Physical Geography

Preface

. It is the object of tlie present volume to enable the general reader who desires information on the various branches of physical geography, or the student who wishes to be aware of its general scope as a science, to obtain an outline of the main facts in language as simple and definite as possible. Physical geography, regarded as a science, does not admit of being treated in such a manner as to render it light reading. It involves not only a statement of numerous facts, but a great classification of facts and much close reasoning. It is, no doubt, of deep interest, and concerns us all very nearly, but like other subjects of real importance, it needs an effort on the part of the reader to appreciate the array of facts and observations on which it is based, the labour of reducing such obser vations to systematic results, and the deductions drawn from the facts and generalisations.

Physical geography occupies at present a definite position as a science. This position is different from that which it occupied fifteen or twenty years ago, when the only works of importance concerning it in our language were prepared. Many of the statements and facts recorded in those volumes are of course still valu- VI

PREFACE.

. able, but the progress of discovery in various directions has rendered information more precise, and has justified inferences and conclusions sometimes very different. The present volume does not claim to be complete, It is an outline carefully prepared, and is intended to supply a serious want. It does not profess to skim merely over the surface of the science, but neither does it pretend to fathom the depths. It contains many carefully arranged facts and statements in the various departments of physical geography, and legitimate de ductions from them. In expressing these deductions, the Author has perhaps, in some cases, given his own views, without pointing out that other physical geographers and geologists have expressed and still hold different opinions. It was not his object to enter into a discussion on any subject, and he only desires that generalisations should be estimated at their true value and according to the evidence.

He believes, however, that where the conclusions arrived at differ most from popular notions, they are not inconsistent with the views of those who are recognised, both in England and on the Continent, as the ablest pioneers of science. It has been decided not to accompany this volume with maps and illustrations. The Physical Atlas, originally published by Berghaus, and admirably rendered into English by Mr. Johnston, still remains the best and most useful work of its kind. The smaller English Edition of the Physical Atlas will be found a valuable companion to the reader in making use of the following pages. Athenæum Club, London, 1866. TAGS ANALYTICAL CONTENTS. PART THE FIRST.

Introduction

.

Chapter I. The Eabth As

A PLANET. General outline of the planetary system. Existence of ether. Incessant and varied motions of masses of matter. Nature of the forces that affect matter. Motion, an expression of heat, light, and electricity, and convertible into one or other of them. Spherical form of the heavenly bodies. Position of the earth ia the solar system. Magnitude of the earth — its superficial area and solid content. Distance of the moon. Effect of the moon on air and ocean. Distance of the earth from the sun. Results of excentricity or alteration of the elliptic orbit. Details of present and former excentricity. Revolution of the earth round the sun. Dimensions of the sun. Conservation of the equilibrium of the solar system. Relation of our solar system with part of the stellar system. Condition of the earth's interior.

Slow succession of deposits. Nature of underlying rocks. Temperature of the interior of the earth. Density of rocks and of the earth. Calculations concerning the thickness of the earth's crust. Material elements — the wide range of some of them throughout the universe. Three forms of matter — solid, liquid, and gaseous. States in which the most important elements and combinations usually CONTENTS. PAGE 1 is exist. Behaviour of certain elements and combinations on exposure to heat. Elements known and employed in their simple states. Important combinations of elements. Limit of natural combinations. m Importance of oxygen gas and the part it plays in nature. Hydrogen and its combinations. Nitrogen. Chlorine. Silicium. Aluminium. Lists of elements and simple combinations. Law of definite proportions.

Nature of mixtures. Importance of water in carrying on the operations of nature. Elective affinity. Cause of change in the materials forming the earth's crust. Limitation of physical geography and divisions of the subject

Chapter II. Physical Eobces

Force of gravitation. Force of cohesion. Particles of matter never in actual contact. Chemical action. Vital energy. Convertibility of motion and heat — various illustrations of this. Aeroliths. Quantity of heat generated by the same amount of force invariable. Result of impact. Calculated result of impact of planets with each other or with the sun. Nature of heat as a form of motion. Unusual conditions of the action of heat. Conduction of heat by different bodies. Conduction of electricity. Development of heat by passage of an electric current. Probable nature of the motive power developed by electricity. Nature of light. Complex condition of rays from the sun. Oscillations and vibrations only appreciated by the senses within certain limits. Difference between waves of light and waves of sound.

