gradually lowered, century after century, this ancient sea, called so appropriately to this day, the “Dead Sea.” In fact, the landscape thoroughly presents an aspect of death. The rocks are bare; nearly every spot on the shores is sterile; the waters themselves nourish with difficulty but a few living beings of the lowest order; the fish, crustaceans, and insects brought down by the Jordan and the surrounding mountain torrents immediately die; aquatic plants are unable to grow. Off the mouth of a rivulet, the Wady-Mojeb, small fish * Wignes, Voyage d’Exploration à la Mer Morte. f Lartet, Bulletin de la Société Géologique de France, vol. xxii. 4.08 TIII) EARTII. are caſticd as far as a point in the lake where the density of the water is l'115, but beyond this spot they inevitably perish. The only animals that Jo" 3. º .V ſº. § º #Nſ. º *** * *ś .*. sº § *...* §§º 4. º § #º "...ºft. crº tº a 3. * , §§§§ - * º Y, dº § Išić mould ºils. - § W ; : ºlºe, "Sº º gº a wº-a-bºy I º º º }: \!. º } ,' A º º A.Y. §: - ! .." & - º §§§ §§ X / ...' ºft *wa. 2’ wº \ §§ Wit. F- º, “ & ſºy ſº º - - º § żºłºś. º - Že t; º: , ºr: **** *A*. . Yºº • W ºu tº º SM U.KY, º]|| § * # §§§ºftº: * - Wºº. § *g 'ſſº, r - #: % 3. º; ... º. * , sº º º º * ', ''A. , Kº **ts sº t º, , º.º. º 3. §§§ as ' º'Nº.º. ºff *...* -A- iſſoodoo $. flownstrºy —3–E–F–w. | Jo I’ig. 105. The Dead Sea and the Jordan. have been found in the mud at the bottom are some species of foraminifera, classified by Ehrenberg, the micrographer. This almost complete absence of living organisms was formerly attributed to the enormous proportion DEAD SEA. 409 * “3 cº [Nºs. d? ** 3 ..., § 3 ; ; # g cº # * : 3 & ## ă ă ă ă # 33 É : # # :*d rº 4 *S'. sº Jºſh ſ R. H 3 4- º “g sº §§ º sº .." & * - : Tufº) Cre §§§§ §§§ - - 10"c. 12 ſº - § §§ §§§ N - §§§ § § §§ Ş º § SSNSºse *—º fºr: º § § §§ ##########$ ſº sº Şs Fig. 166. Section of Palestine from West to East. of sea-salt which is found in the water of the Dead Sea. This proportion is, in fact, very considerable, for it is twice as great as that in the Mediter. ranean; but there is, on the border of the lake, a small pond, the Water of which is not less salt than that of the Dead Sea, and yet a large quantity of small fish live in it, which are immediately killed by an immersion for a few moments in Lake Asphaltites.” It is, then, probably chloride of magnesium and bromine which render the waters of this inland sea so sompletely destructive to animal life. 3. - Chemical analyses have shown that the matters contained in the Dead Sea differ greatly from those of sea-water, not only in proportion, but also in number. Thus chloride of magnesium is found in this lake in much greater abundance than sea-salt itself; the proportion of bromine is also most extraordinary, as it varies from less than 15 to more than 67 thou- sandth parts of the water. On the other hand, iodine, a substance the presence of which is so characteristić of the waters of the ocean, appears to be completely wanting in the water of the Dead Sea; neither are phos- phorus, silver, cassium, rubidium, nor lithium found in its water. It must be concluded that the Lake Asphaltites has never, since its formation, con- stituted a part of the sea, and that it is not, as was long supposed, an an- cient prolongation of the Red Sea, separated from the rest of this gulf by the upheaving of the entrance of Arabah. Ehrenberg, however, had al- ready come to this conclusion by ascertaining that not one of the forami- nifera found in the mud of the Dead Sea belongs to any species discovered in the Red Sea. M. Lartet thinks that the chemical substances contained in the water of Lake Asphaltites proceed from thermal springs spouting out on the shores, and especially from the bed of the lake. One fact which tends to confirm this hypothesis is, that the quantity of bromine increases with the depth of the water; it is at 984 feet from the surface that the largest proportion of this substance is found. The fragments of bitumen which float on the surface of the water, and have gained for the basin the name of Lake Asphaltites, also proceed from the springs in its bed. As regards the saltness properly so called, it must have naturally increased by the gradual concentration of the water. When the latter extended over a larger surface of the country, the proportion of sea-salt dissolved in * Lartet, Bulletin de la Societé Géologique de France, vol. xxiii. 410 TEIE EARTH, \ the liquid mass must have been much less. When the sea retires, it of course leaves a saline sediment; but this sediment is conveyed into it partly by streams and by the Jordan itself, which empties into the lake about 90 cubic yards of water a second (?), containing 6% bushels of sea- salt. At the present time the water of the Dead Sea, the specific gravity of which is in some places from 1-230 to 1 250, has almost reached the point of Saturation; it deposits saline crystals at the bottom, and only dis- solves to a very trifling extent the base of a cliff of rock-salt which over- looks the western coast. All the great lakes of Asia Minor, situated at different altitudes be- tween the two great depressions of the Dead Sea and the Caspian, are likewise rich in chemical substances. Take Van, which covers an area of 1544 square miles, especially contains sulphate of soda, which, during the dry season, when the waters are low, kills all the fish brought into it by the tributary streams. Take Urimiyeh, still more extensive than Lake Van, is chiefly remarkable for the enormous quantity of sea-salt which it holds in a state of solution; in this respect it is only equaled by the la- gunes of the deserts and steppes, where the salt is so concentrated that it is deposited upon the bottom in thick beds. Of this kind is Lake Elton, to the northwest of the Caspian. The bed of this sheet of water consists of immense layers of salt, to which each day adds a fresh sediment. In winter, the rivulets which empty themselves into this small closed basin bring a certain quantity of brine, which afterward evaporates during the heat, leaving upon the soil a bed of crystals several inches in thickness. In summer, when the shores are not, covered with water, they appear to extend as far as one can see, like an immense field of snow. Every year more than 220,550,000 lbs. of salt are extracted from Lake Elton, and yet the saltness of its waters has not perceptibly diminished. - The Great Salt Lake of America is another Dead Sea, into which falls another Jordan, and, by a strange historical coincidence, the Mormons have established themselves upon the shores of this very lake; for this sect call themselves the successors of the Jews, and the chosen people of the New World. This inland sea, the real shape of which has only been known since 1850, by means of the explorations of Stansbury, is one of the most remarkable lacustrine sheets in the world; it is not less than 248 miles in circumference, but its depth is inconsiderable, and does not ex- ceed 32 feet; the average is only about 6 feet. The degree of saltness of the Great Lake varies according to the seasons and the duration of rains and drought; but it is always much more intense than that of the ocean. In fine weather, one might go to sleep on the waves of the lake without fear of being drowned; nevertheless, it is very difficult to swim in it on account of the effort which must necessarily be made in order to keep the legs below the surface. A single droplet fall- ing into the eye causes the most cruel suffering, and the Water, When swal. lowed, causes paroxysms of spasmodic coughing. Stansbury doubts if the most experienced swimmer could escape death if he were exposed far from the shore to the violence of the waves and wind. Although the GREAT SALT LAKE. 411 Great Lake only contains a very small proportion of those salts so destruc- tive to animal life which are found in the Dead Sea, yet neither fish nor molluscs exist in it; life is only represented by sea-weed of the Mostoe tribe, and by a small worm which here and there burrows in the sand Of the shores. The trout which are carried into its waters by the Jordan perish immediately. Nevertheless, the surface of the lake affords hospi- tality to innumerable flocks of gulls, wild geese, Swans, and ducks. Whole armies of young pelicans, tended by their old lame guardian-birds, contem- plate the waves from the top of all the ledges of rock, while the parents go to fish in the Bear, Weber, and Jordan rivers, all of which abound in fish. Not a tree grows upon the shores of the lake nor in the adjacent plains; the only vegetation to be seen far and wide is tufts of Artemista, and other plants which delight in a soil impregnated with saline substances. The line of separation between the water and dry ground is generally undecided; it is impossible to tell where the shore begins or where the lake ends, as so much of the shore presents muddy banks upon which the water spreads in thin sheets and drifts about its flaky foam. Higher up the shore the mud dries in the sun and peels off in scales, which have the appearance of leather; sulphureous exhalations escape from cracks in the soil, and diffuse an intolerable odor in the air. On the western side, vast plains, nearly as level as the surface of the water, extend between the lake and a range of distant mountains. During some of the summer months, these plains, which are crossed by rivulets loaded with chemical substances, are covered by an immense sheet of crystalline salt split up into innumer- able furrows produced by contraction of the soil. Whenever rain falls, or even when the air is simply charged with moisture, the salt becomes deli- quescent, and nothing is to be seen but an expanse of blackish clay, into which beasts of burden sink at every step they make. Formerly the Great Salt Lake, like all other inland seas saturated with salt, spread over a much more considerable area. The parallel basins of the plateau of Utah, and the lateral valleys which run into them, were the gulfs, bays, and straits of the inland sea. At a great height above the present level of the lake, the former alluvial shores and cliffs surround the valleys with their concentric rings traced upon the sides of the mountains. Even in the plains some distance off, the surface of which exhibits a thin bed of vegetable earth, the substratum is lake-clay saturated with sea-salt and the sulphates of lime and magnesia. Agriculture, therefore, is nearly impossible upon these ancient lacustrine beds. In the earliest years of colonization the damp and virgin earth still produced crops to some ex- tent, but subsequently the vegetable soil has lost its nutritive elements, and the clayey substratum, coming in contact with the roots of the plants, withers them up by means of its acrid properties. Similar causes to those which led to the contraction of the Caspian and the Dead Sea have constantly tended to diminish the waters of Lake Utah, and also to Saturate them with an enormous quantity of salt. The Great Basin is separated from the Pacific by high mountains of comparatively recent formation, which arrest the progress of the clouds, and prevent them 412 THE EARTÉ. from pouring upon the plateau the moisture derived from the sea. On the other hand, the evaporation is very considerable upon these high, rocky, and bare plains, and the winds which traverse them are but little impeded from carrying the vapors outside the basin of Utah. In conse- quence of this constant loss, the level of the Great Lake is become lower, the streams are dried up, the springs are exhausted, and the salt has con- centrated more and more in the water. It is probable that, at the present time, an equilibrium is at length established between the annual fall of snow and rain and the mists which rise from the surface of the diminished lake. Since the establishment of the Mormons in the territory of Utah, the level of the lake has alternately risen and sunk.” The various phenomena which take place in the waters of the Great Salt Lake, as well as in those of the Caspian, Lake Urimiyeh, and the Dead Sea, are also produced in a multitude of other lacustrine basins of less impor- tance, with all the variations caused by the difference of climate, the na- ture of the soil, and the composition of the water. But as a great num- ber of these lakes are situated in regions destitute of rain, and owe their Saltness to the copious evaporation which has abstracted so large a part of their waters, they are, in consequence of this diminution, of very small area, and have become converted into lagoons and marshes. Sometimes, indeed, they are reduced to surfaces which are alternately muddy and white with salt, when they have been either wetted by some casual rains or dried up by the solar rays. As a type of these salt-tracts may be men- tioned the steppes of Huiduck in the Ponto-Caspian isthmus, and the Chott Fig. 167. Lakes of Huiduck. Melrºir, a range of marshes which stretch from east to west, over a length of more than 186 miles to the south of Djebel Aouress, formerly commu- nicating with the Gulf of Great Syrtes by the Strait of Gabes, at present choked up by sand. These marshes are separated one from another by isthmuses and islets of dry ground, and extend at unequal levels to 95, 118, 128, 213, 249, and even 279 feet below the sea.f During the rainy season they are sheets of shallow water, which spread far and wide into the plains; during the dry season they are fields of salt, over which the mirage throws its illusions. - - * Fremont, Stansbury, Jules Remy, Engelmann. + Vide below, the chapter on “Upheavals and Depressions." f Dubocq, Mémoire sur le Ziban et l'Oued-R'ir. _MAIPSHIES. 413 CHAPTER, TX. PEAT - BOGS. — UN HEALTHINESS MARSHIES. —SWAMPS OF NORTH AMERICA. g OF MAIRSHIES. MARSHEs proper are shallow lakes, the waters of which are either stag- nant or actuated by a very feeble current; they are, at least in the tem- perate zone, filled with rushes, reeds, and sedge, and are often bordered by trees, which love to plunge their roots into the muddy soil. In the trop- ical zone a large number of marshes are completely hidden by multitudes of plants or forests of trees, between the crowded trunks of which the black and stagnant water can only here and there be seen. Marshes of this kind are inaccessible to travelers, except where some deep channel, winding in the midst of the chaos of verdure, allows boats to attempt a passage between the water-lilies, or under some avenue of great trees with their long garlands of creepers waving in the shade. Whatever may be the climate, it would, however, be impossible to draw any distinction, even the most vague, between lakes and marshes, as the level of these sheets of water oscillates according to the seasons and years, and as the greater number of lakes, principally those of the plains, terminate in shallow bays which are perfect marshes. Some very important lacustral basins, among others Lake Tchad, one of the most considerable in all Africa, are entirely surrounded by swamps and inundated ground, which prohibit access to the lake itself, and prevent its true dimensions from being known. In like manner, a portion of the course of many rivers traverses low re- gions in which marshes are formed, either temporary or permanent, the uncertain limits of which change incessantly with the level of the current. The borders of great water-courses, when left in their natural state, are the localities in which these marshy reservoirs principally exist, which, in the absence of basins and artificial weirs, are of very great importance to the regulation of the fluviatile discharge. The most remarkable marshes of this kind are perhaps those crossed by the Paraguay and several of its tributaries; they consist of wet prairies and interminable sheets of water, which stretch away like a sea from one horizon to the other. They have received the names of Lakes Xarayes, Pantanal, etc. Farther south, cer- tain tributaries of the Parana, the Maloya, the Batel, and the Sarandi, which cross the State of Corrientes from northeast to southwest, are noth- ing but wide marshes, the water of which overflows slowly across the grass on the imperceptible slope of the territory. There is, indeed, one of these marshes, the Laguna Bera, which drains simultaneously into the two great rivers of Parana and Uruguay." These permanent inundations, however, can not fail to disappear, Sooner or later, before the encroachments of cul- tivation. 414 THE EARTH. f : 5-F#EEEEEE|3:=== *...º.S. NTERFETºº-Rº: : -- tav-i- A tº 2...º-º ºś •",V": V. ***.x: . ...-: * ê ºft. Š &A. -, * -- 4. - . . .e. ' 3. º $º * §§ §§ - w . tº à-º' se: ‘. . ... a.ſ. Sºº :- * * *: ... * *.*.*. º £ºś * - as • Aº ‘ ... • º, “-º'-'. * - ** Tig. 168. Salt Marshes of Paraguay. In the same way as the low river-shores are frequently converted into marshes, vast extents of the sea-coasts when but slightly inclined are also covered over by marshes, which are generally separated from the main sea by tongues of Sand gradually thrown up by the waves. In these marshes, most of which once formed a part of the sea and still mark its ancient out- line, the water presents the most varied proportions of saline admixture. In some places, when evaporation is very active, the liquid is much more salt than the sea itself; but in other spots the marsh, fed by fresh water which comes from the interior, is scarcely brackish. The saltness of the water, however, constantly changes in all parts of the marsh, according to the alternations of flow and ebb, and of rainy and dry weather. These half dried-up bays are rarely deep enough to allow of large vessels sailing in them, and their banks are generally overrun by the most luxuriant veg- etation. The shore constantly keeps gaining upon them, and thus tends to the increase of the main land. The coasts which surround the Caribbean Sea and the Gulf of Mexico, and also the Atlantic shores of North America from the point of Florida to the mouth of the Chesapeake, are bordered by a very large number of marine marshes, forming a continued series over hundreds and thousands of miles in length. In this immense series of coast-marshes all kinds of vegetation seem to flourish, and threaten to get the better of the mud and water, and to convert them into terra firma. To the south, upon the shores of Columbia and Central America, the mangroves and other trees of like species plunge the terminal points of their ačrial roots deep into the mud, crossing and recrossing in an arch-like form, and retaining all the débris of plants and animals under the inextricable net-work of their natu- ral scaffoldings. The shores of the Gulf of Mexico, in Louisiana, Georgia, * SWAMPS.—QUAKING-BOGS, 415 Fig. 169. Marshes of Corrientes. and Florida, are bordered by cypress swamps, or forests of cypress (Cu- pressus disticha); these strange trees, the roots of which, entirely buried, throw out above the layer of water which covers the soil multitudes of little comes, the business of which is to absorb the air. For millions of acres nearly all the marshy belt along the sea-shore is nothing but an im- mense cypress swamp, with trees bare of leaves, and fluttering in the wind their long hair-like fibres of moss. Here and there the trees and muddy soil give place to bays, lakes, or quaking-meadows, formed by a carpet of grass lying upon a soil of wet mud, or even upon the hidden water. In Brazil these buoyant beds of vegetation are frequently met with, and the significant name of tremendal has been given to them: in Ireland these are called “quaking-bogs.” The least movement of the traveler who ventures upon them makes the soil tremble to some yards' distance. To the north of Florida, in the Carolinas and Virginia, the belt of cypress swamps continue; but in consequence of the change of climate and vege- tation, the quaking-meadows are gradually converted into peat-mosses. 416 TELE EARTH. Evaporation being much less active in these countries than in those situ. ated farther to the south, and the dry season being much less prolonged, the water arising from rain and inundation remains—as if in the pores of an immense sponge—in all the interstices of the entangled mass of mosses, Sphagnum, Confervae, and other aquatic plants. The whole marsh swells toward the centre, because the droplets, divided by innumerable stalks, can not spread out laterally, and are drawn by capillary attraction into the fresh beds of plants which are formed above the older ones. The sur- face of the marsh is incessantly renewed by a carpet of green vegetation, while below, the dead plants, deprived of air, carbonize slowly in the moisture which surrounds them: these are the beds of peat which form upon the ground just as the layers of coal were formed in previous geo- logical epochs. On the southern side, the first great peat-bog of a well-defined character is the “Dismal Swamp,” which extends along the frontiers of North Car- olina and Virginia. This spongy mass of vegetation rises 10 feet above the surrounding land. In the centre, and, so to speak, upon the summit of the marsh, lies Lake Drummond, the clear water of which is colored reddish-brown by the tannin of the plants. A canal, which crosses the Dismal Swamp to connect it with the adjacent streams, is obliged to make its way along the marsh by means of locks. To the north of Virginia peat-bogs proper become more and more numerous; and in Canada, Lab- rador, etc., they cover vast expanses of country. All the interior of the island of Newfoundland, inside the inclosure formed by the forests on the shore, is nothing but a labyrinth—a great part of which is still unknown —of lakes and peat-bogs; even on the sides of the hills there are marshes on so steep an incline that the water from them would disappear and run off in a stream if it was not stopped by the thick carpet of plants which it saturates. Many a large peat-bog which may be crossed dry-shod contains more water than many lakes filling a hollow of the valley with deep water. Opposite Newfoundland, on the other side of the Atlantic, Ireland is hardly less remarkable for the enormous development of its peat-mosses or bogs. These tracts of saturated vegetation, in which Sphagnum palustre predominates, comprehend nearly two and a half millions of acres—the seventh part of the whole island. The inhabitants continue to extract from them, every year, immense quantities of fuel. The spaces left by the spade in the vegetable mass are gradually filled up again by new layers. After a certain number of years, which vary according to the abundance of rain, the depth of the bed of water, the force of vegetation, and the slope of the soil, the turf “quarry” is formed anew. In Ireland it generally takes about ten years to entirely fill up again the trenches, measuring from nine to thirteen feet in depth, which are made in the bogs on the plains, when a fresh digging of turf may be commenced. In Holland, crops of this fuel may be gathered, on an average, every thirty years. In other peat-moss districts the period of regeneration lasts forty, fifty, and even a hundred years. In France, on the bórders of the Seugne PEAT Boas. 417 (Charente-Inférieure), it has been ascertained that ditches 5 feet deep and nearly 7 feet wide are completely obstructed by vegetation after the lapse of twenty years. As for the beds of peat which carpet the sides of moun- tains, they take centuries to form afresh. g º & As every thing in nature is continually changing and modifying, peaty marshes, like lakes, are all either in a period of increase or a period of decay—some form while others disappear. Independently of the action exercised by the labor of man, the vegetation of peat-bogs may cease to be produced in any basin either because the water flows away natural y through some wide outlet after the heavy rains, or because some river, by changing its course, has exhausted or immoderately swollen the mass of water necessary to the nourishment of the peat; or, again, becºsº the rain, becoming either more rare or more frequent, has dried up the basin, or converted it into an inundated marsh; lastly, the sinking or upheaving of the soil may also, according to the various conditions of the relief of the country, be the cause of the disappearance of the Flora of the peat: bogs. The same causes, acting in contrary directions, give rise to and increase these enormous masses of plants swollen with water. In Ireland, the Low Countrics, the north of Germany and Russia, heaps of trunks of , ormer forest-trees—oaks, beech, alder, and other trees—are frequently dis- covered, which by their decay have made way for the peat-mosses. The Sphagnum, too, often takes possession of ground of which man had pre- viously made himself master, and in many places roads, remains of build- ings, and other vestiges of human labor are found below the modern bed of vegetation by which they are now covered. Certain peat-bogs in Den- mark and Sweden may be considered, on account of the curiosities which have been found in them, as perfect natural museums, in which the relics of the civilization of ancient nations have been preserved for the Savants of our own day. The air above the peat-mosses of Ireland and other countries in the world 's not often unhealthy, either because the heat is not sufficient to develop miasma, or else because the vegetation, by absorbing the water into its spongy mass, impedes the corruption of the liquid, and produces a consid- erable quantity of oxygen. Farther south, the peat-mosses, which are in- termixed with pools of stagnant water, and especially marshes properly so-called, generate an impure air, which spreads fever and death over the surrounding country. Unless marshes are surrounded with dense forests, which arrest the dispersion of the gases, the latter exercise a most injurious influence on the general salubrity of the district; for during dry weather, a vast area of the bed of the marshes becomes exposed, and the heaps of organic débris lying on the bottom decompose in the heat and infect the whole atmosphere. The average of life is much shorter in all marshy countries than in the adjacent regions which are invigorated by running water. In Brescia, Poland, in the marshes of Tuscany, and in the Roman plains, the wan and livid complexion of the inhabitants, their hollow eyes, and their feverish skin, announce at first sight the vicinity of some centre D D 4.18 - TEIE EARTH of infection. There are some marshes in the torrid zone where the des composition of organic remains goes on with a much greater rapidity than in temperate climates; no one can venture on the edges of these districts without peril to his life. As Froebel ascertained in his journey across Central America, the miasma is occasionally produced in such abun- dance that not only can it be smelt, but a distinct impression of it is left upon the palate. One of the most important works of civilization is to deal with these unwholesome regions, which are still, as it were, unde- cided between land and water, and to render them fit for cultivation and to be the abode of man. P A R T IV. SUBTERRA NEAN FORCES. CHAPTER LXI. ERUPTION OF ETNA IN THE YEAR 1865.-MUTUAL DEPENDENCE OF ALL TERRESTRIAL PHIENOMENA. THE Greek mythology, harmonizing in this respect with the ideas Öf most nations which were acquainted with volcanoes, attributed to these mountains an origin altogether independent of the forces which are in ac- tion on the surface of the ground. According to the views of the Hel- lenes, water and fire were two distinct elements, and each had its separate domain, its genii, and its gods. Neptune reigned over the sea; it was he that unchained the storms and caused the waves to swell. The tritons followed in his train; the nymphs, sirens, and marine monsters obeyed his orders, and in the mountain valleys, the solitary naïads poured out to his honor the murmuring water from their urns. In the dark depth of unknown abysses was enthroned the gloomy Pluto; at his side Vulcan, surrounded by Cyclops, forged thunderbolts at his resounding anvil, and from their furnaces escaped all the flames and molten matter the appear- ance of which so appalled mankind. Between the gods of water and of fire there was nothing in common, except that both were the sons of Chronos, that is, of Time, which modifies every thing, which destroys and renews, and, by its incessant work of destruction, makes ready a place for the innumerable germs of vitality which crowd on the threshold of life. Even in our days, the common opinion is not much at variance with these mythological ideas, and volcanic phenomena are looked upon as events of a character altogether different from other facts of terrestrial vitality. The latter, the sudden changes of which are visible and easily to be ob- served, are justly considered to be owing principally to the position of the earth in respect to the Sun and the alternations of light and darkness, heat and cold, dryness and moisture, which necessarily result. As regards vol- canoes, on the contrary, an order of entirely distinct facts is imagined, caused by the gradual cooling of the planet or the unequal tides of an ocean of lava and fire. Certainly, the eruptions of ashes and incandes- cent matter have not revealed the mystery of their formation, and in this respect numerous problems still remain unsolved by scientific men. Nevertheless, the facts already known warrant us in asserting that volcan- 420 a-l THE EARTH, ic crises are connected, like all other planetary phenomena, with the gen- eral causes which determine the continual changes of continents and seas, the erosion of mountains, the courses of rivers, winds, and storms, the movements of the Ocean, and all the innumerable modifications which are taking place on the globe. If, some day, we are to succeed in pointing out exactly and plainly how volcanoes likewise obey, either partially or completely, the system of laws which govern the exterior of the globe, the first and most important requisite is to observe with the greatest care all the incidents of volcanic origin. When all the premonitory signs and all the products of eruptions shall have been perfectly ascertained and duly classified, then the glance of science will be on the point of pen- etrating into, and duly reading, the Secrets of the subterranean abysses where these marvelous convulsions are being prepared. The last great eruption of Etna, that central pyramid of the Mediterra- nean, which the ancients named the “Umbilicus of the world,” is one of the most magnificent examples which can be brought forward of volcanic phenomena; and as it has, moreover, been studied most precisely and completely, it well deserves to be described in some detail. & The explosion had been heralded for some long time by precursory signs. In the month of July, 1863, after a series of convulsive movements of the soil, the loftiest cone of the volcano opened on the side which faces the south. The incandescent matter descended slowly over the plateau on which stands the “Maison des Anglais;” and this building itself was demolished by the lumps of lava which were hurled from the mouth of the crater. In some places heaps of ashes several yards thick covered the slopes of the volcano. After this first explosion, the mountain never be- came completely calm; numerous fissures, which opened on the outer slopes of the crater, continued to smoke, and the hot vapor never ceased to jet out from the summit in thick eddies. . Often, indeed, during the night, the reflection of the lava boiling up in the central cavity lighted up the atmosphere with a fiery red. The liquid, being unable to rise to the mouth of the crater, pressed against the external walls of the vol- cano, and sought to find an issue through the weakest point of the crust by melting gradually the rocks that opposed its passage. Finally, in the night of the 30th to the 31st of January, 1865, the wall of the crater yield- ed to the pressure of the lava;. some subterranean roaring was heard; slight agitations affected the whole of the eastern part of Sicily, and the ground was rent open for the length of a mile and a half to the north of Monte Frumento, one of the secondary cones which rise on the slope of Etna. Through this fissure, which opened on a gently-inclined plateau, the pent-up lava violently broke through to the surface. . . . The fissure which opened on the side of the mountain, and could be easily followed by the eye to a point about two-thirds of the height of Monte Frumento, in the direction of the terminal crater of Ætna, seems to have vomited out lava but for a very few hours. Deing Soon obstruct- ed by the snow and the débris of the adjacent slopes, it ceased to retain EAE UPTION OF ETNA IV 1865. 421 its communication with the interior of the mountain, and now resembled a kind of furrow, as if hollowed out by the rain-water on the side of the cone. On the 31st of January all the volcanic activity of the crevice was concentrated on the gently inclined plateau which extends at the base of Monte Frumento, in the midst of which several new hillocks made their appearance. On the lower prolongation of the line of fracture, all the phenomena of the eruption properly so-called were distributed in a per- fectly regular way. Six principal cones of ejection were raised above the crevice, and gradually increased in size, owing to the débris which they threw out of their craters; these, gradually mingling their intervening slopes, and blending them one with another, absorbed in succession other smaller cones which had been formed by their sides, thus reaching a height of nearly 300 fect. Soon after the commencement of the eruption sº º ſº º 62 :* ---- * * | $º º (* 4'-- 2% s: * gº § *. R sº •w sº is ſº ſº º ~ º Žº º: º º Rºß § º #: 3. §§ 3. ---N-- & º ºſº. " ' º Frºix º º, §3. ". &ºgº.giftºft; Fig. 170. Coulée of Monte Frumento. the two upper craters, standing close together on an isolated cone, vom- ited nothing but lumps of stone and ashes, while jets of still liquid lava were emitted by the lower craters, which were arranged in a semicircle round a sort of funnel-shaped cavity. In consequence of the specific gravities of the substances evacuated, a regular division of labor took place between the various points of the crevice. The projectiles which had solidified the triturated débris, and the more or less porous frag- ments which floated on the top of the lava, made their escape by the higher orifices; but the liquid mass, being heavier and more compact, could only burst forth from the ground by the mouths opening at a less elevation. Two months after the commencement of the eruption, the cone which was the nearest to Frumento ceased to send out either scoriae or ashes. The pipe of the crater was filled up with débris, and the internal activity was revealed by vapors either of a sulphurous character or charged with 422 THE EARTH, hydrochloric acid. These rose like smoke from the slope of the hillock. The second cone, situated on a lower part of the fissure, remained in di- rect communication with the central flow of lava; but it was not in a constant state of eruption, and rested after each effort as if to take breath. A crash like that of thunder was the forerunner of the explosion; clouds of vapor, rolling in thick folds, gray with ashes, and furrowed with stones, darted out from the mouth of the volcano, darkening the atmosphere, and throwing their projectiles over a radius of several hundreds of yards round the hillock. Then, after having discharged their burdens of débris, the dark clouds, giving way before the pressure of the winds, mingled far and wide with the mists on the horizon. The lower cones, which rose immediately over the lava-source, continued to rumble and to discharge molten matter outside their cavities. The vapor which escaped from the Seething wall of lava crowded in dark contortions round the orifice of the Craters. Some of it was red or yellow, owing to the reflection of the red- hot matter, and some was variously shaded by the trains of débris ejected with it; but it was impossible to follow them with the eye, so rapid was their flight. An unintelligible tumult of harsh sounds simultaneously burst forth ; they were like the noises of saws, whistles, and of hammers falling on an anvil. Sometimes one might have fancied it like the roar- ing of the waves breaking upon the rocks during a storm, if the sudden explosions had not added their thunder to all this uproar of the elements. One felt dismayed, as if before, some living being, at the sight of these groups of hillocks, roaring and smoking, and increasing in size every hour, by the débris which they vomited forth from the interior of the earth. The volcano, however, then commenced to rest; the crupted matter did not rise much beyond 100 yards above the craters, while, according to the statement of M. Fouqué, at the commencement of the eruption it had been thrown to a height of 1850 to 1950 yards. º - During the six first days the quantity of lava which issued from the fissure of Monte Frumento was estimated at 117 cubic yards a second, equivalent to a volume twice the bulk of the Seine at low-water time. In the vicinity of the outlets the speed of the current was not less than 20 feet a minute; but lower down, the stream, spreading over a wider surface, and throwing out several branches into the side valleys, grad- ually lost its initial speed, and the fringes of scoriae, which were pushed on before the incandescent matter, advanced on the average, according to the slope of the ground, not more than 1% to 6 feet a minute.” On the 2d of February the principal current, the breadth of which varied from 300 to 550 yards, with an average thickness of 49 feet, reached the upper ledge of the escarpment of Colla-Vecchia, or Colla-Grande, three miles from the fissure of eruption, and plunged like a cataract into the gorge below. It was a magnificent spectacle, especially during the night, to see this sheet of molten matter, dazzling red like liquid iron, making its Way, * These figures, borrowed from the account of the Professor Orazio Silvestri, are the re- sults of measurements made by Viotti, the engineer. ERUPTION OF ETNA IN 1865. 423 in a thin layer, from the heaps of brown scoriae which had gradually ac- cumulated up above; then, carrying with it the more solid lumps, which dashed one against the other with a metallic noise, it fell over into the ravine, only to rebound in stars of fire. But this splendid spectacle lasted only for a few days; the fiery fall, by losing in height, diminished gradually in beauty. In front of the cataract, and under the jet itself. there was formed an incessantly increasing slope of lava, which ultimately filled up the ravine, and, indeed, prolonged the slope of the valley above. From the reservoir, which was more than 160 feet deep, the stream con- tinued to flow to the east toward Mascali, filling up to the brink the winding gorge of a dried-up rivulet. By the middle of the month of February, the fiery stream, already more than six miles long, made but very slow progress, and the still liquid lava found it difficult to clear an outlet through the crust of stones cooled by their contact with the atmosphere; when, all of a sudden, a breaking out took place at the side of the stream, at a point some distance up, not far from the source. Then a fresh branch of the burning river, flowing to- ward the plains of Linguagrossa, Swallowed up thousands of trees which had been felled by the woodman. This second inundation of lava did not, however, last long. The villages and towns situated at the base of the mountain were no longer directly menaced; but the disasters caused by the eruption were, notwithstanding, very considerable. A number of farm-houses were swept away; vast tracts of pasturage and cultivated ground were covered by slowly hardening rock, and—a misfortune which was all the worse on account of the almost general deforesting of Sicily —a wide band of forest, comprising, according to the various estimateg that were made, from 100,000 to 130,000 trees—oaks, pines, chestnuts, or birches—was completely destroyed. When seen from the lower part of the mountain, all these burning trunks borne along upon the lava, as if upon a river of fire, singularly contributed to the beauty of the spectacle. As is always the case in the events of this world, the misfortune of some proved to be a source of gratification to others. During the earliest pe- riod of the eruption, while the villagers of Etna looked at it with stupor, and were bitterly lamenting over the destruction of their forests, hun- dreds of curious spectators, brought daily by the steamboats from Cata- nia and Messina, came to enjoy at their ease the contemplation of all the splendid horrors of the conflagration. The aspect of the current of lava, as it appeared covered with its en- velope of scoriae, was scarcely less remarkable than the sight of the mat- ter in motion. The black or reddish aspect of the cheire was all rough- ened with sharp-edged projections, which resembled steps, pyramids, or twisted columns, on which it was a difficult matter to venture, except at the risk of tearing the feet and hands. Some months after the commence- ment of the eruption, the onward motion of the interior of the molten stone, which, by breaking the outer crust in every direction, had ulti- mately given it this rugged outline, was still visibly taking place. Here 424 THE EARTEI. and there cracks in the rock allowed a view, as if through an air-hole, of the red and liquid lava swelling up as it flowed gently along like some viscous matter. A metallic clinking sound was incessantly heard, pro- ceeding from the fall of the scoriae, which were breaking under the press- ure of the liquid matter. Sometimes, on the hardening current of lava, a kind Öf blister gradually rose, which either opened gently, or bursting with a crash gave vent to the molten mass which formed it. Fumerolles, composed of various gases, according to the degree of heat of the lava which gave rise to them, jetted out from all the issues. Even on the banks of the river of stone the soil was in many places all burning and pierced with crevices, through which escaped a hot air thoroughly charged with the smell of burnt roots. On the slopes of the Frumento, quite close to the upper part of the fis- sure, at a spot where the liquid mass had flowed like a torrent, M. Fouqué noticed a remarkable phenomenon; sheaths of solidified lava were sur- rounding the trunks of pines, and thus showing the height to which the current of molten stone had reached. In like manner, the streams of Ob- sidian which flow rapidly from the basin of Kilauea, in the isle of Hawaii, leave behind them on the branches of the trees numerous stalactites, like the icicles which are formed by melting snow which has again frozen. Below the escarpments of the Frumento, the torrent, which was there re- tarded in its progress, had not contented itself with bathing for a mo- ment the trunks of the forest trees, but had laid them low. Great trunks of trees, broken down by the lava, lay stretched in disorder on the un- even bed of the stream, and, although they were only separated from the molton matter by a crust a few inches thick, numbers of them were still clothed with their bark; several had even preserved their branches. At the edge of the cheire, some pine-trees, which had perhaps been preserved from the fire by their moisture being converted by the heat into a kind of coating of steam, were surrounded by a wall of heaped-up lava, and their foliage still continued green; it could not yet be ascertained if the sources of the sap had perished in their roots. - In some places, rows of firs very close together were sufficient to change the direction of the flow, and to cause a lateral deviation. Not far from the crater of eruption, on the western bank of the great cheire, a trunk of a tree was noticed which by itself had been able to keep back a branch of the stream, and to prevent it from filling up a glen which opened im- mediately below. This tree, being thrown down by the weight of the scoriae, had fallen so as to bar up a slight depression in the ground which presented a natural bed to the molten matter. The latter had bent and cracked the trunk, but had failed in breaking it, and the stony torrent had remained suspended, so to speak, above the beautiful wooded slopes which it threatened to destroy completely. round the very mouth of the volcano, a vast glade was formed in the forest; the ground was covered every where with ashes which the wind had blown up into hillocks, like the dunes on the sea-coast; all the trees ERUPTIONS OF ETNA PL. XX. º I º ºn-ºw ºn Loan o' tº 49es fºr ºval Zara of woº awara of ſº area tºº won tº carºo hea's Cºw - 12* º' - - TTATVºlſºm, atter Sartorius de Waltershausen. Eng" by Frhard HARPER & BROTHERS NEW ERUPTION OF ETWA IV 1865. 425 had been broken down by the volcanic projectiles, and burned by the scoriae and small stones. The nearest trees that were met with, at un- equal distances from the mouths of eruption, had had their branches torn off by the falling lumps of stone, or were buried in ashes up to their ter- minal crown. A spectator might have walked among a number of yel- low branches which were once the tops of lofty pines. Thus, on the pla- teau of Frumento and the lower slopes, every thing was changed both in form and aspect; we might justly say that, by the effects of the erupted matter, the outline of the sides of Etna itself had been perceptibly modi- fied. w And yet this last eruption, one of the most important in our epoch, is but an insignificant episode in the history of the mountain; it was but a mere pulsation of Etna. During the last twenty centuries only, more than seventy-five eruptions have taken place, and in some of them the flows of lava have been more than twelve miles in length, and have cov- ered areas of more than forty square miles, which were once in a perfect state of cultivation, and dotted over with towns and villages. In former ages, thousands of other lava-flows and cones of ashes have gradually raised and lengthened the slopes of the mountain. The mass of Mount Etna, the total bulk of which is three or four thousand times greater than the most considerable of the rivers of stone vomited from its bosom, is, in fact, from its summit to its base, down even to the lowest submarine depths, nothing but the product of successive eruptions throwing out the molten matter of the interior. The volcano itself has slowly raised the walls of its crater, and then extended its long slopes down to the waters of the Ionian Sea. By its fresh beds of lava and scoriae incessantly re- newed one upon the other, it has ultimately reared its summit into the regions of snow, and has become, as Pindar called it, the great “pillarºof heaven.” 426 THE EARTH, CHAPTER LXII. SEA-COAST LINE OF VOLCANOES.—THE PACIFIC “CIRCLE OF FIRE.”—volcA- NOES OF THE INDIAN OCEAN ; OF THE ATLANTIC; OF THE MEDITERRA- NEAN ; OF THE CASPIAN ; OF CENTRAL ASIA. THE earth being generally looked upon as immobility itself, it is a very strange thing to see it open to shoot out into the air torrents of gas, and shedding forth like a river the molten rocks of its interior. From what invisible source do all these fluid matters proceed which spread out in sheets over vast regions? Whence come those enormous bodies of steam, extensive enough to gather immediately in clouds round the loftiest sum- mits, and sometimes indeed to fall in actual rain-showers ? Science, as we have already said, has not completely answered these questions, the posi- tive solution of which would be so highly important for our knowledge of the globe on which we live. * According to an ancient popular belief, Etna merely vomits forth, in the shape of vapor, the water which the sea has poured into the gulf of Cha- rybdis. This legend, although clothed in a poetic garb, has in fact be- come the hypothesis which is thought beyond dispute by those Savants who look upon volcanic eruptions as being a series of phenomena caused chiefly by water converted into steam. - The remarkable fact that all volcanoes are arranged in a kind of line albng the coasts of the sea, or of inland lacustrine basins, is one of the great points which testify in favor of this opinion as to the infiltration of water, and give to it a high degree of probability. The Pacific, which is the principal reservoir of the water of our earth, is circled round by a se- ries of volcanic mountains, some ranged in chains, and others very dis- tant from one another, but still maintaining an evident mutual connec- tion, constituting a “circle of fire,” the total development of which is about 22,000 miles in length. This ring of volcanoes does not exactly coincide with the semicircle formed by the coasts of Australia, the Sunda Islands, the Asiatic continent, and the western coasts of the New World. Like a crater described within some ancient and more extensive outlet of eruption, the great circle of igneous mountains extends its immense curve in a westward direction across the waves of the Pacific, from New Zealand to the peninsula of Alaska; on the east, it is based on the coast of America, rising in the south so as to form some of the loftiest Summits of the Andes. The still smoking volcanoes of New Zealand, Tongariro and the cone of Whakari, on White Island, are, in the midst of the southern Waters of the Pacific properly so called, the first evidence of volcanic activity. On DISTRIBUTION OF VOLCA WOES. 427 the north, a considerable space extends in which no volcanoes have yet been observed. The group of the Feejee Islands, at which the volcanic ring recommences, presents a large number of former craters which still manifest the internal action of the lava by the abundance of thermal springs. At this point, a branch crossing the South Sea in an oblique direction from the basaltic islands of Juan Fernandez as far as the active volcanoes of the Friendly group, unites itself with the principal chain which passes round, in a northeast direction, the coasts of Australia and New Guinea. The volcanoes of Abrim and Tanna, in the New Hebrides, Tinahoro, in the archipelago of Santa Cruz, and Semoya, in the Salomon Isles, succeeding one after the other, connect the knot of the Feejees to the region of the Sunda Islands, where the earth is so often agitated by . violent shocks. This region may be considered as the great focus of the lava streams of our planet. On the kind of broken isthmus which con- nects Australia with the Indo-Chinese peninsula, and separates the Pacific Ocean from the great Indian seas, one hundred and nine volcanoes are vomiting out lava, ashes, or mud in full activity, destroying from time to time the towns and the villages which lie upon their slopes; sometimes, in their more terrible explosions, they ultimately explode bodily, covering with the dust of their fragments areas of several thousands of miles in ex- tent. From Papua to Sumatra, every large island, including probably the almost unknown tracts of Borneo, is pierced with one or more volcanic outlets. There are Timor, Flores, Sumbawa, Lombok, Bali, and Java, which last has no less than forty-five volcanoes, twenty-eight of which are in a state of activity, and, lastly, the beautiful island of Sumatra. .Then, to the east of Borneo—Ceram, Amboyna, Gilolo, the volcano of Ternata, sung by Camoëns, Celebes, Mindanao, Mindoro, and Luzon; these form across the sea, as it were, two great tracks of fire. Northward of Luzon, the volcanic ring curves gradually so as to fol. low a direction parallel to the coast of Asia. Formosa, the Liou-Kiedu archipelago, and other groups of islands stand in a line over the subma- rine volcanic fissure; farther on, there are the numerous volcanoes of Japan, one of which, Fusiyama, with a cone of admirable regularity, is looked upon by the inhabitants of Niphon as a sacred mountain, from which the gods come down. The elongated archipelago of the Kuriles, comprising about a dozen volcanic orifices, unites Japan to the peninsula of Kamtschatka, in which no less than fourteen volcanoes are reckoned as being in full activity. To the east of this peninsula, the range of craters suddenly changes its direction, and describes a graceful semicircle across the Pacific, from Behring Island to the point of Alaska. Thirty-four smoking comes stand on this great transversal dike, extending from conti- ment to continent. Ounimak, which rises on the extremity of the penin- sula of Alaska, the peak of which is 7939 feet in height, serves as the western limit of the New World, and is also pierced by a crater in a state of full activity. Eastward of the peninsula, the volcanic chain extends along the sea- 428 THE EARTH, coast of the continent. Mount St. Elias, one of the highest summits in America, often vomits lava from its crater, which opens at an elevation of 17,716 feet. Farther to the south, another active volcano, Mount Fairweather, rises to a height of 14,370 feet. Next comes Mount Edge- cumbe, in Lazarus Island, and the volcanic region of British Columbia. The whole chain of the Cascades, in Oregon, as well as the parallel ranges of the Sierra Nevada and the Rocky Mountains, are overlooked by a great number of volcanoes; but only a few of them continue to throw out smoke and ashes: these are Mount Baker, Renier, and St. Helens, enor- mous peaks 10,000 to 16,000 feet high. In California and Northern Mex- co, it is probable that the basaltic and trachytic mountains on the coast no longer present any outlets of eruption. Subterranean activity is not 26p B. Q/Zºrºr: a 63 x70 373 13o 276 165 E. zzo + 7.5 >8o zz3 zzo 22.3757 a 6.2 Fig. 171. Curve of Volcanic Islands. manifested with any degree of violence until we reach the high plateaux of Central Mexico. There a series of volcanoes, rising over a fissure crossing the continent, extends over the whole plateau of Anahuac, from the Southern Ocean to the Gulf of Mexico. The Colima, then the celebra- ted Jorullo, which made its appearance in 1759, the Nevado de Tolima, Is- tacihuetl, Popocatepetl, Orizaba, and Tuxtla are the vents for the furnace of lava which is boiling beneath the Mexican plateau. To the south, in Guatemala and the South American republics, thirty burning mountains, much more active and terrible than those of Anahuac, rise in two chains, one of which is parallel to the sea-coast, and the other crosses obliquely the isthmus of Nicaragua. Among these numerous volcanoes there are some, the names of which have become famous on account of the fright- ful disasters which have been caused by their eruptions. Such are the mountains del Fuego and del Agua, above the Ciudad-Antigua of Guate- mala; the Phare d’Isalco, which during the night lights up far and wide the plains of Salvador with its jets of molten stone and its column Of red smoke; Coseguina, the last great eruption of which was probably the most formidable of modern times; the Viejo, Nuevo, Momotombo, WOL CANOES OF AMERICA. 