Transparency to light and heat not identical. Example of ice and water as contrasted with glass and air. Water not transparent to heat. Important consequences of this fact. Absorption and radiation of heat by vapour in the atmosphere. Absorption of rays which are emitted by bodies not transparent to heat (diathermic). Chemical action a form of motion. Its action in combination and decomposition. Electricity developed by heat. Electricity pro duces magnetism. Relations of vital force with the other chief forms of force. Indestructibility of force. Importance of a knowledge of physics to the student ofphysical geography. Nature of polar forces. Magnetism and dia-raagnetism. Posi tion assumed by a suspended magnet. Variation of this position. Lines of no variation. Deflection of the needle. Varia tion of the magnetic intensity. Magnetic storms. Aurora, borealis and australis ........ CONTENTS. IX PAGE

Chapter III. The Succession Oe Bocks

Geology necessary for the study of physical geography. Use of palæontology. 1. LRoclcs and their super-position. — Composition of rocks. Fundamental rock. Granite not a simple rock. Varieties of granite. History and position of granite. Fissures in granite and mineral veins. Value of granites. Circumstances under which the granites have been formed. Water present in granites. Trap and basalt. Basalt an ancient lava. Stratified granite or gneiss. Schists — their nature and origin. Slates and their origin. Slates exhibit results of squeezing. Rocks overlying the slates. Mechanical accumulations and results of organic life. General uniformity of material of which the earth's crust is made up. 2. Order and disturbance of stratification. — Stratification due to water. Position in which strata have been accumulated.

Impossibility of their being visible if it had not been for much and frequent breaking and lifting of deposits. Probable history of the change, and result of denudation. Results of upheaval. Absence of definite order of minerals in all stratified deposits. Identification of strata by their organic contents. Earliest forms of organic existence. Nature of the succession of rocks as indicated by fossils. Absence of proof of continuous history by advancing types. General sub-division and grouping of rocks. Nature and meaning of the principal groups. Indications of time. Sub-divisions of the older or palæozoic group. Laurentian, Cambrian, and Lower Silurian. Upper Silurian and Devonian. Carboniferous system. Permian _ rocks. Limestone, sandstone, and clay, and modifications of them, with numerous conglomerates, all found among palæozoic rocks.

Their sequence determined by fossils. Secondary or mesozoic rocks. Prevalence of limestones during this period in many parts of the world. LNew red sandstone. Lias. Oolitic series. Wealden. Chalk. Interval between secondary and tertiary rocks. Distribution of minerals among tertiary rocks of Europe. Surface deposits of gravel, sand, and boulders. General conclusions concerning the succession of rocks and their relation to successive forms of life. 3. Metamorphosis. — Nature of the changes that have affected rocks. Forces that have acted to produce these changes. Influence of water in producing change. Absence of evidenceof melting heat affecting stratified rocks. Modifications of limestone. Metalliferous ores found in limestone. Water the cause of such results. Clays as aqueous rocks. Conversion of clays into shales and slates, due to water.

Filling of veins and slates, a result of water action. Granite a3 connected with water. All granitoid CONTENTS. X PAGE 32 rocks formed with water. Quiet nature of change and general absence of catastrophes. Circulation and movement in the in terior of the earth not inconsistent with outward tranquillity. Conclusion that there has always been a circulation of water reconstructing and reproducing, as well as destroying and wear ing away the various rocks PART THE SECOND. EARTH.

Chapter IV. Land

Irregularity of the earth's surface. The actual state of the surface liable to change. Present configuration, that most important to us. Grouping of land into continents and islands. Dimensions of tracts of land very variable. Position of land very peculiar. Preponderance of land in one hemisphere. Inquiry if there is any cause for such difference. General statement of distribution of land. Position of the hemisphere of maximum land. Nature ofthe protuberance producing excess of land in one hemisphere. Speculations concerning the cause aud permanence of this protuberance. Determination of oceans by the position of the land. Relative smallness of the depth of water and height of mountains. Smallness of the average slopes leading to the highest and lowest points. Importance of irregularities of surface on climate.

Distribution of the land. High and low plateaux, and plains near the sea. Deep gorges contrasted with mountain chains. Valleys, as distinct from mere gorges. Form and area of land liable to change. Possible origin and extent of such change. Limiting line of sea and land. Advantages of a broken coast line. Natural irregularities of the surface of the land. Continents and islands. Islands parts of submerged continents. Position of the great continent. Dimensions of the great continent. Fringes of islands. Pyramidal termination of the land. Illustrations in various parts of the world. Total length of the geographical axis of the old world. Direction of this axis. Influence of its direction on climate. Details of coast lines. Europe and Asia one continent. Extended coast Une of Europe. CONTENTS XI PAGE 57 Proportion of area to each mile of coast.

Coast of Asia considered alone and with Europe. Proportion of area to a mile of coast in each case. Coast line of Africa. Large area to each mile of coast. Inference from this fact. America and its coast. North America compared with South America in the proportion of area to each mile of coast. Australian coast line and its proportion to the whole land. Advantage of a broken line of coast. General nature of the land. Plateaux or high plains of Europe and Asia. Steppes of Russia. Low plains and valleys. Rivers and waterfalls. Fewness of torrents and waterfalls. Absence of many large lakes in Asia. African mountains and plains — its lakes and rivers. American features — its mountain chains and rivers. Australia — its level surface and absence of mountains and rivers, in proportion to its magnitude.

Islands — their general nature. Different origin of islands. Indian Archipelago. Grandeur of some of the islands. Vast multitude of islands of moderate dimensions. Islands of the South Pacific — extent of submerged continent indicated by these islands. The case of coral islands as bearing on the history of islands. Large extent of submerged area. Islands indicate the ancient history of the earth. Direction and amount of the slopes of lofty mountain chains. Difference of the steepness on the two sides. Position of culminating points of mountain chains. Depressions in oceans probably correspond to mountains on land. Contrast between Europe and America as mountainous countries. Plains are characteristic of America. Great rivers and lakes also remarkable features of that continent. Australia, the land of unwatered plains.

Certain groups of islands rise to some culminating point. Connecting link between physical geography and geology. Theoretic views of the earlier geologists. Supposed great energy of forces in ancient times not proved. No evidence of the first introduction of life. Nature of the development that seems traceable in the preparation of the earth. Enormous denudation not sufficiently taken into account. Ages of the great mountain chains. Absence of any definite limits of land and water. Absence of clue to the first condition of the earth

Chapter V. Mountains

Importance of mountains in physical geography. Only two great mountain axes. Great elevation not the only essential. . The Q, two independent chains. Details of the great mountain system of the Old World. Alpine system — its characteristics. Eastern division — width of the chain. Effect of denudation on the Alps. Pyrenean chain — subdivisions. Glaciers of the Pyrenees. Carpathian mountains. Dinaric Alps. Balkan range. Greek CONTENTS. XII PAGE 74 mountains. Apennines. Scandinavian mountains. Mountains of the British islands. French mountain systems (Cevennes and Vosges). German mountain groups (Fichtelgebirge, Hartz, Erzgebirge). Mountains of the Iberian peninsula (Sierras Nevada, Morena, Estrella, &c.). Crimean mountains. Ural chain. The Caucasus. Taurus and anti-Taurus* The mountain systems of Asia.

Hindoo-koosh. Himalayan chain. Altai mountains. Extension of these chains eastwards. Highest elevations. Thian-shan. Magnitude of the chain. Kuen-lin. Mountains of Arabia. Vindhya mountains and Ghats of Hindustan. Mountains of the Malay peninsula. Mountains of Africa. General distribution. Atlas mountains. Mountains on the east coast. Kilima-njoro and Kenia. Abys sinian mountains. Connection with the mountains of Arabia. American system. The main outline. Rocky mountains. Snowy mountains and Black hills. Oregon chain. Mount Elias. Cordillera of the Andes. Central American or connecting group. Subdivision of the Andes. Andes of Patagonia, and Chilian Andes. Bolivian and Peruvian Andes. Andes of Quito and New Granada. Mountains of Brazil. Alleghany and Catskill mountains. Australian mountains.