429 and other mountains, which are almost worshiped from being so much dreaded.* The depressions of the isthmuses of Panama and Darien interrupt the series of volcanoes which borders the coast of the Pacific. The peak of Tolima, which rises to the great height of 17,716 feet, is the most northern of the active volcanoes of South America, and is also one of the most dis- tant from the sea among all the fire-vomiting mountains, for the distance from its base to the Pacific coast is not less than 124 miles. South of Toli- ma, and the great plateau of Pasto, where there likewise exists a crater, 82. Töl § s§§ -IS § } Z -R- ; F.% * z . ; § : s Nº - § * A. w ºiliº }\\ | - ..Tºlſt!!! % 3. * * #. - - 23 $º \ NW& *- §ºš. 1- JN §§ ...? { s * t ~...~ y W • ºf N Kºśs: * § #!) - Vºftº - ºffſWº £2: º 40. .ANN\Witte, NMAW & SE \ % % à - sº 'ſ)!/? 2. º:, , ºffi!!! - ºffſ % ~3°. ſ ſº º § º: *G.§ Ž sº rº - - º !. will Nº NºS$ºr #Siz 2× % t - º %. §§§ {N}; - - - * , M., - %," lºº ~ & ...” SU-ANº. SESs sº ºf P- •.'… ºf - l %2.'" WMºkºlº *% Sº -. § §ºğ §§§ % # £ºul); - W %; ºğ º: § is: N % ...Tº § #3 ºn ‘…. {\\ Sºº- N "ºğº sºº' SNS S - 2, - - ... ºr , * ‘…2. w n:v. ~. §§§ Sºğ ºšā ###}º Nº SS $v - S$º: - 22,14t º •:--> NS § N S S %2:#22. º zz §. §§§ Š #2322.3%.º. &ºi.º.º. } *~ § ~ Š £&# &#& =::$2% *S. º: 'Wºl ſº Ş *tº º ~- §§ º - º *Nº, 22://; -- - - Nº. W *A****, * Z. Wy St. º 'ſ cº-º: f #. §. ſº º # - § | º 7.9 - j. Hilº. }}}}'', ^- j\\ºssº - Syº. Sº: 23# º "N©!º lº,”: zºº,”, §§§ 2; ºf $ §ſ. ºlº 2. “...’”, * . ... --> **\\\\ - $ºWNººSºº ; - *…* ºr , , ºilº N - , , #º ã);Sº ſº t \\ 2:...sº § #º. x - i.e. Žll, 33: Nº * * * * * * **, ºftsº S *S*-ºx. Sz. º: - 2 -ºš §§ š. %cº. * - ºğ ºğ T -- §§ - Ž. | ºš : º -4 ޺: #º zz - *N :: jššiad SNS Sº Ş. W Ş Økſ. - º sº jñāī -> Ş Yat SS’s % - 2- : 2. & S. § a ºğºlſ|{{{ſº §3222.3%. (.3%.33: - § Cº. $. * Sºr º y NW - ; S. Nº. wº- Rºº. "º. ºft | % Tºº; §6, §§-ſº §§fºlk Sºft).3% \ ...K Gº, •=r- Sº, -ºš & Yº ... .ºir --- ºr - - - w *…*.*. § - § º 2-3 §º \\s. Nº. ź *::::) lſº §:$, ºr Ž% % * ºğºft|lºš$2.3% :- - 82 * . .". -- 5-$4. *-- * ~~ - - 8ć, Fig. 172. Equatorial Volcanoes. stands the magnificent group of sixteen volcanoes, some already extinct and some still smoking, over which towers the proud dome of Chimbo- razo. Occupying an elliptical space, the greater axis of which is only about 112 miles long, this group, comprising the Tunguragua, Carahui- zo, Cotopaxi, Antisana, Pichincha, Imbabura, and Sangay, is often looked upon as but one volcano with several cones of eruption; it is the cluster which, on the southern coasts of the Isthmus of Panama, corresponds sym. * Moritz Wagner. 430 - THE EARTH, metrically to the volcanic group of Anahuac. South of Sangay, which is perhaps the most destructive volcano on the earth, the chain of the Cor- dilleras offers no volcanoes for a length of about 930 miles; but in South- ern Peru the volcanic series recommences, and outlets of eruption still in action open at intervals among extinct volcanoes and domes of trachyte. The three smoking peaks of the inhabited part of Chili, the mountains of Antuco, Villarica, and Osorno, terminate the series of the great American volcanoes;* the activity of subterranean action is, however, disclosed by some other less elevated craters down to the extremity of the continent as far as the point of Terra del Fuego. This is not all; the South Shet- land Islands, situated in the Southern Ocean, in a line with the New World, are likewise volganic in their character; and if the same direction be followed toward the polar. regions, the line will ultimately touch upon the coasts of the land of Victoria, on which rise the two lofty volcanoes of Erebus and Mount Terror, discovered by Sir John Ross. Stretching round the sphere of the earth, the great volcanic circle is extended toward the north by various islets of the antarctic, and ultimately rejoins the archipelago of New Zealand. Thus is completed the great ring of fire which circles round the whole surface of the Pacific Ocean. Within this immense amphitheatre of volcanoes a multitude of those charming isles, which are scattered in pleiads over the ocean, are also of volcanic origin, and many of them can be distinguished from afar by their smoking or flaming craters. Of this kind are some of the Marianne and Gallapagos Islands, which contain several orifices in full activity, and more than two thousand cones in a state of repose. Among these we must especially mention the Sandwich Islands, the lofty volcanoes of which rise in the middle of the central basin of the North Pacific like so many cones of eruption in the midst of a former crater changed into a lake. The Mauna-Loa and Mauna-Kea, the two great volcanic summits of the island of Hawaii, are each more than 13,000 feet in height; and the eruptions of the first cone, which are still in full activity, must be reck- oned among the most magnificent spectacles of this kind. On the sides of the Mauna-Loa opens the boiling crater of Kilauea, which is, without doubt, the most remarkable lava-source which exists on our planet. Round the circumference of the Indian Ocean the border of volcanoes is much less distinct than round the Pacific; still it is possible to recog- nize some of its elements. To the north of Java and Sumatra, the volca- noos of which overlook the eastern portion of the basins of the Indian seas, stretches the volcanic archipelago of the Andaman and Nicobar Isk ands, in which there are several cones of eruption in full activity. On the west of Hindostan, the peninsula of Kutch, and the delta of the Indus, are often agitated by subterranean forces. Many mountains on the Ara- bian coast are nothing but masses of lava; and, if various travelers are to be believed, the volcanic furnace of these countries is not yet extinct. The Kenia, the great mountain of Eastern Africa, has on its own summit * Philippi, Mittheilungen von Petermann, vol. iv., 1861. - VOLCANOES OF THE ATLANTIC. 431 a crater still in action—perhaps the only one which exists on this conti- nent. Lastly, a large number of islands which surround the Indian Ocean on the west and on the south—Socotora, Mauritius, Reunion, St. Paul, and Amsterdam Island—are nothing but cones of eruption, which have gradually emerged from the bed of the ocean. The volcanic districts which are scattered on the edge of the Atlantic are likewise distributed with a kind of symmetry round three sides of this great basin. On the north, Jan Mayen, so often wrapt in mist, and the more considerable island of Iceland, pierced by numerous craters, Hecla, the Skapta-Jokul, the Kotlugaja, and seventeen other mountains of eruption, separate the Atlantic from the Polar Ocean. At about 1500 miles nearer the equator, the peaks of the Azores, some extinct and some still burning, rise out of the sea. The archipelago of the Canaries, over which towers the lofty mass of the peak of Teyda, continues toward the south the volcanic line of the Azores, and is itself prolonged by the smok- ing summits of the Cape de Verde Islands. All the other mountains of lava which spring up from the bed of the Atlantic more to the south ap- pear to have completely lost their activity, and on the coast itself there is, according to Burton, only one volcano still in action — that of the Cameroons. With regard to the “line of fire” along the western Atlan- tic, it is developed at the entrance of the Caribbean Sea with perfect reg- ularity, like the range of the Aleutian Isles. Trinidad, Grenada, St. Vin- cent, St. Lucia, Dominica, Guadaloupe, Montserrat, Nevis, St. Kitts, and St. Eustatius are so many outlets of volcanic force, either through their smoking craters or their mud-volcanoes, their solfataras or their thermal springs. North and south of the Antilles, the eastern coast of America does not present a single vent of eruption. It is a remarkable fact that the two volcanic groups of the Antilles and the Sunda Islands are situa- ted exactly at the antipodes one of the other, and also in the vicinity of the two poles of flattening, the existence of which on the surface of the globe has been proved by the recent calculations of astronomers.” More than this, these two great volcanic centres, which are undoubtedly the most active on the whole earth, flank, one on the west and the other on the east, the immense curve of volcanoes which spreads round the Pacific. The Mediterranean is not surrounded by a circle of volcanoes; but there, as elsewhere, it is from the midst of the sea, or immediately on the sea-coast, that the burning mountains rise — Etna, Vesuvius, Stromboli, Volcano, Epomeo, and Santorin. In like manner, the volcanoes of mud and gas of the peninsula of Apcheron, and the summit of Demavend, 14,486 feet high, rise at no great distance from the Caspian Sea. With regard to the volcanoes of Mongolia—the Turfan, which is said to be still in action, and the Pe-chan, which, according to Chinese authors, vomited forth, up to the seventh century, “fire, smoke, and molten stone, which hardened as it cooled”f-their existence is not yet absolutely proved; but even if these mountains, situated in the centre of the continent, * See above, p. 14. f Chroniques Chinoises. Humboldt, Tableaux de la Nature. 432 THE EARTH, should be in full activity, their phenomena might depend on the vicinity of extensive sheets of water, for this very region of Asia still possesses a large number of lakes, the remnants of a former inland sea, almost as vast as the Mediterranean. What is the number of volcanoes which are still vomiting forth lava during the present period of the earth's vitality? It is difficult to ascer- tain, for often mountains have seemed for a long time to be extinct; forests have grown up in their disused craters, and their beds of lava have been covered up under a rich carpet of vegetation, when suddenly the sleeping force beneath is aroused and some fresh volcanic outlet is opened through the ground. When Vesuvius woke up from its protract- ed slumber to swallow up Pompeii and the other towns lying round its base, it had rested for some centuries, and the Romans looked upon it as nothing but a lifeless mountain like the peaks of the Apennines. On the other hand, it is very possible that some craters, from which steam and jets of gas are still escaping, or which have thrown out lava during the historic era, have entered decisively into a period of repose, ceasing some- how to maintain their communication with the subterranean centre of molten matter. The number of vents which serve for the eruption of lava can, therefore, be ascertained in a merely approximate way. Hum- boldt enumerates 223 active volcanoes; Keith Johnston arrives at the larger number of 270, 190 of which are comprehended in the islands and the Pacific “circle of fire;” but this latter estimate is probably too small. To the number of these burning mountains, standing nearly all of them on the sea-shore, or in the vicinity of some great fresh-water basin, must be added the salses, or mud-volcanoes, which are also found near large sheets of salt water. With regard to the thousands of extinct volcanoes which rise in various parts of the interior of continents, geology shows that the sea used formerly to extend round their bases. PL. XXI - VO LCAN O ES 20 -> --> 4o do tºo --- -20 zºo zºo rºo - ---> zoo. do 6a - * - --- -- - - - * - - –––f-i- - -- - spitzłekges - - º .* 3. * º --- - º -- - Vºcanoer are indºcated. * = ºl-----|- - - - - - &rred dota. *** --- --- - * - was ſ --- - ** l | | | | l ºt-º-º: a cºt Pan- 2a zºo do. —42– --- zzº ra roo - roo zºo do 4o - Drawn by A. Vuillemin - HARPER & B R OTHERS, NEW YORK Fingº by Frhard * FSCA PE OF STEAM FROM CRATE/ES. 43 3 CHAPTER LXIII. & TORRENTS OF STEAM ESCAPING FROM CRATERS.—GASES DIRODUCED IBY THE DECOMPOSITION OF SEA-WATER. — HYPOTHESES AS TO THE ORIGIN OF ERUIPTIONS. —INDEPENDENCE OF THE SEVERAL VOLCANIC OTTLETS. ONE of the most decisive arguments which can be used in favor of a free communication existing between marine basins and volcanic centres is drawn from the large quantities of steam which escape from craters during an eruption, and compose, according to M. Ch. Sainte-Claire De- ville, at least 999 thousandths of the supposed volcanic smoke. During the eruption of Etna, in 1865, M. Fouqué attempted to gauge approxi- mately the volume of water which made its escape in a gaseous form from the craters of eruption. By taking as his scale of comparison the cone which appeared to him to emit an average quantity of steam, he found this mass, reduced to a liquid state, would be equivalent to about 79 cubic yards of water for each general explosion. Now, as these ex- plosions took place on the average every four minutes during a hundred days, he arrived at the result, that the discharge of water during the con- tinuance of the phenomenon might be estimated at 2,829,600 cubic yards of water—a flow equal to that of a permanent stream discharging 55 gal- lons a second. Added to this, account ought to have been taken of the enormous convolutions of vapor which were constantly issuing from the great terminal crater of Etna, and, bending over under the pressure of the wind, spread out in an immense arch around the vault of the sky. In great volcanic eruptions it often happens that these clouds of steam, be- coming suddenly condensed in the higher layers of the atmosphere, fall in heavy showers of rain, and form temporary torrents on the mountain- sides. According to the statements of Sir James Ross, the mountain Ere- bus, of the antarctic land, is covered with snow, which it has just vomited forth in the form of vapor. It has besides been remarked that the vapor which issues from volcanoes is not always warm; often, according to Poep- pig, it is of the same temperature as the surrounding air. As was said long since by Krug von Nidda, a German savant, volca- noes must be looked upon as enormous intermittent springs. The ba- Saltic flows may be compared to streams on account of the water which they contain. It is probable that most of the lava which flows from vol- canic fissures owes its mobility to the innumerable particles of vapor which fill up all the interstices of the moving mass. Being composed in great measure of crystals already formed, as may be proved by an ex- amination of the cheires, in the body of which may be noticed nodules and crystals rounded by friction, the lava would be unable to descend E E 434 TLIE EARTII. {} over the slopes if it were not rendered fluid by its mixture with steam : and the gradual slackening in speed and ultimate stoppage of the flow are chiefly caused by the setting free of the gases which served as a vehi- cle to the solid matter. Owing to this rapid loss of their humidity, ba- salts contain in their pores but a very slight quantity of water in com- parison with other rocks.” Yet even old lavas themselves contain as much as 10 to 19 thousandths of water at the edges of the bed, and 5 to: 18 thousandths at the centre.} - The various substances which are produced from craters also tend to show that sea-water has been decomposed in the great laboratory of lava. Ordinary salt or chloride of sodium, which is the mineral that is most abundant in sea-water, is also that which is deposited the first and most plentifully round the orifices of cruption. Sometimes, the scoriae and ashes are covered for a vast space with a white efflorescence, which is nothing but common salt ; one might fancy it a shingly beach which had just been left by the ebbing tide. After cach eruption of IIecla, the Iceland- ers are in the habit, it is said, of collecting salt on the slopes. The lava from the eruption of Frumento, analyzed by M. Fouqué, contained about 13 ten thousandths of marine salt. Almost all the other component parts of sea-water are likewise found in the gases and deposits of fumerolles; only the salts of magnesia have disappeared, but still are found under another form among the volcanic products. Deing decomposed by the high temperature, just as they would be in the laboratory of a chemist, they go to constitute other bodies. Thus the chloride of magnesium is changed into hydrochloric acid and magnesia; the gas escapes in abundance from the fumerolles, while the magnesia remains fixed in the lava. As M. Ch. Sainte-Claire Deville was the first to ascertain with certain- ty, four successive periods may be observed in every eruption, each of which periods assumes a distinct character, owing to the exhalation of certain substances. After the first period, remarkable especially for ma- rine salt and the various compounds of Soda and potash, comes a second in which the temperature is lower, and during which brilliantly colored deposits of chloride of iron are formed and hydrochloric and sulphurous acids are expelled. When the temperature is below 392° (Fahr.), there are ammoniacal salts and needles of sulphur, which are found in yellowish masses on the scoriae of lava. Lastly, when the heat of the erupted bodies is below 212° (Fahr.), the fumerolles eject nothing but steam, azote, carbonic acid, and combustible gases. Thus the activity of the exhala- tions and deposits is in proportion to the incandescence of the lava. At the commencement of the eruption, the orifices throw out a large quan- tity of substances, from marine salt to carbonic acid; but by degrees the power of elaboration weakens simultaneously with the heat, and the gases * Poulett Scrope, Volcanoes. + Delesse, Bulletin de la Société Géologique de France, 1859. | Fouqué, Phénomènes Chimiques de l'Eruption de l'Etna en 1865. JEXHALATIONS OF WOLCANOES. - 435 ejected gradually diminish in number, and testify, by their increasing rarity, to the approaching cessation of volcanic phenomena. In conse: quence of the difference which is presented by the exhalations during the various phases of eruptions of lava, observers have, at first sight, thought that each volcano was distinguished by emanations peculiar to itself Hydrochloric acid was looked upon as one of the normal products of Vesuvius, and sulphurous vapors as more especial to Etna. It was stated (with Boussingault) that carbonic acid was exhaled specially by the Vol- canoes of the Andes; and, with Bunsen, it was believed that combustible gases prevailed in the eruptions of Hecla.” In his beautiful investigations into the various chemical phenomena presented by Etna and the neighboring volcanic outlets, such as Vesuvius and Stromboli, M. Fouqué appears to have established as a fact which must be henceforth beyond dispute, that the gradual series of these emanations is just that which would be produced by the decomposition of sea-water. Added to this, we also find in lava iodine and fluorine, both of which we should expect to detect in it on account of their pres- ence in sea-water. The salts of bromine, of which, however, only a slight trace is found in sea-water, have not yet been detected in volcanic prod- ucts, which, no doubt, proceeds from the difficulty which chemists have experienced in separating such very small quantities. - The other matters ejected by eruptions are of terrestrial origin, and evidently proceed from rocks reduced by heat to a liquid or pasty state; they consist principally of silica and alumina, and contain besides lime, magnesia, potash, and soda. Oxides of iron also enter into the composi- tion of lava, to the extent of more than one tenth, which is a very consid- erable proportion, and warrants us in looking upon the volcanic flows as actual torrents of iron-ore; sometimes, indeed, this metal appears in a pure state. It is to this presence of iron that lava especially owes its reddish color, and the sides of the crater their diversely colored sides. Compounds of copper, manganese, cobalt, and lead are also met with in lava; but, in comparison with the iron, they are but of slight importance. Lastly, phosphates, ammonia, and gases composed of hydrogen and car- bon, are discharged during eruptions. The presence of these bodies is explained by the enormous proportion of animal and vegetable matter which is decomposed in sea-water. Ehrenberg found the remains of ma- rine animalcula in the substances thrown out by volcanoes. Is the composition of the lava, and especially that of the vapor and gases, the same in those eruptions which take place at a great distance from the Ocean It is probable that, as regards this point, considerable differences might be established between the products of volcanoes placed on the Sea-coast, such as Vesuvius and Etna, and those which rise far in the interior of the land, as Tolima, Jorullo, and Puracé. This compara- tive study, however, which would be calculated to throw light on the chemical phenomena of deep-lying beds, has as yet been made at only a * Fouqué, Revue des Deux Mondes, August, 1866. 436 THE EARTH. few points. Eruptions are rare in volcanoes situated far from the coast, and when they do take place, scientific men do not happen to be on the spot to study the course of the occurrence. Popocatepetl, one of the most remarkable continental volcanoes, produces a large quantity of hy- drochloric acid; the snow from it, which has a very decided muriatic taste, is carried by the rain into the Lake of Tezcuco, where, in conjunc- tion with soda, it forms salt.* When the water, either of sea or rivers, penetrates into the crevices of the terrestrial envelope, it gradually increases in temperature the same as the rocks it passes through. It is well known that this increase of heat may be estimated on the average, at least as regards the external part of the planet, at 1° (Fahr.) for every 54 feet in depth. Following this law, water descending to a point 7500 feet below the surface would show, in the southern latitudes of Europe, a temperature of about 212° (Fahr.). But it would not on this account be converted into steam, but would remain in a liquid state, owing to the enormous pressure which it has to undergo from the upper layers. According to calculations, which are based, it is true, on various hypothetical data, it would be at a point more than nine miles below the surface of the ground that the expansive force of the water would attain sufficient energy to balance the weight of the superincumbent liquid masses, and to be suddenly converted into steam at a temperature of 800° to 900° (Fahr.). These gaseous masses would then have force to lift a column of water of the weight of 1500 atmospheres; if, however, from any cause, they can not escape as quickly as they are formed, they exercise their pressure in every direction, and ultimately find their way from fissure to fissure until they reach the fused rocks which oxist in the depths. To this incessantly increasing pressure we must, therefore, attribute the ascent of the lava into vent-holes of volcanoes, the occurrence of earthquakes, the fusion and the rupture of the terrestrial crust, and, finally, the violent eruptions of the imprisoned fluids. But why should the vapor thus pervade the subterranean strata and upheave them into volcanic cones, when, by the natural effect of its overcoming the columns of water which press it down, it ought simply to rise toward the bed of the sea from which it descended ? In the present state of Science, this is a question to which it seems absolutely impossible to give a satis- factory answer, and geologists must at least have the merit of candidly acknowledging their ignorance on this point. The discoveries of natural philosophy and chemistry, which have been the means Of making known to us the onormous activity of steam in volcanic eruptions, will doubtless, sooner or later, explain to us in what way this activity is exercised in the subterranean cavities. But at the present time the phenomena which are taking place in the interior of our globe are not better known to us than the history of the lunar volcanoes. + Virlet, Bulletin de la Société Géologique de France, May 1st, 1865. + Buff, Briefe über die Physik der Erde. f Otto Volger, Erdbeben der Schweiz. * CONNECTION OF VOLCANOES. 437 Be this as it may, the direct observations which have been made on volcanic eruptions have now rendered it a very doubtful point whether the lavas of various volcanoes proceed from one and the same reservoir of molten matter, or from the supposed great central furnace which is said to fill the whole of the interior of the planet. Volcanoes which are very close to one another show no coincidence in the times of their erup- tions, and vomit forth, at different epochs, lavas which are most dissimilar both in appearance and mineralogical composition. These facts would be tº: |A&_º - º § !, º, * * A. º ſº *** ºff [..."? //, Ž4. 40}=-ºš !º-ſº - - ***º-ºxº º: NSES:-->2<2%.NS) - - Fºx w 3." º Fº Ż:5S 22 ##### N #º s: š#% 30; § ºš *~! * }§ º ſºº i º ~ º I’ig. 173. Line of Fracture between Etna and Vesuvius. eminently impossible, if the craters were fed from the same source. Etna, the group of the Lipari Isles, and Vesuvius, have often been Quoted as be- ing volcanic outlets placed upon the same fracture of the terrestrial crust; and it is added, in corroboration of this assertion, that a line traced from the Sicilian volcano to that of Naples passes through the ever-active fur- nace of the Lipari Isles. Although the mountain of Stromboli, so regular in its eruptions, is situated on a line slightly divergent from the principal line, and, on the other side, the volcanic isles of Salini, Alicudi, and Feli- cudi tend from east to west, it is possible, and even probable, that Vesu- 438 THE E.A.R.T.H. vius and Etna are in fact situated on fissures of the earth which were once in mutual communication. But during the thousands of years in which these great Craters have been at work, no connection between their erup. tions has ever been positively certified. Sometimes, as in 1865, Vesuvius vomits forth lava at the same time as Etna ; sometimes it is in a state of repose when its mighty neighbor is in full eruption, and rouses up when the lava of Etna has cooled. There 1S nothing Which affords the slightest indication of any law of rhythm or Periodicity in the eruptive phenomena of the two volcanoes. The inhab- * ,-\, tº e ~ t - * * - •: * - t -- w - itants of Stromboli state that, during the winter of 1865, at the moment . - e - - ºw e * * & When the sides of Etna were rent, the volcanic impulse manifested itself very strongly in their island by stirring up the always agitated waves of the lava-crater which commands their vineyards and houses. A com- parative calm, however, soon succeeded this temporary effervescence, and in the adjacent island of Volcano no increase of activity was noticed. If * * * le i N4 -. Y Q. & 4 - - & * * * © tº the shafts of Etna, Vesuvius, and the intervening volcanoes, take their rise in one and the same ocean of liquid lava, all the lower craters must necessarily overflow simultaneously with the most elevated. Now, as has often been noticed, the lava may ascend to the summit of Etna, at a height of 10,827 feet, without a simultaneous flow of rivers of molten Sºğsº gºšss - gº § §§§ $º §§ §§§ §NR&S §§§§§§§ §§§ses ** ... vº. *. º, NY - §§§ SSSSSº º: *NSN.J. :: ***NSSN& SºğSºg: º *ššš §§§ SSSSSSSSSS.S. Stº **ś Y'S', ... ... "..… • * * “. . . º. §§§ * - “s = - ...Nº." Fig. 174. Section of the Island of IIawaii. stone from Vesuvius, Stromboli, and Volcano, which are respectively but One third, one fourth, and one tenth the height of the former. In like manner, IXilauea, situated on the sides of Mauna-Loa, in the Isle of Hawaii, in no way participates in the eruptions of the central crater opening at a point 9800 feet higher up, and not more than 12 miles away. If there is any present geological connection between the volcanoes of one and the same region, it probably must be attributed to the fact of their phenome- na depending on the same climatic causes, and not because their bases penetrate to one and the same ocean of fire. Volcanic orifices are not, therefore, “safety-valves,” for two centres of activity may exist on one mountain without their eruptions exhibiting the least appearance of con- nection.* - Isolated as they are amid all the other formations on the surface of the carth, lavas appear as if almost independent of the rest. Dasalts, tra. chytes, and volcanic ashes, are the comparatively modern products which are scarcely met with in the periods anterior to the Tertiary age. Only a very small quantity of these lavas of cruption has been found in the Secondary and Palaeozoic rocks. I'ormerly, most geologists thought that the granites and rocks similar to them had issued from the earth in a pasty or liquid state; they looked upon them as the “lavas of the past,” * Dana, Proceedings of the American Association, 1849. ORIGIN OF WOLCANOES 439 and believed that these first eruptive rocks were succeeded in age after age by the diorites, the porphyries, the trap-rocks, then by the trachytes and the basalts of our own day, all drawn from a constantly increasing depth. They thought also that, in the future, when the whole series of the present lavas shall have been thrown up to the surface, volcanoes would produce other substances as distinct from the lavas as the latter are from the granite. Granites, however, differ so much from the tra- chytes and basalts as to render it impossible for us to imagine that they have the same origin; added to which, the labors of modern Savants have proved that, under the action of fire, granite, and the other rocky masses of the same kind, would have been unable to assume the crystalline tex- ture which distinguishes them. We are, then, still ignorant how volcanic eruptions commenced upon the earth, and how they are connected with the other great phenomena which have co-operated if the formation of the external strata of the globe. 440 THE EARTH, CHAPTER LXIV. GROWTH OF WOLCANOES. — THEORIES OF HUMIBOLDT AND LEOPOLD WON IBUCH AS TO THE UPHEAVAL OF CRATERS. — DIS AGREEMENT OF THESE THEORIEs witH THE FACTs obsBRVED. CoNSIDERED singly, each volcano is nothing but a mere orifice, tempo- rary or permanent, through which a furnace of lava is brought into com- munication with the surface of the globe. The matter thrown out accu- mulates outside the opening, and gradually forms a cone of débris more or less regular in its shape, which ultimately attains to considerable di- mensions. One flow of molten matter follows another, and thus is grad- ually formed the skeleton of the mountain; the ashes and stones thrown out by the crater accumulate in long slopes; the volcano simultaneously grows wider and higher. After a long succession of eruptions, it at last mounts up into the clouds, and then into the region of permanent snow. At the first outbreak of the volcano the orifice is on the surface of the ground; it is then prolonged like an immense chimney through the cen- tre of the cone, and each new river of lava which flows from the summit increases the height of this conduit. Thus the highest outlet of Etna opens at an elevation of 10,892 feet above the level of the sea; Teneriffe rises to 12,139 feet; Mauna-Loa, in IIawaii, to 13,943 feet; and, more gigantic still, Sangay and Sahama, in the Cordilleras, attain to 18,372 and 23,950 feet in elevation. r - This theory of the formation of volcanic mountains by the accumula- tion of lava and other matters cast out of the bosom of the earth presents itself quite naturally to one's mind. Most savants, from Saussure and Spallanzani down to Virlet, Constant Prévost, Poulett Scrope, and Lyell, have been led, by their investigations, to adopt it entirely ; indeed, in the present day it is scarcely disputed. It is true that Humboldt, Leo- pold von Buch, and, following them, M. Elie de Beaumont, have put forth quite a different hypothesis as to the origin of several volcanoes, such as Etna, Vesuvius, and the Peak of Teneriffe. According to their theory, volcanic mountains do not owe their present conformation to the long- continued accumulation of lava and ashes, but rather to the sudden up- heaval of the terrestrial strata. During some revolution of the globe, the pent-up matter in the interior suddenly upheaves a portion of the crust of the planet into the form of a cone, and opens a funnel-shaped gulf be- tween the dislocated strata, thus by one single paroxysm producing lofty mountains, as we now see them. As an important instance of a crater thus formed by the upheaval and rupture of the terrestrial strata, Leo- pold von Buch mentions the enormous abyss of the Isle of Palma, known FORMATION OF CR.4 TERS. 441 º by the natives under the name of “Caldron,” or Caldera. This funnel- shaped cavity is of enormous dimensions, and is not less than four or five miles in width on the average; the bottom of it is situated about 2000 feet above the level of the sea. Tofty slopes, from 1000 to 2000 feet in height, rise round the vast amphitheatre, and abut upon inaccessible cliffs, j}. Hºº§ , 9 §% º 3. Sº § tº 2:…º.º.º. º º cº 5 #: º % º *** Ş º 3% &% 3.4 º N - łºś. ºš * º º º - 3. §§§ g §§ $2S 2 £ºff." º º zºna º 3:3# #$$$$$$º º §§§ ū º §§§ § Wyº; §§ Lath % º º: & º %:#. §§§ i) § - jº. Sº - % #º W º §º # ; sº %2. % - É% ğ. ſº §§ §§ º sº %2. y} ğ. §º S § gº -- Fig. 175. Isle of Palma. the upper ledges of which reach a total altitude of 5900 to 6900 feet in height. The highest point, the Pico-de-los-Muchachos, is covered by snow during the winter months; and although it penetrates into regions of the atmosphere which are of a very different character from those of the rest of the island, the slope that is turned toward the crater is so steep that 4:42 THE EARTH, blocks of stone falling from the summit roll down into the inclosed hollow. The prodigious cavity in the Isle of Palma was, perhaps, the most strik- ing instance that Leopold von Buch could bring forward in favor of his hypothesis; nevertheless, the exploration of this island, since carried out by IIartung, Lyell, and other travelers, is very far from confirming the ideas of the illustrious German geologist. The lofty side-walls of the hollow appear to be formed principally, not of solid lava, which consti- tutes scarcely a quarter of the whole mass, but of layers of ashes and scoria, regularly arranged like beds of sand on the incline of a talus. Basalts and strata of ashes lie upon one another in the greatest order round the inclosed hollow, which would be a fact impossible to comprehend if any sudden upheaval, acting in an upward direction with sufficient vio- lence to break the terrestrial crust, had shattered and ruptured all the strata, and, by a mighty explosion, opened out the immense Caldron of Palma. Finally, if a phenomenon of this kind had taken place, star- formed cracks, like those produced in broken glass, would be visible across the thickness of the upheaved strata, and their greatest width would be turned toward the crater. Now there are no fissures of this kind, and the ravines in the circumference of the volcano, which one might perhaps be tempted to confound with actual ruptures of the ground, become wider in proportion as they approach the sea. The enormous cavity in T’alma is, therefore, a crater similar to those of volcanoes of less dimen- sions. It is, however, certain that the Caldera was once both shallower and less in extent, for the ashes and volcanic scoriae are easily carried away by the rain, which is swallowed up in the bottom of the basin, and has hollowed out for itself a wide drainage-channel in a southwest direction. º # º co sº *= Fig. 176. Section of the Island of Palma from Southeast to Northwest. i M. Elie de Beaumont, as his chief support of Leopold von Buch's hy- pothesis, brought forward the fact that most of the strata of lava-a sec- tion of which may be seen on the sides of Etna, in the immense amphi- theatre of the Val del Bove—are very sharply inclined. The celebrated geologist affirmed that thick sheets of molten matter could not run down steep slopes without being very soon reduced, in consequence of the ac- celeration of their speed, into thin layers of irregular scoria. If this Were really the case, the position of the thick flows of lava in the Val del Bove must have changed since the date of the eruption; it would then be necessary to admit that they have been violently tilted up after having been originally deposited on the soil in sheets, which were either horizon- TVOLCANO OF JOBULLA. 443 tal or very gently sloped. Nevertheless, the recent observations made by Sir C. Lyell, those of Darwin on the cones of the Gallapagos Isles, and of Dana on the lava flows of Kilauea; lastly, the remarks of the Italian * wants who studied on the spot the volcanic phenomena of Vesuvius and Etna, have satisfactorily proved that, in modern times, a great number of rivers of lava, and especially that of the Val del Bove, in 1852 and 1853, have flowed over steep slopes varying in inclinations from 15 to 40 de- grees. It must, besides, be understood that the lava which poured over the steepest slopes was exactly that portion which, not having experi- enced any cause of delay, or met with any obstacle, in its course, presented layers of the most uniform consistence and the most regular action. 4 Z.º. a %as SS J.Sººº...º. $: > ºw Ç ºS Š Yº º §§ --- 㺠§§ ºWNº. -14–-º- * 㺠# § #sº - 62 § & --Fi:::::::== #& S- Z ſº %:# §§ Š #! S * -*=-s: * * * :º- \ $$Wyº Š / \\ ºſlº º º: 㺠#=% & * . ſº I-ºº: - ;, §). º º % f sº sº * %|/? #ji=T J:ſt-1"/ º s º \ º § . à FT-- º \ ºº::#T sººf º º º º \\ § º ! % º §§ Fig. 177. Volcano of Jorulla, Mexico. One of the strongest arguments of scientific men in favor of the theory of upheaval is, that certain volcanic mountains, especially that of Monte- Nuovo, of Pouzzoles, and Jorullo, in Mexico, had been suddenly raised up by the swellings of the soil. Now the unanimous testimony of those who, more than three centuries ago, witnessed the eruption of Monte- Nuovo is, that the earth was cleft open, affording an outlet to vapor, ashes, scoriae, and lava, and that the hill, very much lower than some of the subordinate cones of Etna, gradually rose during four days by the heaping up of the matter thrown out. The total volume of this eruption 444 - THE EARTH, was no doubt considerable, but compared with the amount of matter which flowed down upon Catania in 1669, or with the rivers of lava from Skaptar-Jokul, it is a mass of no great importance. Added to this, if the soil was really upheaved, how was it that the neighboring houses were not thrown down, and that the colonnade of the Temple of Neptune, which stands at the foot of the mountain, kept its upright position ? With regard to Jorullo, which rises to a height of more than 1650 feet, the only witnesses of this volcano making its first appearance were the Indians, who fled away to the neighboring heights, distracted with terror. We have, therefore, no authentic testimony on which we can base an hy- pothesis as to any swelling up of the ground in the form of a blister. Quite the contrary, the travelers who have visited this Mexican volcano since Humboldt have discovered beds of lava lying one over the other, as, in all other cones of eruption; and more than this, they have also ascer- tained that none of the strata in the ground overlooked by the mountain have been at all tilted up.”. It is true enough that local swellings have often been observed in the burning matter issuing from the interior of the earth; in many places the lava is pierced by deep caverns, and entire mountains—especially that of Volcano—have so many hollows in the rocks on their sides that every step of the climber resounds on them as if on a vault. Besides, the lava itself, being a kind of impure glass, is so pervaded by bubbles filled with volatile matter that, when acted upon by fire, so as to expel the water and the gas, it loses on an average, according to Fouqué, two thirds of its weight. But these caverns, these hollows and bubbles, proceed from the mixture of the lava with vapor which is liberated with difficulty from the viscous mass, or are caused by the longitudinal rupture of the strata dur- ing an eruption, and can in no way be compared to the immense blister- like elevation which would be formed by the strata of a whole district being tilted up to a height of hundreds, or even thousands, of yards, leav- ing at the summit, between two lines of fracture, room for an immense cavity. - None of these prodigious upheavals have been directly observed by geologists, and none of the legends invented by the fears of our ancestors, referring to the sudden appearance of volcanic mountains, have been since confirmed. Lastly, the very structure of the peaks which are said to have risen abruptly from the midst of the plains testifies to the gradual accumulation of material that has issued from the bowels of the earth. It is, therefore, prudent to dismiss definitively an hypothesis which marks an important period in the history of geology, but which, for the future, can only serve to retard the progress of science. * Arnold Boscowitz, Les Volcans et les Tremblements de Terre. ARRANGEMENT OF WOLCANIC OUTLETS. 445 CHAPTER LXV. NUMBER AND ARRANGEMENT OF VOLCANIC OUTLETS.–FORM OF WOL- CANIC CONES AND CRATERS. As, when the burning matter seeks an outlet, the earth is generally cleft open in a straight line, the volcanic orifices are frequently distributed somewhat regularly along a fissure, and the heaps of erupted matter fol- low one another like the peaks in a mountain chain. In other places, how- 2.58 ° .30' ..’ p.” Gºº º'Sº SNN ºft,7%.S. cºśW \ iſlº §§ § % % §§§º §§4%º .####jºšćº *ś ºg ºftº ..? & o 3. Žºr 2%, , , "," res, º, § 22. * * * * - , -, *, 'º' ºf 3 º ż ż 2 & $º: º $: Y. ſ * ; ... §§ sº .. §: ex ºf º ** ź ºśſº $º §§§3. Y', \ Hy . is §§ ; : *ś º ſº ‘,-3::::::$ºğ% ::3% *] ºf ºf 3:3% ...: Šiš * . ... tº ;i& §§ # º ºść ~ : *, r*. -ºšš. 5.x:". : ; 2 º’. §§ Pºi ºf $ * * * . . . .,..., " " ' "". §§§ º : * . . . . . . . . . . . . . . . . . . . . . . . ...; §§ º l . .'; ... : * ~ * -- tº º NS$;. :*r- ºve.º. | ". . * ºrsº: *} Hº: ". . .”....Jº'º, º, ºr 8. $. -: … • ‘,-- º % £º *** §§. & º:3 º $º º º ..ºf * º ºšščğ% º * * Zº 3.39. - ***** \\ c e - Nº.2 º'e $3. š § tºil ºğsº Fºo (; 3$: §: NSN f º .*.* § N W % |||} * ; º; × 8: § § % $4%; §§3 ºs § |ft %; *::\, .: § º 23:2 332 tº $3.5 ºf §§ - ££º K9 &’; &== § º' - º - - J - *-, -, -º- - - - #3-s 32"|Sº º §§§St. J Sºlà- &. D Š §§§ SY-SNS SESE (3 AE •. 3r ... º.º. # * . . . J. Sºsº, sº *ś §§§§§ .2%. ſ §§ §§§, Żºłº jº §§§ §§§ § ºš §§§ '...}} tº % - * * º: *S. &ſº i,'º', º: ſ §§§: §º'3 jºššº ſº §§§ ** {} º § wº §§§ §§§. ś 3. §§ \ W ſ §N ſº :*: § § Ş. ºs ºjº WN |WiſſMN §i) § Älſº º Sºjº: o's gº s - § D §§§ *...* * : * - º [. ſº wn ºnvon - §: "|ſº \ §§ NS |\ §º 4 ...!!!" \\ \ N \ w |N | \\ |\ Nº z38°, \ 36 - - - Fig. 17S. Series of Craters, Hawaii. ever, the volcanic cones rise without any apparent order on ground that is variously cleft, just as if a wide surface had been softened in every di- rection, and had thus allowed the molten matter to make its escape, some- times at one point, sometimes at another. From the town of Naples— which is itself built on half a crater in great part obliterated—to the Isle of Nisida, which is an old volcano of regular form, the Phlegraan Fields present a remarkable example of this confusion of craters. Some are perfectly rounded, others are broken into, and their circle is invaded by the waters of the sea: grouped, for the most part, in irregular clumps, even encroaching upon one another and blending their walls, they give to the whole landscape a chaotic appearance. As Mr. Poulett Scrope very justly remarks, the aspect of the terrestrial surface at this spot reminds 446 THE EARTH. one exactly of the volcanic districts of the moon, dotted over, as it is, with CraterS. As the type of a region pierced all over with volcanic orifices, we may also mention the Isthmus of Auckland, in New Zealand, where Dr. Hoch- *s 172°30' º # s sº : } º ſ w † 0. Z % % º º º º º: -ºf #! ...sº º ºğ * g ºv. ', §§ g * *}. % º, sº §§§ * {jº .R. * te - *alſ, 33% % }:k ** g4. s& %g - #: 2. * à i & % §§ Sºlº ſºft § º §§§ W i’s º } º Žº § º § - º: § §§ *ś º §3. º ºr § §§§ º NII Wººtº 3 ºº: Tºº ſº ſº Ö &#& B §º § gº Sº 2. O)5 Hºº. Fº § %}}ºlyE ź º's, º/, ºfº'º. § º ; º #. º § § § º ºf ºf 3 & § §§ § º Śāš. % * º, - - §§. $ºrº r § >†SS$%: =\\ §§§ |- 2: .. - §§ sº * * % º *** º: º ºntº-º: 4 ºf * § r 33 2.3% & §: sº * º & t §§§ ey. Rºt} º §/º f §§W: 9 Hºr tº º: § f §§ º N % #3; º [. t ºf º |||ſº § º w º ſº r ºš \jºš | §§ Fig. 179. Auckland and its Volcanoes. mº stetter has reckoned, in an area of 230 square miles, sixty-one independ- ent volcanoes, 520 to 650 feet in height on the average. Some are mere cones of tufa ; others are heaps of scoriae, or even eruptive hillocks, which have shed out round them long flows of lava. At one time the Maori chiefs used to intrench themselves in these craters as if in citadels; they escarped the outer slopes in terraces, and furnished them with palisades. At the present day, the English colonists, having become lords of the soil, have constructed their farms and country houses on these ancient volca- noes, and are constantly bringing the soil under cultivation.” The Safa, in the Djebel-IIauran, is also a complete chaos of hillocks and * Ford. von IIochstetter, Neu-Seeland. darkish-colored glass. DISPOSITION OF CRATEES. 447 abysses. On this plateau of 460 square miles, which the Arabs call a “ portion of hell,” almost all the craters open on the surface of the ground, and not on the summits of volcanoes scattered here and there on the black \ & |É. § vº" sº § S& Fig. 180. Cone of Tuſſ. Fig. 181. Cone of º sº ſ N º £&^{#3> Tuſt, and Crater of Scoriae. surface. In every direction there may be seen rounded cavities like the vacuities formed in scoriae by bubbles of gas, only these cavities are 600 to 900 feet wide, and 65 to 100 feet deep. Some are isolated; some either touch or are separated by nothing but narrow walls like masses of red or One hardly cares to venture on these narrow isth- muses, bordered by precipices, and intersected here and there by fissures.* The normal form of the volcanoes in which the work of eruption takes place is that of a slope of débris arranged in a circular form round the out- let. Whether the volcano be a mere cone of ashes or mud only a few yards high, or rise into the regions of the clouds, vomiting streams of lava Y N N * \ ! §: S$ SS N sº x *NS-JºS Š § ~§ Š s §§ -*T-SS sº Š *- # ...--"#= ~ > §. at-º. . - º: a ºž ##3% a 2:# à 23°2%, is Z3. º º M \ s s ) \ : 1* . / | | \ | | • \ §§ Š ºšš º *...º. .." § § \ W | | W / §5 § N % % % % % a. Declivities of Tuff. b. Cone of Lava. c. Pyramid of Scoriae. * Wetzstein, Zeitschrift für Erdkunde, 1859. 448 THE EARTH, f Over an extent of 10 or 20 miles, it none the less adheres to the regular form so long as the eruptive action is maintained in the same channel, and the débris thrown out falls equally on the external slopes. The beauty of the cone is increased by that of the crater. The term- inal orifice from which the lava boils out well deserves, from the purity of its outline, its Greek name of “cup,” and the harmony of its curve con- trasts most gracefully with the declivity of the slope. In some volcanoes the symmetry of the architectural lines is so complete that the crator it- self contains a cone placed exactly in the centre of the cavity, and pierced by a second crater in miniature, from which vapor makes its escape. Volcanoes in which the eruptive action frequently changes its position —and these are the more numerous class—do not possess this elegance of outline. Very often the upheaved lava finds some weak place in the walls of the crater; it hollows them out at first, and then, bringing all its weight to bear on the rocks which oppose its passage, it ultimately completely breaks down the edge of the crater, leaving perhaps only one side stand- ing. Among the European volcanoes, Vesuvius is the best example of § º º sº º j}\} % |\}.} º | §§º W º | tº M º § ſº \!\!\!\!\!\!º §§ § º º § º | W ‘. . * º º º % ź º % 2%% , snº i. §ll |%| § §§ º % § - % 1. º § .* 22 * º #. º º s º'Nº.- i *Nº º ºg 'll; | | t . . . º ‘. . | \\ 'i/}}iº,' ' || | ... I ºf ! ! . . . . ! . \\\ º AnnunziºW - §§s - O ...ſtancr %. Pony % - % % ///.2% / * % Fig. 183. Mount Vesuvius. these ruptured craters: before A.D 79, the escarpments of La Somma, which now surround with their semicircular rampart the terminal cone FORM OF WOL CALNOES. 449 of Vesuvius, were the real crater. The portion of it which no longer ex- ists disappeared, and buried under its débris the towns of Herculaneum and Pompeii. Active volcanoes, however, never cease to increase in all their dimen- sions, and sooner or later the breach is ultimately repaired; the remains of the former craters are gradually hidden under the growing slopes of the central cone. Thus a former crater on Etna, which was situated at a point three miles in a straight line from the present outlet, at the com- mencement of the Val del Bove, has been gradually obliterated by the lava of successive eruptions: prolonged explorations on the part of MM. Seyell and Waltershausen have been necessary in order to find it out. The nor- mal form of Etna is that of a cone of débris placed upon a large dome with long slopes, becoming more and more gentle, and descending gracefully toward the sea. In fact, in most of the eruptions, the lava does not rise as far as the great crater, and breaks through the sides of the volcano so as to flow laterally over the flanks of Etna. These eruptions, succeeding one cºš Fig. 185. Section of Etna from West to East. another in the course of centuries, bring about the necessary result of grad- ually enlarging the dome which constitutes the mass of the mountain, thus breaking the uniformity of the lateral talus. The same thing occurs with regard to Vesuvius on the side which faces the sea-coast. There, too, the terminal cone stands on a kind of dome, which has been gradually formed by the coats of lava running one over the other. If Vesuvius continues to be the great volcanic outlet of Italy, and rises gradually into the sky by ,6:2% º % gº : ..., . §º §: º ... Nºw,' … tº ... .º.º.º.º.º.º.º. r sº ºr sº tºº as º 4°ºn.-vº sº Fig. 1S6. Mount Orizaba. F F 450 THE EAIETEI. the superposition of lava and ashes, it can not fail, some time or other, to assume a form similar to that of the Sicilian giant. The volcanoes which present cones of almost perfect regularity are those which have their terminal outlet alone in a state of activity, and vomit out a large quantity of ashes or other matter which glides readily over the slopes. Among this class of mountains, those which attain any consider- able elevation are distinguished by their majesty from all other peaks. Stromboli, although it is not more than 2600 feet in height, is one of the wonders of the Mediterranean. From its proud form, it will readily be understood that its roots plunge down into the sea to an enormous depth; / àºjºſ.' #|| ~. .* gº º tº | º hº g º º Fig. 187. Profile of Orizaba. the slope of débris may be seen, so to speak, prolonged under the Water down to the abysses of 3000 to 4000 feet, which the sounding-line has reach- ed at the bottom of the AEolian Sea. At sight of it one feels as if suspend- cd in the midst of the void, as if the ship was sailing in the air midway up the mountain. This feeling of admiration mingled with dread increases FORM OF VOLOANOE'S. r 451 when this great pharos of the Mediterranean is approached during the night over the dark-waved sea. Then the sky above the summit seems all lighted up by the reflection of the lava, and a misty band of clouds and va- por may be dimly seen girdling round the body of the volcano. In the daytime the impression made is of a different character; but it is none the less deep, for the real grandeur of Stromboli consists not so much in the immensity of the mass as in the harmony of its proportions. Volcanic mountains of an ideal form are those which infant nations have most adored. Among these sacred mountains are the sublime Cotopaxi of the Andes, Orizaba of Mexico, Mauna-Loa of Hawaii, and Fusi-Yama of Japan. The volcanoes of Java, and chiefly those in the eastern portion of Fig. 1SS. Volcanoes of Java. the island, also present a very majestic appearance on account of their iso- lation. Those on the western side are based upon an undulating plateau, which causes them to lose their appearance of height; but on the east all the volcanic mountains rise up from verdant plains like islands above the waves of the sea, and command the horizon far and wide with their Gnor- mous cones. Between the Merapi and Lavoe mountains lies a depression, the highest ledge of which exceeds the level of the sea by only 312 feet. Between Lavoe and Willis the plain is 230 feet in height. Lastly, the plains which separate the Willis and Kelocet mountains nowhere attain an elevation of more than 200 feet above the ocean.