Main chain. Australian Alps and Mont Kosciusko. Extension into New Guinea. New Zealand mountains. Lofty summits and glaciers. Mountains a result of long-continued elevation and denudation

Chapter VI. Hills And Valleys

PLATEAUX AND LOW PLAINS. 1. Hills. — Definition. Distinction between hills and mountains. Examples. Hills at a high level and mountains near the sea. Position of hilly ground. Rolling ground and its probable origin. Malvern Hills, Cotteswolds, and South Downs. Waldai Hills. Transfer of table land into hill country. The Saxon Switzerland and the Quantock Hills. Franconian Switzerland. Origin of hills in such districts as those just referred to. Important influence of denudation. 2. Valleys. — Different conditions of valleys according to geographers. Fine scenery in upland valleys in mountain countries. Valleys, indications of progress. Varieties of valleys according to geologists. Construction of valleys. Modification of natural fissures and gorges. All valleys more or less produced by erosion.

Origin of valleys of erosion in some places. Illustrations of lower valleys. Valleys of Rhine and Danube. Valleys of Asiatic and American rivers. Use of valleys in advancing civilisation. 3. High Plains. — Limitation of the term plateau. Peculiarities of lands thus named. Their relation to geological structure. English plateaux of chalk, oolite and granite. French plateaux CONTENTS. XIII s!7 of limestone and basalt. North German plateau. Carpathian plateau. Central plateau of Spain. Sierras rising through it. Extension of Iberian plain into Portugal. Asia, the country of plateaux. Plains of Arabia and Persia. Plains of Armenia. Salt desert of Persia. Table lands of Tibet. Deserts of Gobi and Scha-mo. Their extension and elevation above the sea. Other plateaux of Tibet. High lands of the peninsula of India.

Plateau of the Deccan. Table lands of the Faro islands — and of the British islands. Table lauds of Africa. Southern plateaux. High plains of Australia. North American plateaux. Great basin of California. Plateaux of Central America — of South America. The Desaguadero. Patagonian steppes. Tabular statement of the levels of plateaux. 4. Low Plains. — -Definition. Low plains of northern Europe. The Rirghis steppes and Siberian plain. Aralo- Caspian plain. The steppes of Russia described. The great plains of northern Asia. Plains of Hindustan. African plains. The Sahara. Desert of Arabia. Low plains of Central Africa. North American plains. Prairies, Savannahs, and pine-barrens. South American plains. Llanos and Silvas. The Pampas. Step-like terraces. Australian plains. Deltas of rivers. Strips of low land on coast lines of South America.

Comparison of Old and New World in the matter of plains. Importance of low plains to human requirements. Low plains, in reference to vegetable and animal life. Ethnological value of low plains PART THE THIRD. WATER.

Chapter VII. The Ocean

Importance of water in the economy of the earth. Nature of the barriers that enclose the ocean. Division into two great oceans. Atlantic canal — its dimensions and proportions — its subsidiary or inland seas on the European side. Inland seas on the American side. Islands. Dimensions of the Pacific Ocean. Its inland seas. The Indian Ocean. The Arctic Ocean. Antarctic Ocean. Natural subdivisions of the great ocean by submarine mountains, forming islands and shoals. Northern and southern basins of CONTENTS. PAGE 125 the Pacific. Subdivisions of these. Subdivisions of the Atlantic. Northern, central, and southern basins of the Atlantic. Inland seas and their formation. Necessity of a knowledge of the ocean floor. Methods of sounding in great depths. Old and modern methods. Results of deep sounding with a deep-sea dredge.

Material at bottom of the Atlantic. Nature of the oaze. Form of bottom of the Atlantic. Bottom of the Pacific. Bottom of the Indian Ocean. Composition of sea water. Origin of saltness of the sea. Various amount of salts in different seas. Atlantic more salt than Pacific. Position of the belt of saltest water in the Pacific. Smallness of salt in the Polar seas. Usual proportion of saline substances. Nature of the ingredients of sea water. Names of elements found. Variation of density of sea water in different seas. Atlantic, Pacific, and Indian Ocean compared. Density of Mediterranean water — Black Sea — North Sea — Baltic. Chemical contents in ordinary sea water. Local differences. Gases and air in sea water. Uses of air in water. Effect of cold on density of water. Capt. Maury's experiment, illustrating the conditions of cooling sea water.

Circulation of the waters of the ocean. Temperature of the sea. Stratum of invariable temperature. Pressure of the water. Animal life at great depths. Limitation of life in deep water not known. Light the ODly limit. Colour of sea water. Blue grotto of Capri. Cause of blue colour of water. Different colours of the water in different seas. Colour of the Black Sea. The water of the sea always in motion. Various kinds of waves. Different kinds of motion of water. Wind-waves, their nature and origin. Growth of wind-waves into storm-waves. Ground swell. Surf. Mechanical force of storm-waves. The tidal wave — its origin and history. High and low water. Conversion of the tide-wave into an advancing wave. Great rise of tide in certain waters. Marginal and local tides. The bore. Nature of the motion of the tide-wave.

Transference of motion without the removal of the body of the water. Different kind of currents. Stream currents— their origin. Various causes that may produce them. Effect of evaporation in narrow seas. The Red Sea current. Under-currents carrying back the water. Periodical currents. The Gulf stream — its commencement and course — its position and condition in the Atlantic — its temperature — its derivation from the equatorial current. History of this current and its counter-current running to the Guinea coast. The Brazil current — its nature, depth, and temperature. Rennel's current. Arctic or Polar current. United States counter-current. Antarctic current. South Atlantic current. The Pacific currents. Black stream of Japan. South Polar current. Mozambique current. Humboldt's current. Eddies and whirlpools.

Maelstrom. Charybdis. Origin of such eddies. Sargasso, or weedy seas. North Atlantic sargasso sea. North Pacific sargasso sea. Nature of such seas. Extension of the sargasso or gulf weed into British seas. . CONTENTS. XV PAGE 149

Chapter VIII. Elvers

Circulation of water on the earth by aid of the atmosphere. Natural course of running water on the land. Uses of rivers. Largest and most rapid rivers not the most useful. Advantage of moderate rivers. Drainage systems. Water-sheds and water-parting. Water-shed not necessarily a ridge. Sources bear no proportion to the rivers. Difficulty of discovering the real sources of rivers. Absence of importance of this inquiry. Sources of the Nile. The great river systems sometimes connected. Example of Amazons and Orinoco. Rivers generally originate near mountain chains. Rapidity of streams not altogether dependent on height of source. Streams of all kinds assist in denudation. River systems — how best considered. The Atlantic system. Vast importance of the streams draining into the Atlantic. Absence of streams on the Scandinavian shores.

Important feeders of the Baltic ; Neva, Niemen, Vistula and Oder. Extent of land drained by these rivers and their tributaries. Rivers entering the German Ocean. The Elbe and its tributaries. The Weser. The Rhine : its sources and tributaries. Its delta. Its total length of course and drainage area. The river systems of the British islands. The French rivers — the Seine and Loire — the Garonne. The rivers of the Iberian peninsula. The Douro and the Tagus, the Guadiana and the Guadalquivir. Extent of area drained. The Mediterranean basin and the rivers draining into it. The Ebro. The Rhone and its tributaries. Its drainage area. Italian rivers — the Arno and Tiber on the west — the Po and Adige on the east. Area drained. The Black Sea. The Danube and its tributaries. The Dniester and Dneiper.