* In the external details of their conformation many of the volcanoes of Java present a regularity of outline which is all the more striking, since they owe it in great part to the monsoon rains, the most destructive agents of the tropical regions. In beating against the mountains, the clouds let fall their burden of moisture on the slopes composed of ashes and loose scoriae. The latter offer but a slight resistance to the action of the temporary torrents which carry them away, and, crumbling down into the plains which surround the base of the volcano, are deposited in long slopes, like those caused by avalanches. In consequence of the fall of all this débris, the sides of the mountain are cut out at intervals by ra. * Junghuhn, Java, seine Gestalt wnd innere Bawart. 452 THE EARTEI. vines or furrows, which gradually widen from the summit to the base of the mountains, and attain a depth of 200, 600, and 660 feet. There are some volcanoes, such as the Sumbing, in which these ravines assume so perfect a regularity that the whole mountain, with its equidistant furrows and its intermediate walls, resembles a gigantic edifice based upon enor- mous buttresses, like the nave of a Gothic cathedral.” Formerly the beauty of the island and the fury of its volcanoes were the cause of its being altogether dedicated to Siva, the god of destruction; and in the very craters of the burning mountains the worshipers of Terror and Death were in the habit of building their temples. In many spots the ruins of these sanctuaries are discovered in the midst of trees and thickets, which the Arab conquerors have left to grow in the formidable cavities of the volcanoes. Semeroe, the loftiest peak in the island, was the sacred mountain par eaccellence ; the Sumbing, which rises in the centre of the island, was the “nail which fastens Java to the earth.” Even in our own time some faithful followers of Siva inhabit a sandy plain, more than four miles wide, which was once the crater of the Tengger volcano; every year they proceed solemnly to pour rice on the summit of an eruptive cone, into the roaring mouth of the monster. In like manner, in New Zealand, the ever-smoking orifice of Tongariro was considered as the only place worthy of receiving the dead bodies of their great chiefs: when cast into the crater, the heroes went to sleep among the gods. But the volcanic divinities, like most of the other rulers invoked by na- tions, did not content themselves with the fruits of the earth or the com- panionship of a few warriors; they also demanded blood, both by their subterranean roarings, by their thundering eruptions, and their devasta- ting rivers of lava. Innumerable sacrifices have been offered to volcanoes to appease their anger: impelled by a mingled feeling of fear and ferocity, the priests of not a few religions have cast victims with great pomp into the gaping hollows of these immense furnaces. Scarcely three centuries ago, when the disciples of Christianity were exterminated over the whole length and breadth of Japan, the followers of the new religion were thrown by hundreds into one of the craters of the Unsen, one of the most beauti- ful volcanoes of the archipelago; but this offering to the offended gods did not appease their anger, for, toward the end of the eighteenth century, this very same mountain and the neighboring summits caused by their eruptions one of the most frightful disasters of any that are mentioned in the history of volcanoes. Actuated by a feeling of dread very similar to that exhibited by the Japanese priests, the Christian missionaries in Amer- ica recognized in the burning mountains of the New World not the work of a god, but that of the devil, and went in procession to the edge of the craters to exorcise them. A legend tells how the monks of Nicaragua climbed the terrible volcano of Momotombo in order to quiet it by their conjurations; but they never returned: the monster swallowed them up. * Arnold Boscowitz, Volcans et Tremblements de Terre. COMPOSITION OF LA VAS. 453 CHAPTER LXVI. COMPOSITION OF LAVAS ; TRACIIYTES; PUMICE-STONE ; OBSIDIAN ; BASALTS ; BAS ALTIC COLONNADES. Lava is the most important product of the volcanic fires. The various kinds of lava differ very much in their external appearance, in the color of their substance, and in the variety of their crystals, but they are all composed of silicates of alumnia or magnesia, combined with protoxide of iron, potash or soda, and lime. When the feldspathic minerals pre- dominate, the rock is generally of a whitish, grayish, or yellowish hue, and receives the name of trachyte. When the lava contains an abun- dance of crystals of augite, hornblende, or titaniferous iron, it is heavier, of a darker color, and often more compact; it then takes the generic for- mation of basalt. Numerous varieties, diversely designated by geologists, belong to this group. Of all the lavas, trachyte is the least fluid in its form. In many places rocks of this nature have issued from the earth in a pasty state, and have accumulated above the orifice in the shape of a dome, “just like a mass of melted wax.” In this way were formed the great domes of Auvergne, the Puys de Dôme and de Sarcouy. In this district the flows of trachytic lava are far inferior in length to the basaltic cheires ; the most important do not exceed four or five miles in length. At the present day, eruptions of trachyte are much more rare than those of other lavas; so much so, that certain authors class all the trachytic rocks among the formations of anterior ages. It is, however, ascertained that most of the American vol- canoes and those of the Sunda Archipelago vomit out lava of this nature; the last eruptions of the AEolian Isles, Lipari and Volcano, likewise pro- duced only trachyte and pumice-stone. This latter substance resembles certain white, yellow, or greenish sco- riae, which issue like a frothy dross from the furnaces of our iron-works, and is, like the compact trachyte, of a feldspathic nature. Some moun- tains are almost entirely composed of it; among others, the Monte Bianco of Lipari, which, viewed from a distance, appears as if covered with snow. Long white flows, like avalanches, fill up all its ravines, from the summit of the mountain to the shore of the Mediterranean; the slightest move- ment caused by the tread of an animal or a gust of wind detaches from the surface of the slope hundreds of stones, which bound down to the foot of the incline, and are borne away by the waves which bathe the base of the mountain. In the southern part of the Tyrrhenean Sea, and especially in the vicinity of the Lipari (AEolian) Islands, the water is sometimes cov- * Poulett Scrope, Volcanoes; the Character of their Phenomena, etc. ºt 454 THE EAAETH. ered with these floating stones, almost like flakes of foam. In the Cordil- leras the currents of fresh water convey the morsels of pumice to consid- erable distances. The River Amazon drifts down large quantities of pumice as far as its mouth, more than 3000 miles from the place where it fell into the river. Bates says that the Indians, who live too far away from the Volcanoes even to know of their existence, assert that these stones, floating down the river by the side of their canoes, are assuredly solidified foam. The external appearance of various lavas differs even more than their chemical composition. The more or less perfect state of fluidity, and the presence in them of a greater or less quantity of bubbles of Vapor, give a very different texture to rocks which are composed of the same elements. Pumice-stone has the appearance of sponge; obsidian looks like black glass, and sometimes even it is semi-transparent. It is entirely liquid, and issues from the interior of the earth like a stream flowing rapidly over the steeper slopes, and coagulating slowly in large sheets in the low ground and on the gentle inclines whither its own weight has drawn it. The surface of obsidian—for instance, that of Teneriffe—shines with a vit- reous glitter; the cleavage of the rock is clean and sharp. Some less degree of fluidity in the current of lava gives it sometimes the appearance of resin; this is the stone which is called pechstein (pitch- stone). When the rock, issuing in a state of fusion from the bosom of the mountain, becomes still cooler, it contains innumerable perfectly-formed crystals, and only owes its fluidity to the particles of vapor in its pores. The external layer of the lava is also immediately covered with scoriae which float in flakes on the fiery stream. These scoriae, too, assume a great variety of shapes; some are mammillated, others are exceedingly rough and irregular. In the Djebel-Hauran, near the crater of Abu-Ga- mim, there is an infinity of needles of red lava, about a yard high on the average, and bent in various directions toward the surface of the plateau; one might often fancy them flames half beaten down under the pressure of the wind. According to M.Wetzstein, these strange stone needles pro- ceed from an eruption of flaky lava. In the Sandwich Islands, and in the Island of Réunion, certain crystals of a ferruginous appearance are group- ed at the outlet of the crater in herbaceous forms of the most curious and sometimes elegant character. Some of the products of the volcano of Mauna-Loa and Kilauea resemble the tow of hemp ! These are the whit- ish filaments which are sometimes carried away by the wind; the Kanakes used to consider them as the hair of Pele, the goddess of fire. Among the old basaltic lavas there are some to which the name of basalt is more specially applied, which present a columnar disposition with wonderful regularity. These form the enormous monuments, much more imposing than those of man, which seem as if they had been constructed by giant builders, turning their mighty hands to the noble art of archi. tecture, which is still practiced, though on a smaller scale, by us their feeble descendants. These magnificent colophades of basalt are every 5 ISASALTIC COLUMNS. 45 f { | W § z §§ º \\ | \ &, Nºss-ºf-E: tº sº §§ --> -- 73%/iWRSS sºil! \ Fig. 180. Flow of Vitreous Lava at Mauna-Loa. where attributed to giants. In Ireland, on the coast of Antrim, the sum- mits of 40,000 prisms, leveled pretty regularly by the waves of the sea, and resembling a vast paved quay, have received the name of the Giant's Causeway. In Scotland, the beautiful cave of the Isle of Staffa, hollowed out by the action of the waves between two ranges of basaltic shafts, is celebrated as the work of Fingal, the demigod. In the Sicilian Sea, the Faraglioni Isles, or Isles of the Cyclopes, situated not far from Catania, at the base of Etna, are looked upon by tradition as the rocks cast by Poly- phemus on the ships of Ulysses and his companions. Many of these prisms are from 100 to 160 feet high, and are not less than 6 to 10 feet in thick- mess. Near Fair Head and the Giant's Causeway some of the shafts con- nected with the perpendicular cliff of the headland are nearly 400 feet in height. In the Isle of Skye, some of the columns, according to M'Cul- loch's statement, are still higher. On the other hand, there are also col- onnades in miniature, each shaft of which is not more than three quarters of an inch to an inch from the summit to the base; instances of these are found in the basalts of the hill of Morven in Scotland. Some geologists have thought that basaltic columns could not be form- ed except under the pressure of enormous masses of water; but a com- parative study of these rocks in different parts of the world has proved that several beds of lava are arranged in columns at heights considerably above the level of the sea. In this colonnade-like formation of lava there is, however, no phenomenon which is entirely peculiar to basalt. Trachyte, also, sometimes assumes this form, and M. Fouqué has discovered a magnif. icent instance of it in the island of Milo, in which there is a cliff composed of prismatic shafts 320 feet in height. Masses of mud when dried in the sun, the alluvium of rivers, beds of clay or tufa, and, in general, all matter which, in consequence of the loss of its moisture, passes from a pasty to a solid state, either in a state of nature or in our manufactories and dwell- ings, likewise assume a columnar structure similar to that of the basaltic 456 THE EARTH, lava. In fact, the entire mass, when gradually losing the moisture which swelled out its substance, can not contract so as to shift the position of all its particles toward the centre; certain points remain fixed, and round each of these the contraction of a portion of the mass takes place. In basalt, in particular, it is the lower layer which assumes the columnar structure, for these alone cool gently enough to allow the phenomena of contraction to follow the normal course. The highest portion of the mass, being deprived, immediately after its issue from the earth, of the caloric and the steam which filled its pores, is almost immediately transformed into a more or less rough and cracked mass. But this very crust protects the rest of the lava against any radiation, and serves as a covering to the semi-crystalline columns which, by the continual contraction of their parti- cles, are slowly separated from the rest of the mass. When a section of a bed of basaltic lava has been laid bare by the water of a river, the waves of the ocean, or earthquake, the rough stone of the top layers may be seen lying, with or without any gradual transition, on a forest of prisms, some- times rudimentary in their shape, but often no less regular than if they had been carved out by the hand of man. Most are of a hexagonal form; others, which were probably subject to less favorable conditions, have four, five, or seven faces; but all are definitely separated from one another by their particles gathering round the central axis. Mr. Poulett Scrope describes a fact which proves the enormous power of this contractile force. The colonnade of Burzet, in Vivarais, contains numerous nodules of oli- vine, many of which are as large as a man’s fist; and, in spite of their ex- treme hardness, have been divided into two pieces, each fixed in one of two adjacent columns. Afthough the two corresponding surfaces have been polished by the infiltration of water, it is impossible to doubt that the two separate portions were not once joined in the same nodule. As natural philosophers have verified by experiments on various viscous substances, basaltic shafts are always formed perpendicularly to the sur- face of refrigeration. Now, this surface being inclined, according to the locality, in a diversity of ways, the result is, that the columns may assume a great variety of directions in their position. Although most of them are vertical, on account of the cooling taking place in an upward direc- tion, others, as at St. Helena, take a horizontal direction, and resemble trunks of trees heaped upon a wood-pile. In other places, as at the Coupe d’Ayzac in Auvergne, the columns of a denuded cliff are arranged in the form of a fan, so as to lean regularly on the wall of the cliff as well as on the ground of the valley. At Samoskoe, in Hungary, a sheet of columnar basalt, very small at its origin, spreads out from the top of a rock like the water of a cascade, and hangs suspended over a precipice, resembling a cupola which has lost its base. Elsewhere masses of basaltic pillars radi- ate in every direction like the weapons in an immense trophy of arms. An exact prismatic form is not, however, the only shape assumed by the cooling lava. The phenomenon of contraction takes place in different ways, according to the nature of the erupted matter, the declivity of the slopes, BASALTTC COLUMNS. 457 and all the other surrounding circumstances. Thus, in consequence of the sinking of the rock, most basaltic prisms exhibit at intervals a kind of joint, which gives the columns a kind of resemblance to gigantic bamboos. In some lavas these joints are so numerous, and the edges of the stone are So eaten away by the weather, that the shafts are converted into piles of spheroids of a more or less regular form. At the volcano of Bertrich, in the Eifel, one might fancy them a heap of cheeses; whence comes the name of “Cheese Cave,” which is given to one of the caverns which opens in the flow of lava. Sometimes, too, crystals scattered about in the midst of the mass have served as nuclei to globular concretions formed of nu- merous concentric layers. Lastly, many currents of molten matter pre- sent a tabular or schistose structure, caused, like that of slate, by the pressure of the superincumbent masses. 458 THE EARTH. CHAPTER LXVII. SOURCES OF LAVA ; STROMBOLI; MASAYA ; ISALCO ; KILAUEA. —LATERAL CREVICES IN VOLCANOES.–ERUPTION AND MOTION OF LAVA. ALTHOUGH lava, when cooled, is easy enough to study, it is more diffi- cult to observe with any exactitude the molten matter immediately on its exit from the craters or fissures; besides this, the opportunities for study which are offered to savants are sometimes very dangerous. Long years often elapse before an inquirer can notice at his ease, and without fear of sudden explosions, the mouths of Etna or Vesuvius filling up to the brink with boiling lava. Stromboli is the only volcano in Europe in which this phenomenon oc- curs regularly at closely-recurring intervals, sometimes of only five min- utes, or even more frequently. When an observer stands on the highest edge of the crater, he sees, about 300 feet below him, the waves of a mat- ter which shines like molten iron, and tosses and boils up incessantly; sometimes it swells up like an enormous blister, which suddenly bursts, darting forth eddies of vapor accompanied by solid fragments. For cen- turies past the lava has never ceased to boil in the cavity of Stromboli, and it is but very rarely that a period of even a few hours elapses without molten matter overflowing. Thus the crater, which, during the day, is white with steam, and during the night red with the glare of the lava, has served as a light-house for mariners ever since the first vessel ventured upon the Tyrrhenian Sea. In Nicaragua, to the north of the Great Lake, the volcano of Masaya (or “Devil's Mouth”) presents a spectacle similar to that of Stromboli, but grander, and perhaps still more regular. After having remained in a state of repose for nearly two centuries, from 1670 to 1853, the monster—which has received the name it bears from the frightful turbulence of its burning waves—resumed all its former activity. In this crater the enormous bub- bles of lava, which ascend from the bottom of the abyss and throw out a shower of burning stones, break forth in a general way every quarter of an hour. The volcano of Isalco, not far from Sonsonate, in the State of San Salva- dor, is also one of the most curious on account of its regularity. Its first breaking out was noticed on the 29th of March, 1783, and since this date* it has almost always continued to increase in size by throwing outside its cavity ashes and stones. Some of its eruptions, remarkable for their com: parative violence, have been aceompanied by flows of lava; but, generally, the crater of Isalco confines itself to hurling burning matter to a height * M. Squier gives another date, the 23d of February, 1770, but it is probably an error. . º º º § º §§ § i : § § § º S$ § º§ º § º º º § º Žº º §§ §§§ º[. c§tº § º § § º [. §§§ § § ſº §§ Nº § º º Nº. º º §§§ & ſº §§§ º §§ § § § ſº g§ ; * ºf º G gº º ºº s # # # § # # Eº # º £26 § § &- 3. º: à º º: 2 º # E- 23 º sº # º § ; §§ d à 㺠ºº % ; : 3:w # # { 3. 2 % º º Ž º º * % * 2. 2.) ſº 3.; s 3.ſº { º % % ſº º º % { º º g % % º º º º % %% % % º % 3% % Xº Ž º % % g Zºº % % % % º º % % % º Sº º غ % % % º º & sº º º ; % % %2. § º % Ø2% % º º º § W º § §§ §§ gº § § & & & G tº § & §§§ §§§ Q 3% % % £º ſ % º &32;% º & 3% % º º W W. º §§ § #. %º §º 2%º § § § º §§ §§ §§§ § º & º º &º § \\ &\ Wºº º §§ Ł ſº t §º. § § § ºA: § º Ø & Wº º § §§ wº §§º lº §§ §§ § § § º º ſº gº ſº 7 & ºft sº º § º º: §§ tº : º & § § § º § º §§§ §§ º § sº sº sº §§ º * **** ;3 A. ; § t R 6. ! º Eº § } § § % º % lºſsºt § {I} § h) º/ º: º W Q Fig. 191. Crater of Mauna-LOa. t º º S. º ; § % Sºb § Sº [. sº §§ * º sº ſº . º º Hºſ º º º §§ §: º º § f º § º ź º: #% AH; º º º % % §3% º º:33%; º y - . §§ & Kºść § º • * * # * zºº §§ § ź. . Eº yº. § 3§ ºÉº º º SW § Xº &P §§ º º § §§§ §§ §§§ º § §§ Sº Sº 3. § º §§ & : º º §§§ § §§ º §§ S&S §§ º SSS § §§§ § º Sº §§ ſº Sº º & §§ §§ º §§§§ º §§§ º Sº & º - NºS § § Nº §§ § Nº §§ Nº. § R §§§ Qº S; Ş. YN º & &ººl º §§ Q lº º sº º §§§ §§ §§§ º & Yº º & § §§ º Sº K &\ Vº SN & &\ * §§§ N §§ tº: º Nº §§ º Nº. frº º §§§§ & º §§ Y.§ §§ º º Nº º º § § & º & §§ º N & SNS º º º º sº j W & º º º \ § - §§ §§ º º § M º º § }\\ º º s § CRATE/? OF KIL.A. UE'A. 461 of 39 to 46 feet above its crater: explosions follow one another at inter- vals of every two minutes.* The total elevation of the cone of débris above the village of Isalco being 735 feet, and the slope of the side of the mass being, on the average, 35 degrees, M. von Seebach, one of the observ- ers of the volcano, has been able to calculate approximately the bulk and regular increase of the mountain. In 1865 the mass of débris was about 35,000,000 of cubic yards, giving an increase of about 491,000 cubic yards every year, or 56 cubic yards every hour. The volcano, therefore, might be looked upon as a gigantic hour-glass.f \tº is: s § *. º º !!!! F} º }:...º.º. º §§ Fig. 100. Craters of Kilauea. Of all the craters in the world, the one which most astonishes those who contemplate it is the crater of Kilauea, in the island of Hawaii. This vol- canic outlet opens at more than 3900 feet of elevation on the sides of the great mountain of Mauna-Loa, which is itself crowned by a magnificent funnel-shaped crater 2735 yards across from one brink to the other. The elliptical crater of Kilauea is no less than 3 miles in length and 7 miles in circumference. The hollow of this abyss is filled by a lake of lava, the level of which varies from year to year, sometimes rising and sometimes falling like water in a well. In a general way, it lies about 600 to 900 feet below the outer edge, and, in order to study its details, it is necessary to get on to a ledge of black lava which extends round the whole circum- ference of the gulf; this is the solidified edge of a former sheet of molten matter, similar to those circular benches of ice which, in northern coun- tries, border the banks of a lake, and even in spring still mark the level the water has sunk from. The surface of the sea of fire is generally cov- ered by a thick crust over its whole extent; here and there the red lava- * Moritz Wagner; Carl von Scherzer. t Zeitschrift für Erdkunde, 1866. 462 TEIE EARTH, waves spring up like the water of a lake through the broken ice. Jets of vapor whistle and hiss as they escape, darting out showers of burning scoriae, and forming cones of ashes on the crust 60 to 100 feet in height, which are so many volcanoes in miniature. Intense heat radiates from the immense crater, and a kind of hot blast makes its way through all the chinks in the vertical walls of the sides. In the midst of the hot vapors, one feels as if lost in a vast furnace. During the night-time an observer might fancy himself surrounded with flames; the atmosphere itself, col- ored by the red reflection of the vent-holes of the volcano, seems to be all on fire. - 48,364 3 *603 • º Tig. 192. Section across the Craters of Kilauea. S N N The level of the fire-lake of Kilauea is incessantly changing. In propor- tion as fresh lava issues forth from the subterranean furnace, the broken crust affords an outlet to other sheets of molten matter and fresh heaps of scoriae, and gradually the boiling mass rises from ledge to ledge, and ulti- mately reaches the upper edge of the basin. Sooner or later, however, the level rapidly sinks. The fact is, that the burning mass contained in the depths of the abyss gradually melts the lower walls of solid lava; these walls ultimately give way at some weak points in their circumfer- ence, a crevice is produced in the outer face of the volcano, and the liquid matter, “drawn off” like wine from a vat, rushes through the opening made for it. The flow increases the orifice by the action of its weight on the sill of the opening, and by melting the rocks which oppose its passage, and then, running down over the slopes, flows into the sea, forming prom- ontories on the shore. In 1840 the crater was full to the brink, when a crack suddenly opened in the side of the mountain. This fissure extended to a distance of 131 feet from its starting-point, and vomited forth a stream of lava 37 miles long and 16 miles wide, which entirely altered the outline of the sea-coast, and destroyed all the fish in the adjacent waters. Mr. Dana estimated the total mass of this enormous flow as equal to 7,200,000 cubic yards—that is, to a solid body fifty times as great as the quantity of earth dug out in cutting through the Isthmus of Suez. The enormous basin of Kilauea, 1476 feet deep, remained entirely empty for some time, and the former lake of lava left no other trace of its existence than a solid ledge like those which had been formed at the time of pre: vious eruptions. Since this date the great caldron of lava has been several times filled and several times emptied, either altogether or in part. Almost all the volcanoes which rise to a great height, get rid, like Ki- lauea, of their overflow of lava through fissures which open in their side walls. In fact, the column of molten matter which the pressure of the gas beneath raises in the pipe of the crater is of an enormous weight, and LA VA-FLQ WS. 463 every inch it ascends toward the mouth of the crater represents an expense of force which seems prodigious. The more or less hypothetical calcula- tions which have been made as to the degree of pressure necessary for the steam to be able to act on the lava-furnace lead to the belief that the out- let-conduits of volcanoes, and consequently the mass of liquid stone to be lifted, are not less than nine miles in depth.* Various geologists—among others, Sartorius von Waltershausen, the great explorer of Etna—believe that the volcano-shafts are of a still more considerable depth. The rocks of the terrestrial surface, limestone, granite, quartz, or mica, are of a spe- cific gravity two and a half times superior to that of water, while the planet itself, taken as a whole, weighs nearly five and a halftimes as much as the same mass of distilled water; the density of the interior layers must therefore increase from the circumference to the centre. With re- gard to the proportion of this increase, it is established by a calculation, the whole responsibility of which must rest upon its authors. Baron Wal- tershausen has ascertained, by means of a great number of weighings, that the lava of Etna and that of Iceland have a specific gravity of 2011. The presumed consequence of this fact is that the rocks thrown out by the volcanoes of Sicily and Iceland proceed from a depth of 77 to 78 miles (?). Thus the shaft which opens at the bottom of the crater of Etna would be no less than 77 miles deep, and the lava which boils in this abyss would be lifted by a force of 36,000 atmospheres, an idea altogether incompre- hensible by our feeble imaginations. There would, then, be nothing aston- ishing in the fact that a mass of lava, which is sufficiently heavy to bal- ance a pressure of this kind, should, in a great many eruptions, melt and break through the weaker parts of its walls, instead of ascending some hundreds or thousands of feet higher, so as to run out over the edge of the upper crater. When the side of the mountain opens, and affords a passage to the lava, the fissure is always perceptibly vertical, and those which are continued to the summit pass through the very mouth of the volcano. . In a general way, these fissures of eruption are of considerable length, and are suffi- ciently wide to form an impassable precipice. Before these fissures be- comé obliterated by the lava or by other débris—such as the snow and earth of avalanches—they may be traced out by the eye as deep furrows hollowed out on the mountain side. In 1669 the lateral fissure of Etna extended over more than two thirds of the southern side—from the plains of Nicolosi to the terminal gulf of the great crater. In like manner, in the Isle of Jan Mayen, the volcano of Beerenberg, 7513 feet high, presents from top to bottom a long depression filled up with snow, which is moth- ing else than a fissure of eruption. On other mountains, especially in Montserrat, Guadaloupe, and Martinique, these fissures have assumed such dimensions that the peaks themselves have been completely split in two. Through outlets of this kind the lava jets out, first making its appear- ance at the upper part, where the declivity is generally steeper, then * Buff, Physik der Erde. 464 THE EARTH springing out below on the more gentle slopes of the lower regions of the mountain. At the source itself the lava is altogether fluid, and flows with consid- erable speed—sometimes, on steep slopes, faster than a horse can gallop; but the course of the molten stone soon slackens, and the liquid, hitherto dazzling with its light, is covered by brown or red scoriae, like those of iron just come out of a furnace. These scoriae come together, and, com- bining, soon leave no interstices between them beyond narrow vent-holes, through which the molten matter escapes. The scoriae then form a crust, which is incessantly breaking with a metallic noise, but gradually consoli- dates into a perfect tunnel round the river of fire; this is the cheire,” thus named on account of the asperities which bristle on its surface. Any one may safely venture on the arch-shaped crust, although only a few inches above the mass in state of fusion, without any fear of being burnt, just as in winter we trust ourselves on the sheets of ice which cover a running stream. The pressure of the lava succeeds in breaking through its shell only at the lower parts of its flow, in spots where the waves of burning stone fall with all their weight. Then the envelope is suddenly ruptured, and the mass springs out like water from a sluice, pushing before it the resounding scoriae, and swelling out gently in the form of an enormous blister; it then again becomes covered with a solid crust, which is again broken through by a fresh effort of the lava. Thus the river, surround- ing itself with dikes which it constantly breaks through, gradually de- scends over the slopes, terrible and inexorable, so long as the original stream does not cease to flow. The only means of diverting the current is to modify the incline in front of it—either by opposing obstacles to it to throw it to either side, or by preparing a road for it by digging deep trenches, or by opening up above some lateral outlet for the pent-up lava. In 1669, at the time of the great eruption which threatened to swallow up Catania, all these various means were adopted in order to save the town. On one side the inhabitants worked at consolidating the rampart, and placed obstacles, across the path of the current to turn it toward the south. Other workmen, furnished with shovels and mattocks, ascended along the edge of the flow, and, in spite of the resistance offered by the peasants, tried to pierce through the shell of scoriae, and thus, by tapping the stream, to open fresh outlets for the molten matter. These means of defense partly succeeded, and the terrible current which, at its source near Nicolosi, had been able to melt and pierce through the volcanic cone of Mompilieri at its thickest point (this cone standing in its path), was turned from its course toward the centre of Catania, and destroyed noth- ing but the suburbs. The radiation from the lava being arrested by the crust of scoriae, which is a very bad conductor of heat, the temperature of the air surrounding a flow of lava rises but very slightly. The Neapolitan guides have no fear * Or serre, in Italian sciara: these are synonyms of the word scie (saw) in the IFrench of the present day. - - LA VA-FLOWS. 465 in approaching the Vesuvian lava in order to stamp the rough medals made of it, which they sell to foreigners. At a distance of a few yards from the vent-holes in the cheire the trees of Etna continue to grow and blossom, and some clumps, indeed, may be seen flourishing on an islet of vegetable earth lying between two branches of a flow of burning lava. And yet, by a contrast which at first sight seems incomprehensible, it sometimes happens that trees which are distant from any visible flow of molten matter suddenly wither and die. Thus, in 1852, at the time of the great eruption from the Val del Bove, on the eastern slopes of Mount Etna, vineyards and vines, covering a considerable area, and situated at a dis- tance of more than half a mile below the front of the flow, were suddenly dried up, just as if the blast of a fire had burnt up their foliage. In order to explain this curious phenomenon, it is necessary to admit that some rivulets of the great lava-river must have penetrated under the earth through the fissures of the soil, and have filled up a subterranean cavity in the mountain exactly below the vineyards that were destroyed : the roots being consumed, or deprived of the necessary moisture, the trees themselves could not do otherwise than perish.* On lofty mountains in a state of eruption, the masses of snow and ice, which are covered by the fiery currents which issue from the volcanic fis- sures, do not always melt, and some have been preserved under the scoriae for centuries, or even thousands of years. Lyell has discovered them un- der the lava of Etna, American geologists under the masses thrown out by the crater of Mount Hooker, Darwin under the ashes in Deception Isl- and, in the Tierra del Fuego, M. Philippi under the flows of the volcano Nuevo de Chillan, which in 1861 erupted through a glacier. There every bed of snow which falls during the winter remains perfect under the coat of burning dust which is ejected from the outlet of eruption, and sections made through the mass of débris show for a great depth the alternate black and white strata of the volcanic ashes and the snow. In 1860 the crater of the mountain of Kutlagaya, in Iceland, hurled out simultaneous- ly into the air lumps of lava and pieces of ice all intermingled together. In like manner, the immense flow of lava in Iceland have left in a per- fect state of preservation the trunks of the Sequoias, and other American trees, which adorned the surface of the island during the ages of the Ter- tiary epoch, at a time when the mean temperature of this country was 48° (Fahr.), that is, 42° to 44° above that which it is at present.S Al- though the radiation from the lava is so slight that it neither melts the ice nor burns the trunks of buried trees, yet, on the other hand, the heat and fluidity of the lava are maintained in the central part of the flow for a very considerable number of years. Travelers state that they have found deeply-buried lava which was still burning after it had remained for a century on the mountain side. * Lyell, Philosophical Transactions, 1858. f Mittheilungen von Petermann, vol. vii., 1863. f Wallich, North Atlantic Sea-bed. § Carl Vogt, Nordfahrt. G. G. 466 THE EARTH, Tºnº **...sº *%laws' ºw"w W. }% - p *. Sºś § // º % º .### = S. sº % % SNNW *Uś. §§§§ § % §§ %,\º §§%%; Sºğ º §§ rif, *44/.4% ºf :32:3:º §§§ §§§ º º 㺠JS$ ** , Wº% ºğ % º sº §. £%assº; % \%| º & % º º º §§ % §S㺠ɺ - 'Nº!//º3. % § & "tº § § º § º ºx ſ w ſ 22 sº º §Yºß - ###gºlº §§§ 2% - ſº sº §§ºanshugyº-ºš||\} š: %; § La Silla T SS §§ §º º § %|º § %&N - §§§ 3. º Wºź º §. §§§ c Hiiissº §§/ O 40 lacier. Şft\}\ § - - §) **Nº, º d § - § § 33 - \ § §§§ :NS: º SS º § ºr. º # N º: % - S$ Sº º jº t § %iº Wºś w º ºšš. As ¥ # W §2/Nº & § %. iº §§ § §AsSN %|\\ % & tºº §: 7|{{ § * sº % wº *º sº rºws t *** 2 * illiº *2 Śly ºws |*Mºº º slº * "W ** ." - Ål Żſh % t § \ * d usly 'iſlwy 3 *ussº.sº º •es § N *Wºnsº Pig. 193. Nevado de Chillan. Although the lava covers up and often preserves the snow and the ice, which are doubtless defended against the heat by a cushion of spheroidal particles of humidity, it immediately converts into steam the which it comes in contact. The liquid mass, being suddenly water With augmented to about 1800 times its former volume, explodes like an enormous bomb- shell, and hurls away, like projectiles, all the objects which surround it. A serious occurrence of this kind is recorded, which took place in 1843, a few days after the formation of a fissure in Mount Etna, from which a cur- rent of molten matter issued, making its way toward the plain of Bronte. A crowd of spectators, who had come from the town, were examining from a distance the threatening mass, the peasants were cutting down the trees in their fields, others were carrying off in haste the good cottages, when suddenly the extremity of the flow was seen s from their to swell up like an enormous blister, and then to burst, darting forth in every direc- tion clouds of steam and volleys of burning stones. Every thing was de- stroyed by this terrible explosion—trees, houses, and cultivated ground; and it is said that sixty-nine persons, who were knocked down cussion, perished immediately, or in the space of a few hours. by the con- This disas- ter was occasioned by the negligence of an agriculturist, who had not emptied the reservoir on his farm; the water, being suddenly converted into steam, had caused the lava to explode with all the force of gun- powder. The quantity of molten matter which is ejected by a fissure in one sin- gle eruption is enormous. It is known that the current of Kilauea, in 1840, exceeded 6550 millions of cubic yards. That which proceeded from Mauna-Loa in 1835 produced a still larger quantity of lava, and extended as far as a point 76 miles from the crater. Flows of this kind are certainly rare; but there are some recorded in the earth's history wh ich are still LA VA-FM, O WS. 467 more considerable. Thus the volcano of Skaptar-Jokul, in Iceland, was cleft asunder in 1783, and gave vent to two rivers of fire, each of which filled up a valley; one attained a length of 50 miles, with a breadth of 15 miles; the other was of less dimensions, but the depth of the mass was in Some places as much as 492 feet. A subterranean fissure, 99 miles in length, which cleaves in two the ground of Iceland, was doubtless filled up with lava along its entire length, for hillocks of eruptions sprung up on various points of this straight line. It has been calculated that the whole of the lava evacuated by the Skaptar in this great eruption was not less in bulk than 655,000 millions of cubic yards, a mass equivalent to the whole volume of Mont Blanc ; it would be a quantity sufficient to cover the whole earth with a film of lava 0-0393 inch in thickness. As to the celebrated flow from the Monti Rossi, which threatened to destroy Catania in 1669, it seems very trifling in comparison; it contained a mass of molten stone which was estimated at 1310 millions of cubic yards. On how tri- fling a scale, therefore, are these ordinary eruptions compared with the surface of the globel They are, however, phenomena perceptible enough to man, in all his infinite littleness. - 468 THE EARTH, CHAPTER LXVIII. VOLCANIC PROJECTILES.– EXPLOSIONS OF ASHES.— SUBORDINATE VOLCA- NOES.- MOUNTAINS REDUCED TO DUST.- FLASHES AND FLAMES PRO- CEEDING FROM VOLCANOES. TIIE lava swelling up in enormous blisters above the fissures from which it flows in a current over the slopes is far from being the only substance ejected from volcanic mountains. When the pent-up vapor escapes from the crater with a sudden explosion, it carries with it lumps of molten mat- ter, which describe their curve in the air, and fall at a greater or less dis- tance on the slope of the cone, according to the force with which they were ejected. These are the volcanic projectiles, the immense showers of which, traced in lines of fire on the dark sky, contribute so much during the night-time to the magnificent beauty of volcanic eruptions. These projectiles have already become partially cooled by their radiation in the air, and when they fall are already solidified on the outside, but the in- side nucleus remains for a long time in a liquid or pasty state. The form of these projectiles is often of an almost perfect regularity. Each sphere is in this case composed of a series of concentric envelopes, which have evidently been arranged in the order of their specific gravity during the flight of the projectile through the air. The dimensions of these projec- tiles vary in each eruption; some of them are one or more yards in thick- ness; others are nothing but mere grains of Sand, and are carried by the wind to great distances. - In most eruptions, these balls of lava, still in a fluid and burning state, constitute but a small part of the matter thrown out by the mountain. The largest proportion of the stones ejected proceed from the walls of the volcano itself, which break up under the pressure of the gas, and fly off in volleys, mingled with the products of the new eruption. This is the origin of the dust or ashes which some craters vomit out in such large quantities, which, too, are the cause of such terrible disasters. When the impetus of the gas confines itself to forming a fissure in the side of the mountain, the fragments of rocks which are broken up and re- duced to powder are comparatively small in quantity. They are projected in clouds out of the fissure, and, falling like hail round the orifice, are grad- ually heaped up in the form of a come on the side of the mountain from which they arose. In Europe the enormous circumference of Etna pre- sents more than 700 of these subordinate volcanoes, some scarcely higher than an Esquimaux hut, and others, like the Monti Rossi, Monte Minardo, Monte Ilici, several hundred yards high, and more than half a mile wide at the base. There are some which are entirely sterile, or covered only by a EXPLOSIONS OF ASHE'S. 469 scanty vegetation of broom, and are marked out by a red, yellow, or even black color on the main body of Etna; those situated on the lower slopes are covered with trees or planted with vines, and sometimes contain ad- mirable crops in the very cavity on their summit. These cones of ashes, springing up like a progeny on the vast sides of their mother mountain, give to Etna a singular appearance of vital personality and of creative energy. The same phenomenon occurs on the volcanoes of IIawaii, which carry on their declivities thousands of subordinate comes. ºº:: £º Fig. 105. Cone of Ashes modified by the Wind. In the formation of these hillocks a real division of labor takes place. The rocks and heavier stones fall either on the edge of the crater or in the gulf itself. The ashes and light dust are shot up to a much greater height, and, hurried along by the impulse of the wind, fall far and wide, like the chaff of corn winnowed in a threshing-floor. Thus the slope of the come toward which the wind directs the ashes is always more elongated, and rises to a greater height on the edge of the crater. On Etna, where the §§§º. 3 §§§ sº - 5. º i Nº.3 º º Sº º t; - º º 3 tº gº ſºlº º iº, ſº tºº § §ºSS$ §: º § § tº §§§SS - §§ WN § §§ º § § º § & §§sº § § §§ §§ §§§ º - º - * º WN §§ * §ſº Yºlº ſ §§ §§ W *iº § sº - º & º § º i. j § - ~ º º N §§ º §§§ §§§ º - ºğ º a sº '-º', ; S.C." - "... * * * . º Sº º # ſ º | & N - §º: -*.*.*.* * * * § | X \% ſº ** --> -- deºxyff .*.* … .º.S. f. . º:: ... Rºº? E. º º g *: º & ~~~~2.2°.22°3′Nºżāºš º § - % ś 'S - Jº. 2. - c tima and Val del Bove. § | Fig. 196. Cone of E § wind generally blows in the direction of west to east, the eastern slope of the hillocks is more developed than on the opposite side. It must, per- haps, be attributed to the action of the wind blowing on the heights, and 470 THE EARTH, not, as Siemsen,* the geologist, supposes, to the obliquity of the shaft of the crater, that all the scoriae and ashes fall to the north of the orifice of the volcano Nuevo de Chillan, in Chili. The phenomena which take place when the ashes issue from the mouth of the crater itself do not differ from those which are observed at the out- lets in fissures. In the former case, however, the mass of rocks reduced to powder is so considerable that the rain of ashes assumes all the propor- tions of a cataclysm. It has sometimes happened that, during a paroxysm of volcanic energy, the whole summit of a mountain, for a depth of several thousands of feet, has been hurled into the air, mingled with a cloud of vapor and the smoke of burning lava. Thus Etna, if we are to believe AElianus, was once much loftier than it is in our time, and on the north of the present terminal cone there may, in fact, be noticed a kind of platform which seems to have been the base of a summit twice as high as the pres- ent crest. The whole of the Val del Bove is probably an empty space left by the disappearance of a former cone. With regard to Vesuvius, it is known that, in the year 79 of the present era, the whole of that part of the mountain which was turned toward the sea was reduced to powder, and that the débris of the cone, nothing of which now remains except the semicircular inclosure of La Somma, buried three towns and a vast extent of plain. The ashes and dust, mingled with white vapor rising in thick eddies, ascended in a column to a point far above the summit of the volcano, until, having reached those regions of the atmosphere where the rarefied air could no longer sustain them, they spread out into a wide umbrella-like shape, the falling dust of which ob- scured the sky. Pliny the Younger compared this vault of ashes and smoke to the foliage of an Italian pine curving at an immense height over the mountain. Since this memorable epoch the height of the column of vapor has been measured which has issued from Vesuvius at the time of several great eruptions, and it has been sometimes found that it reached 23,000 to 26,000 feet; that is, six times higher than the summit of the vol- cano itself. One of these explosions of entire summits which caused most terror in modern times was that of the volcano of Coseguina, a hillock of about 500 feet high, situated on a promontory to the south of the Bay of Fonseca, in Central America. The débris hurled into the air spread over the sky in a horrible arch several hundreds of miles in width, and covered the plains for a distance of 25 miles with a layer of dust at least 16 feet thick. At the very foot of the hill the headland advanced 787 feet into the bay, and two new islands, formed of ashes and stones falling from the volcano, rose in the midst of the water several miles away. Deyond the districts close round the crater, the bed of dust, which fell gradually, became thinner, but it was carried by the wind more than 40 degrees of longitude toward the west, and the ships sailing in those waters penetrated with difficulty the layer of pumice-stone spread out on the sea. To the north, the rain * Mittheilungen von Petermann, vol. vii., 1863. ER UPTION OF COSEG UMWA. 471 of ashes was remarked at Truxillo, Honduras, and at Chiapas, in Mexico; on the south, it reached Carthagena, Santa Martha, and other towns of the coast of Grenada; to the east, being carried by the counter-current of the trade-winds, it fell on the plains of St. Ann's, in Jamaica, at a distance of 800 miles. The area of land and water on which the dust descended must be estimated at 1,500,000 square miles, and the mass of matter vomited out could not be less than 65,500 million cubic yards. 25 - 233;ºx. #EEA. J. C. --- - : #sº tºº ==ºfºº º, s , , Bºzº tº ſº, 5 E-E-9 * * ~ * ; F = Hº:: º ------~--------~~- - sº *...* :- ==S Ef Pº º: # '. ! ; § - ºmº #EEF, • *E* º º º t ºrrºr - #Effè==º § E ** #EEE:#ER wº-ºº: Eº-º-º: Höß. 30° *—555 :*:- ==== i Fig. 197. Eruption of Coseguina. The uproar of the breaking up of the mountain was heard as far as the high plateaux of Bogota, situated 1025 miles away in a straight line. While the formidable cloud was settling down round the volcano, thick darkness filled the air. For forty-three hours nothing could be seen ex- cept by the sinister light of the flashes darting from the columns of steam, and the red glare of the vent-holes opening in the mountain. To escape from this prolonged night, the rain of ashes, and the burning atmosphere, the inhabitants who dwelt at the foot of Coseguina fled in all haste along a road running by the black water of the Bay of Fonseca. Men, women, children, and domestic animals traveled painfully along a difficult path, through quagmires and marshes. So great, it is said, was the terror of all animated beings during this long night of horror, that the animals them- 472 THE EARTII. selves, such as monkeys, serpents, and birds, joined the band of fugitives, as if they recognized in man a being endowed with intelligence superior to their own.” A large number of volcanoes have diminished in height, or have, indeed, entirely disappeared, in consequence of explosions, which reduced their rocks to powder, and distributed them in thick sheets on the ground ad- jacent. Mount Baker, in California, and the Japanese volcano of Unson, have thus raised the level of the surrounding plains at the expense of a diminution in their own volume. In 1638, the summit of the peak of Ti- mor, which might be seen like a light-house from a distance of 270 miles, exploded, and blew up into the air, and the water collecting, formed a lake in the enormous void caused by the explosion. In 1815, Timboro, a vol. y26° % | (ſºlº tº: º: {{!! ºxy t - - * * } }ºlº !. {{x}}}} & t; §§ ) § {{{{{{{{!!, ś § §§ º § §§ !ºſt - § §§§ # + § º º - º º F - - ---- sº ºrv, e s tº ..º. *** % $º º!. " "Túð3 * - 120° ISO Fig. 19S. Truption of Timboro. 'ano in the island of Sumbara, destroyed more men than the artillery of both the armies engaged on the battle-field of Waterloo. In the island of Sumatra, 550 miles to the west, the terrible explosion was heard, and, for a radius of 300 miles round the mountain, a thick cloud of ashes, which obscured the sun, made it dark like night even at noonday. This immense quantity of débris, the whole mass of which was, it is said, equiv- * Landgrebe, Naturgeschichte der Vulkane. #. FLAMES FROM VOLCANOES. 473 alent to thrice the bulk of Mont Blanc—that is, 2,358,000 millions of cubic yards (?)—fell over an area larger than that of Germany. The pumice- stone which floated in the sea was more than a yard in thickness, and it was with some difficulty that ships could make their way through it. The popular imagination was so deeply impressed by this cataclysm, that at iłruni, in the island of Borneo, whither heaps of the dust vomited out by Timboro, 870 miles away to the south, had been carried by the wind, they date their years from “the great fall of ashes.” It is the commencement of an era for the inhabitants of Bruni,just as the flight of Mohammed Was for the Mussulmans. - The fiction of the steam against the innumerable particles of solid mat- ter which are darted out into the air is the principal cause of the electrici- ty which is developed so plentifully during most volcanic eruptions. In consequence of this friction, which operates simultaneously at all points in the atmosphere which are reached by the volcanic ashes and vapor, sparks flash out which are developed into lightning. The skies are light- ed up not only by the reflection from the lava, but also by coruscations of light which dart from amid the clouds. When the vast canopy of vapor spreads over the summit of the mountains, numerous spirals of fire whirl round on each side of the clouds, which, as they unroll, resemble the foli- age of a gigantic tree. Doubtless, also, the encounter of two aerial cur- rents may contribute to produce lightning in the columns of vapor; yet, when the latter are slightly mingled with ashes, they are rarely stormy.* Although the evolution of electricity in the columns of vapor and ashes vomited out by volcanoes has never been called in question, the appear- ance of actual flames at the time of volcanic eruptions was for a long time disputed. M. Sartorius von Waltershausen, the patient observer of Etna, has maintained that neither this mountain, nor Stromboli, nor any other volcano, has ever presented among its phenomena any fire properly so called, and that the supposed flames were nothing more than the reflec- tion of the red or white lava that was boiling in the crater. On the other hand, Elie de Beaumont, Abich, and Pilla positively assert that they have seen light flames on the summit of Vesuvius and Etna. It would, however, be very natural to believe that inflammable gases might be liberated and take fire at the outlet of those immense shafts which place the great sub- terranean laboratory of lava in communication with the outer air. This question was, however, resolved in the affirmative at the time of the recent eruption of Santorin, and popular opinion was right in opposi- tion to most men of Science. All those who were able to witness, at its commencement, the upheaval of the lava at Cape Georges and Aphroessa, have certified to the appearance of burning gas dancing above the lava, and even on the surface of the sea. All round the upheaved hillocks, bubbles of gas, breaking forth from the waves, became kindled as they came in contact with the burning mass, and were diffused over the wateis in long trains of white, red, or greenish flames, which the breeze alter- * Arago, (Euvres Complètes, vol. i. 474 THE EARTH, nately raised or beat down; sometimes a smart puff of wind put out the fire, but it soon recommenced to run over the breakers: by approaching it carefully, fragments of paper might be burnt in it, which lighted as they dropped. On the slopes of the volcano of Aphroessa, fire, rendered of a yellowish hue by salts of soda, sprung out from all the fissures, and rose to a height of several yards. On the rather older lava of Cape Georges the trains of flame were less numerous; there, however, bluish glimmers might be seen flitting about in some spots over the black ridges of lava.” Added to this, are not the flames at Bakou, on the coast of the Caspian Sea, produced by the volcanic action of the ground? The “growing mountains” in the neighborhood are mud-volcanoes, and we must doubt- less attribute to the same subterranean activity the production of the hy- drogen gas which burns in an “eternal flame” in the temples of the Parsif During some of the evenings in autumn, when the weather is fine and the sun has heated the surface of the ground, the flames occasionally make their appearance on the hills, and for several hours may be seen the mar- velous spectacle of a train of fire stretching along the country without 3. burning the ground, and even without scorching a blade of grass. * Fouqué, Revue des Deux-Mondes, August 15, 1866; Dekigallas; Schmidt. † Arnold Boscowitz, Volcans et Tremblements de Terre. FRUPTIONS OF MUD. 475 CHAPTER LXIX. STREAMS OF MUD EJECTED BY CRATERS.–MUD-VOLCANOES. NExT to lava and ashes, streams of water and mud are the most Con- siderable products of volcanic activity, and the catastrophes which they have caused are perhaps among the most terrible which history has to re- late. By means of these sudden deluges, towns have been swept away or swallowed up, whole districts dotted over with habitations have been flooded with mud or converted into marshes, and the entire face of na- ture has been changed in the space of a few hours. The liquid masses which descend rapidly from the mountain height do not always proceed from the volcano itself. Thus the local deluge may be caused by a rapid condensation of large quantities of steam which es- cape from the crater and fall in torrents on the slopes. A phenomenon of this kind must evidently take place in a great many cases, and it was doubtless by a cataclysm of this kind that the town of Herculaneum, at the foot of Vesuvius, was buried. As regards the lofty snow-clad volca- noes of the tropical and temperate zones, and also those of the frozen re- gions, the torrents of water and débris—the “water-lava,” as the Sicilians call them—may be explained by the rapid melting of immense masses of snow and ice, with which the burning lava, the hot ashes, or the gaseous emanations of the volcanic furnace have come in contact. Thus, in Ice- land, after each eruption, formidable deluges, carrying with them ice, sco- riae, and rocks, suddenly rush down into the valleys, sweeping away ov- ery thing in their course. These liquid avalanches are the most terrible phenomena which the inhabitants of the island have to dread. They show three headlands formed of débris, which the body of water descending from the sides of Kutlugaya in 1766 threw out far into the sea, in a depth of 246 feet of water.” Other deluges no less formidable are caused by the rupture of the walls which pen back a lake in the cavity of a former crater, or by the forma- tion of a fissure which affords an outlet to liquid masses contained in sub- terranean reservoirs. It would be too difficult to explain otherwise the mud-eruptions of several trachytic volcanoes of the Andes—Imbambaru, Cotopaxi, and Carahuarizo. In fact, the mud (lodozales) which comes down from these mountains often contains a large quantity of organized beings, aquatic plants, infusoria, and even fish, which could only have lived in the calm waters of a lake. Of this kind is the Pimelodes cyclo- pum, a little fish of the tribe of the Siluridae, which, according to Hum- boldt, has hitherto been found nowhere except in the Andini caverns and * Olafsen and Povelsen, British Quarterly Review, April, 1861. 476 THE EARTH. Š - º N § *N tº SNM N §WºšNY: g - - Şū): % §§.” ſia" tº ºš Nº. ###$!!. % (ºf § * º ºft º º | § § ñºsº; #}; j ºf Nº. & wº \ º 3- º § |||} º : º W. § sº ES š É / º: s º § ºss É § sº āş ...; º; % º ºš & jº º ###$$º # ##º ºš ºf gº §|\\ |ºlºß a ſº % -- & [] WA º º %.º.º. Ǻ flºº %/*% º àº; àºj NS º %. |. |ſ. §º § ºğ. º i º º| º/ \Wiii., a ºs:...- ...& º ºfºº º yº ºs º- º Fig. 199. Crater of Sete Cidades. in the rivulets of the plateau of Quito. In 1691 the volcano of Imbam- baru vomited out, in combination with mud and snow, so large a quantity of these remains of organisms that the air was contaminated by them, and miasmatic fevers prevailed in all the country round. The masses of water which thus rush down suddenly into the plains amount sometimes to millions, or even thousands of millions of cubic yards. Although, in some cases, these eruptions of mud and water may be looked upon as accidental phenomena, they must, on the contrary, as re- gards many volcanoes, be considered as the result of the normal action of the subterranean forces. They are, then, the waters of the Sea or of lakes which, having been buried in the carth, again make their appearance on the surface, mingled with rocks which they have dissolved or reduced to a pasty state. A remarkable instance of these liquid eruptions is that presented by Papandayang, one of the most active volcanoes in Java. In 1792 this mountain burst, the summit was converted into dust and disap- peared, and the débris, spreading far and wide, buried forty villages. Since this epoch a copious rivulet gushes out in the very mouth of the crater, at a height of 7710 feet, and runs down into the plain, leaping over the blocks of trachyte. Round the spring, pools of water fill all the clefts in the rocks, and boil up incessantly under the action of the hot Vapors which rise in bubbles; here and there are funnel-shaped cavities, in which JERUPTIONS OF WATER AND MUD. 477 black and muddy water constantly ascends and sinks with the same reg- ularity as the waves of the sea; elsewhere, muddy masses slowly issuing from small craters flow in circular slopes over mounds of a few inches or a yard in height; lastly, jets of steam dart out of all the fissures with a shrill noise, making the ground tremble with the shock. All these vari- ous noises, the roaring of the cascades, the explosion of the gaseous springs, the hoarse murmur of the mud-volcanoes, the shrill hissing of the fumerolles, produce an indescribable uproar, which is audible far away in the plains, which, too, has given to the volcano its name of Papandayang, or “Forge,” as if one could incessantly hear the mighty blast of the flames and the ever-recurring beating of the anvils. In volcanoes of a great height it is rarely found that eruptions of water and mud are constant, as in the Papandayang; but temporary ciections of liquid masses are frequent, and there are, indeed, some volcanoes which vomit out nothing but muddy matter. The volcano of Aqua (or water), the cone of which is gently inclined like that of Etna, and rises to about 13,000 feet in height, into the regions of snow, has never vomited any thing but water; and it is, indeed, stated that lava and other volcanic products are entirely wanting on its slopes.” Yet in 1541, this prodigious inter- mittent spring hurled into the air its terminal point (coronilla), and poured over the plains at its base, and over the town of Guatemala, so large a quantity of water, mingled with stones and débris, that the inhabitants were compelled to fly with the greatest haste, and to reconstruct their capital at the foot of the volcano of Fuego. This new neighbor, however, showed that he was as much or more to be dreaded than their former one, for the violent eruptions from the mountain compelled the inhabitants of the second town to again migrate, and to rebuild their capital at a point 20 miles to the northwest. Several volcanoes in Java and the Philippines also give vent, during their eruptions, to large quantities of mud, sometimes mingled with or. ganic matter in such considerable proportions that they have been utilized as fuel. In 1793, a few months after the terrible eruption of Unsen, in the island of Kiousiou, an adjacent volcano, the Miyi-Yama, vomited, ac- cording to Kampfer, so prodigious a quantity of water and mud that all the neighboring plains were inundated, and 53,000 people were drowned in the deluge; unfortunately, we have no historical details of this catas. trophe. Of all the eruptions of mud, the best known is that of Tungura- gua, a volcano in Ecuador, which rises to the south of Quito to 16,400 feet in height. In 1797, at the time of the earthquake of Riobamba, a whole side of the mountain sank in an immense downfall, with the forests which grew on it; at the same time, a flow of viscous mud issued from the fissures at its base, and rushed down into the valleys. One of these cur. rents of mud filled up a winding defile, which separated two mountains, to a depth of 650 feet, over a width of more than 1000 feet, and, damming * Juarros, Landgrebe, Natur Geschächte der Vulkane, vol. i. f Otto Volger, Das Buch der Erde, vol. i. f Wide above, p. 452. 478 THE EARTH, º up the rivulets at their outlet from the side valleys, kept back the water in temporary lakes: one of these sheets of water remained for eighty-seven days. t The volcanic mud, therefore, has this point of resemblance with the lava —that it sometimes flows out through the crater, as on Papandayang; sometimes through side Craters, as on Tunguragua. Doubtless, when the volcanic muds have been better studied, we shall be enabled to trace the transition which takes place by almost imperceptible degrees between the more or less impure water escaping from volcanoes, and the burning lava more or less charged with steam. This transition is, however, already noticed in the ancient matter which the water has carried down and de- posited in the strata at the foot of volcanic mountains. These rocks, known under the name of tufa, trass, or perperino, are nothing but heaps of pumice, scoriae, ashes, and mud, cemented together by the water into a species of mortar or conglomerate, and gradually solidified by the evapo- ration of the humidity which they contained. Of this kind, for instance, is the hardened stone which, for eighteen centuries, has covered the city of Herculaneum with a layer of 50 to 150 feet in thickness. Among rocks of various formations, there are but few which exhibit a more astonishing diversity than the tufas. They differ entirely in appearance and physical qualities, according to the nature of the materials which have formed them, the quantity of water which has cemented them, the greater or less rapidity with which their fall and desiccation take place; lastly, the num- ber and distribution of the chinks which are produced across the dried mass, and have been filled up with the most different substances. Many kinds of tufa resemble the most beautiful marble. - The small hillocks, which are specially called mud-volcanoes, or Salses, on account of the salts which are frequently deposited by their waters, are cones which differ only in their dimensions from the mighty volcanoes of Java or the Andes. Like these great mountains, they shake the ground, and rend it, in order to discharge their pent-up matter; they emit gas and steam in abundance, add to their slopes by their own débris, shift their places, change their craters, throw off their summits in their explosions; lastly, some of these salses are incessantly at work, while others have pe. riods of repose and activity. In nature, transitions merge into one another so perfectly, that it is difficult to discover any essential difference between a volcano and a salse, and between the latter and a thermal spring.” Mud-volcanoes exist in considerable numbers on the surface of the earth, and, like the volcanoes of lava, the neighborhood of the sea-coast is the principal locality where we find their little cones. In Europe, the most re- markable are those which are situated at the two extremities of the Cau- casus, on the coasts of the Caspian Sea, and on both sides of the Straits of Yenikale, which connect the Sea of Azof with the Black Sea. On the east, the mud-springs of Bakou are especially distinguished by their combina- tion with inflammable gases; on the west, those of Taman and Kerteh flow * Humboldt, Cosmos, vol. i. MUD- VOLCANOES. 479 all the year round, but especially during times of drought, pouring out large quantities of blackish mud. One of these mud-volcanoes, the Go- rela, or Kuku-Oba, which, in the time of Pallas, was called the “Hell,” or Prekla, on account of its frequent eruptions, is no less than 246 feet in height, and from this crater, which is perfectly distinct, muddy streams have flowed, one of which was 2624 feet long, and contained about 850,000 cubic yards.” - - The volcanitos of Turbaco, described by Humboldt, and the maccalube of Girgenti, which have been explored, since Dolomieu, by most European Savants who have devoted themselves to the study of subterranean forces, are also well-known examples of mud-springs, and may serve as a type to all the hillocks of the same character. In winter, after a long course of rains, the plain of the maccalube is a surface of mud and water forming a kind of boiling paste, from which steam makes its escape with a whistling moise; but the warmth of spring and summer hardens this clay into a thick crust, which the steam breaks through at various points and covers with increasing hillocks. At the apex of these cones a bubble of gas swells up the mud like a blister, and then bursts it, the semi-liquid flowing in a thin coat over the mound; then a fresh bubble ejects more mud, which spreads over the first layer already become hard, and this action continues incessantly until the rains of winter again wash away all the cones. This is the ordinary course of action of the salse, sometimes interrupted by vi- olent eruptions. On the coasts of Mekran the mud-volcanoes are not only subject to the action of the seasons, but also depend on the action of the tides, although many of them are from 9 to 12 miles from the Indian Ocean. At the time of the flow the mud rises in great bubbles, accompa- nied by a hoarse murmur, like the distant roar of thunder. The highest cone is not more than 246 feet high, and stands 7 miles from the shore.f In a general way, the expulsion of mud and gas is accompanied by a discharge of heat; but in some Salses, like those of Mekran, the matter ejected is not higher in temperature than the surrounding air, as if the expulsion of the mud from the ground was an entirely superficial phe- nomenon. Occasionally, in peat-bogs, the ground-cracks, and cold mud is ejected from the fissure; and then, after this kind of eruption, the spongy soil sinks and again levels down. Is this eruptive phenomenon similar to that presented by the mud-volcanoes, and caused by the fermentation of gases in the midst of substances in a state of putrefaction? This is M. Otto Volger's idea; and it would be difficult to give any other explana. tion of this phenomenon. * Amsted, Intellectual Observer, January, 1866. f Arnold Boscowitz, Volcans et Tremblements de Terre. f Walton, Nautical Magazine, February, 1863. 480 THE EARTH, CHAPTER LXX. WOLCANIC THERMAL SPRINGS.—GIEYSERS.— SPRINGS IN NEW ZEALAND.— FUMEROLLES.—SOLFATARAS.—CRATERS OF CARBONIC ACID. VoLCANoFs, both of lava and mud, all have, either on their sides or in the vicinity of their base, thermal springs, which afford an outlet to their surplus water, gas, and vapor. Most even of those mountains which are at present tranquil, but which were once centres of eruption, continue to manifest their activity by vapors and gas, like furnaces in which the flames are extinct, but the smoke is still rising. Although lava and ashes no longer make their escape from the crater or lateral fissures, yet numerous fumerolles and hot springs, formed by the condensation of the steam, gen- erally serve as a vehicle for the gas pent up in the depths of the moun- tain. We may reckon by hundreds and thousands the “geysers,” the “vinegar springs,” and other thermal springs in countries once burning with volcanoes, the fires of which are extinct, or at least quieted down for a period more or less protracted. Thus the former volcanoes of Auvergne; the mountains of the Eifel, on the Rhine, the craters of which contain nothing but lakes or pools; the Demavend, with its mouth filled up with Williſº § é% A º - Pºº 32.3% Rºžº (£ flºº §§ 3\,: ** * • *-- ºf ºngº. §ºğ w º Nº º ſ ; º º - - S. º º §§ § NZ §§ 5: Sº ºº: §§§§ à º ºaſillſ. %; NExº º ſ غ ſº - 2.3 ſº 4%. sº §§ 㺠“ - %|\}% ºft\{3%\}% § §§§ \º ºšš | ſº Fig. 200. Crater of Demavend. Snow—all still exhale here and there, through springs and fumerolles, as it were, a feeble breath of their once mighty vitality. The volcanic regions of the earth where thermal springs gush out are very numerous: in Europe we have Sicily, Iceland, Tuscany, and the pen- THERMAL SPRINGS, 481 insula of Kertch; in America—that land so rich in volcanoes—the Springs warmed by subterranean vapor are still more numerous, and there are some on the sides of the volcano Nuevo de Chillan which gush out through a thick bed of perpetual snow.” A lateral gorge of the valley of Napa, in California, called the “Devil's Cañon,” may be quoted as one of the most striking examples of the active production of thermal waters, The narrow ravine, filled with vapor rising in eddies, opens on the side of a red and bare mountain, that one might fancy was scorched by fire. The entry to the ravine follows the course of a rivulet, the boiling Waters of which are mingled with chemical substances horrible to the taste. Innumerable springs—some sulphurous, others charged with alum or salt.—gush out at the base of the rocks. There are both warm and cold springs, and hot and boiling; some are blue and transparent, others white, yellow, or red with ochre. In a cavity which is called the “Sorcerers’ Caldron” a mass of black and fetid mud boils up in great bubbles. Higher up, the “Devil's Steam-boat” darts out jets of gaseous matter, which issue puffing from a wall of rock: fumerolles may be seen by hundreds on the sides of the mountain. All these various agents either murmur, whistle, rumble, or roar, and thus a tempest of deafening sounds incessantly fills the gorge. The burning ground, composed of a clayey mud—in one spot yellow with sulphur, and in another white with chalk—gives way under the feet of the traveler who ventures on it, and gives vent to puffs of vapor through its numberless cracks. The whole gorge appears to be the Common out- let of numerous reservoirs of various mineral waters, all heated by some great volcanic furnace.f The ravine of Infernillo (Little Hell), which is situated at the base of the volcano of San Vincente, in the centre of the Republic of San Salvador, presents phenomena similar to those of the “Devil's Cañon.” There, too, a multitude of streams of boiling water gush from the soil, which is cal- cined like a brick, and eddies of vapor spring from the fissures of the rock with a noise like the shrill whistle of a locomotive. The most considera- ble body of water issues from a fissure 32 feet in width, which opens un- der a bed of volcanic rocks at a slight elevation above the bottom of the valley. The liquid stream, partially hidden by the clouds of vapor which rise from it, is shut out to a distance of 130 feet as if by a force-pump, and the whistling of the water pent up between the rocks reminds one of the furnace of a manufactory at full work. One might fancy that it was the respiration of some prodigious being hidden under the mountain. The hottest springs which gush out on the surface of the ground, such as those of Las Trincheras and Comangillas, do not reach the temperature of 212° (Fahr.); but we have no right to conclude from this that the water in the interior of the earth does not rise to a much more considera- ble heat. It is, on the contrary, certain that water descending into the * Philippi, Mittheilungen von Petermann, vol. vii., 1863. f Henry Auchincloss, Continental Monthly, September, 1864. f Wide above, p. 235. H. H. 482 THE EARTH, deepest fissures of the earth, although still maintaining a liquid state, may reach, independently of any volcanic action, a temperature of several hun- dred degrees; being compressed by the liquid masses above it, it is not converted into steam. At a depth which is not certainly known, but which various savants have approximately fixed at 49,000 feet, water of a temperature exceeding 750° (Fahr) ultimately attains elasticity sufficient to overcome the formidable weight of 1500 atmospheres which presses on it ; it changes into steam, and in this new form mounts to the surface of the earth through the fissures of the rocks.” Even if this steam, passing through beds of a gradually decreasing temperature, is again condensed and runs back again in the form of water, still it heats the liquid which surrounds it, and increases its elasticity; it consequently assists the gen- eration of fresh jets of steam, which likewise rise toward the upper re- gions. Thus, step by step, water is converted into steam up to the very surface of the earth, and springs out from fissures in the shape of fume. rolles. In Iceland, California, New Zealand, and several other volcanic regions of the world, jets of steam mingled with boiling water are so considerable as to rank among the most astonishing phenomena of the planet. The most celebrated, and certainly the most beautiful, of all these springs is the Great Geyser of Iceland. Seen from afar, light vapors, creeping over the low plain at the foot of the mountain of Blafell, point out the situation of the jet of water and of the neighboring springs. The basin of siliceous stone which the Geyser itself has formed during the lapse of centuries is no less than 52 feet in width, and serves as the Outer inclosure of a fun- nel-shaped cavity, 75 feet deep, from the bottom of which rise the water and steam. A thin liquid sheet flows over the edges of the basin, and de- scends in little cascades over the outer slope. The cold air lowers the temperature of the water on the surface, but the heat increases more and more in all the layers beneath; every here and there bubbles aré formed at the bottom of the water, and burst when they emerge into the air. Soon bodies of steam rise in clouds in the green and transparent water, but, meeting the colder masses on the surface, they again condense. Ulti- mately they make their way into the basin, and cause the water to bubble up; steam rises in different places from the liquid sheet, and the tempera- ture of the whole basin reaches the boiling-point; the surface swells up in foamy heaps, and the ground trembles and roars with a stifled sound. The caldron constantly gives vent to clouds of vapor, which sometimes gather round the basin, and sometimes are cleared away by the wind. At intervals, a few moments of silence succeed to the noise of the steam. Suddenly the resistance is overcome, the enormous jet leaps out with a crash, and, like a pillar of glittering marble, shoots up more than 100 feet in the air. A second and then a third jet rapidly follow; but the mag- nificent spectacle lasts but for a few minutes. The steam blows away; the water, now cooled, falls in and round the basin; and for hours, or even * Wide above, p. 436. TIIEEMAL SPRINGS. 483 days, a fresh eruption may be waited for in vain. Leaning over the edge of the hole whence such a storm of foam and water has just issued, and looking at the blue, transparent, and scarcely-rippled surface, one, “” hardly believe, says Bunsen, in the sudden change which has taken place. The slight deposits of siliceous matter which are left by the evaporation of the boiling water have already formed a conical hillock round the spring, and, sooner or later, the increasing curb of stone will have SO COll- siderably augmented the pressure of the liquid mass in the spring that the waters must ultimately open a fresh outlet beyond the present cone. From the experiments and observations made by Forbes as to the forma- tion of the layer of incrustations round the jet, this spring must have com- menced its eruptions ten centuries and a half ago, and they will probably cease in a much shorter space of time. Not far from the Geyser, the mound of deposits from which is not less than 39 feet in height, there are a number of pools which once acted as basins for springs which gushed up through them, but are now nothing but cisterns filled with blue and limpid water, at the bottom of which may be seen the month of a former channel of eruption. A shifting in the position of the centre of activity takes place in the Geyser, just as in mud-volcanoes and incrusting springs. Several springs lying on the same terrestrial fissure as the great jet d'eau, the Strokkr, the Small Geyser, and some others, present phenomena which are nearly similar, and are evidently subject to the action of the same forces. The vicinity of the active volcanoes of Iceland warrants us, how- ever, in supposing that the water produced by the melting of the snow on Blafell does not require to descend many thousands of yards into the earth in order to be converted into steam. There is no doubt that, at no very great depth below the surface, they come in contact with burning lava, which gives them their high temperature. By reproducing in miniature all the conditions which are thought to apply to the Icelandic springs that is, by heating the bases of tubes of iron filled with water and sur- mounted by a basin—Tyndall succeeded in producing in his laboratory charming little geysers, which jetted out cvery five minutes. About the centre of the northern island of New Zealand the activity of the volcanic springs is manifested still more remarkably even than in Ice- land. On the slightly-winding line of fissure which extends from the southwest to the northeast, between the ever-active volcano of Tongariro and the smoking island of Whakari, in Plenty Bay, thermal springs, mud- fountains, and geysers rise in more than a thousand places, and in some spots combine to form considerable lakes. In some localities the hot va- pors make their escape from the sides of the mountains in such abundance that the soil is reduced to a soft state over vast surfaces, and flows down slowly to the plains in long beds of mud. For a distance of more than a mile a portion of the Lake of Taupo boils and smokes as if it was heated by a subterranean fire, and the temperature of its water reaches on the average to 100° (Fahr.). Farther to the north, the two sides of the valley, through which flows the impetuous river of Waikato after its issue from 484 THE EARTH. the Lake Taupo, present, for more than a mile, so large a number of water- jets, that in one spot as many as seventy-six are counted. These geysers, which rise to various heights, play alternately, as if obeying rhythm in their successive appearances and disappearances. a kind of While one 17t.” E, of Paris * - -v- As j} ; % N f ** { § - § cºe, 1 ; 2 º' Wł iſºl. gº $º- *** #A fift §§§º& ..” N ...Sººº. ğ. - §nsºns § §: §§ § .** ..º. **ś º § sº ºś, *…* : ***** Ş., ſº §Aºya, º Sº _ſ. § rººt: §% º ; :) - sº-Mºſº &ºmº *. : i) wº ‘ī, §º’. 2.” P § º tºº. - £º f". ** *///wſ “ºut º - tº...º. ** - 4. ğ. º jº ū. §º i º º Jº # /šºs, ºº, Š *e. # /* {º} } Å. 'º' 5 sº ^{< tº ſº º É. #. S. ... awº ..!ººğ . Jºº. §§§ * - *\\ wº. §§ º º . 2. w º 7... i. º?" & . - º # % th. l ! wi *_ , §º º *~, *. * * , *:::::: § N § sº. * * , § { } <> - ** - łºwº st ºl.% ºnſ, \, {}.”ft Nº. *Thes &’ §%R."; Tº, & 㺠Wi. i. - §§ ... } { Q §§§ $ y Wºº fºg § º () / §§§ { } { ºšāºšš §§§º ºf ,-Z" T--~~~~ ** \- .../ “NJ Fig.201. Volcanic Region of New Zealand. springs out of the ground, falling back into its basin in a graceful curve bent by the wind, another ceases to jet out. In one spot a whole series of jets d'eau suddenly become quiet, and the basins of still Water emit nothing but a thin mist of vapor. Farther on, however, the mountain is THERMAL SPRINGS, ETC., OF NEW ZEALAND. 485 all activity; liquid columns all at once shine in the sun, and white cas- cades fall from terrace to terrace toward the river. Every moment the features of the landscape are being modified, and fresh voices take a part in the marvelous concert of the gushing springs. * About the middle of the interval which separates the Lake of Taupo from the coast of Plenty Bay, several other volcanic pools are dotted about, all most remarkable for their thermal and jetting springs. One of them, however, is among the great wonders of the world. This is the Lake of Rotomahana, a small basin of about 120 acres, the temperature of which, being raised by all the hot springs which feed it, is about 78° (Fahr.). Dr. von Hochstetter has not even attempted to count the basins, the funnels, and the fissures from which the water, steam-mud, and sulphurous gases make their escape. Here and there, indeed, he noticed, all together, Salses, Solfataras, fumerolles, and springs. The most magnificent of all these jets is the Tetarata, about 82 feet above the eastern bank of the lake. The : sgº jº. T. - sº N Se-TS-2T lºss ~~ § sº-3 º N §§ S. NSN Fig. 202. Section across the terraced Basins of Tetarata. basin, from the centre of which the water and steam spout out, is a kind of crater, 286 feet in circumference, which is surrounded by ramparts of red clay 32 feet in height, resembling the sides of a crater. The basin is full of clear water, which has entirely covered the former with a coating of silex, white as marble. The water in this dazzling basin assumes a de- licious blue shade, which is rendered more beautiful by the reflection of the steam unrolling its spiral clouds. The liquid which flows from the basin runs into another pool, likewise covered by a coating of silex, and, falling from terrace to terrace, thus reaches the level of the lake. These glittering steps, over which the water spreads in thin sheets, and then falls in cascades, form a wonderful spectacle of splendor and grace. Sometimes —say the natives—the whole body of liquid in the upper basin is sudden- ly upheaved in an enormous column, and the pool empties 30 feet of its depth; in this case nothing can be wanting to complete the grandeur of the picture. Have these wonderful springs existed for any great length of time, and are they destined to be preserved for centuries in all their beauty 2 These are points as yet unknown. When the New Zealand springs have been studied for a considerable number of years, it will perhaps be possible to describe the various modifications which are taking place in consequence * F. von Hochstetter, Neu-Seeland. 486 THE EARTEI. of the increase or relaxation of the subterranean action in these regions. In several parts of Europe thermal springs have gradually lost both their heat and their mineral qualities, owing to the cooling of the furnace which heated them, and are becoming more and more similar to ordinary springs: of this kind, for example, are the springs of Bertrichbad, in Luxembourg.” The gases which make their escape from the fumerolles situated above hidden beds of lava do not differ from those produced by great volcanic eruptions; they are the hydrochloric, sulphuric, and carbonic acids, either in a state of purity or in combination with alkaline, earthy, or metallic bases, and, as in the moving currents of lava, they indicate by their com- position the degree of intensity of the subterranean heat. The most pre- cise indications on these points have been furnished by the analyses of MM. Bunsen, Ch. Sainte-Claire Deville, and Fouqué. When they issue from the earth, fumerolles deposit on the edges of the fissure various substances, such as Sulphur, alum, and borax, which have been sublimated in the subterranean laboratory; the vapors then spread out into wide eddies, and are lost in the air. There is no spot in Europe where these fumerolles can be better studied than in the former crater of the Isle of Volcano. The cavity, at the bottom of which all these chem- ical operations take place, is more than a mile in circumference, and its southern sides rise to 980 feet in height; the bottom of the abyss may be about 320 feet wide. Through the mist of vapor which fills the immense caldron a spectator sees the lofty cliffs, red or golden yellow in color, and streaked here and there with most varied hues. On the slopes leading to the bottom of the gulf the crumbling stones give way under the tread, and yet it is necessary to descend at a running pace, for in some places the hollow soil is burning like an arch over an oven. Vapor creeps along slowly over the slopes. The air is saturated with hydrochloric and sul- phurous acid gases, and is difficult to breathe. An incessant noise of dull sobbings and whistlings fills the hollow, and on overy side there are small orifices between the stones, whence jets of steam spring eddying out. This is the spot whither the workmen—who seem accustomed to live in the fire, like the legendary salamanders—resort to gather the stalactites of gilded sulphur which still crackle from the effect of heat, and the fine needles of boracic acid, white as Swan's-down. At night the masses of vapor accumulated above the crater are colored with a red glare, as if from the reflection of an immense fire. w Sometimes the rain which falls into the amphitheatre forms there a tem- porary lake; but a great part of the water makes its escape through the fissures in the ground, and flows in a stream over the external slopes, the remainder being rapidly evaporated by the heat of the mountain. Some of the fumerolles, the gases of which were analyzed in 1865 by M. Fouqué, attain a temperature above 680° (Fahr.). Other jets of less heat make their appearance in various parts of the island, and even in the waters of the bay. From the edges of the great crater these vapors may be seen * See chapter on “Springs.” ISLE OF WOI, CAIVO. 487 at the base of the slopes rising from the bed of the sea, and developing into wide, whitish-colored spirals, similar in hue to the mud of potters' clay. In certain places the temperature of the sea-water heated by these gases is so high that voyagers can afford themselves the childish Satisfac- tion of boiling their eggs in it. \ N N \ a-mººn º *=ºssºmsºmºsºmºrrºr-º-m--> * §§§§º ſ § $ $$ % % º iº. ºº tº- d #. ºğ C. º * W § §§ & ſ Wºś - º Ž º *** AVºS fº NWS §§ º º ſ § §§ § & 2 º ſ § & AYºº S$)"; sº ºf . º º S&\} * º º §§ sº | W / *º § º § §§§ ºt M. - Nº {} jºs § Nº. *~ ſº- * Fig. 203. Island of Volcano. N The solfatara in the Isle of Volcano produces scarcely 10 tons of sul- phur every year. This does not seem much ; but if we were to calculate by centuries and geological periods the quantities deposited by the Jume- rolles, it would seem really enormous. Thus the mines of Sicily, which have been worked for Some centuries, furnish every year to commerce no 488 THE EARTH, less than 300,000 tons of Sulphur, and yet the mining operations in these districts are altogether of a primitive character. A large number of beds are unexplored, and nearly a third of the sulphur brought to the surface evaporates in the furnaces or is lost in the débris. These almost inex- haustible veins appear to have been all produced, like the deposits of the Isle of Volcano, by jets of vapor saturated with sulphur. Sometimes carbonic acid gas is the only gas which is discharged from the caverns and craters of volcanoes. This fluid, being much heavier than the atmosphere, does not ascend, like the other gases, and become lost in the air, but accumulates in weighty masses round the outlet. Plants which are bathed in this mephitic air rapidly wither, and all animated beings die from asphyxia, unless their heads rise up above the deadly at- mosphere. In the island of Java there is a small crater called Pakereman, or “Valley of Death,” the amphitheatre of which, after the heavy tropical rains, is entirely filled with carbonic acid gas. No plant grows in this vast cavity. According to the statements of Loudon, the ground is strewn with the skeletons of animals. At one time there might have been seen in it the remains of human beings who had been doomed to perish from asphyxia in the poisoned air. In Europe there is no spring of carbonic acid which can be compared to that of Java; those which have been studied in Italy, Auvergne, and on the banks of the Rhine are most of them nothing but very inconsiderable emanations, filling, perhaps, a con- fined cave, or the lower part of a small cavity well sheltered from the wind. Insects, and sometimes a few birds, are the only victims of this destructive gas. The famous cave in the vicinity of Naples is well known, into which, to satisfy the idle curiosity of travelers, the guides are cruel enough to bring some wretched dogs, and, forcing them into the layers of carbonic acid gas which hang over the soil, cause them to pant for breath, and ultimately die. At one time the crater, which is now filled up by the gloomy Lake of Avernus, which the ancients looked upon as the entrance to the infernal regions, gave vent to so large a quantity of carbonic acid gas that birds flying over the lake fell as if struck by lightning; hence is derived the Greek name of the lake, “without birds.” SUBMARINE VOLCANOE'S. 489 CHAPTER LXXI. SUBMARINE VOLCANOES. THE bed of the sea is, of course, inaccessible to our observation, but still there can be no doubt that the phenomena of submarine volcanoes resem- ble those of the burning mountains which tower so high above the ocean. Whenever the crest of an isle of scoriae rises above the waves, all that We see of its eruptions suffices to prove that they take place exactly in the same way as those of the volcanoes on the main land. There exist, how- ever, in several places, former submarine craters which, since their period of activity, have been upheaved, with the plains surrounding them. The history of these craters, written legibly in their strata, is just the same as that of other volcanic outlets. Still, as would necessarily be looked for, on account of the pressure exercised by the immense body of sea-water, the cones of débris which have been formed under the pressure of the waves are, without any exception, more flattened than mountains of the same nature which have taken their rise on the terra firma. With regard to the lava which issues from submarine fissures, it sooner becomes Solid- ified, and does not flow to such great distances. Often, also, it is con- verted, under the superincumbent weight of the water, into basaltic col- onnades. We can, too, readily understand that the vapor must rapidly condense while passing through the mass of cold water. It is only when the mouth of the crater is very close to thé surface of the ocean that col- umns of vapor are freely discharged and ascend into the air. - Most submarine eruptions which have been known in modern times have taken place at no great distance from some of the great insular or conti- mental volcanoes. The Sicilian Sea, the Greek Archipelago, the waters near St. Michael in the Azores, the portion of the Caspian which surrounds the Peninsula of Apcheron, the seas of Japan and of the Aleutian Isles, the Gulf of Darien, and the coast of Iceland, form, probably, a part of the same subterranean regions of activity as the volcanoes situated on the adjacent shores. There is, however, one volcanic district which is exclusively sub- marine; this is the narrowest part of the Atlantic, embraced between the two extreme points of the coasts of Guinea and Brazil. In this tract of the ocean the water is often agitated by violent shocks, and ships tremble as if they had run upon a sand-bank. Smoke, as if from a conflagration, rises above the waves, and pumice-stone and other light scoriae are floated about by the current. Even islands of ashes have been noticed to emerge from the midst of the sea, which, being washed away by the waves, have diminished, and ultimately disappeared.* + * Daussy, Darwin, Poulett Scrope. 490 THE EARTEI. The submarine cones proceeding from the bottom of the sea which resist the action of the water are those which have their layers composed of lava. The group of Aleutian Isles contain at least two mountains which have emerged from the water within a recent period. According to the ac- counts of the Chinese and Japanese chroniclers, several volcanoes have risen from the bed of the sea on the coasts of Japan and the Corea during the historical period. In the year 1007 a roar of thunder announced the appearance of the volcano of Toimmoura, or Tanlo, on the south of the Corea, and then, after seven days and seven nights of profound darkness, the mountain was seen; it was no less than four leagues in circumference, and towered up like a block of sulphur to a height of more than 1000 feet.* More than this, the celebrated Fusi-Yama itself, the highest mountain in Japan, is said to have been upheaved in a single night (?) from the bosom of the sea twenty-one and a half centuries ago. With respect to marine volcanoes of a more recent epoch, we may mention all the isles of either * 23 £8 + ) (A §ººt º - §§§n |\{º} § §§ §§ § S % | % % O % § § & t ſº º § sº 36 ſº º p' . . . . * º \ | §§ cºncoln Rock W \\ Wº: W. s Wº U. “S §§§ \\\\ fº jº º &6 Jö 6 § º & § % tºº º mº § sº § i. 㺠sº, & | ſº sº | * %\SP &/#}\\\\\ $º Z N Ž *%| º º ſº % Z | % º º ºº: s NY º -- & ! Aft º R& | Øſº g Fig. 204. Isle of St. Paul: the measurements are in metres. * Stanislas Julien, Comptes Rendus, vol. x., 1840. 7OLCAAWO OF TAAL. 491 extinct or still burning lava which rise in pyramids like Stromboli, or ex- tend in a graceful semicircle like the crater of St.Paul in the Indian Ocean. Lakes also exhibit a number of volcanoes of the same kind. Such are Momotombo of Nicaragua, and the Taal of the Lake of Bongbong, in the island of Luzon. sº Fº º [] \ == º ɺ $ºſſ |}/ º º * . | 2% \\ |. | -------- | | =3 * - º ~ Sº º Nº \- %; iT |T &ºº º§ *~-§ S~ *- § N~. : -ºº \ºº f % § § N N *-§§Essº *~ *~ =j§ N § Š § §§ SS§ \ º Tººlſ |||} % % N º~ S º § § \ \\ Š §§ \ § º º º/3.3. % zº º º º: ...tºrº ºf Sº ſ ºn razºº & ºf: - º: º ºs Nºjº ** **, ºsºtº, ºrs E. §§§§ $9's - º º; SSSº ººliº - 22 %tº Sùnº 22 tº &\}; º ! |S NºN S º N | W ſº | | º § º \ N º Yº: Šº 2:Bº:SE jºsë -- Fig. 205. Volcano of Taal. The sudden appearance of lava which has most impressed the popular imagination for many years past, and has also been best studied by scien- tific men, is the formation of hillocks of lava in the Santorin group. This circular archipelago is doubtless the remains of a great cone, 30 miles in circumference, which once rose in the midst of the Sea. In consequence of the action of the waves, earthquakes, and subsidences, the sides of this cone were broken in upon and finally ruptured by the water. When the IIel- lenes established themselves in the islands of the AEgean Sea, the shattered mountain was divided into three fragments: one fragment, assuming the 492 THE EARTH. form of a crescent, and comprehending the larger portion of the former vol. cano, constitutes the island of Thera, or Santorin; on the west, the little Isle of Therasia bends round in continuation of the ring of land; and, on the southwest, a great rock, the Islet of Aspro, rises as if to bear witness to the rampart of lava now disappeared. The outer slopes of Santorin and Therasia, partially covered with pumice-stone somewhat resembling a coat- ing of snow, are rather gently inclined toward the sea, but the escarpments, turned in the direction of the basin, which was once the crater, are in some places nearly perpendicular for a height of 650 and even 1300 feet. The various layers, which correspond on the two sides of the gnlf—on the sides of Therasia and of Santorin—are vividly marked out in bands of a red, yellow, blue, black, or white color. 23°Elde Paris ** \ º t ğ ğº jº §§ º % §§§ § * §§§ º *M**** §º y ſº º º §§§§ º º I / & W Sº ºf ºğ % §§§ |W[º]ºffº —A A-Liº A Fig. 206. Santorin. 23:Flåsfºs In the centre of this crater, after a series of upheavals and eruptions, an islet of lava emerged about the year 196 B.C. It was named Hiera (Holy), and on the summit a temple to Neptune was built. This islet, which was RAIMENT ISLE.S.–SANTORIN. 493 several times increased in the centuries which followed—in the years 46, 713, 726, and 1427 A.D.—is now known under the name of Palaeo-Kaïmeni. Not far from this isle, another smaller one, Mikro-Kaïmeni, rose in 1570 or 1573. At the commencement of the eighteenth century, from 1707 to 1711, another mass of lava, Neo-Kaimeni, an island no less than four miles in cir- cumference, emerged within the annular crater formed by the crescent- shaped Santorin and the Isle of Therasia. In 1768 Neo-Kaimeni was shaken by a violent eruption. From this date to 1866 no visible change took place above the water, but soundings proved that the bed of the sea had gradually risen. At a point near Mikro-Kaïmeni, a bank of rocks, sit- uated in 1794 at a depth of 80 to 100 feet, was in 1835 only 13 feet from the surface. “Such is the singular fecundity of Santorin,” says a histo- rian of this volcano, “that isles seem to grow up round it like fungi in a Wood.” At the end of January, 1866, subterranean roarings, a gradual sinking of the ground, and the coloring of the water, announced an approaching eruption. The centre of the shock was felt just below the little village of Vulcano, situated on the edge of a creek where ships used to cast anchor in order that the water, mingled as it was with acid gases, might destroy the molluscs and sea-weed attached to their keels. On the 3d of Febru- ary a brilliantly black mass of lava was seen, which rose slowly from the bottom of the water, and increased in size every day with perfect regu- larity. This mound, designated by the name of George's Isle, attained in a few weeks a height of 164 feet, and ultimately became united to Neo- Kaimemi, having filled up the creek of Vulcano. On the 7th of February, another mound, the Isle of Aphroessa, rose at a little distance to the South, and, gradually filling up the channel which separated it from Neo-Kaſmeni, became converted into a promontory. Afterward other islets made their appearance by the side of the two principal cones. All round them the sea, agitated by the gases which rose in great bubbles, exhibited in turn the most diversified hues. It was in succession reddish-colored, milk-white, or shaded with green or a chemical blue; it was, besides, generally tepid or hot. The fish, either asphyxiated or killed by the heat, floated in mul- titudes on the surface, and mariners avoided steering their ships any where near the eruption for fear the pitch between their planks should melt in the water heated to a temperature of 160° to 170° (Fahr.). The summit of the crater of Neo-Kaimemi was shaken by frequent explosions. On the 20th of February lumps weighing 220 pounds were Suddenly darted out to a distance of several hundred yards, showers of ashes fell upon the vines of Santorin, and clouds of débris, making their escape from the Crater, shot up to a height of 6500 to 9800 feet. It was not before the end of the year 1866 that the cone of George's Island opened out for itself a crater by an explosion which destroyed the whole of the upper portion of the mound. But the intensity of the eruptive phenomena soon after gradually dimin- ished. Currents of lava more than half a mile long were in some places * Pègues, Histoire des Phénomènes du Volcan de Santorin. 494 THE EARTH, more than 300 feet in depth. It is evident that the reason why the mol. ten matter has thus formed in heaps close to the outlet, instead of flowing in long streams, as on the sides of Vesuvius and Etna, is that the lava, soon becoming cool by its contact with the salt water, was necessarily compelled to arrest its progress.” Fig. 207. Kaïmeni Group. The cones of shifting ashes which are thrown out by the eruptions of submarine volcanoes are not able to resist the action of the waves for any length of time; and however great may be their dimensions, they are cer- * Fouqué, Revue des Deux-Mondes, August, 1866. ISLE OF JULIA. 495 tain ultimately to disappear, unless they are based on solid foundations which have entirely emerged from the water. As an example of this we may mention the celebrated Julia, or Graham's Island, which appeared in º º āşäß º º Exº º & # * | § º N §§§ & Sº § 3. \. sº g Fig. 208. Graham's Island, or Isle of Julia. July, 1831, throwing up heaps of dark-colored scoria about 25 miles south of the shores of Selimonte, in Sicily. An English captain, proud of being able to increase the British domains, hurried to hoist his flag over the smoking stones. The islet gradually increased round the crater, and be- fore long it measured as much as four miles round. Dut, at the conclu- sion of the volcanic eruption, the work of demolition commenced, and, in conformity with M. Constant Prévost’s prediction, the slope of débris was gradually undermined at the base by the waves and currents. In October nothing remained but a little mound. Six months after, the newly-discov- ered island, which was also claimed by the King of Naples through his di- plomatists, was nothing more than an oval reef about half a mile long. A few years later the sounding-line showed a depth of 787 feet. In July, 1863, the isle again appeared, and in a few weeks rose to the height of 200 to 260 feet; but it existed only for a short space of time, for it soon again sank, being demolished stone by stone by the dash of the waves. It appears, however, that, previously to 1831, the volcano had made its appearance on one or two other occasions. It is said that a smoking isl- and existed in this spot about the year 1801, and the shoal is pointed out in old charts. This island, first rising up above the waves and then sink- ing down again into the depths of the sea, seems to recall the recollection of that mysterious country mentioned in the “Arabian Nights,” which plunged down into the ocean just at the moment when the voyagers were going to land on it. º Near the island of San Miguel, one of the Azores, there is another sub- marine volcano, which likewise vomits out at each of its great eruptions a temporary cone of scoriae, which rises above the level of the sea. In the 496 THE EARTH, years 1658, 1691, 1720, and 1812, a smoking islet made its appearance, and on each occasion it was destroyed after a few weeks of existence. Never- theless, in 1812, an Englishman found time to take possession of it in the name of his government, and to give it the name of “Sabrina.” In 1867 a fresh eruption took place at about the same spot, but the volcanic cone did not reach the surface of the sea, and M. Fouqué, the indefatigable ex- plorer of volcanoes, noticed nothing but floating scoriae, gases thrown out, and flames dancing over the water. In the Icelandic seas, the land of Nynoë, which appeared in 1783 at a point 31 miles to the southwest of Cape Rekianess, enjoyed a much longer life, for it lasted a whole year. There, just as in the seas of Sicily and the Azores, the ashes washed away by the waves are deposited at the bottom of the water in vast layers of tufa mingled with shells and other débris. Some day or other these beds of volcanic stone will appear on the surface, just as the tufas of the Euga- nean hills in the valley of the Po, and the Phlegraean fields at Naples, and will tell the tale of the submarine eruptions of the present period. PERIODICITY OF ERUPTIONS. 497 CHAPTER IXXII. PERIODICITY OF ERUPTIONS.–INFLUENCE OF TEMPERATURE ON WOLCANIC PHIENOMENA.—EXTINCTION OF FURNACES OF LAVA. ONE of the most important questions in respect to volcanoes is that of the order in which their phenomena take place. Every thing in nature acts in sure conformity to regular laws of periodicity; but When this rule has to be applied both over vast spaces and long intervals, it may readily remain unknown to us for a very long time. The fact is, that the rhythm of the great volcanic revolutions has not yet been discovered, and, up to the present time, the whole of these events appear to us as if they were a perfect chaos. Even in the volcanic region which is the best known, and which savants have the best studied, that is, in the area which includes Southern Italy, Sicily, and the Lipari Islands, the succession of movements (except as regards Stromboli) has taken place with the greatest apparent want of order. Etna and Vesuvius have remained in a state of repose for centuries, and then suddenly, and after unequal intervals, they have expe- rienced sometimes one convulsion only, sometimes a series of shocks more or less violent and numerous. Besides, as we have seen, there is no neces- sary coincidence between the phenomena of the two volcanoes. Some- times, indeed, it happens that a period of extraordinary activity in one volcano is contemporary with protracted tranquillity in the other. True enough, during the dark night of the Middle Ages, phenomena like this were almost entirely lost sight of in history, but documents collected since the sixteenth century evidently prove that the geologist must limit him- self to studying the symptoms of periodicity in each smoking mountain by itself. - In this last respect there is no want of evidence which renders highly probable the existence of some sympathetic tie between the eruptions of volcanoes and the more or less regular phenomena of the surrounding at- mosphere. This, indeed, is a proverbial article of faith with mariners as regards a large number of active craters. The fishermen of Stromboli have for centuries all agreed in stating that the mountain serves as a ba- rometer for them in pointing out the approach of winds and storms by a great increase of violence in its eruptions. At the time of the autumnal equinox, as well as in winter, the boiling lava in the crater runs out much more often through the outlet, and sometimes opens out a way of issue in the sides of the mountain, so as to flow down to the sea. The fact is, that the atmospheric pressure above the column of lava being diminished dur- ing stormy weather, does not act with the same energy on the compressed mass; the molten matter rises more rapidly in the crater, and flows out in greater abundance. Added to this, as the smoke of the volcano gen- II 498 THE EARTH, erally mounts up a thousand yards above the level of the sea, and some- times rises in a column to the higher regions of the atmosphere, the con- tests which take place among the aërial currents may often be seen more or less clearly ; thus, by experience, a knowledge may be obtained before- hand of the changes of weather which will gradually make their way down from the sky above. “By the smoke of this volcano,” said Pliny, eighteen centuries ago, “the natives can predict the winds three days in advance, which leads them to believe that these vapors are in obedience to AEolus.” The inhabitants of Lipari say, also, that the vapors from the crater of Volcano form clouds of much greater volume when storms are brewing. This, then, would be another gigantic barometer, regularly indicating the diminished pressure of the atmosphere. According to both travelers and natives, the epoch of the equinoxes, when the monsoons blow, is the time when the eruptions of the Peak of Ternate, Taal, and other volcanoes of the Indian Archipelago are most terrible. In like manner, in the Isle of Chiloe, Fitzroy was told that the eruptions of Osorno always announced the approach of fine weather, and, in consequence, an increase in the weight of the column of air. With regard to phenomena, other than the oscilla- tions of the aërial masses, these may also be foretold by means of the vol- canic movements, if we are to put faith in the statements of those who live at the very foot of the smoking mountains. Thus, in Japan, the vol- canoes generally begin to vomit out lava about the time of the flow of the tide, and inundations caused by exceptionally high tides always take place after eruptions and earthquakes.” In 1827, Scuderi, a Sicilian, tried to prognosticate all the meteorological phenomena by the form and direc- tion taken by the masses of vapor which were vomited out by the crater of Etna.f M. Emile Kluge, by classifying all the known eruptions in seasons and months, has ascertained that these crises take place in summer especially, and that earthquakes are more frequent in winter. According to this ge. ologist, there is no doubt that the cruptions of volcanoes depend on the changes of seasons. The melting of the snow and ice, the falls of rain, the oscillations in temperature, and the weight of the air, are, in his idea, the real causes of the subterranean fires; the latter, too, being the mere result of chemical reaction, and among the purely external phenomena of the planet. Not, therefore, in the abysses of a sea of fire, but at a depth of six to nine miles at most, must we seek for the furnaces in which the burn- ing matter is elaborated. Nevertheless, although we may be warranted in looking upon the year itself, with its return of seasons and atmospheric phenomena, as a kind of day in the life of volcanoes, we are none the less in complete ignorance in respect to the great secular periods of Plutonic activity in the various parts of the world. Like all terrestrial phenomena, that of the eruption of lava and ashes is limited in its duration. The volcanoes which rise "P * Siebold, quoted by Perrey. + Memoire dell’Academia Gioenia. # Ueber die Periodicität vulcanischer Ausbrüche; Neues Jahrb. für Mineral., 1862, part V. EXTINCTION OF WOLCANOES. 