The Don and Kuban. The Nile and its course. The Niger .and Senegal. The Orange river, the Gambia and the Coanza. The great river systems of America. The Plata and its main branches. The Amazons and the various names of its different parts. The Orinoco. The Magdalena. The Rio del Norte. The Mississippi-Missouri and its great tributaries. The smaller rivers of the United States. The St. Lawrence and its lakes. The Pacific system. The African rivers Zambesi and Great Fish river. The Tigris and Euphrates. The Indus. The Ganges and Brahmapootra. The Irawaddy. The great rivers of China. The rivers of Tartary. The rivers of America entering the Pacific. The rivers of Australia. The rivers entering the Arctic oceau. European and Asiatic streams. North American streams. Internal drainage. Caspian Sea.

The Volga, Ural and Kur. The sea of Aral and the Sir. Tabular statement of the principal systems of drainage. Large parts of the earth left undrained by the great river systems CONTENTS. PAGE

Chapter IX. Laees And Waterfalls

1. Lakes.— Their nature— mode of formation— varieties— cause of varieties. Tarns. Permanent and changeable lakes. Difference between lakes and ponds. Examples of lakes and pools. Salt lakes once part of the ocean. Deposits of salt formed in salt lakes. Lagoons, sometimes formed by mud. Proportion of the land covered with water. Estimate of the total area of lakes. Proportion of fresh and salt water lakes. English lakes — their names and proportions. Scotch, Irish and Welsh lakes. Absence of lakes in France.' The lakes of the Alps. Swiss lakes: — lake of Geneva — lake of Lucerne — lake of Zurich— lake of WaUenstadt — lake of Constance — lakes of Neuchatel and Bienne. Italian lakes: — Lake of Como — Lago Maggiore — Lake Lugano — Lago di Garda. Rivers issuing from the Swiss and Italian lakes.

Comparison of the lakes on the two sides of the Alps. Lakes of the Pyrenees. Lakes of Northern Europe. Wurm-see, in Upper Bavaria. - Ammer-see. — Chiem-see. — Neusiedler-see. — Platten-see. South Italian lakes. — Lakes Thrasymene, Bolsena, Vico and Albano. Lakes of northern Europe. Swedish lakes, — Wenern, Western, and Malar. Lake Hielmar and Lake Barken. Finland and its lakes on the central plateau. Lakes Ladoga, Onega, Saima, and Ilnien. Lake Enare in Lapland. Lakes near the Arctic Ocean. General Character of the north European lakes. Aralo-Caspian depression and the Caspian Sea. Fresh water lakes of northern Asia. Lake of Baikal. Drainage of this lake. Lakes of western Asia. Tengis, Tehany, and the Persian lake Urumiyah. Lake Van, in Armenia, and Lake Seistan in Iran. Smallness of the lakes in Asia, south of the main mountain chain.

Depressed basins as distinct from mountain lakes. Details of the Caspian Sea. The Sea of Aral. The Dead Sea and its peculiarities. Lakes of Africa. Victoria Nyanza, one of the head waters of the Nile. Its connection with Albert Nyanza. Details of Albert Nyanza. Lake Tanganyika. Lakes Nyassa and Shirwa. Lake Tchad, — its peculiarities and difference at different seasons. Australian lakes. — Lake Torrens and Alexandrian lake. North American lakes. Great Bear and Great Slave lakes. Athabasca, Wollaston and Deer lakes. Winnipeg and Winnipegoos. Lake Superior. Lakes Huron and St. Clair. Lake Michigan. Lake Erie. Lake Ontario. Total area of the North American great lakes. Difference of level of these lakes. Lake Champlain. Lakes in Florida. Lake Pontchartrain. Central American lakes. Nicaragua. South American lakes.

Lake Titicaca. Lakes in Brazil. General conclusions as to the nature of lakes. 2. Waterfalls. — General account of rapids or waterfalls. Such phenomena not universal with large bodies of water. Falls of the Rhine. Cascades of Switzerland. The Handek and the CONTENTS. XVII PAGE 169 Staubbach. The Norwegian Falls. — Sarp-fos, Riukan-fos, and Voring-fos. The Ostud-fos. Rapids. Former rapids of the Rhine and Danube. African water-falls. Falls of the Zambesi described by Livingstone. Ripon Falls and Murchison Falls as the Nile, described by Speke and Baker. American falls of Nia gara. Details of these falls. Differences of level and body of water estimated. Falls of Kakabika