499 - g *º " ãºzºº/?!? §§ % º § Šºšyº º % sº §§ ſºft - § ś%2 %% -º ɺ ºšº sº NºSYºYº! - ŠE: ×2% Nº/ šš g SºSN Yº §§ Sºğ § Wy % & º º §§§º % jº |ɺ ºlº ºf S$ | Ø Wºjſ!/º º \º § º -º-º-º: S$ >''' sº 3: §§§ sº ºft %º |||}| % \ | sº º sº ºº º F. ºr = 'º º ſ/ iſ% N à º : Sº Wºº &# % N g: #. #:: . ; - \ W § - º º gº §- . g º \º º sº § - W. * tº W. à 3: º º \\ fºº º/|\}| out of the ground are extinguished either after a short existence or after §S. %| 2-2:5-tº- \\\\ºšsº --> thousands of eruptions. Over the whole surface of the earth there are a large number of former volcanoes the nature of which has been disclosed to us by modern geology alone. Some date from an epoch so remote that beds of modern formation have to a great extent covered their sides and filled up their craters. Others, like the hills of Auvergne, are still visible, with their cones of scoriae or their domes of trachyte, their fissures and cheires of lava, such as they once were when the plains at their bases were arms of the Sea. Among these well-preserved, volcanoes there are, indeed, some—especially that of Denise, near the Puy-en-Velay—which were in a state of full activity at an epoch when man had already established him- self in the adjacent districts, for in the tufa of their eruptions skeletons have been found of the ancient inhabitants of Gaul. Lastly, numerous volcanoes which have burnt during the historical period are now extinct, and perhaps forever. The cycles of these lava-furnaces are doubtless con- nected with those of the continents themselves; the configuration of land and sea must change before these furnaces can again be lighted up. Con- timents and oceanic basins must also shift their position on the surface of the globe before they can be extinguished. | º Ž Fig. 209. Coulée of Puy de Pariou. 500 THE EARTH, - CHAPTER LXXIII. BARTIIQUAKES.—WIBRATIONS OF THE GROUND.—VARIOUS IIYPOTIII:SES. As volcanic eruptions sufficiently show, this planet is not the immova- ble mass which our imaginations depict it when comparing it to the at- mosphere which surrounds it, to the ever-mobile waves of the ocean, or even to the animated beings which wander over its surface. On the con- trary, the ground which we tread under our feet vibrates very frequently. Without alluding to those great shocks which overthrow cities, bring down the sides of mountains, and open vast cracks across plains, there are other less violent vibrations, which have been recorded by the annalists of geological history, and may be reckoned by thousands as regards civil- ized countries and modern times alone. There can be, however, no doubt that the great majority of slight earthquakes pass unnoticed, being blend- ed, especially in towns, with the confused rumbling of noises and murmurs. Various seismological instruments, recently invented or brought to perfec- tion, reveal a large number of oscillations which it would be impossible to discover in any other way. An attentive observation of the levels of air- bubbles and of micrometrical threads reflected on the surface of a bath of mercury has, indeed, warranted M. d’Abbadie in asserting that the earth is in a state of constant vibration. The intervals of immobility which he has noted have never exceeded thirty hours. What is the cause of these trepidations of the ground? A great num- ber of savants, who have accepted the hypothesis of a pyriphlegeton, or central fire, do not hesitate to look upon these vibrations of the earth as the repercussion of the undulations of the great burning sea. Each of the shocks which are felt on the surface of the earth would then take its rise below the envelope of the planet, and would be at first produced in the form of a current or tide in the burning mass which is supposed to exist. As IIumboldt says, an earthquake would be “the reaction of the liquid nucleus against the outer crust.” Added to this, most geologists who base their arguments on the hypothesis of a central fire admit that earth- quakes must necessarily be in connection with volcanic phenomena, and that they invariably proceed from the same cause. Following out the comparison which must always present itself to the mind, the mouths of volcanoes are safety-valves, and, on account of the obstruction of these out- lets, the pent-up lava or vapor shakes the superincumbent layers of the terrestrial envelope, seeking to find some way of issue. This theory has the merit of being very simple, and, in a large number of cases, seems to harmonize very satisfactorily with the facts that have been observed. But we must never forget, however probable this hypothesis as to the Vol- DISTRIBUTION OF EARTITQUAKES, 501 canic action may be, it has not as yet become a certainty; and the duty for the geographer still is to study events impartially, and to suspend his judgment until a satisfactory conclusion evidently results from the whole body of facts observed. In the first place, it is important to know if those regions on the surface of the globe in which earthquakes take place with the greatest frequency are distinguished from other parts by any peculiar features in the form Of their vertical outline, or in the nature of their rocks. The volcanic dis- tricts in Europe, such as the environs of Vesuvius and Etna, the islands of Santorin and Milo, and the south of Iceland, are not the only places which are subject to severe shocks; the former districts, too, have never been SO violently agitated as the mountains of the Abruzzi and Calabria, the islands of Rhodes and Cyprus, the limestone districts of Carniola and Istria, the Alps of the Valais, the environs of Basle, certain plateaux in Spain, and the hills at the mouth of the Tagus. The mountains of Scotland, and es- pecially those in the county of Perth, have also experienced repeated shocks: out of two hundred and twenty-five earthquakes recorded in the British Isles, eighty-five have taken place in this one county. In Africa, the soil of Algeria, so rich in saline and thermal springs, but devoid of Vol- canic craters, is sometimes very severely shaken. The districts of the Nile, which are likewise without volcanoes, have also suffered much from subterranean movements. In Asia, the peninsula of Guzerat, a spot in which astonishing modifications of the shape of the coasts were produced during a great earthquake, is situated more than 1240 miles from the near- est volcanoes, the Demavend and the burning mountains of Thian-Chan; but, on the other hand, the Philippines and Japan, which are volcanic coun- tries, are also frequently agitated by movements of the ground. Again, the sea-coast of Syria, the towns of Aleppo and Antioch, the scenes of some of the most destructive earthquakes that are recorded in history, no lon- ger possess very active volcanoes, and the lavas of the Djebel-Hauran, on the southeast, have long been extinct. In South America, most of the great shocks have taken place in the region of the Andes, or not far from their bases. The Argentine town of Mendoza, which was overturned in the violent earthquake of 1861, is comparatively not far from a lava-fur- nace, since the volcano of Maypu rises at a distance of only 87 miles. The equatorial Andes are often convulsed by violent oscillations of the soil, and are also the theatre of great volcanic activity, many of their summits be- ing domes of trachyte, or craters still vomiting out ashes, mud, or smoke. Nevertheless, according to the testimony of Boussingault, the most ener- getic shocks experienced in Columbia—those which destroyed the towns of Latacunga, Riobamba, Honda, Merida, and Barquesimeto, and were sim- ultaneously felt over a very extended area—presented no coincidence whatever with any volcanic phenomena, and their centre of agitation was situated at a considerable distance from the smoking peaks.” The plateau of Caraccas, celebrated for the catastrophe of 1812, is situated more than 600 miles eastward of the Grenadini volcanoes of Huila and Tolima, and * Annales de Chimie et de Physique, 1855. 502 - THE EARTH, at rather a less distance from the craters of the Antilles, from which it is separated by wide arms of the Sea. Finally, the region in North America where oscillations of the ground are most frequent and most severe is the alluvial plain of the Mississippi, far distant from any volcanic district, and even from any great chain of mountains. Thus, although the history of earthquakes is known only for a few centuries, and over but a small por. tion of the earth's surface, it is certain that severe oscillations of the ground are felt in countries the most diverse, which bear no resemblance to one another either in their formation or their aspect. The only fact which seems well established is, that shocks are more frequent in moun- tainous than in flat countries. Nevertheless, if, as Mr. Mallet thinks, all. earthquakes not followed by an eruption are “incomplete efforts to open a volcano,” if they are produced by the endeavors made by the planet to get rid either of gas or the molten matter within, the ground ought to be most frequently agitated in continental plains, far from volcanoes and mountains; for in those localities there would be no natural “vent-holes” through which to discharge the overflow of the interior fluids, and there, too, according to the common theory, the terrestrial layers must be the thinnest. - Those who look upon every volcano as a safety-valve for the adjacent regions put forward in favor of their theory certain facts which have at- tained to the dignity of legends, although their reality is far from being certain, as M. Otto Volger has more than sufficiently proved.* Thus it is said that, at the time of the earthquake at Lisbon, Vesuvius, which was vomiting out a considerable quantity of vapor, suddenly sucked in the cloud which it was throwing out, and that the current of lava issuing from its sides was suddenly stopped. But these statements are founded solely on a much less precise expression in the account which Kant the philoso- pher devoted to the catastrophe at Lisbon. Humboldt tells us “that, after having vomited out for three months a high column of smoke, the volcano of Pasto ceased to throw out vapor at the exact moment when, at a distance of 248 miles, the earthquake of Riobamba and the mud-eruption of Tunguragua caused the death of 30,000 to 40,000 Indians. Even the great name of Humboldt must not, however, lead us to forget that, on the plateaux of the Andes, communication is both rare and difficult, and that the population scattered over that space of 248 miles does not afford all the guarantees which would be considered requisite in scientific observa- tion. Lastly, the assertion that Stromboli relaxed its incessant activity during the Calabrian earthquake in 1783 is based on nothing but the vaguest information. According to the pamphlets of that date, all the Lipari Isles were to be swallowed up in the sea, leaving but a few shoals to mark the places they once filled ! As may be seen, the facts which have been brought forward as the foundation of the theory that all earth- quakes are caused by the movements of lava or vapors are deficient in the requisite authenticity, and can not be looked upon as exempting geologists from the necessity of direct observations. * Erdbellen in der Schweiz, vol. iii., p. 385. # Tableaux de la Nature, vol. ii. CAUSES OF EARTHQUAKES, 503 CHAPTER LXXIV. pARTHQuakes of volcANIC origiN.—SUBTERRANEAN DOWNFA*T ExPEOSIONS OF MINES AND POWDER-MILLS. There are a certain number of cases in which, independently or any theory, we can without difficulty substantiate a relation of cause and effect between a volcanic eruption and an earthquake. Thus, When the sides of a smoking mountain, such as Etna or Kilauea, are suddenly cleft asunder to pour forth a stream of lava, and at the same time the ground is strongly agitated, it is evident that the earthquake is caused by the fracture of the volcano. This local phenomenon is precisely analogous to that produced by the explosion of a mine or a powder-mill. When the fissure is of a considerable length and the fractured sides of the volcano present a great thickness, the shock is a violent one, and reverberates in long oscillations in all the adjacent districts. When, on the contrary, the rocks of the volcano, having been diminished in thickness and partially, melted by the rising lava, yield more easily to the pressure which bursts them, the ex- plosion is only felt in the immediate vicinity of the fissure. Thus, at the time of the last great eruption of Etna, the trepidations of the ground, which coincided with the formation of the fissure, were in general Very slight, and the sharpest of them—which was, however, perceptible in the town of Aci Reale—was not felt beyond the Etnean region properly so called.” History also affords several examples of volcanic eruptions dur- ing which the ground was not perceptibly shaken. In May, 1855,Vesu- vius vomited out a considerable quantity of lava without the least trace of any motion of the ground being perceived either in the observatory on the volcano or at Naples. When the ground of a volcanic region is convulsed by shocks, and We are unable to observe the least connection, either as regards coincidence or immediate succession, between these phenomena and the eruption of a cone of ashes or the emission of a current of lava, we evidently have no scientific reason for asserting with any certainty that these shocks origi- nate in the subterranean furnace of burning matter, or that they are caused by vapor endeavoring to break through the terrestrial crust. For still stronger reasons, a similar assertion would be contrary to all the rules of scientific observation when applied to earthquakes which take place far from any volcano. Certainly, according to the “safety-valve” hypothesis, oscillations of the ground ought to take place just in those very localities of the planetary envelope in which there exists no orifice communicating with the lava. But how is it, then, that undulations of the soil are not * Mariano Grassi, Eruzione dell' Etna. 504 THE EARTH, constantly produced at places far from these gigantic vent-holes situated on the sea-coast 2 Why is it, too, that frequent eruptions of Vesuvius and Etna did not precede the Calabrian earthquakes, and afford an issue to the pent-up vapor and lava º The hypothesis that volcanic forces are the cause of earthquakes being one that can not be justified in every case, we must have recourse, in re- spect to many of these phenomena, to some other theory—one, in fact, which in all time has suggested itself to the minds of various people, and was taught by the Greek philosophers. Some two thousand years ago Lucretius propounded this idea in magnificent language—an idea which has now been scientifically adopted by Boussingault, Virlet, Otto Volger, and other geologists. - “Learn, now, the cause of earthquakes, and first be assured that the in- terior of the globe is, like the surface, filled With winds, caverns, lakes, precipices, stones, rocks, and a large number of rivers, the impetuous waves of which hurry along in their course numerous submerged blocks. The shakings of the surface of the globe are occasioned by the falling in of en- ormous caverns which time has succeeded in destroying. Whole moun- tains thus sink in ruin, and the violent and sudden shock is spread far and wide in terrible vibrations. Thus a chariot, the weight of which is not, however, very gonsiderable, makes all the houses near tremble as it passes, and the fiery steeds, drawing behind them the iron-armed wheels, shake all the places round. It might well happen that an enormous mass of earth should fall by reason of decay into some great subterranean lake, and that the globe should tremble in a series of undulations. In like manner, on the surface of the earth, a vessel filled with liquid in a state of agitation can not resume its equilibrium until the water contained in it has found its level.” Various savants have recently collected a large number of facts which are in favor of the theory of earthquakes once propounded by Lucretius, although only generally, and without the necessary proofs. In a vast number of cases this theory is certainly the true one, for it is often possi- ble to catch in the act, so to speak, the phenomena which give rise to the oscillations of the ground and subterranean thunders. Thus great land- slips, such as those of the Diablerets, Rossberg, and other mountains of the Alps, have caused real earthquakes, the waves of which were felt at a considerable distance from the scene of the catastrophe. Even the falls of moraines, séracs, and avalanches of snow shake the ground very severely over considerable areas, so much so that in the mountains of Allemont, in Dauphiny, the inhabitants consider all the vibrations of the ground as the reverberations of distant downfalls of snow or rocks.” The subsidence of rocks or shifting soil is accompanied by similar phe- nomena. In September, 1814, near Alais, for twenty-four hours a series of detonations were heard like a cannonade, and then, after a formidable cracking noise, the ground sank 13 feet for a breadth of more than 88 * Fournet, Annales des Sciences Physiques de Lyon, vol. viii., 1845. CAUSES OF EARTHQUAKES, 505 yards. Not far from the town of Wagstadt, in Silesia, in 1827, a tract of more than two acres in area sank in a similar way with a great crash. In Carniola, where earthquakes are not unfrequent, heaps of fallen rocks are noticed in the numerous caverns, which heaps correspond with the funnel- shaped cavities on the surface of the ground. These subsidences, which man sometimes personally witnesses, either in districts hollowed out by natural caves, or in mining regions pierced with subterranean galleries, may cause local shocks, or, in proportion to the mass of rocks falling, give rise to earthquakes felt simultaneously over vast extents of country. In fact, certain rocky strata sometimes leave intervals between them of very considerable depth, as may easily be noticed on the sides of mountains; and they may, besides, be composed of substances which are more or less easily dissolved and washed away by the infiltrated water. When these voids extend so far that the rocks above, sometimes hundreds or even thousands of yards in thickness, can no longer maintain their position by means of their own cohesion, the whole mass must necessarily fall down on the beds beneath. It is, indeed, impossible to imagine that it can be otherwise; the enormous quantities of salt, gypsum, lime, silex, and other substances which springs bring up to the surface must of necessity leave great voids in the depths below, and, in consequence, the subsidence of the rocks above these vacant spaces becomes inevitable. Only imagine, if it is possible, the potency of the shock produced by the sudden fall of sev- eral millions of cubic yards.” - Earthquakes produced by artificial causes in no way differ from natural shocks in the effects which they produce; they, indeed, furnish us with excellent terms of comparison. The explosions of mines and the passage of heavily-laden trains cause a motion of the ground over areas increasing in extent as the initial pressure is more considerable and as the rocks pre- sent a greater degree of elasticity. Cannonades, the reaction of which on the earth is, however, trifling in proportion to the effect produced, are heard at distances which seem prodigious, if the ear is applied to the sur. face of the agitated ground. Vibrations of the layers of the earth—in fact, real earthquakes—are thus prolonged for more than 250, or, indeed, for 375 miles. Thus, in 1832, the bombardment of Antwerp was heard, it is said, in the Erzgebirge, in the centre of Germany. Twenty-five years ago, at the time of the explosion of the powder-mills of Mentz, a very large area of ground was made to tremble. More than 10,000 lbs. weight of the gunpowder exploded (the greater part) blew up in open Vaults, and could not, therefore, react on the ground; yet the shock was felt, either as a slight trembling of the ground or as distant thunder, as far as 100 to 125 miles away—far beyond the districts to which the sound of the detonation was carried by the wind. The shock was felt at several towns in Suabia, at Wurzburg, at Kissingen, in Fulda and Meiningen, in Thuringia, near Cassel, and at Wildungen.f Doubtless the observations made on Carth- quakes in the various countries of the world, whether these phenomena * Otto Volger, Erdbeben in der Schweiz. f Ibid. 506 f THE EARTEI. º - º &\ºğ §§ sº & § ºś * §§ º º # º : w e; J-2T151 ;§§ º g º § sº § º ºść †† \ ; :; §:f º:§º: ºs#. ſº * Fig. 210. Area over which was felt the Explosion of Gunpowder at Mentz. are produced with or without the intervention of man, will some day en- able us to estimate approximately the force that is necessary for shaking some given area of the earth's surface. These would be comparative studies which could be made without prejudice in favor of the hypoth- esis of the central fire or any other theory. GREAT CATASTR012HES. 507 CHAPTER LXXV. GREAT CATASTROPHES.–EARTHQUAKE AT LISBON. —EARTHQUAKES AT SEA. AREA OF DISTURBANCE, As a natural consequence of the fellow-feeling which tends to unite all men together, writers of the earth's history have been prone to give to earthquakes a geological importance bearing a proportion to the number of persons overwhelmed and the quantity of the productions of human labor destroyed. A shock which shakes a vast city filled with stone buildings, in which thousands of individuals are assembled, may cause the most terrible disasters, while a much more violent one felt by the inhab- itants of a nearly desert country is soon forgotten and passed over by history. According to Otto Volger, the earthquake at Lisbon was scarce- ly more violent than was that of the valley of Viége, a hundred years after (?); but it remains memorable on account of the thousands of human beings who perished in it, while the shock of Viége, which only killed two poor mountaineers, was soon forgotten. The sudden vibrations which overturn cities in a few seconds are, in fact, the most frightful catastrophes that can be imagined by man. All other disasters are announced by some precursory signs. The stream is- suing from the volcano advances but slowly, and its progress across vil- lages and cultivated land may be foreseen. The floods of rivers threaten the embankments long before they break through them, and preparation may generally be made for the irruption of water. Even the hurricane is preceded by atmospheric signs; but earthquakes generally happen Sud- denly and unexpectedly, and in an instant, without a single sign to ex- plain the catastrophe, whole cities are demolished, and the inhabitants destroyed by thousands. The earthquake of San Salvador only lasted ten seconds, and this space of time was sufficient for the destruction of the town. The successive vibrations which devastated Calabria in 1783 were felt during barely two minutes. The terrible movements of the earth which destroyed Lisbon succeeded each other during the space of five minutes; but it was the first shock, lasting from five to six seconds, which caused the greatest damage. The inhabitants sometimes make use of the brief respite given them by the intervals between the great shocks, not in taking refuge in the open air, but in increasing still more their chances of death: struck with terror, they rush into the churches, the roofs of which fall in upon them. After some of these castastrophes the corpses may be counted by tens of thousands: the shocks in Sicily in 1693, and Calabria in 1783, must have caused in each of these two countries the death of 100,000 persons. Lastly, records of more or less credibility Speak 508 THE EARTII. of earthquakes in Syria, Japan, and the Sunda Archipelago, which resulted in a sudden loss of life still more considerable. In 526, more than 200,000 people met with their death at Antioch and the adjacent towns. These undulations, which are so terrible in their consequences, are sim- ultaneously felt over vast areas. Thus the commotion which destroyed Lisbon on the 1st of November, 1755, and demolished the greater part of Oporto and several other places in Portugal, threw part of the walls of Cadiz into the moats, and, it is said, on the testimony of the Governor of Gibraltar, that the greater part of the towns of Morocco, Tetuan, Tangiers, Fez, Mequinez, and even the capital itself, were overthrown by the earth- quake. Kant, the philosopher, and Hoffmann, who were the historians of the earthquake at Lisbon, mention a great number of other countries in Europe, Africa, and even the New World, which must have participated in the violent disturbance. The vibrations extended over an area of 15,400,000 square miles; that is to say, about a twelfth part of the terres- trial surface. The statements upon which the various accounts of the catastrophe are founded are not always of any great value; it is now proved that the extent of the area over which the undulations of the earth were felt on this occasion has been singularly exaggerated. In the whole of Europe, popular imagination was so struck by this event, which, in the course of a few minutes, and, indeed, on a day of festival, destroyed so many thousands of persons under the ruins of a great capital, that it was naturally led to look upon the earthquake at Lisbon as a phenomenon without parallel, the scene of which was, if not the whole world, at least a great part of the terrestrial surface. All the oscillations which were felt in Europe, either on the same day or about the same time, were considered in a general way as the result of the great commotion at Lisbon; and gradually a sort of legend was established attributing to the same cause a considerable number of geological facts of an undecided date, such as the downfall of rocks, the formation of lakes, the breaking up of ice, and changes of temperature in thermal springs. Thus a shock which, “by a strange chance,” was felt at Turin alone on the 9th of November, a week after the catastrophe at Lisbon, was attributed to this vast disturbance. The movements of the soil described as having taken place at New York on the 18th of November are also reckoned among the undulations which were then spread far and wide. The Lake Ontario was also added to the immense area of disturbance, because stong vibrations agitated its shores during the month of October; that is to say, before the day of the disas- tor. As a matter of fact, there is no positive proof that the terrestrial wave spread farther than Morocco on the south, the Castiles on the east, or in a northerly direction farther than Angoulême and Cognac.” This, however, constitutes an area of 1118 miles in length; and if, as the diame- ter of the area of disturbance, the same distance is taken in the direction from cast to west, we shall find that the area of the earth shaken by the great terrestrial wave of Lisbon was more than 1,158,000 Square miles, or * Otto Volger, Erdbeben in der Schweiz, vol. i. EFFECTS OF EARTIIQUAKES. 509 about six times the size of France. As a term of comparison, We Will mention the earthquake which was felt in France on the morning of the 14th of September, 1866, the undulations of which were propagated to the north as far as Rouen, and to the south as far as Bordeaux. The area Of disturbance of this shock must be estimated at about 77,218 Square miles, or the fifteenth part of the surface agitated by the earthquake at Lisbon. O 2* º º º sºft aft *el B + O C S-> # Ée. © -E" Fºs+ E=E º º -Es- º º-ºº- #=##### #### EE-- #Eä § É E==#: #=== *===#| \ Chá * S.4 BExº ătă \ ==E, ### - É Fº FE cº- E: - =EE ÉÉ º- #######.º: Bă EEE É####### E--> Eºrº º *>>>>> Fig.211. Chart of the Earthquake of the 14th of September, 1866. At the time of this latter event there was one fact which contributed much to extend the apparent area of disturbance; this was, that a marine wave, harmonizing with the shock of the earth, was spread across the At- lantic in all directions. But the water, being more easily moved than the soil, necessarily transmitted the wave to a greater distance than the com- paratively rigid beds at the bottom of the sea. At the mouth of the Ta- gus, the wall of water formed by the waves rose, it is said, to a height of nearly 56 feet; then, filling up all the estuary that extends in front of Lis- bon, swept over the quays of the city and rushed among the houses. At Cadiz a wave of nearly equal size rushed above the ramparts, and caused much more havoc than the earthquake itself. On the coasts of Madeira and of Holland, the mouth of the Elbe, the sea-shores of Denmark and 510 tº TEIF EARTH, Norway, and, lastly, the whole circumference of the British Isles, the sea felt the reaction of the shock communicated to the waves in the waters off Disbon, and its level underwent rapid fluctuations. The undulations of the wave, variously modified by currents and tides, struck even upon the shores of the New World. At Barbadoes and Martinique, where the flow of the tide never exceeds 28 inches, the wave produced by the transatlan. tic earthquake attained a height of 18, 16, and even 19 feet. Thus the ma- rine wave resulting from the shock was carried to a distance of nearly 3728 miles in a straight line. In 1854, at the time of the earthquake of Simoda, the wave which reached the coast of California had traversed 2485 miles the whole width of the Pacific Ocean. ~, When violent shocks agitate the ground, towns situated on the sea- shore have often suffered much more from the sudden irruption of the wa- ter than from the shaking of the earth itself. When the waves receive the shock from the neighboring coasts, or else when the centre of disturb- ance is at the bottom of the ocean, the masses of water rise to a formida- ble height, and dash upon the shores as if during a hurricane. In 1788, at the time when the shock in Calabria overthrew the towns and villages on the main land, a terrible bore, after having swept away at Once 2000 per- sons assembled on the coast of Scylla, rushed into the port of Messina, sank all the ships, and undermined the base of the superb row of palaces which bordered the shore: more than 12,000 individuals perished, it is said, under the ruins. On the 7th of June, 1692, at the time of the earth: quake which shook Jamaica and the neighboring seas, the waves rushed violently upon the town of Port Royal, and in the space of three minutes covered more than 2500 houses with a depth of 33 feet of water. The ships were thrown in every direction on to the land, and the frigate Swan was stranded upon the roof of a house. In like manner, according to the statement of Acosta, the terrible wave which destroyed Callao in the year 1586, and carried a great ship right up on to the Lima road at a point 52 feet above the mean level of the sea, must have been altogether 89 feet in height. The Japanese, whose islands have often suffered from earthquakes and sea-bores caused by submarine shocks, say that these frightful phe- nomona are caused by the blows of the tail of a monster striking against the shore. Thus the Greeks attributed the vibrations of the soil not only to Pluto, the “shaker of the world,” but also to Neptune, the “agitator. of the waves.” EAJ&T/I- WA WE'S. 511 CHAPTER LXXVI. MOVEMENT OF TERRESTRIAL WAVES. — VARIATIONS CAUSED IRY TIIIE IN E- QUALITY OF VERTICAL OUTLINE AND THE I)IVERSITY OF I.OCKS.—Aſ EAS OF DISTURBANCE.-NOISE OF EARTIIQUAIXES.—FRIGIIT OF MEN AND AN- IMALS. WHATEVER may be the nature of the first shock, whether it proceed from a sudden Swelling up of lava or vapor, or whether it be caused by the falling in of upper strata upon the subjacent beds, the effects produced will always be the same as regards observers who are above the central point where the phenomenon is produced. They will experience a shock tending upward. Even when falling with the ground, they might well fancy themselves raised, like the aëronaut, whose balloon is falling toward the earth, sees the country mounting up toward him. Around the central point of disturbance, where the shock takes place in all its violence, and is felt vertically, in a manner more or less irregular, according to the num- ber of shocks, the movements become more and more oblique, and are propagated across the strata of the earth in a direction which ultimately becomes perceptibly horizontal.” The phenomenon of undulation which is produced in solid rocks is perfectly analogous to that which may be ob- served in water when a stone falls into it: a series of concentric waves is formed round the centre of the shock, and gradually disappears in the dis- tance. Terrestrial waves which are formed thus are very long and very flat, on account of the inflexible nature of the rocks through which the movement is transmitted. There does not, however, exist a single authentic meas- urement from which the dimensions of each wave may be deduced. The observer feels them pass rapidly under his feet during an Carthquake, and is often able to notice the rocking of houses and towers, as well as the to- and-fro motion of church-bells; but these movements are much more mark- ed than those of the ground, and the movements of the earth have not been clearly distinguished on any occasion. As to the direction followed by the waves, the tendency generally dif. fers much, owing to the inequalities in the relief of the ground, from the regular direction it would otherwise take. This direction is often very difficult to discover, owing to the want of necessary instruments, and all the local circumstances which may modify the movement. It appears, however, that in mountainous countries, like Switzerland and the Pyro- nees, the great undulations are propagated in the direction of the valleys. In striking against the tilted strata at the base of mountains, the corru- - * Robert Mallet, Observation of Earthquake Phenomena. & 512 THE EARTH, gations of the soil act like the waves of a river dashing against the shores; they break up, and, changing their course, run along at the foot of the heights in the same direction as the stream of the valley. After this first rupture in its movement, the undulation is communicated to the rocky masses of the mountain, and traverses their whole thickness. Beyond these lofty groups which disturb the movement, without always opposing to it any insurmountable obstacle, the vibrations corrugate the soil of the - ſº Wºº- U-y Fig. 212. Transmission of Earth-waves. plains in a more regular way; but the intensity weakens proportionately to the square of the distance, and finally ceases to be perceptible to man. It must also be remarked that, at the periphery of the area of disturbance, the various shocks are generally produced at longer intervals than at the centre of the earthquake. The stronger the waves are, the more rapidly are they propagated, and thus it follows that between the different undu- lations, which generally become weaker and weaker, the interval always increases with the distance. In the centre the shocks all seem to blend together; toward the circumference they succeed each other like waves of slighty-agitated water. Among the causes which contribute to disturb the regular movement of terrestrial oscillations, the diversity of geological formations must also be reckoned. The swiftness of the transmission of the movement varies considerably, according to the composition of the rocks, the quantity of water they contain, and the hardness and elasticity of their layers. In order to explain the difference that exists between the various strata as regards the propagation of terrestrial waves, Mr. Mallet makes a striking comparison. If a person applies his ear to a railway-rail which is struck with a violent blow at a point about a mile away, the compact iron trans- mits to him nearly instantaneously the wave of the sound; immediately after, the observer will feel the undulation which is transmitted through the soil below the rail; then he will hear the noise transmitted by the at- mospheric waves. If a canal flows along by the side of the railroad, a man plunged in the water would perceive the sensation of the blow, but not at the same time. In fact, the mean swiftness of the wave is 1138 feet in the air, 4692 in the water, and about 11,040 in a bar of iron. It is a long-established fact that, during earthquakes, the shocks are prop- agated much more easily through compact rocks than through formations interrupted here and there by faults, fissures, caves, and soft ground. Mr. Mallet has proved these facts by direct and oft-repeated experiments, made EARTH.WAVES. 513 not far from the town of Holyhead in Wales. When mines of powder were exploded, the waves of disturbance, which were the more rapid as the charge was stronger, were propagated 951 feet a second in wet sand, 1283 feet in a rock of friable granite, and 1640 feet in a compact granite. Subsequently Mr. Mallet, having made some direct observations as to the speed of transmission of the waves during the earthquake at Calabria in 1857, found, that it was about 820 feet a second. According to the same geologist, the starting-point of the shock was nearly three miles below the surface. - Without having made any exact investigations, the Hellenes and the Romans, who inhabited a soil frequently shaken by earthquakes, had found out the fact that caverns, wells, and quarries retarded the disturb- ance of the earth, and protected the edifices built in their neighborhood. The town of Capua was, it is said, saved from the effects of the earth- quakes to a much greater extent than the adjacent cities on account of the numerous springs in its gardens. Vivenzio also asserts that in build- ing the Capitol the Romans took care to sink several wells in order to weaken the effect of terrestrial oscillations, and this plan succeeded in preserving the building from all damage. In like manner, the great con- structions at Naples were built above vast caves, in which the force of the subterranean commotion is lost. IIumboldt has described this curious fact —that at St. Domingo the inhabitants of the town spontaneously formed the idea, similar to that of the Greek and Roman naturalists, of digging out deep cavities as the only means of securing the stability of their dwellings. Besides, as may readily be supposed, the longer, thicker, and lower the walls of the edifices are, the better they resist the shock. In all towns partly destroyed by earthquakes, it is said that walls of this form were rarely demolished. When the undulations of the soil are propagated along the whole length of a block of low houses, there is hardly an in- stance in which the latter have been shattered; in countries, therefore, in which the movements of the soil generally assume the same direction, dis- asters can nearly always be provided against by setting the principal walls of the edifice in the direction of the terrestrial undulations. The buildings which always suffer the most are those which have vault. ed roofs, elevated in the form of domes or cupolas. The thrusting action of the heavy masses which crown the edifice causes the walls to separate when they are in a state of vibration from the effects of the subterranean shocks; the dome falls down inside, while the walls give way in an out- ward direction. A considerable area is covered with ruins all round the piece of ground on which the foundations stand, and, in Consequence, the danger of being crushed becomes very great to any persons who are near the scene of the catastrophe. It was the earthquakes, and not the barba- rians, which, according to the evidence of Mr. Mallet, destroyed so large a number of the palaces and temples of Rome during the period between the fifth and ninth centuries. In like manner, in more modern times, ca- IX. K. 514 THE EARTEI. thedrals and churches have often been overthrown, while other houses Were saved. This well-known fragility of vaulted roofs, when shaken by undulations of the soil, will explain the cause of those frightful calamities which took place in various churches at the time of the earthquakes of Lisbon, Calabria, Caraccas, Mendoza, and San Salvador, when kneeling multitudes were crushed in the ruins. The difference presented by rocks, as regards the speed with which the earthquake wave is propagated through them, and the various obstacles which impede it, has the effect of giving to the areas of perceptible dis- turbance shapes which are perfectly irregular. The movements, there- fore, are not produced round the initial point with a regularity which can be at all compared to that of the wavelets which surround with their reg- ular circles the centre of agitation in a disturbed water. Some earth- quakes, as far, at least, as it is possible to judge from incomplete observa- tions, seem to be propagated in very elongated ellipses. Others appear to have had for their area a space of a polygonal shape; thus the great paroxysm of the valley of Viége, which extended over 108,878 square miles, was felt three times farther in a northern than in a southern di. o” 2° ** 6° 8.” -- - # #:E % #º 2% à --- ź 2. -3 Fig. 213. Area'aſſected by the Earthquake of Viége in 1855. EAIRTH.WAVES. 515 rection. Sometimes, outside the limits of the ground in a state of vibra: tion, a region has been remarked which likewise shakes, like a kind of trembling islet surrounded by immovable land. At other times Vast tracts have not experienced any apparent disturbance, while the ground all round them was trembling. On the 25th of July, 1846, the shock of which the severest impulse was felt below St. Goar, on the banks of the Rhine, propagated its undulations in France and Germany over a surface estimated at 24,207 square miles; but a belt about 100 yards wide, be- tween Pyrmont (Westphalia) and the right bank of the Rhine, appears to have remained immovable.* According to the testimony of Humboldt, this fact of rocks not participating in the general movement of the Sur- rounding formations has been frequently noted at the time of earthquakes in the Andes. The natives say of these intermediate zones, thus exempt- ed from the vibrations of the ground round them, that they form a bridge (hacen puente), meaning by this that the oscillations are transmitted at a great depth below the inactive beds at the surface. It is difficult to im- agine how such phenomena could take place if the oscillations of the soil were caused by the movement of the waves in a subterranean Sea of fire: if it were so, the upheaved terrestrial crust would undulate like an object floating on the surface of the water, and the burning waves, spreading out in a circle, would also give a perfectly round periphery to the Super- ficial area of the earthquake. To the two kinds of movement which have been observed in earth- quakes—the upward shock and the long undulations spreading in the manner of marine waves—most of the savants since Aristotle also add the rotating or gyratory movement (vorticosum). The fact is, that in great cataclysms, when the different shocks cross each other in the ground, it has been thought that proofs of these twisting movements have been felt and even seen. At Quintero, in Chili, three great palm-trees, says Hum- boldt, twisted round one another like willow-wands, after each had swept a small space round its trunk. Otto Volger, who does not believe in the existence of rotatory movements, mentions, however, the example of the steeple of Graechen, which twisted during the earthquake in the valley of Viége in 1855: it is true that this twisting may have been caused either by a movement of the soil being communicated to the edifice, or by the want of equilibrium between the different parts of the steeple. Mr. Mal- let also explains, by a difference between the centre of form and the cem- tre of gravity, the gyratory movement which the stones of two small ob- elisks underwent during the earthquake at Calabria in 1783; he absolute- ly denies that the rotatory movement of the earth could take place, as the Italian naturalists had alleged. ** - & & As to the speed of the propagation of terrestrial waves, it was, even recently, very difficult to estimate, owing to the want of precision in the transmission of intelligence and the irregularity of the clocks in the dif. ferent cities. Since 1853, the period at which the electric telegraph was * Daubrée, Comptes Rendus, 1847. 516 . THE EARTH, applied for the first time in describing the shocks of the earthquake of Soleure, almost certain means are at our disposal for noting the passage of terrestrial waves in different localities; but up to our time it has scarcely been employed save in an exceptional way, and too often some of the desirable conditions of exactitude have been neglected. The incomplete information gathered by Otto Volger about the great earthquake of Viége in 1855 has warranted him in fixing approximately the speed of the undulation; it was at the rate of 2861 feet a second from the centre of vibration as far as Strasbourg, and 1898 feet only in the di- rection of Turin. Robert Mallet, after having made his celebrated exper- iments on the speed of transmission of shocks in the rocks at Holyhead, instituted comparative investigations into the speed of the undulations of the great earthquake at Calabria in December, 1857, and found the aver- age rate 774 feet a second. Since that time English observers established at Travancore, in the south of IIindostan, have estimated the movement of the undulations of a local shock at about 656 feet. The result of the calculations varying thus in proportion of one to four, it is impossible to indicate any average figure for the rate of transmission of terrestrial waves; it is certain that the rapidity, as well as the force and direction of the movement, differs according to the nature of the rocks, and the po- sition of the chains of mountains and valleys. The noises which are heard during earthquakes differ in intensity still more than the other phenomena, and are much more difficult to classify, owing to the deep sensation that is felt when the earth is heard to roar, and the part which the imagination never fails to play when memory seeks to recall the past. The sounds, besides, heard at the time of the sub- terranean downfall sometimes exceed in their violence all known noises, and it is in vain to seek for suitable terms in which to describe them. In a general way, the noises of earthquakes may be compared to explosions of mines, discharges of artillery, peals of thunder, the rolling of carriages, the fall of avalanches, or the roar of cataracts. The diversity of these noises is explained by the difference of the phenomena which may be tak- ing place in the interior of the carth—the falling in and reboundings of rocks, the overflow of subterranean water, the irruption of masses of air through fissures, and distant echoes reverberating far and wide in the abysses. It is a strange thing that sometimes during one and the same carthquake certain persons can not find terms strong enough to express the frightful noises that they have heard, while others think they have only felt the shock unaccompanied by the least sound. According to M. Otto Volger, this singular difference of sensation proceeds from the fact, well known to natural philosophers, that the scale of sounds perceived by the car differs in different individuals; just as in a meadow some persons do not hear the cry of the cricket—the note is too shrill for them, so, when the ground is shaken, those who are shaken with it would not all be able to hear the sounds produced by the cataclysm on account of nothing but the deepness of their tone; the noises would be too deep for their TERROR CAUSED BY EA/PT/IQUAMES. 517 ears, . At a distance from the centre of the shock the noise gradually diº minishes in intensity, but it always remains difficult to distinguish clearly, because the sound is transmitted with unequal speed both under the ground and in the atmosphere. Through the terrestrial strata the noise of the paroxysm travels with more rapidity than the shock itself; the shock is heard before it is felt; then, when the wave has passed, the sound is heard anew, being transmitted more slowly by the air. This inequality in the passage of the sound through the different mediums results in a great confusion of roaring and rattling, of which it is very difficult to give any just account. Observers have compared the noise of a distant carth- quake sometimes to the rumbling of thunder, sometimes to a stormy wind or the flapping of the wings of a large bird, and sometimes even to a dis- charge of musketry, the crackling of fire, or the whistle of a locomotive. One might fancy that in this manifestation of its mighty vitalityºmature makes use of all the sounds known to the human ear. All this diversified uproar and these frightful noises sufficiently explain the instinctive terror which takes possession of nearly every one during the time of an earthquake, even when the shocks have not caused any fatal consequences. Nevertheless, as IIumboldt remarks, a feeling of insecurity is the cause which generally most contributes to upsetting moral force. The earth which we felt so firm under our feet becomes as flucturating as the waves; one hardly dares to walk a step for fear of being swallowed up in the opening ground. All our ideas as to the nature of things be- come confounded, and, by a sudden reaction of his physical or his moral nature, the man who feels that he is being deprived of the earth he stands on loses all confidence in his own personal powers. It is a widely-spread opinion, which, however, is not as yet undeniably confirmed, that animals manifest the greatest uneasiness at the approach of an earthquake. In certain countries, indeed, where these convulsions of the ground frequently take place, care is taken to observe attentively the ways of domestic animals, in order to detect the presentiment of the coming shock and to prepare for the danger. It may perhaps be the case that slight vibrations, perceptible only to the delicate senses of animals, precede the subterranean downfalls; but very often it is probable that remarks of this kind are made after the catastrophe, and that imagination, excited by the fright, plays no inconsiderable part in the descriptions. Be this as it may, it is said that, before an earthquake, rats, mice, moles, lizards, and serpents frequently come out of their holes, and hasten hither and thither as if smitten with terror. Even the crocodiles have fled away from their marshes and hurried toward terra firma, roaring with fear.* At Naples it is said that the ants quitted their underground passages some hours before the earthquake of July 26, 1805, and that the grasshop- pers crossed the town in order to reach the coast; also that the fish ap- proached the shore in shoals. A fact which is better attested is the fright of animals during the catastrophe itself. At the time of the earthquake * Humboldt, Relation IIistorique, vol. v. f. Landgrebe, Naturgeschichte der Vulkane, vol. ii. 518 THE EARTH, which shook the valley of Viége in 1855, the wild birds which most dread the fowler, such as owls, woodpeckers, and peewits, collected on the trees close to the dwelling-houses, and uttered plaintive cries, as if to demand the succor of man. Birds of long flight—swallows and others—at once took wing, and flew away to distant parts. For several days, also, the frogs ceased their croaking.” * Otto Volger, Erdbeben in der Schweiz, vol. iii. SECONDAA; Y EFFECTS OF SHOCKS, 519 CHAPTER LXXVII. SECONDARY EFFECTS OF SIICCIXS.—SPRINGS.—JETS OF GAS.-FISSURES.- DEPRESSIONS AND ELEVATIONS OF THIE GROUND. , EARTHQUARES very frequently exercise a considerable influence on the discharge of springs rising to the surface of the ground. A great many instances have been brought forward of springs, both thermal and cold, which have suddenly dried up or have increased in volume, accompanied by either an augmentation or diminution of temperature. These phenom- ena can be easily understood. After each downfall of rocks or fracture of the ground, the conduits through which the subterranean rivulets flow may be either altogether or partially obstructed; the water must then seek some other course, or must flow in a diminished stream through the old channel. Sometimes, also, the breaking down of some barrier which penned back the subterranean water opens up a free passage to it, and the spring is thus augmented in its discharge. Again, the waters of several subterranean currents of various temperatures may become mingled in consequence of some catastrophe, and the springs, therefore, are rendered either warmer or colder. In August, 1854, on the occasion of a violent earthquake in the central Pyrenees, the heat of a spring at Baréges was raised from 64° to 82° (Fahr.), and its discharge, which was 2729 gallons a day, increased to 6338 gallons. The effect more generally produced on springs by the occurrence of an earthquake is to render the water muddy by filling it with the débris which has fallen from the rocks disturbed, and been raised by the ascend- ing body of water. During a series of observations made on the artesian well at Passy in 1861 and 1862, M. Hervé-Mangon ascertained that at the time of each of the subterranean shocks of Western Europe which were recorded by M. Perrey during the above-named interval, the water in the well was charged with sediment. On the 14th of November, 1861—the day on which a great earthquake occurred in Switzerland—the sediment in the well at Passy suddenly increased in quantity from 956 grains per cubic mêtre to 2268 grains; the next day it decreased to 1404 grains. This skillful chemist, by numerous processes, established several other strik- ing coincidences between the impurity of the water and the vibrations of the ground. It is not at all probable that these geological facts are de- void of any mutual relation; it appears, on the contrary, that the artesian spring at Passy, and doubtless also most other springs gushing out to the surface, might be looked upon as actual “seismometers.” At the time of earthquake shocks a kind of clearing out takes place of the natural or ar- tificial conduits through which the spring water passes. According to the observations of M. François, who devoted considerable study to the action 520 \ THE EARTEI. of earthquakes on the mineral springs of the Pyrenees, the results of a shock are rarely felt for any length of time; after the lapse of two or three days the effects are no longer perceptible. In all countries frequently affected by earthquakes, the inhabitants nev- or fail to tell numerous stories as to sudden eruptions of water, mud, gas, or flames. Phenomena of this kind may be, in fact, produced in many dis- tricts, for shocks violent enough to close up or to enlarge the conduits of springs may equally well open out fresh channels, and thus afford an out- let to water pent up under deep layers of rocks. In like manner, the hy- drogen gases which are formed in the ground by the decomposition of or- ganic matter may find an outlet by the breaking down of the rocks above them, and burn spontaneously, like the gases at Baku. Nevertheless, these curious eruptions, however probable they may appear, have not as yet been scientifically observed, and no idea seems to have been formed as to the real importance they might have. Even Mr. Mallet, the great advo- cate of the constant connection between earthquakes and volcanic phe- nomena, has not ventured to look upon these sudden jets of water, mud, and gas as facts on which science may depend. With regard to the sud- den appearances of flashes and sparks, these may be explained in many cases by the collision of stones, which strike against one another as they fall. Occasionally, during earthquakes, the ground is rent open for very con- siderable distances. In 1783, at the time of the terrible shocks which dis- turbed Calabria, the phenomena of ruptures of the ground ranked among the grandest and most frightful effects of the catastrophe. Whole moun- tain-sides, undermined by water, slid down en masse, and tumbled into the plains below, covering all the cultivated ground. Cliffs fell down in a body, and rocks opened, swallowing up the houses which stood upon them. At the western base of the granitic chain of the peninsula, the ground af. fected by the shock was cleft open for a length of more than 18 miles, and in some places, especially near Polistena, the fissure was several yards in width. Elsewhere other clefts were opened, one of which, near Cergulli, was no less than 131 feet in depth for a length of more than a mile, and 32 feet wide. In the environs of Rosarno, on the shore of the Gulf of Ni- cotera, well-like cavities were hollowed out with circular margins, doubt- less caused by the gushing out of springs. Finally, districts with a level surface were cleft in every direction by cracks radiating in the shape of a star; the ground was broken up in a similar manner to mud which has cracked from the loss of its moisture. In February, 1835, on the occasion of the earthquake at Conception, in Chili, similar phenomena were ob- served: every where, says Fitzroy, contact ceased between the shifting ground of the plain and the bases of the rocky hills. Not only do fissures sometimes form in the ground during earthquakes, but after commotions of this kind the level of the terrestrial surface is oc- casionally permanently changed. When the catastrophe is caused by some subterranean downfall, it is perfectly natural that the surface layers, EFFECTS OF EARTHQUAKES. 521 being suddenly deprived of their supports, should be included in the sub- sidence; and, in fact, several instances have been brought forward of these sinkings in the level of the ground. In some countries it is said that phe- nomena of a directly opposite class have been observed, and whole dis- tricts have been suddenly upheaved a few inches, or even several feet. If the facts are certain (and there seems but little doubt about them), they would go to prove that earthquakes, from which these upheavals result, are caused by the pressure of confined vapor. Among shocks of this kind we must mention the great geological catas- trophe, unfortunately but too well known, which, in the year 1819, changed the shape of the country of Cutch over a vast area. A part of the Great Runn sank down over an extent of some thousands of square miles, and, in consequence of the inroads of the salt water, it became a tract of land of an undetermined character—during drought a desert without water, and during the monsoons a Salt lagoon. A rampart several miles in length, 164 feet broad, and 9 feet in height, was also raised in a straight line across one of the former mouths of the Indus. This rampart is called by the in- habitants of the adjacent districts “God’s wall” (Ullah Bund), to distin- guish it from the Ally and Mora barriers, which the sovereigns of the coun- try had constructed farther up stream. According to Mr. A. Barnes, the earthquake which produced this strange phenomenon of elevation and de- pression was felt over an area of more than 95,500 square miles." 67 68 - 69 w w Mora Bund! LE THURR ou HETIT DESERT sº º Ally|Bunder * 2::::::::= | §, %| # * || Ilahº § º º 2, * Fig. 214. The Runn of Cutch and the Ullah Bund. With regard to the earthquake at Conception in 1835, the affirmative evidence on the point is so abundant, that the raising of the coast at this 522 THE EARTH, place must be regarded as a positive fact;” but it must remain unknown whether some enormous depression in the interior of the continent did not compensate for the temporary upheaval of the sea-coast. Still more recently, on the 23d of January, 1855, at the time of an earthquake which violently shook New Zealand, and especially the two shores of Cook's Straits, the ground on which the town of Wellington stands was raised 23 inches, a cape in the vicinity was elevated nearly 10 feet, while a fis- sure of about 40 miles in length opened in the southern island on the oth- er side of the straits, and the alluvial plain of a small stream sank consid- erably. Also, in 1861, the coast of Torre del Greco, at the foot of Vesu- vius, was suddenly raised 3% feet for a length of more than a mile. All these are extraordinary phenomena, and a just hesitation must at present be felt in venturing to give any explanation of them. There is another geological fact which has been little studied as yet, which, however, must be perhaps attributed to oscillations of the ground: this is the curious arrangement that is assumed in some plains by the boul- ders, pebbles, and drifts of sand. Thus, in the Desert of Atacama, in many spots regular figures are to be met with—circles, squares, or lozenges— composed of small fragments of quartz or other stone. In the entirely uninhabited plains of Safa, at the foot of the former volcanoes of Djebel- Hauran, M. Wetzstein likewise remarked a multitude of small figures with regular angles, formed something like mosaics, over very considera- ble areas. Must we look upon these designs as some immense symbolical work to be attributed to the ancient inhabitants of the district, or are they, in fact, the sports of nature, and phenomena similar in character to the figures shaped out by grains of sand agitated on vibrating plates? This question remains to be solved by future observers. * Wide below, p. 529. f F. von Hochstetter, New Seeland. f Tschudi, Ergänzungshaft; Mittheilungen von Petermann, 1860. PERIODICITY OF EARTHQUAKES, 52 3 CHAPTER LXXVIII. PERIODICITY OF EARTHQUAKES. — THE MAXIMUM IN WINTER. — TIIE MAX- IMUM AT NIGHT. — COINCIDENCE WITH HURRICANES. – INFLUENCE OF THE HEAVENIY BODIES. *: f FROM time immemorial it has been asserted by the natives of the coun- tries which are most frequently ravaged by earthquakes, that these com- motions bear some intimate relation to the movements of the atmosphere, and very generally coincide with certain racteorological conditions, such as rainy seasons, numerous storms, warm and damp winds.” Neverthe- less, most geologists, considering these oscillations of the ground to be nothing more than the half-exhausted quiverings of a great ocean of fire, have even recently denied the possibility of any such coincidence. In 1834, Professor Merian, having classed, according to their appearance in the various seasons of the year, 118 earthquakes which occurred at Basle and in the countries round it, ascertained, to the surprise of the scientific world, that these phenomena are much more frequent in winter than in summer. This fact, which was at first called in question, has since been indubitably established by the investigations of Alexis Perrey and Otto Volger. Only, in proportion as the list of shocks becomes more numer- ous, the difference between the winter maximum and the summer max- imum tends to disappear, for the simple reason that, in the two opposite hemispheres, the seasons follow one another at six months’ intervals, and that the various phenomena in connection with the seasons are thus brought into a state of equilibrium on each side of the equator. It is therefore necessary to study, in each region separately, the order in which the occurrence of earthquakes is divided among the different seasons. The comparative frequency of these phenomena during the winter season is 21 De- 2~ Zº 2/ & \- /~ S–/ ^->" N Fig. 215. Monthly Distribution of 656 Earthquakes in France. NumberS. 83 || 6% 53 || 55 || 42 36 || 47 ſo Tso K &6 6o 78 Jan. Feb. March. April. May. June. July. TAug. TSept. TOct. TNov. Toec. them much more easy to be observed. Thus the 656 shocks enumerated in France by Alexis Perrey up to the year 1845 are divided in the pro- portion of 3 to 2 respectively, for the half years commencing in Novem- * Luigi Greco; Ferdinand de Luca; Alexis Perrey. 524 wa THE EARTH, ber and May. In the regions of the Alps, where there are no volcanoes, the difference between the number of earthquakes in winter and summer is, on the other hand, enormous. By comparing the four months of May, June, July, and August, with December, January, February, and March, we see that the shocks are three times as numerous in the second season as in the first. In Italy, according to the same author, the difference was much less perceptible, since out of 984 earthquakes, 453 took place in the summer season, from April to September, and 531 during the winter half º Fig. 216. Monthly Distribution of 1230 Earthquakes in Switzerland. |-|-- \ \- Numbers.' tºo | *3 | * I wº 58 || 54, ko 47 117 in 85 || 168 Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. year, from October to March. Nevertheless, even in this region, where most of the great subterranean movements are evidently in connection with volcanic action, these phenomena are perceptibly more frequent dur- ing the cold portion of the year. If we limit ourselves to the study of some particular centre of shocks, the difference observed between the seasons in respect to the frequency of subterranean shocks is still more considerable. As an instance of this we may mention, on the authority of Otto Volger, the remarkable region of the Mid-Valais, where, out of a total number of 98 known earthquakes, one only took place in summer, while 72 were felt in winter. The pro- N Fig. 217. Monthly Distribution of 98 Earthquakes in the Mid-Valais. Ds – C Numbers. 32 16 3. To To Toº TTL o | 1 | 6 || 5 24. Jan. T Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. DeC. portion is nearly the same in the region of Hohensax, on the southern slopes of Säntis, not far from the former fork of the Rhine. Not only are subterranean commotions more frequent in winter than in summer, at least in the regions of Central Europe and on the coasts of PERIODICITY OF EARTHQUAKES. 525 Fig. 218. Monthly Distribution of 98 Earthquakes in Southern Sántis. -— 21 Numbers: -44. 41 9. Tº TTTTTTS TO To Liz Y2O Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Noy. Dec. :k the Mediterranean as far as Asia Minor and the Caucasus,” but this re- markable fact has also been observed—that the shocks are felt more fre- quently at night than in the day, and this holds good in all seasons of the year. In all earthquake regions this is uniformly the case. In Switzer- land, out of 502 earthquakes, the date and time of which are known, only 182 took place between six o'clock in the morning and six o'clock in the evening; 320–that is, nearly double—were felt during the twelve hours of the night. There is, therefore, for every diurnal period, a series of al- ternations resembling those of the annual period ; but there is, in truth, Fig. 219. Switzerland: Distribution of 435 Earthquakes every other IIour. TY 4 N-ITU-T / Numbers. Tº 55 F-I-5, 2, 36 10 27 $1 2 & &2 48 Stitt (2 - 4 4-6, Jó-8 8-10 tº tº 2 - 4 & - 6 , , 6- 6 6-10 ao -12 Night. Day. Night. no reason for astonishment in this, as, in an entirely general point of view, every day, in its rain, its storms, and all its meteorological phenomena, may be looked upon as an epitome of the whole year. Looking at it in a certain way, midday is summer, and midnight is the winter of each diur- nal revolution. Have we not, then, a good right to infer, from the regu- lar fluctuation of subterranean agitations, these fluctuations correspond- ing with the lapse of seasons and hours, that these great events depend, at least in certain countries, on some external phenomena, and not on the tremblings of a sea of lava? “Are they not,” as Volger says, “connected with the whole body of laws which govern the return of light and dark- ness, heat and cold, snow and rain, drought and running water?” The greater number of earthquakes would thus be facts essentially connected with the conditions of climate. It is also related that, during the hurricanes in the West Indies, the ground is severely shaken, as if the wind, which tears down trees, over- throws buildings, and drives the waves into immense water-spouts, had also laid hold of the layers of the rocks, and had shaken them on their bases. Is it the fact that the inhabitants, under the influence of terror, fancy that the ground itself participates in the immense convulsion ? Such hallucinations would not seem very wonderful when we consider that at each fresh fury of the cyclone, nothing but death is expected. * Moritz, Bulletin de l'Académie St. Pétersbourg, vol. viii. 526 THE EARTH. Fig. 220. Monthly Distribution of 2249 Earthquakes in Europe. 400 ~ r - `s *. ~ Jºſ ... 300 200 100 Numbers. 363 298 284 254 2SO 227 238 258 238 2S7 352 320 Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. Nevertheless, the evidence relative to this coincidence between hurri. canes and earthquakes is so abundant and positive, that it is difficult not to put faith in it. In 1844, on the occasion of a hurricane which de- stroyed hundreds of vessels in the roads of Havana, a shock, which was not connected with any volcanic phenomenon, agitated the ground of the island.* Still more recently, during the cyclone of the 6th of September, 1865, which ravaged Guadaloupe, the Saintes, and Marie-Galante, the earth suddenly shook at the most terrible moment of the tempest, and several houses were thrown down. What is the cause of this coincidence between earthquakes and cyclones? Does the electric storm itself pene- trate into the depths of the earth? or do the torrents of rain produce subterranean downfalls? These are questions to which, at present, it is impossible to reply. - - * However this may be, we must at any rate admit that there are at least two classes of earthquakes; one class proceeding from the pressure and eruption of vapor, and lava, the other caused by the downfall of rocks; both, however, producing the same impression on the senses of man, and developing themselves in the same way over vast areas. Perhaps to these two classes of shocks it may be necessary to add a third—those shocks, namely, which originate in the relations existing between our planets and the other bodies in space. Thus, according to Wolf, there is a constant relation between earthquakes and the spots on the sun. Finally, the in- vestigations carried on with so much perseverance by Alexis Perrey prove unquestionably that the successive phases of the moon exercise consider- able influence on movements of the ground. Like the ocean, the earth, too, has its tides. The frequency of earthquakes, even of those which are only revealed to us by the delicate instruments of M. d’Abbadie, augments, like the height of the flow of the tide, at the epoch of the syzygies. This frequency increases when the moon approaches the earth, and diminishes when it is farther away; in a word, the time when the sea oscillates with the greatest force is also the time when the earth itself most frequently trembles. “Our planet,” says M. Boscowitz, “is engaged in a constant exchange of forces and influences with the heavenly bodies, which, like it, occupy ethereal space.” * André Poey, Comptes Rendus de l'Académie des Sciences, 1865. U PHEAVALS AND DE PRESSIONS -- - *—” ” *_1^2_ SPITZE O C Carºline *Is º - | --- –– H.-- -- - º sº Upheavals : A N | T A R C T I C F R. 9 Z E N 0 C B A N -- – Depressions - º º - |- -- - — - –l-l- . -i o zo' W, ſº o TT - - wo so do -o- zºn rºo rºo abo rºo rºo -2'- -- 80 do -o Drawn by A. Vuillemn after Ch Darwin Fººd by Erhard, 12 R Duºuay Trouin HARPER & BROTHERS, NEW YORK OSCILLATIONS OF TEIE GEOUND, 527 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 TEM- IPERATURE. –LOCAL UPIII. AVALS. & THE solid ground, which people once considered as the symbol of im- mobility, is, on the contrary, in a state of constant oscillation. The crust of the earth, carved out incessantly by the various meteorological agents on one side, drawn by the other bodies revolving in space on the other, modified by water and pressed upon by vapors, gases, and molten matter, never ceases to undulate as a raft rising and sinking on the waves of the Sea. At rare intervals there are great earthquakes; more often this un- dulation of the ground consists in mere vibrations, which are scarcely per- ceptible except by the aid of instruments. The terrestrial crust is not only continually shaken by these transient shiverings; it is, besides, actu- ated by uniform movements of incalculable force, which at some points raise it, and at others depress it, as compared with the level of the sea. While we are busy on its surface, the earth itself is shifting under our feet. - These swellings up and depressions, which recall to mind the phenom- ena of organized bodies, often take place so slowly, that to verify them with any degree of certainty, successive generations of observers would require the lapse of many years, or even centuries. The “patient earth” seems to revolve inertly in space, and yet it is at work without intermis- sion in modifying the form of its seas and its coasts. During each geo- logical period, the continental surface, motionless in appearance, rises in Some spots to a great height above the ocean, and in others it sinks be- neath the water; every where, indeed, the ancient relief and outline of the ground are being slowly modified. In accordance with what law, in what geographical order, and at what comparative rate of progress do these gradual oscillations take place, which result, in the long run, in effecting a change in the general aspect of the globe 2 Science is not as yet in a po- sition to give a positive answer to these questions. But, in the mean time, until geologists are able to estimate exactly the dimensions and prog- ress of each wave of upheaval which is formed by the crust of the earth, it is, at all events, possible to bring together the principal facts which bear upon the subject of the Oscillatory movements of continents and the bed of the sea. Small broken shells, the Scattered remains of polypes, almost invisible grooves marked here and there on the sides of rocks—all these signs, 528 THE EA RTH, which most people would pass by with indifference, are become, thanks to the patience and sagacity of observers, so many undeniable proofs of the regular movements of the ground. It is, however, only on the sea-coast and in the vicinity of seas that savants can positively verify these mani- festations of the vitality of the globe. Considering the ocean as a fixed level-mark, which is almost motionless in relation to the elevated or de- pressed masses of the land, they can easily prove the general elevation of a region by noticing on the shore the parallel lines formed at different epochs by the friction of the sea-water. But farther inland the marks of the same kind which are traced out on their banks by rivers and lakes are very seldom able to furnish incontestable evidence of vertical oscillations of the soil. The more or less shifting level of lakes and running water depends on several geological circumstances, and it is only when all these circumstances are perfectly well known that the ancient terraces and slopes of erosion which exist in fluvial and lacustrine basins can be made to serve as marks to measure the progress of terrestrial oscillations. As a matter of fact, geologists are, therefore, compelled to limit themselves to bringing under notice those oscillatory movements of the earth's crust which are taking place on sea-coasts. In studying the oscillations of the earth, it is important to be very care- fully on our guard against the numerous causes of error which arise from the eternal combat which is always taking place on the shore between the land and the sea. Neither the gradual encroachments of alluvial shores, nor the progressive erosions which, in so many places, the coast has to undergo from the sea, are to be considered, without due examination, as proofs of the upheaval or subsidence of a region. The sand which is driven up by the waves of the sea, and the alluvium which is drifted down in the currents of rivers, are deposited on most low coasts in sufficiently considerable quantities for the belt of shore to increase constantly in breadth. Even where this zone sinks slowly with the land adjacent, as is taking place at the north of the Adriatic, the alluvium may nevertheless form on the shore a kind of cushion, and may defend the plains of the in- terior against the waves of the sea. On the other hand, there are a great many steep beaches and cliffs which, being assailed in front by the waves and the tide, and worn away obliquely by lateral currents, recede gradu- ally before the inroads of the sea; but in cases of this kind it is usually impossible to detect the slightest depression in the general level of the country. Gentle geological elevation of the ground may, indeed, actually coincide with a falling back of the shores. The coasts of Aunis and Sain- tonge present an example of this apparent anomaly. In movements of the soil it is necessary also to distinguish those which are produced by the slow pressure of subterranean forces, and those which are occasioned by temporary causes, such as the more or less quantity of water contained in the surface layers, the activity of evaporation, and the bringing into cultivation of the country. Thus, when peat-mosses form in the low-lying lands of the valleys, taking the place of lakes and marshes, LOCAL OSCILLATIONS. 529 they hold the water in their masses of moss just as an immense sponge, and, gradually swelling, ultimately rise to a height of several feet above the former level of the soil. On the other hand, those tracts of peat-moss which have been dried by draining operations gradually sink; the mosses wither, die, and are reduced to dust. One might fancy that the soil was slowly sucked toward the interior of the earth by some secret force. There is, however, no reason to be astonished at these alternate phenom- ena of swelling and shrinking which are afforded by peaty soil, as a mere variation of temperature is sufficient to produce similar results in the com- pact strata of mountains. In the daytime the particles of rocks dilate un- der the influence of the solar rays; in the night time they become cool, and contract in consequence of radiation, and the total mass sinks to a very slight extent, which is sometimes perceptible by means of instru- ments. Thus Moesta, the Chilian astronomer, has been enabled to ascer- tain that the National Observatory of Chili, situated on the hill of Santa Lucia, near Santiago, rises and descends alternately in the space of twen- ty-four hours. The daily oscillations of the rock, which in turn dilates and shrinks, are, indeed, considerable enough to render it necessary to in- troduce this element of calculation into the mathematical formulae devoted to the regular observations. Similar phenomena, but occasioned by dif. ferent causes, are produced under the Observatory of Armagh, in Ireland. After heavy rains, the hill on which the edifice stands rises perceptibly; then, after active evaporation has got rid of the extra water contained in its pores, the hill again sinks. The shocks of greater or less violence communicated to the soil in vol- canic districts produce alterations in the level which are much more con- siderable than the slight oscillations caused by the heat of the sun or the various atmospheric agents. But these alterations of level are none the less merely local phenomena, and although they are doubtless connected with the same class of facts as the slow upheavals and depressions, they must be clearly distinguished from the long-protracted movements which bulge up the crust of the earth under whole continents. As an instance of the local undulations which are mere accidents in the history of the planet, we may mention that which the earthquake of Conception caused to take place temporarily in February, 1835, at the Isle Santa Maria and the adjacent coasts of the Chilian main land. An enormous mass of earth was suddenly elevated. The shore nearest the town was raised perpen- dicularly a yard and a half, while the island, uprooted, so to speak, by the violence of the subterranean shock, was upheaved obliquely 24 yards at its southern point, and 34 yards at its northern extremity. Two months aft- erward the shore at Conception was scarcely 23 inches above its former level, and the island had also sunk in proportion. Finally, toward the middle of the year, every trace of the upheaval had disappeared, and the sea-water came exactly up to the same winding line of débris which it washed before the catastrophe.* * Fitzroy, Voyage of the “Adventure” and the “Beagle.” L L 530 THE EA BTEI. The famous columns of the supposed Temple of Serapis, which rise on the shore of the Mediterranean, not far from Pozzuoli, likewise bear on their marble shafts proofs of purely local oscillations. Spallanzani some time ago showed that these columns, the bases of which were surrounded with rubbish, must at some former date have been immersed in the water of the sea to a depth of about 21 feet; for up to this height the calcareous cases of the serpulac may be noticed on the shafts, and also the innumera- ble holes that the pholades have hollowed out in the thickness of the mar- ble, which is eaten away circularly by the waves. The temple, having been repaired in the reign of Marcus Aurelius, must certainly, at that time, have been above the level of the sea. It is not known at what date it sank, together with the hillock on which it stands. It might, perhaps, have taken place during the year 1198, in which year, the Solfatara of Pozzuoli produced an eruption. With regard to the emergence of the colonnade from the water, it is probable that it happened in the year 1538, at the time when the Monte Nuovo made its appearance. If these sup- posed dates are the real ones, the lower half of the Temple of Serapis must have been bathed for 340 years in the waters of the gulf. But this event can only have been caused by some local agitation of the earth; for, dur- ing the same period, the adjacent coasts of Naples have not altered their level to any perceptible extent.* * Lyell, Principles of Geology, vol. i. QJPEIEA VAL OF SCANDINA VIA. 531 CHAPTER LXXX. UPHEAVAL OF THE SCANDINAVIAN PENINSULA; OF SPITZBERGEN ; OF THE COASTS OF SIBERIA ; OF SCOTLAND ; OF WALES. ON all those coasts where heaps of modern shells now left dry, and the ledges cut out at different heights in the faces of the cliffs, furnish un- questionable testimony of a progressive upheaval of the ground, Savants who desire to study the progress of the phenomenon must, of course, do so both by direct measurements and by comparing the levels taken at longer or shorter intervals. More than a hundred and thirty years ago, Celsius, the Swedish astronomer, formed the idea of resorting to these means, not with the intention of verifying the growth of the Scandinavian peninsula—a fact which to him did not seem at all probable—but in order to prove the supposed alteration in the level of the waters of the Baltic Sea. He was aware, from the unanimous testimony of the inhabitants of the sea-coasts, that the Gulf of Bothnia was constantly diminishing both in depth and extent. Old men pointed out to him various points on the coast over which, during their childhood, the sea used to flow, and, be- sides, showed him the water-lines which the waves had once traced out farthér inland. Added to this, the names of places, the position more or less upon the main land of former ports now abandoned, and of edifices built once upon the shore; the remains of boats found far from the sea; lastly, the written records and popular songs, could leave no doubt what- ever as to the retreat of the sea-water. At this epoch, when savants still believed in the immovable solidity of the rocky frame-work of the globe, Celsius was naturally bound to attribute the constant growth of the sea- coast to the gradual depression of the level of the sea. In 1730 he felt himself warranted, by comparing all the evidence he had collected, in pro- pounding the hypothesis that the Baltic sunk about 3 feet 4 inches every hundred years. Then, in the course of the following year, having, in com- pany with Linnaeus, made a mark at the base of a rock in the island of Loefgrund, situated not far from Jefle, he was able personally to verify, thirteen years afterward, that the retreat of the Baltic Sea was taking place quite as rapidly as he had supposed. The difference of level ob- served during these thirteen years was 7 inches, or 4 feet 5 inches for a century. From 1730 to 1839 the upheaval of Loeffgrund amounted to 2 feet II inches only.* Celsius was accused of impiety by the divines of Stockholm and Upsal. The Parliament, indeed, wished to cut the matter short by a vote; the two orders of peasants and nobility declared themselves incompetent in the * Lyell; Robert Chambers. 532 TLIE EARTH, matter, while the representatives of the clergy, followed timidly by the burgesses, condemned the new opinion as an abominable heresy.” Never- theless, the geologists who, since the last century, have visited the coasts of Sweden, have been compelled to verify and complete Celsius's observa- tions. They have, however, been forced to reject the first hypothesis of the gradual subsidence of the water, and to recognize as a fact that the movement, attributed in error to the liquid mass of the Baltic, was that of the continent itself. As, indeed, had been already laid down by Antonio Lazzaro Moro, an Italian savant, it was the earth, and not the sea, which was the moving and shifting element. In fact, if the sea-level was pro- gressively/sinking, as was once supposed, the water, the surface of which, owing to gravity, must always remain horizontal, would retreat equally all round the Scandinavian peninsula, and on all the sea-shores. But this is not the case. At the northern extremity of the Gulf of Bothnia, at the mouth of the Tornea, the continent is emerging at the rate of 5 feet 3 inches a century, but by the side of the Aland Isles it only rises 3} feet in the same time; south of this archipelago it rises still more slowly; and farther down, the line of the shore does not alter as compared with the level of the sea. The terminal point of Scania is gradually being buried under the waters of the Baltic, as is proved by the forests which have been submerged. Several streets of the towns of Trelleborg, Ystad, and Malmog have already disappeared; the latter has sunk 5 feet 2 inches since the observations made by Linnaeus, and the coast has lost, on the av- crage, a belt 32 yards in breadth. -- On the west coasts of the Scandinavian peninsula the phenomena prov- ing a recent upheaval of the ground are just as numerous as on the eastern shores; but the rapidity of the ascending movement has not yet been measured, although it is certainly less considerable than in Sweden. The terminal point of Jutland, bounded by an ideal line tending obliquely from Fredericia toward the northwest, rises, according to Forchhammer, 11.70 inches a century. At Christiania the increase is perhaps still less, for, ac- cording to Eugène IRobert, the pavement of the ancient town appears to have remained stationary for three hundred years. Tastly, farther to the north, the present position of several cdifices situated in the island of Munkholm, near Trondhjem, proves, as Keilhau the geologist says, that during a thousand years the elevation of the ground has been less than 20 feet. This is all that is positively known. Nevertheless, a comparison of the various lines of level, and an examination of all the other indications of a slow upheaval, seem to show that, in spite of the numerous inequali- tics in the rate of progress of the phenomenon, that portion of the coast which is nearest to the pole is rising the most rapidly out of the water. Elevated beaches, which can be traced by the eye like the steps of an amphitheatre, are arranged in stages at various heights on the slopes of the mountains. IIeaps of modern shells are found at heights of 500 to * Anton von Etzel, Die Ostsee. # Von IIoſſ, Veránderungen der Erdoberfläche, vol. iii., p. 318, 319. UPHEA VAL OF SCANDINA WIA. - 533 650 feet above the level of the sea, and the great branches of pink coral formed by the Lophoſielia prolifera, which lives in the sea at a depth varying from 1000 to 2000 feet, are now raised up to the base of the cliff.” The pine woods, too, which clothe the summits, are continually being up- heaved toward the lower snow-limit, and are gradually withering away in the cooler atmosphere; wide belts of forest are composed of nothing but dead trees, although some of them have stood for centuries.f The whole body of facts known on the subject of the movements of the ground of Scandinavia will therefore warrant Savants in comparing the whole peninsula to a solid plane turning round a line on which it rests, and raising one of its ends so as to lower the other in the same proportion. The gulfs of Bothnia and Finland, like vessels tilted up out of the horizon- tal, slowly pour their waters into the southern basin of the Baltic. Fresh islets and ranges of islets appear in succession, rocks are laid dry, and if the elevation of the bed of the sea continues to take place with the same regularity as during the historic ages, it may be predicted that in three or four thousand years the archipelago of Qvarken, between Umea and Vasa, will be changed into an isthmus, and the Gulf of Tornea will be converted into a lake similar to that of Ladoga. Later still, the Aland Islands will become connected with the continent, and will serve as a bridge between Stockholm and the empire of Russia. It is, besides, very probable, if not tº certain, that the great lakes and innumerable sheets of water which fill all the granite basins of Finland have taken the place of an arm of the sea which once united the Baltic to the great Polar Ocean. The erratic blocks of granite scattered about all over Russia can only have been carried thither by trains of ice which have made their way over the sea from the mountains of Sweden. The shells belonging to polar waters, which are found as far as the basin of the Volga, also testify in favor of the existence of a former arm of the sea. The name of Scandinavia itself signifies “Isle of Scand,” and the name of Bothnia (Botten) proves that these coast prov- inces were formerly a marine bed. Here philology steps in to aid geol- ogy and tradition. - This is not all. The Baltic Mediterranean also communicated with the North Sea by a wide channel, the deepest depressions of which are now occupied by the lakes Mâler, Hjelmar, and Wenern. Considerable heaps of oyster-shells are found in several places on the heights which command these great lakes of Southern Sweden. On the rocks now laid dry, which surround the Gulf of Bothnia, banks of these molluscs have also been dis- covered exactly similar to those of Norway and the western coasts of Den- mark. With regard to the celebrated Ajoekkenmoddings of the Danish islands, they are in great part composed of oyster-shells, which the inhab- itants, in the Age of Stone, evidently used to collect in the bottoms of the neighboring bays. It has been proved by the investigations of M. de Baer * Carl Vogt, Nordfahrt. - t Keilhau, Bulletin de la Société Géologique de France, First Series, vol. vii. f Von Maack; Eugène Itobert. 534 THE EARTH. I- , 8 * 2Oo º （4） ſĢ įĒĒĒĒĖ…--§ä ¿]ĒĒĒĒĒĒĒĖĖĘĚ№ }E| |×ģ|| •·$$$$---- çº|-≡ &&ſ@ĒğĒļļāĚĚĒ Ķī£№r-r-r-3~~~~ĶĒĒĒĒĒĒĒĒĒĒĒĖĖ（~~~~ ~~~~， ，####ĒĶĒĖĖĘĘĢĒĒĒĒĒĒĒĒĒĒ Ë${\ſēſ№№!!!№.±ĖĘĘĢĢĒĘ æ:#ffff;į№ ſº：№r:№ºt***，№. § șĚ º .N - -- * Fig. 221. Elevation of the Bed of the Gulf of Bothnia. Now the Baltic Sea, into which its numerous tributaries ±ĒRĶĒĒĒĒĒĒĒĒĒĒĖĘĒĒĒĒĒĒĒĒĖĘĒĒĒĒĒĒĒĒĒĒĒĒ § Ligne deat odderdane wood arur. § * șĒĢĒĢĒĖĘ §Œ œ§§§§· -----ſąſiae№|- ĢĒĒĒGººſ№;ĢĒ№ți -}șžjËģËķēķis"; ∞ £，:§§，º º_ºffſ4 ~~ ！*: /- -„…e?�**$\{2}43m.- �� É Ligne dercºter dari, coop are } §），3 that the oyster can not live and grow in water holding more than thirty- Seven parts in a thousand of salt, or less than sixteen or seventeen parts bring a large quantity of fresh water, does not contain, on the average, in a thousand. ELEVATION OF SCANDINA WIA. 535 more than five parts in a thousand of salt; and, indeed, in some of the gulfs, the water, now devoid of all its former inhabitants, has become en- tirely fresh. And yet—the heaps of oyster-shells prove it—the Baltic Sea and the inland lakes were once as salt as the North Sea is at the present day. Whence, then, could this saltness proceed, except from some for- mer strait which occupied the depressions in which the Swedish engineers have dug out the Trolhatta Canal? Besides, when the sluices were being constructed, there were found, not far from the cataracts, and at a height of 40 feet above the Cattegat, various marine remains, mingled with relics of human industry—boats, anchors, and piles. According to M. de Baer, it is not, at the most, more than five thousand years before our century that we must date the closing up of the straits which used to exist between Southern Sweden and the great mass of the northern plateaux. Since Leopold von Buch has placed beyond all doubt the important fact of the gradual upheaval of the northern portion of the Scandinavian pen- insula, several geologists have ascertained that the elevation does not take place in a mode that is perfectly uniform. During by-gone centuries the movement has sometimes been accelerated and sometimes slackened, as is proved by the inequality of the elevated sea-beaches which run along the sides of the mountains on the coasts of Norway. Some of these steps or shelves that the waves have carved out in the rock are wide and gently inclined; others are abrupt, and can scarcely be distinguished from the slopes above them. Lastly, the measurements made by M. Bravais along the lines of crosion of Altenfjord have proved that they are not parallel, and that the rocky masses situated at the ends of the gulfs have been more energetically upheaved than the layers lying nearer the sea. Thus the upper bank of Altenfjord has risen at the eastern end to a height of Fig. 222. Bank of Altenfjord. 219 feet above the level of the sea, but at the entry of the bay it has only risen 91 feet. In like manner, the lower shelf, throughout the whole of its immense circuit round the gulf, presents a slight inclination toward the sea, being no less than 88 feet high on the east, and only 45 feet at the outer promontories. Thus the action of upheaval is evidently stronger in the vicinity of the mass of mountains than it is on the coast; but this does 536 THE EARTH. & not afford any sufficient reason for saying that at a certain distance to the west, under the bed of the sea, the movement of the ground entirely ceases.” M. Carl Vogt has propounded an ingenious hypothesis to account for this inequality of elevation. According to his theory, rocks of various na- tures—schists, Sandstones, or limestone—which compose the mountains of the Scandinavian peninsula, incessantly swell in consequence of the infil- tration of snow-water, and, owing to fresh crystallizations taking place by means of moisture, are gradually converted into masses of stratified gran- ite. This hypothesis, which has been much discussed by geologists, would certainly explain the raising of the lines of erosion of the Norwegian coast near the groups of mountains, but it would fail to account for the intervals of comparative repose, and especially for the sinking of the ground, which many geological facts prove to have taken place during the glacial period. It is, therefore, necessary to admit that other forces have been in action in the Solid mass of Scandinavia. Added to this, we must not lose sight of the fact that the upheaval of this peninsula is not an isolated event, and that the other countries of the north of Europe and Asia, notwithstanding the diversity of their rocks, all appear to be actuated by a similar movement of ascension. The islands of Spitzbergen exhibit generally, between the present sea-shore and the mountains, former sea-beaches which are gently inclined, and half a mile to two miles and a half in breadth, on which are found, up to a height of 147 feet, heaps of bones of whales and shells of the present period. These re- mains, surrounding all the snow-clad slopes of Spitzbergen, prove that this archipelago, like Scandinavia, is gradually emerging from the waves of the I’olar Ocean. The northern coasts of Russia and Siberia are likewise rising, as is attested by popular tradition and the evidence of learned travelers. MM. De Keyserling, Murchison, and DeVerneuil have found, at points 250 miles to the south of the White Sea, on the banks of the Dwina and the Vaga, beds of sand and mud containing several kinds of shells sim- ilar to those which inhabit the neighboring seas, and so well preserved that they have not lost their colors. In like manner, M. De Middendorf states that the ground of the Siberian towndras is in great part covered with a thin coating of sand and fine clay, exactly similar to that which is now deposited on the shores of the Frozen Ocean: in this clay, too, which contains in such large quantities the buried remains of mammoths, there are also found heaps of shells perfectly identical with those of the adjacent ocean. Far inland, besides, trains of driftwood are seen, the trees forming which once grew in the forests of Southern Siberia; these trees, having been first carried into the sea by the current of the rivers, have been thrown up by the waves on the former coasts, which are now deserted by the sea. It is this half-rotten wood which is called by the natives “Noah's wood,” fancying that they have before them the remains of the ark of the deluge. More than this, there are also direct proofs of the upheaval of Siberia. The island of Diomida, which Chalaourof noticed in 1760 to the * Bravais, Voyages en Scandinavie, vol. i. f Malmgren, Mittheilungen von Petermann, vol. ii., 1863. GRADUAL UPRISING OF LAND. 537 east of Cape Sviatoj, was found to be joined to the continent at the date of Wrangell's voyage, sixty years later. It is, besides, very probable that this upheaval of the ground is prolonged to the east over a great portion of the circumpolar land of North America, as far as northern Greenland,” for numerous indications of this phenomenon have been recognized in the Arctic Isles scattered off the coasts of the continent. At Port Kennedy Mr. Walker found shells of the present period at a height of 557 feet above the sea; a bone of a whale lay at a height of 164 feet.f The cliffs of Scotland also present phenomena similar to those of Scandi- navia. T’arallel water-marks traced out by the waves on the escarpments of rocks, and collections of shells peculiar to the neighboring scas, attest the gradual elevation of this portion of Great Britain. The clevation, too, must have been of a much more regular character than that of the coasts of Norway, for, according to Robert Chambers, not the slightest variation of level is noticed on the ancient terraces. This ascending movement is still continuing; for it has been ascertained that the marine cliffs which were once situated above the estuaries of the Forth, the Tay, and the Clyde contain not only organic remains of recent ages, but also heaps of pottery of Roman origin. The former Roman port of Alaterva (Cramºnd), the quays of which are still visible, is now situated at some distance from the Sea, and the ground on which it stands has risen at least 24% feet. In other places the débris scattered on the bank show that the coast has risen about 26% feet. Now, by a remarkable coincidence, the ancient wall of ...Antoninus, which, at the time of the Tomans, served as a barrier against the Picts, comes to an end at a point 26 feet above the level of high tides. The general upheaval of the region may therefore be estimated at 0°195 inch a year; but since 1810 the movement has become ſhore rapid, as is proved by the tide-meters at the port of Leith, and it is, at present, at the rate of 0:546 a year.S Farther to the south, on the sides of the mountains of Wales, there are numerous indications of the presence of the sea during the present period. Mr. Darbishire lately discovered, not far from Snow- don, at a height of 1357 feet, a bed of drift containing fifty-four species of shells of similar kinds to those still existing in the northern seas of Eu- rope; the same soil was, however, found at a point 650 feet higher, but de- void of shells. Thus, from Wales to Spitzbergen and the eastern coasts of Siberia, the ground has continued to rise slowly during a portion of the Glacial period, and also during the present epoch. The area of upheaval includes a por- tion of the earth's surface which is not less than 160 degrees of longitude. In the face of these facts, are we to consider the phenomena of upheaval as mere local accidents produced by the swelling of rocks and volcanic shocks, or must we look upon them as the results of some general cause acting in various ways over the surface of the whole planet 2 The latter hypothesis appears to us to be the more probable. * Wide below, p. 555. f Samuel Haughton, Natural History Review, April, 1860. f Arch. Geikie, Edinburgh New Philosophical Journal, New Series, xiv. § Smith, Geological Magazine, September, 1866. 53S THE EAAETH. CHAPTER LXXXI. UPIIBAVAL OF THE MEDITERRANIEAN REGIONS.—FORMER LIBYAN STRAIT, —COASTS OF TUNIs, SARDINIA, CORSICA, ITALY, AND WESTERN FRANCE. TIE countries of the South of Europe certainly possess a more grace- fully-indented outline than any other regions on the face of the earth. The peninsulas which they throw out present the greatest variety of con- tour and aspect, and they have thus become, as it were, imbued with vital- ity, owing to their numerous articulations, similar to those of an organized body. Correspondent with this multiplicity of external shapes are the singular irregularities and exceptional contrasts in the movements of the ground. A certain complication is here and there manifested between the upheaved regions and those which are subsiding. Nevertheless, a suffi- cientºnumber of observations have been collected to warrant us in admit- ting, in a general way, the elevation of most of the countries which sur- round the basin of the Mediterranean. These regions, which in several places have been caused to oscillate by volcanic forces, constitute a con- siderable area of upheaval, extending from the deserts of the Sahara to Central France, and from the coasts of Spain to the steppes of Tartary. The mountainous peninsula of Scandinavia is situated in the middle of the upheaved regions of Northern Europe, and, by a kind of polarity, the long depression of the Mediterranean occupies the centre of the vast areas in the South of Europe and Northern Africa, which are gradually rising. This immense space was once bounded, toward the tropical zone, by an- other sea, or at least by a strait several hundreds of miles in width, which commenced at the Gulf of Syrtes, and, filling up the depressions of the Berber Sahara, joined the Atlantic in front of the archipelago of the Ca- naries. In 1863 MM. Escher von der Linth and Desor ascertained, accord- ing to M. Charles Laurent, that the sands of these regions are entirely identical with those of the nearest Mediterranean shores, and contain the same species of shells. One of these witnesses of the past, the common cockle (Cardium edule), is found not only on the surface of the ground, but also at some depth, and likewise up to a height of 900 feet upon the sides of the hills. The Algerian Sahara has, therefore, risen to this extent during a recent geological period. Various depressions, the surface of which is lower than the level of the Mediterranean, have been gradually separated from the sea, and, in the present day, they exhibit nothing but marshy pools or interminable plains. At a recent, and perhaps historical epoch, Lake Tritonis of the ancients, now the Sebkha Faraoun, into which flowed the Igharghar, has ceased to be a prolongation of the Gulf of Gabes, and has become a mere marsh. It was the last remnant of the UPIIEA VAL OF THE MEDITERRANEAN ſº EGIO.W.S. 539 arm of the sea which separated the mountainous regions of Atlas from the African continent, both so distinct in their general character, as well as in their fauna and flora. To the existence of this African Mediterranean, which is now replaced by white sands, beds of salt, and rocks devoid of verdure, MM. Escher von der Linth and Lyell in great part attribute the enormous extent of the former glaciers of Europe. It is, in fact, very nat- ural to think that, before the drying up of this inland sea, the masses of air blown to the north would become saturated with moisture while pass- ing over the water, and, rising gradually to the higher regions, would con- stantly convey fresh layers of snow to the summits of the Alps, instead of melting the snow, as the fj/in now does, heated as it is by the reflection from the burning sand of Africa.” It is, however, possible that the Swiss mountains have decreased in height since the Glacial period. The same slow oscillation of the ground which emptied the Libyan Mediterranean has, perhaps, by its reaction, lowered the foundations of the Alps, and brought them nearer to the level of the sea.f On the coasts of the Mediterranean, the indications which would lead us to infer the fact of some upheaval of the ground are plentiful enough. Thus the shores of Tunisia are constantly cncroaching on the sea. The ancient ports of Carthage, Utica, Mahedia, Porto Farina, Bizerta, and oth- ers, are now filled up. The bays are done away with, the points advance farther and farther into the sea; and these phenomena take place with a rapidity sufficient to show that we are witnessing the effect of a vertical impulse similar to that which once upheaved the beds of the Saharan seas. In like manner, Sicily appears to be constantly elevated by the forces in action under the beds of its surface. On the heights which command Pa- lermo, caves have been observed at an elevation of 180 feet, which have been hollowed out by the sea during a period characterized by existing species of shell-fish.