Chapter X. The Phenomena Op Ice

The properties of ice very different from those of water. Formation of snow in the air. Mode of crystallisation of snow. Snow in stars and pellets. Snow formed in the upper air in all parts of the world. Cause of this explained. The snow-line, explanation of the term. Position of the snow-line in Peru, in western Africa, in the Himalayan mountains and in the Andes. Difference of height in different latitudes and climates. Snow-line in Atlas mountains, in Sicily, and in the Alps. — In Norway and in the Arctic circle. Difference between southern and northern hemisphere in the position of the snow-line. Cause of this difference. Limits of snow at the sea line in the western and eastern partB of the old world. Local absence of snow in certain sheltered spots. Number of days of snow-fall iu different climates.

Average at Rome — at St. Petersburg. Large falls on the east coast of North America. Snow not injurious to vegetation. — Condition of fallen snow. Hail — its nature. How and when formed. Large hail stones. Paths of hail stones. Narrow breadth of country generally injured by hail. Places where hail is most common. Ice expands during formation from water. Cause of this expansion. Pressure tends to prevent the formation of ice. Difficulty of forming ice at great depth in water. Purity of ice. Result of the expansion of water while becoming ice, in preventing a great thickening of ice on a body of water exposed to intense cold. The sea less readily frozen than fresh water. Formation of pack-ice from snow. Possible results of change in the distribution of land and water, producing what is called " perpetual snow," over large tracts.

No real "perpetual snow." Mode in which mountains are relieved of their load of snow. Formation of a tongue of ice beyond the snow, and deeper in valleys than the snow-line. Movement of this ice and formation of a glacier. Neve, or Firn, the feeder of the glacier. Process by which nevi or glacier ice is formed. Mode by which it is increased in the course of years and rendered uniform. Essential conditios for a glacier. Kind and rate of its motion. Winter cold penetrates but a little way. Imperfectly formed glaciers. Glaciers rent by fissures. Water passes through these. Production of streams b CONTENTS. PAGE 18S of stone at the surface called moraines. Production of icebergs. Increase of glaciers by successive streams of ice. Their passage over obstacles. Nature of the motion of glaciers. Ice does not move like a tenacious fluid.

Property of regelation. Illustra tions of this mode of behaviour of ice. Example in snow pressed and squeezed in a ravine. Result of pressure on the bottom and sides of the ravine resembles that of solids. Effect in known cases illustrated in the Alps. The Alps not the only places where evidence of this kind is to be obtained. Examples in New Zealand, — in the Himalayas, — in Norway and Greenland. Indications of glacial action far away from glaciers. Examples in the British islands, in Northern Europe and North America. Examples in Asia Minor. Icebergs — their nature, mode of formation and proportions. Great depth below the surface of the sea. Result when melted. Icebergs not easily seen and studied at sea. Time when they are most numerous in the Atlantic. They advance less towards warm latitudes in the southern hemisphere.

Their appearance when seen under favourable circumstances. Their colour, changes of form, ancl frequent change of position. Ice formerly advanced much further over the northern hemisphere than it now does. Nature of the proofs of this statement. Periods of cold existed in much earlier times in the world's history. Proofs of this seen in smoothed and striated rocks be neath old deposits. Permian and old red sandstone glacier periods possible. Theory of a uniform ice-cap alluded to. Con dition of the planet Mars in reference to this theory .

Chapter XI. Speinqb

Disappearance and history of the part of the rain-fall that neither runs off the earth's surface nor is evaporated. Passage of such water through rocks. Its issue above the sea level. Occasionally brought back again into circulation. Water rising out of the earth called spring water. Various kinds of springs. Land springs in open rocks. Quality of the water obtained from them. Natural purification of water. Absorption of water into strata. Nature of Artesian springs and wells. Meaning of the term Artesian. Springs in fissured rocks and at faults. Course of water under such circumstances. Limestone districts rich in springs of this kind. No spring water chemically pure. Substances generally present in spring water. Water with very small : quantities of foreign substances, in France and Germanv Other waters with large quantities.