Ş. On the eastern coast of the island, Gemellaro has recorded a recent upheaval of more than 42 feet. In Sardinia, not far from Cagliari, M. De la Marmora points out, as existing at heights of 242 and 231 feet, deposits which contain remnants of pottery mixed with mod- ern shells, which deposits, in his idea, were on a level with the sea at a date when the island was inhabited by man. Certainly M. Emilien Dumas, an excellent observer, considers that these remnants of pottery and heaps of shells are nothing but the remnants of the cooking of food, similar to the kjoekkenmoddings of Denmark. If this be the case, there would be nothing to prove that Sardinia was upheaved at any recent epoch. But are the enormous banks of oyster-shells which cover the ground at the Lake of Diana, 6 feet above the level of the sea, and are continued far un- der the water, to be considered as nothing but the débris of Roman ban- \. quets? Such an idea does not, at least, appear at all probable to M. Au- capitaine and a number of other observers. * Wide the chapter on “Winds.” t Lyell, Inaugural Address to the British Association at Bath, 1864. f Guérin, Voyage Archéologique à la Régence de Tunis. § Lyell, Antiquity of Man. 540 THE EA RTPI. The facts of upheaval brought forward by geologists as regards the other regions of the coast of the Mediterranean are not as yet sufficiently verified, and it can not be positively asserted that these shores have risen above the sea during the present period. Nevertheless, the body of evi- dence is of considerable importance, and merits serious consideration. Thus, round the former island of Circe, now become a promontory of Tus- cany, the rocks, which have much the appearance of a former sea-beach, are pierced by pholades.* With regard to the discovery of banks of mod- ern shells made by Risso near Villefranche, at the extremity of the Cape of Saint Hospice, M. Emilien Dumas disputes its scientific value. Never- theless, it is plain that this coast, and the whole of the adjacent shore as far as Spezzia, were covered by sea-water at a recent geological epoch. All that is necessary to prove this is to examine the caves of Menton, of Ventimiglia, and of the Cape of Noli, which were hollowed out by the waves at some former date, and open like rows of arched doors and win- dows along the façade of some palace. - The southern coasts of France do not afford any direct evidence of an upheaval of the soil; but various indications possess a value which can not be disputed. Astruc, of Languedoc, brings forward a great number of facts, which prove that, at the time of the Romans and in the Middle Ages, the marshes extended much farther inland. The ancient Roman road from Beaucaire to Béziers describes a wide curve toward the north, doubtless to avoid the plains on the shore, which were then entirely under water. Ancient cities with Gallic names—as Uffernum (Beaucaire) and Nemausus (Nismes)—are found along the ancient road, while all the places situated ſo the south bear Latin or Roman names—as Aigues Mortes, Fran- quevaux, Vauvert, and Frontignan (Frons Stagn?)—and appear, therefore, to be of more modern origin. It is, besides, proved by various documents that ancient ports have filled up, and have been converted into terra firma. Astruc also points out the remarkable fact that the Romans, who highly appreciated thermal springs, were not aware of the abundant wells of I3alaruc, although the eddies of steam could not have failed to point them out if they had not been covered at that time by the waters of the Lake Thau. This is an important argument in favor of the hypothesis of a gradual elevation of this part of France. - 3eyond the Mediterranean basin this movement of general upheaval appears to continue toward the north and west. Thus, at Seixal, opposite Lisbon, they have been compelled to cease building ships of the line on account of the increasing diminution of the water, which is attributed both to the deposits of mud and also to the upheaval of the rocks. On the At- lantic coasts of France a great number of phenomena of a similar nature have also been adduced. To many geologists, especially to M. Bravais, it seems probable that the whole of France, agitated by a slight and almost imperceptible tremor, is being slowly upheaved on the southern side, and turns on a base-line passing through the peninsula of Brittany. At all * Romanelli, Breislak, quoted by, Böttger, Mittelmeer. UPITEA VAL OF THE COAST'S OF EUROPE. 541 events, the coasts of Poitou, Aunis, and Saintonge appear to have risen since the commencement of the historical epoch. Guérande, Croisic, Bourgneuf, and Sables d'Olonne show upon their shores unquestionable traces of recent elevation. The former Gulf of Poitou, the entrance of which, two thousand years ago, was not less than 18 to 25 miles in width, which, too, penetrated inland as far as Niort, has constantly contracted its dimensions since the above-named date, and is now nothing more than a small bay, known under the name of the Creek of Aiguillon.* The con- stant deposit of marine alluvium would scarcely be a sufficient cause for this rapid increase of the land; it is therefore probable that at this spot the upper layers of the ground are regularly in a course of upheaval. Farther to the south, La Rochelle, which owes its name to the position which it once occupied on a rock almost isolated in the midst of the water, now only communicates with the sea by a narrow channel, often choked up with mud. Brouage, another fort which, in the Middle Ages, was a town of important trade, is now nothing more than a ruin, some distance from the sea. The district of Marennes, to which the name of “Colloque des Iles” was once given, is now entirely connected with the main land, and the arms of the sea which cross it have been converted into draining- channels, salt marshes, and oyster-beds. In like manner, the peninsula of Arvert, situated between the mouth of the Seudre and that of the Gironde, ceased to be an archipelago during the course of the Middle Ages. At Rochefort it has, indeed, been calculated approximately how much the ground has risen, the slips for ship-building, dug out in the time of Louis XIV., having been gradually elevated more than a yard. # “The bank is pushing up,” say the inhabitants of the coast, who have long since ob- served the gradual upheaval of the ground. * De Quatrefages, Les Côtes de la Saintonge. f Babinet, Revue des Deux-Mondes, September 15, 1855. 542 TIIE EARTEI. CHAPTER LXXXII. COASTS OF ASIA MINOR.—ANCIENT OCEAN OF IIYIRCANIA.—COASTS OF PALESTINE AND EGYPT.-TIII, ADIRIATIC GULF. & T’IIENOMENA of upheaval are also very common in the islands and round the edge of the eastern basin of the Mediterranean. Like Sicily and sev- eral parts of the coasts of Italy and Greece, a considerable number of isl- ands—as Malta, Rhodes, and Cyprus—are surrounded with circular ter- races more or less elevated above the level of the sea, and composed of calcareous or sandy rocks of recent formation.* The northern portion of the island of Crete has risen more than 60 feet during the present geolog- ical period. A study of the shores of Asia Minor proves that there also the ground has continued, since man inhabited that region, to rise with a rather rapid movement. During historic times this part of the continent has gained a considerable belt of land at the expense of the AEgean Sea. It is not the alluvium of the rivers, or the matter washed up by the sea, which has caused this increase of the land, for the Anatolian rivers are very inconsiderable, and the water which bathes the coast can not, on ac- count of its great depth, throw up much sand. It must, therefore, be in consequence of a slow upheaval of the earth's crust that the ruins of Troy, Smyrna, Ephesus, and Miletus have gradually become more distant from the coast, and appear to be receding still farther inland. Prom the same cause so many islands in the AEgean Sea which were once separate are now united, or are connected with the main land, and form headlands or hills surrounded by low-lying plains. The testimony of ancient authors is unanimous as to these encroachments of the shores. Thus it is said that the two halves of Lesbos, Issa, and Antissa have become united, that the bays have been converted into inland lagoons, and that various islands have joined on to the main land at Mindus, Miletus, the Parthenion Cape, at Ephesus, also at points near Halicarnassus and Magnesia. At the time of IIerodotus, the mountain of Lade, not far from which the Ionian galleys fought a battle with the Persian fleet, was an island; at the present day it forms part of the main land, and stands in the midst of the plain of the Meander. Since the date of Strabo and Pliny, several other islands have similarly become headlands. The former Latmican Gulf is converted into a lake, known under the name of Akiz. The encroachments of terra firma on this gulf have added to the eastern coast of Asia Minor about 67 Square miles in less than two thousand years. This retirement of the Sea took place likewise in preceding ages, for the town of Priene (Samsoun), which at the time of Strabo was 4% miles from the shore, had been built at a pro- vious date on the sea-coast. In like manner, the village of Ayasoulouk, * Albert Gaudry, Revue des Deux-Mondes, November 1, 1861; Newbold. f Raulin ; Leycester and Spratt. Vide p. 545. - FIFVATION OF ASIA MINOI8. 543 where the ruins of the ancient city of Ephesus may still be seen, is at the present time two leagues from the coast, and the former estuary which was commanded by the town is now converted into a marshy plain. Would the little river Meander, the total length of which is not more than 341 miles, have been able, by nothing but its alluvial deposits, to fill up lakes and estuaries of so large an area, and to modify so considerably the outline of the shore ? It is therefore important that the discharge of this river and its annual deposit of alluvium should be exactly measured, in order that we may arrive certainly at the real cause of these encroach- ments on the part of the Anatolian coast, where, according to the ancient saying of Pausanias, “all is unstable and changing.” According to M. De Tchihatcheff, this portion of the coast of Asia Minor has gained, since his- toric times began, an extent of about 185 square miles, equal to the area of the Isle of Wight.* * Similar phenomena are, however, likewise taking place on the southern coast of Asia Minor. Near Adalia, the Lake of Capria, which was very extensive at the time of Strabo, first ceased to communicate with the Sea, and then gradually emptied, being now nothing but a marshy hollow : the surface of the peninsula has thus been increased by an area of 154 square miles. On the north of Asia Minor a great number of signs prove that there also the water has retreated before the shores and rocks of the continent. During the present geological period the area of the Euxine has been diminished, and, according to the traditions of the Crimean Tar- tars, it is still diminishing. Banks of modern shells have been left by the sea at considerable heights on the hills of Thrace and Anatolia; round the Crimea, salt lakes, stagnant marshes, now exist far inland in the place of former gulfs. Certainly enough the Black Sea, before the opening of the Bosphorus, received from its tributary rivers more water than the sun and wind could evaporate, and must necessarily have much exceeded the level to which it now reaches. But if the earth itself had remained sta- tionary, and had not slowly risen, the sea-water would not have left the marks of its presence at any point higher than the former Strait of Isnik, the site of which is now dotted over with lakes which once formed a part of the sea. It is, perhaps, in consequence of the upheaval of the ground that this strait was closed, and the water of the Black Sea, gradually accumulating in its basin, was compelled to open by force a new outlet through the volcanic fissures which have now become the Bosphorus. A geological examination of Southern Russia and the plains of Tartary will preclude us from entertaining any doubt as to the fact that the Cas- pian Sea, the Sea of Aral, and all those innumerable sheets of water which are scattered over the steppes, were separated from the Euxine and the Gulf of Obi by a gradual upheaval of the continent. The plains are still covered with salt and marine remains. The inland seas and the scattered lakes are still inhabited by seals, and their fauna altogether presents an es- sentially oceanic character. Herodotus, Strabo, Ptolemaeus, and all the * Asie Mineure. Von Hoff, Veránderungen der Erdobeyſlâche. † De Tchihatcheft, Le Bosphore et Constantinople. 544 - THE EARTEI. authors of antiquity attribute to the ancient Hyrcanian Ocean an extent far larger than that of the Caspian of our day; most of them, indeed, con- sidered this inland sea as a prolongation of the Frozen Ocean. This lat- ter opinion, no doubt erroneous as regards a date two thousand years ago, would certainly have been true of some anterior epoch. After Humboldt's profound investigations on Central Asia, we shall not, at the present day, show too great temerity in assuming that, during some portion of the present period, a vast strait, like that which once ran along the Southern base of the Atlas, extended from the Black Sea to the Gulf of Obi and the Frozen Ocean.* The vast depression of the Caspian plains which is below the level of the sea, and, according to Halley, was produced by the shock of some wandering comet, is, on the contrary, really owing to a slow ele. vation of the ground. The observations of level made on the coasts of the Mediterranean have enabled us to ascertain not only that the larger portion of this inland ba- sin of the ancient world, and many of the regions bordering on it, have gradually risen, but that they have, in addition, pointed out the limits of the area of upheaval. They may be distinguished with some degree of precision on the coast of Syria and Palestine; it may be noticed that in this region the surface of the ground is corrugated like that of water, and forms a series of waves and depressions fluctuating in contrary directions. The shores of the Gulf of Iskanderoun are regularly gaining in width by means of the elevation of the ground as well as of the matter thrown up by the sea; but at Beyrout a tower is shown which is sinking farther and farther into the water. More to the south, the former Isle of Tyre is now connected with the continent, and several parts of the peninsula bear traces of the sojourn of the sea during some recent epoch. Lastly, Kaisa- rieh and Some other towns in Palestine are included in an area of subsi- dence, as is proved by the remains of fortifications which are now visible below the level of the Mediterranean. On the east, all the Egyptian coasts were still rising at a comparatively very recent epoch, for the Bitter Lakes and the banks of the Nile exhibit former sea-beaches on which modern shells are found. But at the present day the ground is sinking continuously and imperceptibly. Ruined towns are situated in the midst of the marshy plain of Lake Menzaleh, which is covered by the sea during the greater part of the year. Farther on, a for- mer branch of the Nile, with the banks which bordered it, is entirely hid- den by the waters of the Mediterranean. The same phenomenon occurs on the other side of the Delta. In 1784 the sea made an irruption into the interior of the land, and formed the Lake of Aboukir in the midst of a plain on which important towns once stood. In like manner it may be in- ferred, from the ancient descriptions of Alexandria and its environs, that a considerable subsidence of the ground must have taken place there during * In Captain Maury's magnificent studies, in which, however, imagination sometimes has as large a share as science, he endeavors to prove, by very ingenious arguments, that the up- heaval of the Andes, by modifying the system of winds and rain over the whole earth, was the cause of the gradual drying up of the plains of the Caspian and Aral. COAST'S OF EG YPT-THE ADRIATIO. 545 the centuries of our era. Artificial caves and catacombs, dug out in the days of the Ptolemies, and incorrectly known as “Cleopatra's Baths,” are now invaded by the waves.” On the shores of the Red Sea, not far from Suez, some sepulchral caves hollowed out in the calcareous rock have like- wise been inundated, owing to the subsidence of the ground. Perhaps this movement in the ground of Egypt is common to all that portion of the Mediterranean which may be called the Egyptian Sea; for in the isl- and of Crete the western point has constantly risen during the modern epoch, but the side nearest to Egypt is gradually sinking under the water. As Strabo himself expressly said, Nature is seeking to destroy the Isthmus of Suez, which she once formed between the two continents. Man, in his operations of cutting through it, is only anticipating the geological labor of centuries to come. - Along the shores of the Adriatic Sea, to the north of Zara and Pesaro, geographers have noted other phenomena of depression which mark the northern limit of the great Mediterranean area of upheaval. In the mid- dle of the sixteenth century Angiolo Eremitano propounded the opinion that the isles of Venice were sinking at the rate of about a foot a century, and this hypothesis, which was based upon a comparison of the buildings and the pavement of the streets with the water, has since been fully con- firmed. In the Isle of St. George, Roman constructions are now found be- low the level of the lagoons; in other places paved roads are covered by the water, and churches and bridges have sunk in comparison with the surface of the sea. In 1731 Eustache Manfredi noted the same subsidence of the soil under the edifices of Ravenna, but he, in error, attributed it to the gradual elevation of the level of the Adriatic. In addition, an entire town—Conca—once situated not far from the Cattolica, at the mouth of the Crustummio, has been entirely submerged for some centuries, and, when the sea is calm, the remains of two of its towers may still be seen under the waves. M. Giacinto Collegno thinks that all these alterations of level are produced by the deposit of the alluvium brought down by the Po and the other rivers descending from the Apennines and the Alps. This is a cause which must certainly contribute in no small extent to the general depression of the Venetian coasts of the Adriatic Sea, but proba- bly it is not the only cause, for the opposite coasts of Dalmatia and Istria are also sinking, in spite of the compact nature of their rocks. At Trieste, at Zara, and in the Isle of Poragnitza, various works of man—such as pave- ments, mosaics, and sepulchres—may be seen below the level of the Sea.f Moreover, as Lyell remarks, the artesian borings which have been made in the delta of the Po to a great depth below the sea have brought up nothing but river alluvium, which unquestionably establishes the fact of a gradual depression of the ground. The earth which is penetrated by the boring-rod at the bottom of the artesian wells was once situate above the level of the sea. * Lyell, Antiquity of Man; Pococke; Wilkinson; Schleiden. # Donati, Histoire Naturelle de la Mer Adriatique; Schleiden, La Plante. M M 546 THE EARTII. CHAPTER LXXXIII. SUBSIDENCE OF THE SHORE OF THE CHANNEL of IIoILAND, OF SCHLESWIG, OF PRUSSIA. WIIETIIER it be that the whole of Central Europe participates in the movement of depression to which the shores of the Adriatic are subject, or whether the latter be merely a local phenomenon, it is nevertheless the case that the southern coasts of the Channel and North Sea are also sink- ing, although very slowly. On the coast of Brittany and Normandy, mu- merous forests which have been submerged, and buildings surrounded by the sea-water, prove that the ground has sunk during the present period. In 709, the monastery of Mount St. Michael was built in the midst of a forest ten leagues (?) from the sea; it now stands, like an island, in the midst of sand-banks. The inroads of the sea are still continuing, especially in the IBay of La Hougue and in the harbor of Carteret.* It appears, how- ever, that various undulations, like those on the coast of Syria, also exist on these coasts, fortin several places banks of sand and modern shells have been discovered at heights from 40 to 50 feet above the level of the sea. At some remote epoch, but nevertheless contemporary with man, the val- ley of the Somme was also upheaved, but for thousands of years it has been slowly subsiding, as submarine forests are found along the coast, and the peat-bogs of Abbeville, the bottom of which is situated below the I3ay of Somme, afford no other débris but the remains of animals and veg- 6tables which lived on the earth or in fresh water. When these peat- mosses began to grow, the ground of the valley must have been higher than the surface of the neighboring seas.; In Flanders and IIolland the phenomena of subsidence have been, if not more considerable, at least more important in their results, on account of the very low level of these countries in comparison with the sea. A mere enumeration of the successive catastrophes brought about by this gradual depression constitutes a terrible history. The plains of Dordrecht have be- come a forest of reeds (Biesbosch). The Zuyder Zee itself—once a marsh, next a lake, and thén an arm of the sea—is still continuing to sink: at the present time there is, it is said, sufficient depth for ships of heavier burden than those which used to navigate it in former centuries. Like a raft gradually sinking under the waves, IIolland would be slowly swallowed up in the abyss if it were not that the inhabitants, accepting the contest with the elements, have walled in their country by means of dikes, and laid it dry by immense operations of drainage, which will never cease to be a subject of astonishment. Several savants, at the head of whom stands * Donissent, Congrès Scientifique de Cherbourg, 1860. f Lyell, Antiquity of Man. & UBSIDENCE OF HOLLAND. 547 11:... tº §.º. *:::::\\ º º ºvºzerº, cºº ׺ś. Fig. 223. Biesbosch. the eminent geologist M. Staring, are of the opinion that the gradual de- pression of the land which is thus embanked is caused only by the subsi- dence of the alluvial ground, the weight of the dikes, and the incessant passage of men and cattle. IIowever great may be the importance of these combined causes, the phenomena of subsidence which have been noted for the last fifteen centuries are considerable enough to Warrant us in accepting M. Elie de Beaumont's hypothesis as to the depression of the ground of Holland. If, at least, we may judge by the mean level both of the pavement of the towns and of the fields under cultivation, the move- ment of depression is most rapid at the mouths of the rivers—the Scheldt, the Meuse, and the Rhine. At Calais the streets are more than a yård above the high tide, while the cultivated ground descends to the limits of the tide. At Dunkirk the height of the streets is not more than 23 inches, and the fields are plowed at a level of a yard below the sea. At Furnes and Ostend the streets are still lower, and the level of the polders is al- ways sinking. Near the mouths of the Scheldt it is 113 feet below the high tide. Farther to the north the ground gradually rises, but the streets of Rotterdam and Amsterdam are lower than the level of the equinoctial tides.” 㺠All the adjacent coasts—those of the south of England, and of Cornwall and Yorkshire, as well as those of Hanover and Schleswig–likewise afford certain proofs of a considerable subsidence by their submarine peat-mosses, their submerged forests, and their former coasts now become islands. On the western coasts of Schleswig the subsidence has been, on the average, * Bourlot, Variations de Latitude et de Climat. 548 THE EA RTH, =%;== ić ºš º ŽS º º I'ig. 224. Coast of Friesland. 13 feet during the present period. In this locality, at the bottom of the port of Husum, there was discovered, in the midst of a submerged forest of birches, a tomb of the Age of Stone, necessarily dating from a period ante- rior to the subsidence of the ground on which it stood. On the eastern coasts of Schleswig and Holstein many phenomena of the same nature have been remarked, which can only be explained by a gradual subsidence of the shore. The remains of an old castle situated at the mouth of the Schlei are covered by the water. Farther on, the stumps of the trees of an ancient deer-forest of the Middle Ages may be seen under the water about half a mile from the shore. In the Straits of Fehmarn are found the remains of an ancient wall; and, lastly, near Travemunde, two blocks of stone, which stood on the beach at the end of the last century, are now surrounded by water.” These are facts which will not permit us to at- tribute, solely and wholly, to the action of the waves the transformation of several peninsulas into islands, and lakes by the sea-shore into arms of the sea. According to John Paton, Denmark and Schleswig-Holstein have lost, since the year 1240, an area of about 1225 square miles, or one eight- centh of the whole surface of the territory. Farther to the east, all round the southern basin of the Baltic, the in- roads of the water have led several geologists to admit that the ground of these countries is slowly subsiding. Rugen is broken up into islets and peninsulas; Bornholm is surrounded by submarine forests, one of which, according to Forchhammer, is 26 feet below the line of the shore. Other submerged forests fringe the coasts of Pomerania and Eastern Prussia. * Von Maack, Das urgeschichtliche Schleswig-Holsteinische Land, 1860. DEPRESSION OF FIRIESLAND AND DENMARK. 549 The islands of Wollin and Usedom, situated in front of the mouths of the Oder, have gradually been eaten away by the waves. The Sandy bar which impedes the entrance to the port of Swinemunde used to form a peninsula of Usedom, indeed, during historical periods.” Lastly, accord- ing to the evidence of Barth, the point of Samland has been overwhelmed by the water, as may be easily recognized by the fact that the church of St. Adalbert, which was built about the end of the fifteenth century at a point 4% miles from the sea, is now found in a state of ruin only 100 paces from the beach. These are facts which can not be questioned. Nevertheless, we are not yet warranted in considering them as positive proofs of the subsidence of the ground, for Voigt, and several other scientific observers, class them among the simple phenomena of erosion and deposit. However this may be, there are very strong reasons for considering the channel and the Southern waters of the North Sea and the Baltic as a trench of depression, an elongated valley 1100 miles in extent, separating the area of upheaval of Northern Europe from that which is bounded at its northern extremity by the coasts of Poitou. * Anton von Etzel, Die Ostsee. 550 THE EARTH. CHAPTER LXXXIV. UIPIIIEAVAL OF THE COASTS OF CIIILI AND DIERU.—IPROBAIBLE DEPRESSION OF TIII, COASTS OF LA PLATA AND BIRAZIL. —COASTS OF NORTII AMIERICA AND GREENLAND. THE New World—that double continent, the architecture of which is distinguished by general features of such simple grandeur—likewise ex- hibits a remarkable regularity in the action of its gentle oscillations. The latter are much more easy to study than the movements of the more in- dented and irregular peninsulas of Europe, and are also better known: since the epoch when the illustrious Darwin noted the fact that a great part of South America was constantly rising, savants and observers have only had to confirm the result of his investigations. It is principally on the coasts of Chili that the traces of the general up- heaval of the country are quite self-evident. Round every headland, at § § § s º N fl. º § ë N § º Sº * º Tig. 225. Coasts of Puerto San Joyge. (* & N the outlets of many of the valleys which cut deep into the mountainous masses on the coast, former sea-beaches may be distinguished, on which shells of the present epoch, like those of the creatures which are now live ing in the neighboring bays, are scattered about or even heaped up in thick layers. These beaches, which are separated from one another by cliffs or escarpments of various heights, resemble the steps of a gigantic staircase. From these it may be readily seen that the coast was not raised by any uniform movement, and that intervals of comparative re- pose have elapsed between each of the stages furnished by the growing mass of rocks. On the hills of the Isle of Chiloe, Darwin found heaps of modern shells at a height of 347 feet. On the north of Conception, several lines of level cut out by the waves during the present period are found at an elevation of 600 to 1000 feet. Near Valparaiso these levels are no less than 1295 feet above the lovel of the sea; but north of this town they be: come lower. At Coquimbo they scarcely exceed 110 feet, and on the fron- tier of Bolivia they are only 65 to 80 feet above the sea-level. Thus the rising action of the rocks is especially developed in those regions of the ELE VATION OF THE COAST'S OF CIIILI AND PERU. 551 sea-coast which are in the same latitude as the loftiest summits of the Chilian Andes—Aconcagua, Maypu, and Tupungato. We may infer from this that these high peaks indicate the axis of the portion of the upheaved crust, and that the mountains themselves tend to increase more rapidly than the plateaux and shores situated below them. In fact, in Chili, as in Norway, the terraces which overlook former bays or the mouths of val- leys are not horizontal, as they appear to be; they rise gradually toward the mountains, and increase in height as they recede from the present coast. The upheaving force acts, therefore, with more energy under the Chilian Andes than under the rocks of the adjacent coast. The white summits are gradually mounting up into the sky. Trigonometrical measurements carried on for a long series of years will some day enable us to recognize this increase in the giants of Chili, and their upward progress into the regions of cternal snow; but, up to the present time, the only calculations which have been made on the subject of the rapidity of the upheaval of the Andes are based merely on the study of the sea-shores extended at their base. Comparing the present state of things with the evidence derived from history, Darwin proves that, during seventeen years, between 1817 and 1834, the ground at Valparaiso has risen 10 feet 7 inches, or about 7% inches a year. This rather rapid move- ment was preceded by a state of comparative inaction, for, from 1614 to 1817, more than two centuries, the elevation of the shore, as proved by an examination of the localitics, certainly could not have exceeded 5 ſect 11 inches. At Coquimbo, Conception, and the island of Chiloe, the emerge- ment of the shore has taken place still more slowly. But, however im- perceptible the phenomenon may be, it is none the less taking place during the course of ages, and must ultimately completely change the aspect of the American coasts. Several ancient ports which were once frequented are now inaccessible; other harbors have been formed, thanks to the fresh protecting points which have emerged. Numerous islands, always desig- nated by the Indian name huapi, have become promontories. The indications of a gradual upheaval are equally visible on the coasts of Bolivia and Peru. In the eastern Zone of the Desert of Atacama the ground is covered at considerable heights with shells and saline efflores- cence, and seems as if it had been abandoned by the ocean only the day before. Above Cobija, Iquique, and several other coast towns, stages are marked out similar to those at Coquimbo, and, like the latter, were once washed by the water of the Pacific. In front of Arica the sea has receded 165 yards in the space of forty years, and the merchants of the town have been, in consequence, compelled to lengthen their landing-stage. But in 552 - THE EARTH. front of Callao, on one of the cliffs of the island of San Lorenzo, a most in- teresting proof has been found of the elevation of the shore during the pe. riod it was inhabited by man. At a height of 85 feet above the sea, Dar- win discovered, in a bed of modern shells deposited on a terrace, roots of 1200 ft. Fig. 227. Valley of Rio Santa Cruz. sea-weed, bones of birds, ears of maize, plaited reeds, and some cotton thread almost entirely decomposed. These relics of human industry ex- actly resemble those which are found in the Auacas or burial-places of the ancient Peruvians. There can be no doubt that the island of San Lorenzo, and probably the whole of the adjacent coast, have risen at least 80 feet since the IRed Man inhabited the country. It nevertheless appears that in our days the ground on which Callao stands has again sunk, for the place where the ancient town stood is now in great part under water. This de- pression is doubtless merely local, and only temporarily affects the gen- eral ascending movement of the coast; for farther to the north, at Colon and at Santa Marta, and several other points of the coast of New Granada, the ground has visibly risen since Europeans first landed on the continent. By admitting, however, that Callao forms, in fact, the northern limit of the area of upheaval, it results that the mass raised presents from north to south a length of at least 2480 miles. It is almost equal to the distance from London to Tobolsk. The movements of the eastern coast of South America which are at pres- ent going on have not been recognized so certainly as those of the west- ern shore, doubtless on account of the extremely slow rate at which they. proceed. An investigation of geological facts proves that the ground rose during the post-Pliocene period—that is, during the age of shell-fish still existing, and of the great animals which were the contemporaries of our ancestors, the megatherium, the mastodon, and the glyptodon. The Ar- gentine pampas have preserved the uniform appearance of the ocean which once covered them. The parallel terraces of Patagonia, extending for more than 500 miles, vary but a few yards in height along all the points of their immense development, and the arms of the sea which wind in be- tween the terminal promontory of America and the Tierra del Fuego re- tain all their ancient outlines. At the present time this portion of the continent appears to be oscillating in a contrary direction, and to be sink- ing by an imperceptible movement toward the level of the Atlantic. At the foot of the high cliffs of Patagonia the sea is incessantly increasing at the expense of the continent, and, although the breakers are not possessed of force sufficient to demolish the rocky beds for more than 18 to 16 feet below the surface, the depth of the sea nevertheless augments with an *. OSCILLATIONS OF SOUTH AMERICA. 553 even slope, in proportion to the distance from the shore, even over the site of the former cliffs. The bed of the sea must therefore be sinking, and with it the enormous mass of the plateaux which, during the recent period of the great mammals, rose with such marvelous regularity. * On the coast of Brazil, especially at Bahia, various recent depressions seem to indicate that there also the surface of the continent is regularly sinking. The ascertained facts were not, however, sufficiently numerous to justify any categorical assertion, until Professor Agassiz, in company with some other geologists, undertook his recent exploration of the River of the Amazons. In the first place, he verified the remarkable fact that, in spite of the enormous quantity of sediment drifted down by its current, this river does not form any deposits at its mouth. Instead of throwing out into the ocean a long peninsula of alluvium, like that of the Mississip- pi, or at least forming, beyond the regular coast-line, a delta similar to those of the Rhone, the Nile, or the Po, the Amazon, on the contrary, widens out in a large gulf toward the sea, and, in the great estuary, it is difficult to say exactly where the mouth, properly so called, commences. The banks of the river, and the islands which lie in its outlet, are not com- posed of alluvium brought down by the current of fresh water, but are all formed of rock with horizontal strata deposited by the water of the river at some former epoch, and long since solidified. Thus, in the contest which takes place in the estuary of the Amazon, as in every other river-mouth, between the currents of fresh and salt water, between the fluviatile allu- vium and the erosions of the sea, the latter always prevail. Instead of en- croaching on the ocean, the valley of the Amazons has been invaded by the latter for at least 300 miles; for the geological study of the ground on the two shores of the estuary proves that rocky layers, exactly similar toºthose farther up stream, exist on the coast as far as the valleys of the Itapicuru and the Parnahyba. These two rivers once fell into the Ama- zon, but, in consequence of the erosion of their shores and those of the great current which they joined, the sea has advanced, as it were, to meet them, and they have thus, by degrees, become entirely independent of the Amazon system. In a similar way, the stream of the Tocantins is now only indirectly connected with the great central river, and sooner or later it must ultimately become isolated, as the Itapicuru and the Parnahyba already are. The action of erosion, caused doubtless by a constant sink- ing of the ground, is still continuing. The shores are noticed to recede all round the estuary at Maranhao, at Piauhy, at Macapa, and on the coasts of Marajo. On the shores of the latter island, near Soure, a wide gulf, into which flows the Igarape Grande, has recently been formed across a forest for a space of more than 18 miles from bank to bank. The rocks in the vicinity, which once rose above the sea-level, are gradually becoming cov- ered. At Bragança, the bay, which used to advance scarcely a mile and a harf into the land, now penetrates for nearly five miles. The light-house of Vigia, which was built at sºme distance from the sea, was a very few years afterward washed by the waves. A signal-mast, which was set up 554 THE EARTH, in December out of reach of the water, was surrounded by the sea in the June following. Facts of this kind render very probable the existence of a see-saw movement, which is upheaving all the western coast of America from the island of Chiloe to Callao, and depressing the eastern side of the Argentine Andes, of Patagonia, and Brazil. Thus a large portion of the South American continent is constantly gaining on one side that which it loses on the other, and is gradually making its way through the ocean in a westward direction. Agassiz assigns to this phenomenon of displace- ment a very ancient origin, for in his view the Antilles, which once formed the isthmus joining the two Americas, have been gradually submerged, and the rivers of Guiana, once tributaries of the Orinoco, have become in- dependent rivers. In North America the vertical oscillations of the ground have not been recognized over so considerable a length as in the southern continent, but the few observations which have been already made on some points of the coast, in California as well as round the Gulf of Mexico, render the hypoth- esis very probable that a general upheaval is taking place, to which one of the parallel chains of the Rocky Mountains, or of the Sierra Nevada, serves as axis. The shore-belt of Tamaulipas and Texas increases so rap- idly in width, not only because the south wind—which here blows almost the whole year through—throws up a large quantity of sand, but also be- cause the ground itself is rising. During eighteen years—from 1845 to 1863—the shores of the Bay of Matagorda have risen 11 to 22 inches. In consequence of this gradual increase in the land, which is also proved by the heaps of shells left far from the shore, it has been found necessary to transfer the port of Indianola to Powderhorn, a place 4} miles nearer the entry.* The peninsula of Florida is likewise being upheaved by some sub- terranean forces, as is proved by the coral-banks which are rising abówe the level of the sea. Those mysterious clevations, the “mud-lumps,” which are scattered around the coast near the mouths of the Mississippi, the ori- gin of which M. Thomassy has tried to explain by attributing them to the pressure of subterranean water, also appear to testify in favor of a gen- cral upheaval of the region. - The eastern side of North America is not rising uniformly, for, although it is proved that the coasts of Labrador and Newfoundland are being slowly elevated, it is also proved that other regions are sinking. Lyell has ascertained that certain parts of the coasts of Georgia and South Car- olina are subject to a movement of subsidence, and it is in consequence of a gradual depression, no less than from a constant action of erosion, that Sullivan and Morris Islands, at the entrance of Charleston Roads, are inces- santly diminishing in area. In like manner, all that portion of the coast which has as its centre the Bay of New York, and is bounded on the north by Cape Cod, and on the south by Cape Hatteras, has gradually sunk un- der the water of the Atlantic ; and the subsidence has not yet ceased, at least as regards the coasts of New York and New Jersey. An isle which, * Adolf Douai, Mittheilungen von Petermann, April, 1864. f Wide above, p. 250. MOVEMENTS OF THE COAST'S OF WORTH AMERICA. 555 on a map of 1649, is marked down as possessing an area of 290 acres, is at the present day not more than 100 square yards in extent at low tide, and at high tide is entirely submerged. If we are to put faith in tradition, ...the Straits of Hell Gate, which form the entry to the port of New York, are of recent origin. Two centuries ago the natives related to the Dutch colonists established in the island of Manhattan that, at the time of the fathers of their grandfathers, it was possible to cross dry-shod from one bank to the other, and that the sea only penetrated into the straits at the time of the great equinoctial floods. The land-surveyors employed on the survey have calculated that the shores of the Bay of Delaware lose, on the average, nearly eight feet every year. As far as it is possible to judge from the observations made since the colonization of the country, the slow subsidence of this portion of the American coast may be estimated at 23% inches every century.* In the vast island of Greenland, which lies in the axis of North America, the progress of gradual subsidence, succeeding to a period of upheaval, appears to be much more rapid. For a long time the Esquimaux have been acquainted with this phenomenon, and the Danish colonists on the western coast have also been enabled to verify the facts since the last century by noticing, for a length of more than 620 miles, rocks, advanced promontories, and, indeed, their own dwellings, gradually disappearing under the inroads of the water. According to Wallich, this receding movement is still going on as regards the bed of the sea to the south of Iceland, and the sunken land of Bass, marked out on all the old charts, has really existed. On the north of Greenland, from latitude 76°, and in Gren- nell's Land, as well as in the other polar regions of the New World, the directly contrary phenomenon is taking place. In his voyage undertaken to discover the open sea, Hayes noticed on all the coasts the existence of ancient sea-beaches, which had gradually risen to a height of 100 feet; added to this, all the cliffs of the headlands had been polished up to this height by the action of the ice. * Cook, Geological Survey; Arnold Guyot, American Journal, March, 1861. 556 TEIE EARTH, CHAPTER LXXXV. REEFS OF THE SOUTH SEA.—DARWIN’s THEORY AS TO UPHEAVALS AND DEPRESSIONS. THE study of shores has not only enabled us to note the upheaval and subsidence of great continental masses; it has also made known to savants the Oscillations of the tracts of ocean, for the numerous islands which lie either alone or in groups in the Indian Ocean have served as evidence to prove the movement of the ground on which they stand. Lines of erosion, parallel terraces, banks of modern shells, and all the other marks of the former presence of the water, point out, in each of the islands of the Pa- cific, as well as on the coasts of Europe and the New World, the various upheavals which have taken place. But, in addition, most of these islands are surrounded with living girdles of corals, which exactly measure all the changes in level, either elevation or depression, to which the shores are subject. The discovery of this fact, that the terrestrial oscillations are, so to speak, rendered visible by the work of polypes, is doubtless one of the most important achievements of modern geography; and it is to the pa- tient investigations and sagacity of Darwin that science is indebted for it. Dy comparing his own observations with those of the explorers who pre- ceded him, the English geologist has been enabled to point out, just as if he had witnessed them with his own eyes, the various movements which raise or depress the bed of the ocean, over an area as great as that of the two continents of Europe and Asia. All the travelers who have crossed the South Seas have been struck with astonishment at the sight of the reefs raised by the polypes in the midst of the water. Some of these reefs circle round at a distance from islands, or even archipelagoes; they then form barriers of coral. Others, situated far from any land, are distributed in the shape of rings, or of more or less elongated crescents, round lagoons or bays remarkable for their pale green water; these are the atolls. In those parts of the ring where the constructions of the polypes and madrepores have not yet reached the surface, the waves which flow over the submarine bar rise in foamy breakers; in other parts of the reef there are just visible above the waves rocks of a dazzling white or a delicate pink hue. Next comes a semicircular range of islets, like Druidical stones set up by giants in the open sea. Lastly, upon the emerged group which occupies that portion of the atoll which is most exposed to the violence of the waves and wind, cocoa-nut trees and other tropical growths wave in the air, either in mere groups or in regular groves. This is the most common form of the reefs among all the thousands of atolls which are dotted over the South Seas. ATOLLS, OR CORAL-REEFS. 5 5 7 2205' § * * §: § }ºš ŠEŠ §: ŞS. --> → & Fig. 228. Keeling Atoll. When these coral-banks have not as yet reached the surface, their position is only pointed out by a circle of breakers; those that have attained the last stage of their development form a circular grove, which, seen from above, would look like a coronal of leaves floating on the blue water. How have these wonderful reefs been raised ? As was long ago proved by Chamisso, the French traveler, the polypes love to build in the midst of water which is breaking into foam; it may therefore be readily under- stood that wherever a submarine bank exists, the coral-reefs assume, like the breakers themselves, a more or less annular form. But in spots where the sounding-line reveals no shallows near the atolls, how have the polypes been able to raise from the bottom of the abyss their calcareous habita- tions? In order to explain this phenomenon, scientific men once hit upon a strange hypothesis; they looked upon every atoll as the circumference of a crater, which the submarine forces of the globe had raised up to a dis- tance of a few yards from the surface, so as to form a base to the opera- tions of the polypes. Although this explanation might be true enough for a very limited number of atolls, it would be incomprehensible how thousands and thousands of volcanoes should have been elevated to the same height below the level of the sea. Nor could it be understood why the craters of these supposed volcanoes should so often assume very elon- gated forms. Lastly, it would be impossible to conceive why, taking into account the multitudes of annular reefs, of which several archipelagoes 558 TIIE EARTII. are composed, and especially the double range of the Maldives, 465 miles long by 50 miles broad, no atoll has ever distinguished itself by an erup- tion of lava or ashes. i% ! ſ §). Fig. 229. Atoll of Ebon. The form of these reefs, therefore, has no connection with volcanic phe- nomena, properly so called, and, like so many other facts in the terrestrial history, can only be explained by being attributed to slow movements of the surface. The subsidence of the bed of the sea will account for the formation of atolls and barriers of reefs; on the other hand, a gradual ele- vation of the ground explains the position of the corals which fringe the shore at a certain height above the waves. Thus, whether they rise or sink, the reefs formed by the polypes may serve as a measure of the ver- tical oscillations to which continental coasts, islands, and even the abysses of the Sea are subject. It is easy enough to verify the movement of land which is rising, as, in this case, we see the banks of coral resting upon the beach, and Sprinkling with their débrist that portion of the shore which is above the level of the OSCILLATIONS OF TII/7 SEA-BOTTOM. 59 5 sea. Often, too, the channels can be distinguished which once separated them from the coast, and on the high ground of several islands calcareous banks are found, which evidently owe their origin to polypiers. With re- gard to the coral islands which are not included in the area of upheaval, they are surrounded by annular reefs, constructed in the midst of the water at some distance from the shore. When this distance is but small, and the coral banks are not very thick, there is nothing to prove that the level of the coast has changed; for the observations of Savants prove that polypes can live and build their rocky habitations at a depth of from 100 to 150 feet. Generally, however, the walls of coral and calcareous sand, which form the outer sides of the recſ, descend much lower. Most of them lie on slopes composed of their own débris, and are immersed in the sca at a slope of 45° to depths of several hundreds and even thousands of feet. ſ: %;sº §: ºſſºſ ºffº ºo: Fig. 230. Isle of Vanikoro. It is evident that in a case like this the bed of the ocean must have sub- sided. The polypes commenced their work of construction a few yards below the surface, and then, in proportion as the ground sank on which their coral edifice stood, they continued to build upward and upward, in order to approach the light. The mountainous islands, which they sur- round with their reefs, gradually diminish in height, leaving between them- selves and the barrier of coral a channel of increasing width and depth. The time is approaching when, first having been reduced to the state of islets, they will become divided into isolated peaks, which one after the other will be submerged, and disappear in the sea. Then all that remains g 560 THE EARTH, Will be an atoll, inclosing within its increasing walls a lagoon, in which calcareous débris is slowly gathered; narrow beaches and reefs, like the pieces of Wreck still floating above a foundering ship, surround the spot where the island has been swallowed up. The natives of the atolls of Ebon relate that they have heard their fathers say that an elevated island, the hills of which were shaded by cocoa-nut trees and bread-fruit trees, once occupied the greater part of the lagoon. The isles disappeared, but the reefs are still maintained just above the level of the water.* When the subsidence of a whole archipelago of submarine peaks takes place slowly and regularly, it may often happen that the sea, striking forcibly against the cuter walls of the reefs, breaks this barrier, and hol- lows out for itself a free passage across the central lagoon. Then the banks of cofal rise in the midst of the breakers on both sides of the newly- formed channel, and the original atoll is thus divided into two annular isles. In proportion as the submarine mass sinks, other ruptures of the same kind take place in each of the isolated fractions of the atoll, and the archipelago of reefs is ultimately composed of a considerable number of islets, which, in their turn, are also broken up. In this way are formed these wonderful groups of annular banks arranged in immense ovals. º, ZZ º »SSºgº: º % % Fig. 231. Section of Isle Vanikoro. The Atoll Ari of the Maldives is an example of this astonishing forma- tion of coral islands. If we could represent in a drawing the shapes that the ensemble of the groups has successively assumed during the course of centuries, we should obtain a series of curves similar to those which geog- raphers avail themselves of to delineate the slopes of a mountainous group. Sometimes, however, the movement of a depression is so rapid that the Sea does not confine itself to opening channels here and there across the atolls. The coral insects do not build fast enough to maintain their dwellings on a level with the surface; they gradually perish, and ::::::: gº §§ º 23:3: § - ** zººsº & 3% # E: §:# ź33 & 2. §§ § sº & & § & & 3. : & & & X? Š §: & X& S& § 2.83. 3& & % sº § Fig. 232. Growth of Coral on a Mountain slowly subsiding. * Doane, Nautical Magazine, Sept., 1863. ATOLL AR P L. XXIV. - *. % ... #9– §§ *::::: - 43.3%; - º §§ ...” gº º § ; §§ * sº wº gº; aſſº }º * 7&Eas: of J’Ba is * : *%. • * sº ‘. . ºšk. º 3.3%. ſº ºr º . Tº - 49 §3% 7.3, º sº sº; * º, , §: 㺠º º jº §ºss; §. º: -- §: §§ *śs. §: sº. Ziº, §§§ § {:}; **; - & 㺠+...+ $: •,• : '.' . º, º * , Rºy †: &% - sº 3. .# . - Fº - -º º::: s&z. º. . . ‘. . . - ğº #.º *: §º ºr. Tº - *::tº ×4,” - # ** & *::::: - .recº-Yº, . & **:: St. *º-. § * *. #º $$. - sº.: "º *…* . #sº -i. sº,... ºº iš. ***. **#: jº. & 4 ºr sº ~º a s & #3. &: Aume-dou. *S \; šć. “\ºsºx' * ** º %3 {{ ºf sºs" - º Ax, - xx; ... *% * }* &tº * 3: .. :: ***. sº *... * ; º; ; W º: - $ º * Sºx §.3° 25': §.S. §§§ w tº º 'º Sº... .ºOº. -> -- º, º sº. ºumgha-tie yºg Y § #: - -- º: 4. * §§ - < *s % ºf . gº . - “sº ** §§§ É. - § { * ...” .# ATO LL # # ROSS º: #3, & := x: 3. *** - ----------. Eng? by T. rhard- HARPE.R. & B R ()'ſ H F R.S. j\ }; W Y () R K OSCILLATIONS OF THE SEA-BOTTOM, 561 the atolls, which, layer by layer, have been raised by innumerable genera- ...tions of constructors, disappear, and form annular shoals. Of this kind IS the great bank of Chagos, south of the Maldives, which the sounding-line Profile º Fig. 233. Great Bank of Chagos. shows to have once been one of the largest atolls in the Indian Ocean. In the group, indeed, of the Maldives, several islets, which were recently in- habited and green with vegetation, are now slowly being swallowed up beneath the surface of the water.* * Darwin, Coral Reefs. N N. 562 THE EARTH, CHAPTER LXXXVI. THE GREAT AREAS OF UPHEAVAL AND DEPRESSION.—MOBILITY OF THE SO-CALLED IRIGID CRUST OF THE EARTH. OWING to the evidence which is furnished by coral reefs, which evidence, however, is supplemented at a large number of points by other indications, it is now possible to fix almost exactly the limits of the areas both of up- heaval and subsidence, which divide between them the hemispheres in- cluded within the coasts of South America and Africa. While the group of the Sandwich Islands is rising, as if it were still subject to the forces which are elevating the American continent, a gradual subsidence may be noticed in the archipelagoes of the central basins of the South Seas, the Bass and Society Islands, and also the Gilbert, Marshall, and Caroline Isl- ands; in one word, all this “milky way” of islands, islets, and reefs, which extends diagonally across the Pacific for a length of more than 9000 miles, and with an average width of 1200 miles. These islands are the remnants of a former continent, which has sunk down, with the people who inhabited it. Since the first European navigators visited these seas, several islands have disappeared, and others, such as Whit-Sunday Island, have consider- ably diminished in size. In a parallel line with this great area of depression, which is at least twice as large as Europe, lies a wave of upheaval which coincides with the semicircle of volcanoes running round the western side of the basin of the South Sea. New Zealand, which is situated on the southern end of this rising, and is based on a long furrow of fire, is rising in certain places so considerably, that English colonists, who have only arrived there a few years, have been able to notice that the headlands increase in height, and that banks of rocks are gradually obstructing the entrance of the ports. At the commencement of the present geological epoch, the moun- tains of Zealand were at least 1900 feet lower than they now are, and the ice-floes, from a continent situated to the £ast, floated with their load of erratic rocks on to the incipient islets, and were there stranded. But since that time the New Zealand Alps have risen ten successive times, as is proved by the ten terraces lying in stages on the sides of the mountains.” Even at the present day the latter are still increasing. In ten years the shores at Lyttleton have risen three feet. The New Hebrides, the Shlomon Islands, the northern and western coasts of New Guinea, the numerous isl- ands which compose the great Sunda Archipelago (which latter are proved by their altogether Asiatic fauna, as studied by Wallace, to have once * Julius IIaast. F. von Hochstetter also asserts that the eastern coast is being upheaved, but he thinks that the western coast has sunk, and that the axis of a see-saw movement passes through the two jelands. AIEEAS OF UPHEAVAL AND DEI2RESSION. 563 formed a portion of the neighboring continent), are all now rising, after having quite recently subsided, and banks of coral emerging from the sea are incessantly being added to the shores. At the angle of the Asiatic continent the wave of elevation divides in a fork, so as to run round the Chinese Sea, which is bordered by the gradually-depressed coasts of Cochin-China and Tonquin. To the north the upheaved region is continued toward America by the Philippine, For- mosa,” Liou-Kieou Islands,f and Japan; that is, all the islands from Borneo to Kamtschatka, through which passes the fissure of eruption of the vol- canoes of the Western Pacific. Quite recently Russian travelers have dis- covered, on the coast of the great island Saghalien, heaps of modern shells, lying not far from the shore, on beds of marine clay, and also former bays, which are now converted into lakes or salt marshes. In like manner, it has been proved that the regions of the Amoor are gradually being up- heaved; for, in order to maintain its level, the river has constantly to hollow out its bed between the cliffs, and on the plateau by the river-side, semicircular sheets of water may still be seen, which are evidently former windings of the Amoor. On the west of the Sunda Archipelago, Sumatra, fringed on its eastern coasts by peninsulas which once were islands, and, indeed, still bear the name (poulo), seems to be the starting-point of another movement of up- heaval, which embraces all the coasts situated round the Bay of Bengal. The Nicobar and Andaman Archipelagoes are gradually rising. Ceylon is likewise rising; at least part of it, as is proved by the banks of coral lying in gradations one above another on the hills, and also by the tradi- tions of the natives. But it is probable that the extremity of the isle is undergoing a slight see-saw movement, for Adam's Bridge, the chain of ‘. 2.38 49 2.5 Gulf of Manaar 77° E. of Pai-is Fig. 234. Bridge of Adam or Rama. shoals which joins Ceylon to the Coromandel coast, which, too, according to the legend, formerly served as a road to the triumphal army of Hanou. * Ferd. de Richthofen, Zeitschrift der Geologischen Gesellschaft, vol.xii. t Swinhoe, North China Branch of Asiatic Society, No. 11, May, 1859. * 564 THE EARTH. man, the monkey, appears to have once been a perfect isthmus. Scarcely three centuries have elapsed since the peninsula of Rameseram, whither thousands of Hindoos went every year in pilgrimage, has become detached from the main land, and formed an islet, like the ruins of a fallen pier.” Farther to the north there has been an upheaval. If we may put faith in the Brahmin legend, Veruna, the god of the sea, two thousand three hun- dred years ago, ordered the waves to abandon the iow plain of Malayala, which extends along the Malabar coast between Mangalore and Cape Co- morin. With regard to the basin of the Lower Ganges, it appears to form a part of the area of upheaval of the Bay of Bengal, and, with all its southern part, to be gradually rising; for the tributaries of the river which traverse this region—the Coosy, the Mahanada, and the Soane— are constantly shifting their mouths farther up-stream. The last-named water-course has retreated more than four miles during the last eighty years. According to Mr. Ferguson, at the confluence of the Ganges and Gogra we find the western limit of the wave of upheaval, which commences at the islands of New Zealand, 8000 miles away toward the southeast. Almost the whole of the space occupied by Australia and the Indian Ocean, properly so called, is situated, like the central basin of the Pacific, in an area of gradual depression. While, from New Guinea to Sumatra and the Philippines, a new continent is emerging from the water, the old Australian continent, so remarkable for its fauna and its flora, which seem to belong to some former geological period, is gradually sinking down, to- gether with the surrounding isles—the Louisiade Archipelago, New Cale- donia, and the reefs of the Coral Sea. Up to the present time, one portion alone of Australia is known to be experiencing a continuous movement of clevation—the district of IIobson’s Bay, near Melbourne, which, according to M. Becker, is rising at the rate of about four inches a year. Be this as it may, the great mass of the continent is imperceptibly sinking, and the polypes which surround the coast are compelled to heighten their reefs more and more. The Indian Ocean, to the west of Australia, is almost entirely devoid of islands; but all those that emerge from the depths of the sea over a space of more than 3700 miles in width are atolls, which would be slowly submerged if the polypes were not incessantly building up the edges of the reefs. Among these islands are the celebrated Keel- ing Atoll, which Mr. Darwin has studied so profitably for science, and the |Maldive Archipelago, that double chain of submarine mountains, every peak of which is crowned with a coral tiara raised above the water. Thus the space which extends over two thirds of the circle of the globe, from the eastern coast of America to the western shores of the Indian Ocean, presents two areas of upheaval and two areas of subsidence suc- ceeding one another from east to west. Next to the American continent, which is slowly rising, we have the innumerable low-lying islands of Oceania, the greater part of which would have long ago disappeared if * Ritter, Erdkunde. f Duncan, Asiatic Researches, vol. v.; Von Hoff, Veránderungen. f Gregory, Philosophical Society of Brisbane. º ELEVATION OF PARTS OF OCEANIA AND AFRICA. 565 it were not that the labor of the polypes has maintained them on a level with the waves. Next, there is developed, in a vast semicircle, pointed out from afar by its volcanoes, a large zone of isles and sea-coasts which are gradually rising, as if to replace in the future the old continent of Australia. Lastly, the same causes which are depressing the bed of the Central Pacifies are likewise lowering that of the Indian Ocean, with its shallows and its reefs. Beyond lies the enormous mass of Africa, the coasts of which have not yet been explored by scientific men, except, perhaps, over some small ex- tent. Nevertheless, sufficient observations have been made to Warrant us in considering Eastern Africa and the islands adjoining it as a third wave of upheaval, corresponding with those of America and the Sunda Islands. The banks of coral which surround Mauritius Island, Reunion, and Madagascar, and those which border the African coast from Mozam- bique to Mombaze, bear witness to the elevation of the ground. In like manner, the southern coasts of the Red Sea still exhibit at various eleva- tions evident traces of the recent presence of sea-water. Most of the trav- elers who have visited these places, Ferret and Gallinier, Rüppel, Salt, Valencia, and Niebuhr, have been struck by the sight of reefs emerged from the sea, former sea-beaches white with salt, and bays which are now left far inland, and are converted into marshes. Quite recently M. Lejean has recognized the fact that, by the upheaval of the ground, the former port of Djeddah is completely separated from the sea, and has become a mere lake; this port, at the time of Niebuhr, was still accessible to ships of small tonnage. The inhabitants of the coast assert that both the bed and the shores of the Red Sea change every twenty years. Not far from the Isthmus of Suez, on the north, the slow elevation of the ground is replaced by a contrary movement; but on the western side it is not yet known where the first signs are to be found of any rising of the ground. The observations of M. Eugène Robert on the coast of Sene- gal would perhaps show that this portion of Africa is in an area of up- heaval. It is, however, a fact, that beyond the African continent, Madeira, St. Helena, and probably the Canary Islands, the remains of the ancient Atlantis, are gradually sinking into the ocean. All these facts tell in favor of the hypothesis according to which the equatorial position of the circum- ference of the globe presents three waves of upheaval, separated from one another by three intervening depressions. The centre of each depression lies in the middle of an ocean; the three upheaved regions are the great Sunda Archipelago, a kind of continent in process of formation, and the enormous masses of Africa and America. As will be understood, these regular oscillations must take place in obe- dience to some general law still unknown, although none the less certain. We can not consider them, with Berzelius, to be nothing but mere acci- dents, produced by the subsidence or the rupture of the terrestrial crust. Neither must these regular movements be confounded with volcanic trem- blings, for they are distinguished from the latter by their excessive slow- 566 - THE EARTH, ness, as well as by their character of generality. Moreover, all these facts, whatever may be their origin, are determined by causes affecting the whole mass of the planet. If earthquakes have their tides, as is said to be proved by the greater frequency of these phenomena at the time of the full and new moon, We can not doubt that the slow oscillations of the terrestrial envelope also have their regular cycles. Only the reason & these secular tides still remains unknown. Must we seek for it in some alteration of the physical conditions of the globe, or in the revolutions of some astronom- ical period? As far as regards these points, we are reduced to mere hy- pothesis. Some day or other, when scientific men have observed all the lines of level from the north to the south pole, and all the débris which have been left by the sea, as it were so many precise measurements, on sea-coasts and mountain-sides, we shall be able to exactly specify the di- mensions of each wave of upheaval, and also what the impulsive force is which actuates them. We shall then know whether the regions that are elevated are always equal in extent to those that subside, and whether the surface, like that of every vibrating body, presents certain “nodal lines,” round which the agitated portions arrange themselves in rhythmical figures. We shall know, too, whether continents and seas, alternately ele- vated and depressed as if by some secular tide, are slowly shifting their positions round the planet, assuming therein various harmonic forms. Per- haps even it will be proved that in the bowels of the earth an exchange of solid particles is taking place similar to the circulation of the aërial and liquid particles of the atmosphere and the ocean. The globe, a simple mass as it is of condensed gas, is not entirely congealed; it has retained, like every other body, some remains of its former fluidity, and, just as in a lump of metal coming out of a furnace, the particles which compose it never cease to turn slowly round and round one another. Be this as it may, it remains an unquestionable fact that an incessant movement is causing an undulation in the so-called rigid crust of our globe. The continental masses are still elevated through a long course of ages; next, they sink only to rise again with slow and majestic oscilla- tions. Scandinavia, which is at present rising, sank during the Glacial pe- riod, and the population which at that time made it their abode were forced to abandon their valleys step by step as they became converted into fjords. In like manner, the Chilian Andes and the mountains of New Zealand, which are at the present time increasing in height, previously sank by degrees, the former 8000 and the latter 5000 feet, before they rose as they are now doing. It is likewise proved that at a great number of other points—in Peru, in Egypt, in North America, and in Greenland— changes of the same nature have taken place during the present era of geological history, without any violent revolution having thrown the earth into confusion. Continents rise and sink as if through some gentle action of respiration; they move in long undulations, which may be compared to the waves of the sea; the far-reaching glance of Science can already trace out these undulations through the long lapse of centuries. “The time OSOILLATIONS OF THE CRUST OF THE EARTH. 567 will come,” says Darwin, “when geologists will consider the quiescence of the terrestrial crust through a long period of its history to be as improba- ble as an absolute calm in the atmosphere during a whole season of the year.” In the universe every thing is changing and every thing is in motion, for motion itself is the first condition of vitality. In by-gone days, men who, through isolation, hatred, and fear, were left in their native ignorance, and filled with a feeling of their own weakness, could recognize in all that surrounded them nothing but the Immovable and the Eternal. In their ideas the heavens were a solid vault, a firmament on which the stars were fastened; the earth was the firm, unshaken foundation of the heavens, and nothing but a miracle could disturb its surface. But since civilization has connected all the nations of the earth in one common humanity—since history has linked century to century—since astronomy and geology have enabled science to cast her retrospective glance on epochs thousands and thousands of years back, man has ceased to be an isolated being, and, if we may so speak, is no longer merely mortal: he is become the consciousness of the imperishable universe. No longer connecting the vitality either of the stars or the earth merely with his own brief and fleeting existence, but comparing it with the duration of the existence of his own race and of all the beings who have lived before him, he has seen the celestial vault re- solve itself into infinite space, and has recognized the earth as nothing but a little globe rotating in the midst of the “milky way.” The firm ground which he treads under his feet, and long thought to be immovable, is re- plete with vitality, and is actuated by incessant motion; the very moun- tains rise or sink; not only do the winds and Ocean-currents circulate round the planet, but the continents themselves, with their summits and their valleys, are changing their places, and are slowly traveling round the circle of the globe. In order to explain all these geological phenomena, it is no longer necessary to imagine alterations in the earth's axis, ruptures of the solid crust, or gigantic subterranean downfalls. This is not the mode in which Nature generally proceeds; she is more calm and more regular in her operations, and, chary of her might, brings about changes of the grandest character without even the knowledge of the beings that she nourishes. She upheaves mountains and dries up seas without dis- turbing the flight of the gnat. Some revolution, which appears to us to have been produced by a mighty cataclysm, has perhaps taken thousands of years to accomplish. Time is the earth's attribute. Year after year she leisurely renews her charming drapery of foliage and flowers, just as, during the long lapse of ages, she reconstitutes her seas and her continents, and moves them slowly over her surface. I N D E X. The references are throughout to the pages of the volume. An asterisk (*) indicates that the topic is pictorially illustrated. Aar, ancient glaciers of,” 217. . Ablation of glacier8, 197. Adam, bridge of,” 563. s Adelsberg, grotto of,” 257. Adige, river and valley,” 211. Talus formed by tor- rents,” 293. Adour, river,” 345. Dars at its mouth, 366, 368. Africa: Continent of, 60. Orographical map of," 67. Section across,” 115. The Ethiopian pla- teau, 116. Itiver systems, 277. Aiguilles, mountain peaks, 124. Aïn Musa, Wells of Moses, 231. Aletsch, glacier of,” 208. Alios añá Brandes, S1. Alps, the : Alpine clubs, 119. Ratio between passes and summits, 135. Apparent chaos, 148. View of the system,” 140. An ethnological bar- rier, 149. Roads across, 150. Downfalls in, 160. Snow-line of, 163. Glaciers of,” 207. Erosions #' 200. Devastations by torrents, 292. Lakes of, 388. Altitudes, diminish from equator to poles, 139. Altenfjord, bank of,” 535. Aluta, lake and defiles,” 294. Amazon River: Dasin oſ,” 277. Compensation of floods,” 318. Amount of discharge, 37S. America: North America,” 52. South America,” 5S. Continents of, 59. Itiver systems of 275. Amou-Daria, river,” 362. Anahuac, table-land of Mexico, 118. Amdes, the : General characteristics of, 153. also Volcanoes.) Antarctic Continent, its place in continental har- mony, 77. - Arctic Ocean, general characteristics, 77. Arno, river, 332. Artesian Wells: In the Sahara,” 95, 233. Theory of, 232. Some notable ones, 233. Temperature of, 233. Depths estimated by increase of tempera- ture, 234. Arveiron, river, sources of,” 199. Ashes from volcanoes,” 469. Asia: Continental aspect, 64. Orographical map of,” 71. Great plateaux of 111. Mountain chains of, 151. River systems of 272. Asphaltites, lake,” 40S. Atacama, desert of, 105. Atlantic Oceam : General characteristics of, 76. Its double basin, 76. Submarine volcanoes in,” 489. Atolls, coral islands,” 557, 560. t Auckland, volcanoes im,” 446. . . Awstralia: Its continental aspect, 64. Orographic- al map of,” 78. Its river system, 278. A depress- ed basin, 564. Avalanches, 169. Defensive works against, 171. Avoca, valley of,” 195. Axes, geological, of the earth, 63. Their trans- verse position in the two hemispheres, 75. Course of 280. Its risings, 320. (See Bars of rivers,” 363. How removed, 366. Bauerngraben, lake, 260. Basalt, 454. Basaltic columns, 456. Bayous, 347, 349. Black earth of Russia,” S5. Blanc, Mont, 14S. Bogs. (See Marshes.) #. channel of,” 131. Bothnia, gulf of,” 584. J3oulders, dispersion of,” 217. Bourgogne, valleys of erosion in,” 291. Brandes and Alios, 81. IBrienz, lake,” 294. Bugors of the Caspian,” 404. Cactus, 103. Callao, earthquake at, 510. Campine of Belgium, S3. Carbonic acid gas from volcanoes, 4.SS. . Carpathian mountains, destitute of glaciers, 211. §. valley of," 152. Caspian Sea,” 404. Caussade, plateau of," 113. Caverms: Inhabitants of, 253. The Mammoth Cave, 254. Chasms of Carniola,” 254. Grotto of Lueg,” 255. Of Adelsberg,” 257. Of Planina," 259. Chagos, great bank of,” 561. Chijian, Nevado de,” 466. Circle of Fire, the, 55. Circle of inland lakes,” 55. Circumpolar Circle,” 54. Climates: Changes in, 43. continents, 75. Cluses, cuts in mountains, 182. Cobi, desert of 96. Cogne, valley of,” 289. Colorado, desert of, 103. Great cañon of,” 153. Cols, necks in mountain ranges, 135. - Columbia River, the, 275. Comtiments: Formation of 39. A lost continent, 42. Harmonious arrangement, 46. Three double con- tinents, 59. Terra quadrifida,” 61. Continental analogies, 64. General pyramidal form, 64. Their water-basins, 65. Circle of junction of continent- al points,” 66. , Contrasts between the conti- ments, 69, 74. Continental areas, 70. General elevation of 72. Counterpoises in, 74. Contrasts and Harmony in Nature, 77. Coral reefs,” 556. Cordilleras, the, 155. Coseguina, volcano,” 47 l. Cosmogony: Laplace's hypothesis, 24. Objections to it, 27. Hindoo legends, 47. Greek legends, 4S. The world, according to IIomer,” 49. Mundus tripartitus,” 62. Craters of volcanoes,” 448. Crevasses in glaciers,” 182. Cutch, earthquake at,” 521. Contrasts of in different Danube, river,” 370. Débouchements, law of 136. Dead Sea, the,” 407. Débris of torrents,” 203, 321. Deltas: In general, 346,349. Of the Ganges,” 352. Of the Nile,” 354. Of the Po, 356. Of the Rhone,” 857. Advance of deltas,” 359. --- Deluges, hypothesis of periodical, 67. Demavend, crater of,” 4S0. Deserts: Semicircle of," 56. Characteristics of 90. The Salmara, 90. Of Egypt and Arabia, 95. Of 570 INDEX. Persia and India, 96. Of Cobi, 96. Of Utah, 102. Of Colorado, 103. Of South America, 104. Devil's Calion, the, 4S1. Dikes. Upon the Rhone,” 333. Upon the Missis- šippi, 334. Upon the Po, 336. Natural dikes, 345. Dombes, lake region of France,” 386. Downfalls of Mountains (see also Upheavals): Gen- eral character, 159. Subterranean downfalls, 505. Durance, river, 331. Earth, the : Its rank in the stellar system, 13. Form and dimensions, 14. Metrical notation, 15. Ro- tation upon its axis, 16. Tèevolution around the Sun, 17. Distance from the sun, 17. Solar and Sidereal year, 17. Its orbit around the sun,” 20. Great cosmical year, 22. Nutation, 22. Great cos- mical movement through space, 23. Probable end, 23. , Laplace's hypothesis of its formation, 24. Estimated thickness of crust, 28, 31. Theory of a central fire, 30. Geological history of the earth, 32. Ideal pyramid mountain,” 33. Or- ganic remains, 34. Fossils, 35. Oscillations of its surface, 527. Mobility of its crust, 566. Earthquakes (see also Volcanioes): General charac- teristics, 500. Theories respecting earthquakes, 501. Itelations to volcanoes, 503. Subterranean downfalls, 504. Artificial earthquakes,” 505. IEarthquake at Lisbon, 507. In South America, Sept., 1866,” 509. At Callao, 510. At sea, 510. Movements of terrestrial waves,” 511. Variations caused by rocks, etc., 513. Earthquake at Viége,” 514. Areas of disturbance,” 515. Characteristics of shocks, 516. Iºſſects upon animals, 517. Sec- Ondary effects of shocks, 519. Springs, fissures, Ctc., caused º, earthquakes, 519. The Runn of Cutch,” 521. Periodicity of earthquakes,” 523. Connection with meteoric influences, 524. Two great classes of earthquakes, 526. Upheavals and depressions caused by earthquakes, 526. Eaux-Bonnes, peaks,” 126. Ebon, atoll of,” 558. JEgypt (see also Nile): General notice of 95. heavals and depressions, 544. Elevation, influence upon temperature, 156. Embarras of the Mississippi, 321. England, geological map of,” 37. Equinoxes, the," 20. Eruptions (see also Volcanoes and Earthquakes): Of JEtna, in 1865,” 420. Material thrown out, 433. Their periodicity, 497. Estavelles, supplementary springs,” 228. lºstom, lakes of,” 393. Estuaries, 340. Etna : Eruption of, in 1865,” 420. Former erup- tions,” 425. Line between Etna and Vesuvius,” 437. Section of Etna,” 449. Cone of Etna,” 469. Europe: Continent of, 60. Orographical map of,” 63. Its advantageous position, 70. Plateaux of, 72, 112. Central mountains of, 144. Itiver sys- tems of, 273. Explosions in mines, etc.,” 506. Up- Fayoum, Iºgypt,” 331. Felou, cataract,” 302. Finland, lakes of,” 385. Tire, central of the earth, 30, 31. I'loods. (See Invundations and Rivers.) Fogs, dry, 84. Föhn, dry south wind, 168. gº Torces, modifying the form of the universe, 44. Forks of rivers,” 264, 266. - Iorests: A protection against avalanches, 171. Re- lations to irrigation, 223. * Fossils : Modes of preservation, 34. Order of their creation, 36. Frumento, Monte,” 421. Fumerolles of volcanoes, 434,486. Furos, net-works of rivers, 348. Ganges, delta of," 353. Garāa, lake,” 388. gº g Garonne, river, sources of," 274. Inundations of, 323. Gavarnie, mountains," 126. Gaves of the Pyrenees,” 876. George's Island, 493. Geysers, the,482. Giétroz, glacier of,” 190. Gironde, the, 341. Glacial period, the, 211, 219. Glaciers: First and second orders of, 176. Move- ments of, 177. Windings of,” 180. Cascades of, * 180. Slopes of 181. Marginal crevasses,” 182. In- tersecting crevasses, 183. Transverse crevasses,” 184. Longitudinal crevasses,” 185. Terminal cré- vasses,” 186. Supericial torrents,” 187. Chasms filled with snow,” 188. Ponds in, 188. Glacier of Giétroz,” 190. ijébris on glaciers, 192. Glacier tables,” 193. Moraines of glaciers,” 194. Glaciers of Geisberg and Rothmoos,” 194. Mud-ribbons in the Mer-de-Glace,” 196. Measurements of movement, 197. Ablation of, 197. Sub-glacial streams, 198. Terminal arches of glaciers, 199. Contrast between ice and vegetation, 200. Gla- ciers of Langthal and Gurgl,” 201. Advance and retirement of glaciers, 20ſ. Appearance of the glacier-bed, 204. Glacier of Vernagt,” 204. Dis- tribution of glaciers, 206. Glaciers of the Alps,” 207. Glacier d'Aletsch,” 20S. Glaciers of Central Lurope, 210. Of the Himalayas, 211. Of Scandi- navia, 212. Of the Arctic regions, 213. , Paucity of glaciers in tropical America, 215. Antarctic glaciers, 215. Diminution in size of European glaciers, 216. Ancient tropical glaciers, 220. In- !ºnce of glaciers on the circulation of water, Goldau, overthrow of,” 161. Golemas. (See Dikes.) Gothard, Mont St., 146, 148. Graham's Island,” 495. Greenland, glaciers of, 213. Gross-Glockner, the,” 126. Grottoes. (See Caverms.) Guano, 105. Guiding-banks for rivers,” 315. Gurgl, glacier of,” 201. Guscha, Piz-à-Lun de,” 127. Gypsum, amount thrown up, 244. Hawaii: Section of,” 438. Volcanic craters in,” 445. IIeaths: Of Holland and Germany, 83. Cºngº- tions in, 84. Extent of heath-smoke in 1857," 84. Himalaya Mowntains: The apex of the earth, 63. Their geographical position, 151. Peaks of, 152. Snow-line of 165. Glaciers of, 211. IIoang-Ho, river, 338. Huiduck, lakes of,” 412. IIumidity of the American continent, 97. IIydrographical systems, general view of, 271. Ice: Transformation of snow into, 173. Melting point of 175. Banded structure of,” 175. Break- ing up in rivers, 322. Formation in lakes, 396. Ice-period, ancient, 219. Igharghar river, the,” 288. Indian Ocean, general characteristics of 77. Inwndations: Alpine, 189. . . Of the Rhone,” 322. General features of 324. Means of preventing, 325, 328. Growth of land by,” 326. Isalco, volcano, 45S. Isére, river,” 335. Islands: How formed in rivers,” 306. Curve of vol- canic islands,” 428. Atolls, or coral islands,” 557. Java, volcanoes of,” 451. Jordan, the,” 408. Jorullo, volcanic hill,” 443. Jura Mountains: Their general aspect,” 145. Com- pared with the Alps, 146. Valleys and combes of,” 147, 390. Kaïmeni, volcanic island,” 402. Karaboghaz sea, 403. Karakorum mountains, 151. Kilauea, volcano,” 461. Kinchinjinga, peak, 153. Kouen-Lun, mountains, 151. Kurile islands, volcanoes of, 427. INDEX. Lakes: Filled up by torrents,” 289, 295. Lakes of" Aluta, Thun, and Brienz,” 294. Lacustrine lakes,” 296. Lake of Geneva,” 297. Drying up of lakes, 380. General formation of lakes, 383. Lakes of Finland,” 385. Lakes of the Dombes,” 386. Alti- tudes and depths of Italian lakes,” 387. Of Swiss lakes,” 388. Lake Garda,” 3SS. Lake of Neuchâ- tel,” 389. Lake of Oo,” 391. Lakes of Nors Elf,” 392. Lakes of Estom,” 393. Various phenomena of lakes, 394. Storms upon lakes, 395. Currents in lakes, 396. Formation of ice in lakes, 396. Lakes as regulators of rivers, 399. Fresh and salt lakes, 400. The Caspian sea or salt lake,” 401. The Karaboghaz, 403. The Dead Sea,” 407. Lake Van, 410. The Great Salt Lake of Utah, 410. Lakes of Huiduck,” 412. Land: Relative proportion to water on the earth,” 50. The Oceanic hemisphere;’ 51. The conti- nental hemisphere,” 52. The circumpolar circle,” 54. The circle of inland seas and lakes,” 55. The semicircle of deserts,” 56. Landes: Of Gascony,” 81. Landes of northern Europe, 85. landes, 344. Langthal, glacier of,” 201. Lºs hypothesis of the formation of the earth, Stilt-walking on, $3. The French Lava : Composition of, 435, 453. Cones of lava,” 447. Sources of lava, 458. Flow of lava, 462, 466. Levées upon river banks, 334. Lisbon, earthquake at, 507. Llanos, of South America, 99. Loire, river, 286. Floods of 334. Luchon and Val d'Aran,” 142. Lys, river,” 286. Mammoth Cave, the, 254. º Maps (colored, geological and orographical): En- gland, 37. North America,” 52. South Amer- ica,” 58. Europe,” 62. Africa,” 66. Australia, etc.,” 73. The Alps,” 149. Mer-de-Glace, etc.,” 178. Glaciers of Geisberg and Rothmoos,” 194. Glaciers of Langthal and Gurgl, $ 201. Glacier of Vermagt,” 204. Glacier d’Aletsch,” 208. Former glaciers of the valley of the Adige,” 211. Middle course of the Mississippi,” 311. I)elta of the Ganges,” 353. Lake Garda,” 388. Eruptions of Etna,” 425. General chart of volcanoes,” 432. Steam in eruptions,” 433. The crater of Mauna- Loa,” 460. General map of upheavals and de- pressions,” 526. Atoll Ari,” 560. Marcadau, Sierra de,” 143. Marshes: General characteristics of 413. Marshes of Paraguay,” 414. Marshes of Corrientes,” 415. Marshes of Florida, Carolina, and Virginia, 415. The Great Dismal Swamp, 416. Marshes of New- foundland, 416. Marubia, or lake-risings, 395. Masaya, volcano, 458. Mauna-Loa, volcano,” 460. Maypures, rapids of,” 300. Mediterranean Sea: Its western shores,” 57. Up- heavals of its shores, 538. Melr’ir Chott, marshes, 412. Mentz, gunpowder explosion at,” 506. Mer-de-Glace: General view of,” 168. Slope of the Mer-de-Glace,” 181. Ribbons of mud in,” 196. Meteoric action, slow course of 161. Meuse River: Its meanderings,” 308. and depressions of its shores, 530, 544. . . . Mississippi River: Mud islands in,” 249. River sys- tem of 269. Middle course of,” 311. Old chan- nels of,” 311. Channel at Vicksburg,”314. Floods of the Mississippi, 319. The embarras, 321. La- goons of 327. Ilevées along, 384. Gap at New Or- eans,” 838. Bayous and channels,” 350. Mouths of the Mississippi,” 350. Depths of current in the Gulf,” 352. Advance of its delta,” 359. Bars at its mouth,” 364, 36S. General course of the Mis- sissippi, 376. Mistral, an ačrial current, 377. Moeris, lake, 329. Moraines, in glaciers,” 194, 218. Moulins in glaciers, 187. Upheavals w 57I Mountains: Great bounding ranges, 52. General characteristics of, 117. Sacred mountains, 119. The pleasure in climbing mountains, 120. Vari- ous forms of mountains, 122. Poverty of terms to describe mountains, 122. Special terms in va- rious languages, 123. Elements in the grandeur of mountains, 129. Geological considerations re- specting mountains, 130. Depressions in mount- ain ranges, 130. Origin of valleys and gorges, 130. Actual and apparent slopes of mountains, 137. Mass of mountains as compared with that of the earth, 138. Hypotheses as to the general law of mountain chains, 139. Theory of parallel upheavals, 139. , Cooling power of mountains, 156. Highest points reached by man, 157. The SOroche, 158. Downfall of mountains, 150. Snow- fall upon mountains, 162, 16S. Avalanches, 169. Mourzouk, oases of, 93. The Oueld-R'ir,” 94. Movements of the Earth: Rotation upon its axis, 16. Ičevolution around the sun, 19. Precession of the equinoxes, 21. Nutation, 22. The great cosmic- al movement, 23. The rotation of the earth as modifying the course of rivers, 372. Mud islands of the Mississippi,” 249. Mud volcanoes,” 475. Mundus tripartitus,” 62. Nantua, plateau of,” 114. Nefouds, Arabian deserts, 95. Névé, or snow-ice, 173. In the arctic regions, 213. New Zealand, volcanic region of,” 4S4. Niagara, cataract of,” 297. Profile of 303. Nile Iriver, the : Slope of,” 282. Periodical rising of, 317. Its flood,” 330. Its delta,” 354. Nors Elſ, lakes of,” 392. Oases: General characteristics of 92. Oases of Mourzouk, 93. Of the Oued-R'ir,” 94, 233. Obsidian, 453. Oceans : Harmony in their shapes, 76. General characteristics of 76. Similarities and contrasts, 77. The Atlantic, 76. Submarine volcanoes of the Atlantic,” 489. The Pacific,” 53. basin of the Pacific, 76. IPacific and Atlantic, 271. Oo, valley and lakes of,” 391. Orinoco, river, bifurcations of,” 265. Orizaba, volcano,” 449. Orographical maps and charts. (See Maps.) Oscillation of the earth's surface, 527. Ossau, Pic du Midi,” 124. Oued-R'ir, oases of,” 94. Artesian system oſ,” 233. Oules, of the Pyrenees, 134. Ourdinse, Valley of,” 134. IDouble Tributary rivers of the The Indian Ocean, 77. rº, gºans Its basin,” 53, 76. Its tributary riv- ers, 271. Pakereman, or Valley of Death, 4SS. Palestine, section of,” 409. Panbouk-Kelessi, natural bridge,” 240. Papandayang, volcano, 476. Paradoxides IIarlani,” 37. Passes, Alpine, 136. Peat-mosses, 417. Peninsula, 67. Pinsk, marshes of,” 269. Pitahayas, or cactus, 103. Pitch-stone, 454. - Plains: General characteristics, 78. Often synony- mous with descrts, 79. Variations in the features of plains, 79. Plains of the New World, 97. Planina, grotto of,” 259. Plata, river and estuary, 347. Plateaua : Comparative view of 72. Distinction between plateaux and plains, 107. Importance of plateaux, 108. Their comparative, altitudes, 109. Their distribution, 110. Great plateaux of Central Asia, 111. Of Europe, 112. Of America, 113. Of Africa,” 115. Po River: Its slope,” 2S2. Utilization of its waters, 331. Dikes upon its banks," 336. Delta of,” 856. Poik, subterranean river,” 258. Polders of Holland, 84. Ponto-Caspian Isthmus,” 270. 572 INDEX. Poudreuses, avalanches, 170. Promontories, great continental, 65. Pumice-stone, 453. Puy de Pariou, Coulée of,” 499. Pusztas of Hungary, 85. Pyramus, river,362. Pyrénées, the . Their general form,” 141. Compared with the Alps, 143. An ethnological barrier, 143. General aspects of, 210. Gaves of,” 376. #º volcano,” 447. Reefs, coral,” 557. Regelation of ice, 175. Reservoirs, natural and artificial, 328. Rhine River: Bifurcation of,” 267. Course of, 283. Old meanderings of,” 312. Middle course of,” 316. Dikes of,” 333. Rhone River: General characteristics,” 297. Floods of, 319. Inundation of,” 323. Delta of,” 337. Bars of, 367, 371. Riñihue, cut of,” 264. Rivers: Various designations of, 261. Determina- tion of main branch, 262. Basins and water-sheds, 263. Forks and bifurcations,” 264. River systems of North America, 269. Of France, 270. General view of river systems, 271. Functions of rivers, 280. Slope of rivers,” 282. Mountain torrents, 284. Inequalities of discharge, 285. The Lys, War, and Loire, 286. Wadys, or temporary, streams 287. The Igharghar,” 288. Erosion by torrents, 289. Talus of débris,” 293. How rivers regulate their slopes, 304. Windings and cuttings,” 307. Reciprocity of curves,” 307. Shifting of courses,” 309. Guiding banks for rivers,” 315. Periodical risings, 317. Begulating the flow of rivers,” 332. Mouths of rivers, 339. Their course modified by the earth's rotation, 372. Their right and left banks,” 375. Amount of water brought down, 377. Comparative discharge,” 378. Amount of sediment, 379. Relations of rivers to civiliza- tion, 381. Relations of rivers to lakes, 399. Rivers, swbterraneam : General features of, 245. The Sorgues of Vaucluse,” 245. The Touvre,” 246. Submarine streams, 247. In the Gulf of Florida, 248. In Yucatan, 248. Mud lumps of the Missis- sippi,” 249. System of subterranean rivers, 251. How they are produced, 252. The Timavo, 256. Rocks, their capacity for absorbing moisture, 224. Tosa, Monte, profile of,” 149. Itossberg, downfall of, 160. Sahara, desert of 90. Sahel, desert of, 91. St. Lawrence, river, 269, 341. St. Paul, volcanic island,” 490. - Salt, whence it comes, 104. Saltness of Seas, 400. Salt Lake, the great, 410. Saltpetre, its origin, 105. San Francisco, cataract, 298. San Miguel, Submarine volcano, 495. Santorin, volcanic island,” 492. Savannas, of America, 98. Scheldt, river, islands in,” 307. Sea-coasts, extent of 71. Seasons, order of in the two hemispheres,” 19. Sediment of rivers, 379. Seiches, lake risings, 394. - Seine River: Meanderings of,” 309, 310. Ancient and present level, 323. Selvas of the Amazon, 97. Senegal, river,” 342. Séracs in glaciers, 186. Sete Cidades, volcano,” 476. Slopes of mountains, 137. Snow: General characteristics of, 162. Effects of the sun, rain, and atmosphere upon, 168. How transformed into ice, 173. Snow cornice,”,178. The snow-line, 163, 166. Snow-line of the Alps, 163. In South América,” 165. In the Himalayas, 165. - Soroche, snow-blindness, 158, Solfataras, sulphur mines,” 487. Sorgues of Vaucluse,” 245. Soulina, mouth of the Danube,” 370. Sphagnum palustre, peat-moss, 416. Splugen, Einshorn de,” 125. Springs: How they originate, 223, 228. Springs near mountain tops, 224. Chains of springs and fountains, 225. Variations in their discharge, 227. Estavelles,” 228. Intermittent springs,” 229. As- cending springs, 231. The Wells of Moses, 231. Cold springs, 234. Hot springs, 235. Constitu- ents of their water, 236. "Amount of heat, 237. Mineral springs, 238,242. Incrusting springs, 239. Metallic veins, 240. Salt springs, 241. Sa- line springs at Touzla,” 243. Springs affected by earthquakes, 519. - Stalactites, 252. Steppes of Russia, 85, 87. Streams. (See Rivers.) Stromboli, volcano, 458. Submarine volcanoes, 4S9. Swamps. (See Marshes.) Taal, volcanic island,” 491. Talus, formed by torrents,” 203. Tamarugal, pampa of, 104. Tauretunum, overthrow of, 160. Tchornosjorn, the black earth of Russia,” 85, 86. Temperature: How affected by elevation, 156. In- crease in descending, 234, 436. Influence upon volcanic phenomena, 498. Terra quadrifida,” 61. Tetarata, volcanic basin,” 485. Thermal springs, 480. Thun, lake,” 294. Tides, 339. Timavo, subterranean river, 256, Timboro, volcano,” 472. - Torrents. (See Rivers.) Touvre, subterranean river,” 246. Touzla, saline springs of,” 243. Trachyte, 453. Tunguragua, volcano,477. Tuff, volcanic scoriae,” 447. Tundras of Russia, 88. |Ullah Bund, earthquake at,” 521. - Upheavals and Depressions: General features,” 526. Of Northern Europe,” 531. Of the shores of the Mediterranean, 530. Of the coasts of Asia Mi- nor, 542. In Egypt, 544. Subsidence of Holland,” t;46. Of the English coast, 547. Upheaval of Chili and Peru,” 550. Depression of La Plata and Brazil,” 550. Upheaval of Northern Ameri- ca, 554. Rise of coral reefs,” 556. Darwin's theo- ry of upheavals and depressions, 556. Great area of upheavals and depressions, 562. Utah, basin of, 102. Walleys: Their origin, 130. Various formations, 132. Growth of valleys, 134. Valleys of erosion,” 291. Van, lake, 410. Vanikoro, coral island,” 559. War, river, 286. Velleja, overthrow of, 159. Vermagt, glacier," 189, 204. - t Vesuvius: General features of, 437. Line of frac- ture between it and Etna,” 437. The Crater of Vesuvius,” 448. Viége, earthquake at,” 514, • * * Viso: Crest of the mountain,” 123. Its position, 147, Ice-fields near, 210. e Volcanoes: General theories respecting, 419. Sea- coast line of,426. The Pacific circle of fire,” 426. Curve of volcanic islands,” 428. American Vol- canoes,” 429. Volcanoes of the Indian Ocean, 30. Of the Atlantic, 431. Of the Mediterranean 431. Of the Caspian, 431. Of Central Asia, 481: Probable number of volcanoes, 432. General map of volcanoes,” 432. Independence of Vol- canic outlets, 438. Growth of volcanoes, 440. Theories of Humboldt and Von Buch, 440. The Isle of Palma,” 441. Arrangements of outlets of volcanoes,” 445. Volcanoes in New Zealand,” 446. Etna, Vesuvius, and Orizaba,” 448. Vol- canoes of Java,” 451. Superstitions connected with volcanoes, 452. Stromboli, Masaya, Isalco, INDEX. 573 , Sandwich Islands,” 458. Projectiles from volca- noes,” 468,473. Eruptiºn of Vesuvius, 79 A.D., 470. Of Coseguina,” 471. Of Timboro,” 472. Mud yolcanoes, 475. , Volcano of Demavend,” 480. Solfatara of volcanoes,” 487. Submarine volcanoes, 489. Periodicity of eruptions, 497. Extinct volcanoes, 499. Volga, river,” 374. Wadys, temporary torrents, 287. • Water: Relative proportion to land, 50. Relations to glaciers, 222. Power of penetrating the Soil, 223. Amount conveyed by rivers, 377. Weald of Kent, the,” 41. Wells. (See Springs and Artesian Wells.) Wolſenschiessen, peak,” 127. Yangma, glacier,” 220. Year: Solar and sidereal,” 17. The astronomical year, 19. The great cosmical year, 22. Zambesi, cataract,” 299. TEIE END, VALUABLE & INTERESTING WORKS FOR PUBLIC AND PRIVATE LIBRARIES, PUBLISHED BY HARPER & BROTHERS, NEw York. Jºž" For a full List of Books suitable for Libraries, see HARPER & BROTHERS’ TRADE- List and CATALOGUE, which may be had gratuitously on application to the Publishers personally, or by letter enclosing Siac Cents. ſº HARPElt & BROTHEIts will send any of the following works by mail, postage pre- paid, to any part of the United States, on receipt of the price. FLAMMARION'S ATMOSPHERE. The Atmosphere. Translated from the French of CAMILLE FLAMMAR to N. Edited by JAMES GLAISIIER, F.R.S., Superintendent of the Magnetical and Meteorological Department of the Royal Observatory at Greenwich. With 10 Chromo-Lithographs and 86 Woodcuts. 8vo, Cloth. HUDSON'S HISTORY OF JOURNALISM. Journalism in the United States, from 1690 to 1872. By FREDERIok Hudson. Crown 8vo, Cloth, $500. PIKE'S SUB-TROPICAL RAMBLES. Sub-Tropical Rambles in the Land of the Aphanapteryx. By Nicholas PikI., U. S. Consul, Port Louis, Mauritius. Pro- fusely, Illustrated from the Author's own Sketches; containing also Maps and Valuable Meteorological Charts. 8vo, Cloth, $3 50. TYERMAN'S OXFORD METHODISTS. The Oxford MethodistS : Memoirs Of the Rev. Messrs. Clayton, Ingham, Gambold, Hervey, and Broughton, with Biograph- ical Notices of others. Éy the Rev. L. TYERMAN, Author of “Life and Times of the Rev. John Wesley,” &c. Crown 8vo, Cloth, $2 50. TRISTRAM'S THE LAND OF MOAB. The Result of Travels and Discoveries on the East Side of the Dead Sea and the Jordan. By H. B. TRISTRAM, M.A., LL.D., F.R.S., Master of the Greatham Hospital, and Honorary Canon of Durham. With New Map and Illustrations. Crown 8vo, Cloth, $2 50. SANTO DOMINGO, Past and Present; with a Glance at Hayti. By SAMUEL EIAzARD. Maps and Illustrations. Crown Svo, Cloth, $3.50. LIFE OF, ALFRED COOKMAN. The Life of the Rev. Alfred Cookman; with Some Account of his Father, the Rey. George Grimston Cookman. By HENRY B. RIDGAWAY, D.D. With an Introduction by Bishop FostER, LL.D. Portrait on Steel. 12mo, Cloth, $200. HERVEY'S CHRISTIAN, RHETORIC. A System of Christian Rhetoric, for the Use of Preachers and Other Speakers. By GEora E WINFRED HERVEY., M.A., Author of “Rhetoric of Conversation,” &c. Svo, Cloth. CASTELAR'S OLD ROME AND NEW ITALY. Old Rome and New Italy. By EMILIo CASTELAR. Translated by Mrs. ARTiiuſ: ARNoLD. 12mo, Cloth, $1 75. THE TREATY OF WASHINGTON: Its Negotiation, Execution, and the Discus- Sions Relating Thereto. . By CALEB Cushing. Crown Svo, Cloth, $200. PRIME'S I. GQ A-FISHING. I Go a-Fishing. By W. C. PRIME. Crown Svo, Cloth, Beveled Edges, $250. HALLOCKS FISHING TOURIST. The Fishing Tourist: Angler's Guide and Ref. erence Book. By CIIARLEs HALLock, Secretary of the “Blooming-Grove Park Association.” Illustrations. Crown Svo, Cloth, $2 00. SCOTT'S AMERICAN, FISHING. Fishing in American Waters. By GENIo C. Soott. With 170 Illustrations. Crown Svo, Cloth, $3 50. ANNUAL RECORD OF SCIENCE AND INDUSTRY FOR 1872. Edited by Prof. Sºngºr F. BAIRD, of the Smithsonian Institution, with the Assistance of Emil nent Men of Science. 12mo, over 700 pp., Cloth, $200. (Uniform with the An- mwal Record of Science and Industry for isł1. 12mo, Cloth, $200.) COL, FORNEY'S ANECDOTES OF PUBLIC MEN. A cdotes of º By Jolin W. For NEY. 12mo, Cloth, $200. ºf Public Men. MISS BEECHER's HOUSEKEEPER AND HEALTHKEEPER: Containing Five #º º: ; º and Healthful Cooking; also, many Directions OT SeCUll’II) of Hea. &I) appiness. Approved by Physici illustrations. 12mo, Cloth, #. pp. y Physicians of all Classes. FARM BALLADS. By WILL CARLEToN. Hand º Ornamental Cloth, $2.00; Gilt Edges, $2 ºn Somely Illustrated. Square 8vo, 2 Harper & Brothers’ Valuable and Interesting Works. FOETS OF THE NINETEENTH CENTURY. The Poets of the Nineteenth Con- tury. , Selected and Edited by the Rev. Robert ARIS WILLMoTT. With English and American Additions, arranged by EvºBT A. DUYokINoiz, Editor of “Cyclo- paedia of American Literature.” Comprising Selections from the Greatest Au- thors of the Age. Superbly Illustrated with 141 Engravings from Designs by the most Eminent Artists. In elegant small 4to form, printed on Superfine Tinted Paper, richly bound in extra Cloth, Beveled, Gilt Edges, $500; Half Calf, $5 50; Full Turkey Morocco, $9 00. THE REVISION OF THE ENGLISH VERSION OF THE NEW TESTAMENT. §§ an Introduction by the Rev. P. SoilAFF, D.D. 618 pp., Crown Svo, Cloth, $3 00. This work embraces in one volume: I. ON A FRESH REVISION OF THE ENGLISH NEW TESTAMENT. By J. B. LIGHTFoot, D.D., Canon of St. Paul's, and Hulsean Professor of Divinity, Cambridge. Second Edition, Revised. 196 pp. II. ON THE AUTHORIZED VERSION OF THE NEW TESTAMENT in Connection with some Recent, Proposals for its Revision. By RioIIARI) CIIENEvix TRENOII, D.D., Archbishop of Dublin. 194 pp. : III. CONSIDERATIONS ON THE REVISION OF THE ENGLISH VERSION OF THE NEW TESTAMENT. By J. C. ELLIOOTT, D.D., Bishop of Glou- cester and Bristol. 17.8 pp. NORDHOFF'S CALIFORNIA. California: For Health, Pleasure, and Residence. A Book for Travelers and Settlers. Illustrated. 8vo, Paper, $2 00; Cloth, $2 50. MOTLEY'S DUTCII REPUBLIC. The Rise of the Dutch Republic. By Jon N Lo- Tuiltop Mori, EY, LL.D., D.C.L. With a Portrait of William of Orange. 3 vols., 8vo, Cloth, $10 50. MOTLEY'S UNITED NETHERLAND’S. History of the United Netherlands: from the Death of William the Silent to the Twelve Years' Truce—1609. With a full View of the English-Dutch sºlº against Spain, and of the Origin and De- struction of the Spanish Armada. By JoHN LOTIII:OP MOTLEY, LL.D., D.C.L. Portraits. 4 vols., 8vo, Cloth, $1400. - NAPOLEON'S LIFE OF CAESAR. The History of Julius Caesar. By His late Im- perial Majesty NApoleon III. Two Volumes ready. Library Edition, 8vo, Cloth, $3 50 per vol. Maps to Vols. I. and II. sold separately. Price $1 50 each, NET. HAYDN'S DICTIONARY OF DATES, relating to all Ages and Nations. For Uni- versal Reference. Edited by BENJAMIN VINGENT, Assistant Secretary and Keeper of the Library of the Royal Institution of Great Britain ; and I&evised for the Use of American Readers. 8vo, Cloth, $500; Sheep, $600. MACGREGOR's ROB ROY ON THE JORDAN. The Rob Boy on the Jordan, Nile, Red Sea, and Gennesareth, &c. A Canoe Cruise in Palestine and Egypt, and the Waters of Damascus. By J. MAOGREGOR, M.A. With Maps and Illus- trations. Crown 8vo, Cloth, $2 50. WALLACE'S MALAY ARCHIPELAGO. The Malay Archipelago; the Land of the Orang-Utan and the Bird of Paradise. A Narrative.9f Travel, 1854-1862. With Studies of Man and Nature. By ALFRED IłUSSEI, WALL AGE. With Ten Maps and Fifty-one Elegant Illustrations. Crown Svo, Cloth, $2 50. WIIYMPEI's ALASKA. Travel and Adventure in the Territory of Alaska, for- merly lºussian America—now Ceded to the United States-and in various other parts of the North Pacific. By FREDERLok WilyMPER. With Map and Illustra- tions. Crown Svo, Cloth, $2 50. ORTON'S ANDES AND THE AMAZON. The Andes and the Amazon; or, Across the Continent of South America. Iły JAMES ORTON, M.A., Professor of Natural History in Vassar College, Poughkeepsie, N. Y., and Corresponding Member of the Academy of Natural Sciences, Philadelphia. With a New Map of Equatorial America and numerous Illustrations. Crown 8vo, Cloth, $200. WINCIIELL's SKETCHES OF CREATION. Sketches of Creation: a Popular view of some of the Grand Conclusions of the Sciences in reference to the His: tory of Matter and ºf Life. Together with a Statement of the Intimations of science respecting the Primordial Condition and the Ultimate Destiny of the Earth and the Solar System. By ALEXANDER WINOIIPLL, LL.D., Professor Of Geology, Zoology, and Botany in the University of Michigan, and Director of the state Geological Survey. With Illustrations. 12mo, Cloth, $200. yS MASSACRE OF ST. BARTHOLOMEW. The Massacre of St. Bartholo- willºs Preceded by a History of the Religious Wars in the Reign of Charles IX. By IIENRY WurtE, M.A. With Illustrations. Svo, Cloth, $1 75. | 3 9015 04186 7436 º S$2:$£§§§§: *>\s*：'， ， ！ ...tº. 3 sº 3"> º H.º.º. º & sº sº º ... • * *... . --~ ; ; * > * ， ' ’ ”№ſ （， ） - º-···• • • ► ► ► ► ► ►► -！ ）-* ***************, ·-··，º ：-|-* ：.*ºp ºº！！！ ：-） •¿• • • •* --- -№ ſ'： ?>：- - ¿¿.·· º,” ºr.º.º. tºº...A º -. caerae aeſ，...，,.，：;~· * · * * *******----¿ • ww.· §），-- -##- · -§:sº- ！3！！！）.*，· ·¿¿.*¿¿. *** · * * · ****** • • • • •*，…）， |-！ ********* ~~~~（~~~~. --º-º-º-*****… :-），。 ·！ ±aerº* * * * * * ！！！！！！！！！！！！！！ ·--·！！！！！！！！！！！！！！！!！！！！！ ſae sae|-·• --··، -£§:№ſ----|-|× {， ！-- · -|- ∞ √ √∞ √° √∞ √° √≠ √°√∞（.***- && （$*$% ∞ √≠ √≠ √ ·№rsºrs！！！！！！！! -*****~*~*~~~~ ~~ ·-*、、、、、、、、） -----：:: ~~~~ <;esº！~， ， -∞ √°√∞.'，-æ：ææ æses，sae -·.· -·------ſaeſaeºğ?ae ſae.|（， ）;·* （ {|-**** （§§§§· ■ ■ ■ ■”.· wae ;ºš，5）- ■■ º: tº: *A vºw ºf gr: ºf ºx *s tº º vºſ， ººº !！！，” ·}§§§, №.?，?，！，:-- *** ** * -“）， º§$%$&#%>$2&§::№ž · ·<！--****…！！！！！！！！！··№tº§§ſae:§¿*ae ·∞ √° √∞',·،· |×ſaeſae ſ.ſ.&&§§§-*（?·-§§----。№ºaeae№Ę§§ ：-·ſae aerarzae za zez∞:'， ±·ź№:№g！！！！！！！ º ： - ·， ， ， ， ！∞-3： sae·- - *********************） ∞ Nº. -E*№.*ae ---- -ſaevºaeae ••••• • •■■■>.■ · · · · · · · · · · * * · · · · · · · ·:·º·:·º· = £----ſºr.«¿， ！ ， ！#???！$$$（）-§§§）.*}°′′º § 3:#ffae· ſaeaeae§§§Ř®*****！ “----- §§§žğ&-&3&&*********--* * （º.---- ~ ~ ~ ~ ~ ~ ~ • • • ~~~~ ··· ！！！!！-- * v º§！！！„…№ J Ķ ' ***** &-- * * * mºtº º º * º ！， ſº ºr **** *.*.*. º: º: *** sº ºw * * * * * * * º *...sº º Nº. º sº º ſº **** * * ſae *« §§§）， · ſ · · · · · ·: º， ， ， ， ， «“ ***aer w.º.º.v. -*-|（23）！ºſſ -！ 5 -， ，* ...，x^***^- -ºº， ** * * wºgae waes • • ►wº ·* ：-§， 23.ſae; ?:.* *; **** !！!· · · · · -* ، ، ، ,，,- vae！|- œ Œ -ſºº （* * *, **， ** ∞ ·... *ſ 5， aix， « ae ſae aeraeaeae- ！&&&&&&&&&&#;&5:..?！!！！！!！！！！ y， ſº ） . sº"， y ， ----*****， * ！！！！！,，， ， 、 （~~~- 5 eº:， exºs. №s: :-）！！！！！！！！ ， ， · ·，≤） ::::：&dº º （* · · · · * （º. ！！！！！！!！！！} ****.***.**）： § ^ * * * * * * ſº： <！-- * -·wae, ºº， w'; ººººº … :） ，، -|× ſae----- •■ ſwaes sae · *** •}}■ ■ ■ ■ ■ ■<！-- šķxx%;&#ş"…，，.，，， sae， ::::::：::::：:：:：::：：:::::：:：::！ ſae: **** ■*******！ ·- ··<！-- *** ºvezaevae º szyn，·ſº：---.-^----■■■■ ***-ſº ： ſººr：№№ºr:· --§§§§§§§ #：：* √æ√≠√∞ √°.ș，∞· -،··~ -Ķ3:$;&#;&、、、。 ·--№， ， ， ， ** *********** -！•• ←wrºwº--§§§§::::：: ----·- ·*、、、、、、、、、、、）- ae -， ，- -·· ſae （?：?）· · |- -∞ √∞v√≠√≠ #***** -|- ·−， ×× ſae· · ·¿ŠŒŽšœ3Ķ: - -：¿¿.**、。--*** -· - ~~~~ſae·- -· * * * * *·|-'.·-º-º-º-º-º-º-º-， ！！！ * ſae：* ¿?¿|×· ¿??¿§§§§©®°¶√¶·-~~ - -ſæ，Ķ§§§§§§- *: №ſſº - |-s. - r - ~~~~ ~ ~ ~ ~ ~ ~ ， ， ， º·- -|-ſae;L.），· ~∞*** •** ?.ſae· - ··№ .|-.*.*） •º ſgszaeszczaessaeg&ggaeggae-…-_- ------ - *¿ §§§§§§§§§§§§§§§ſys，-- -（$$$$2&§§§5&&&&