Physical geography

Front matter

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I'KKSK.NTlil) BY

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Chapter I

Geology . ..... . . Page 13

CHAPTER H.

Form of the Great Continent — The High Lands of the Great Continent : the Atlas, Spanish, French, and German Mountains — The Alps, Balkan, and Apennines . . . . . ... .33

CHAPTER m.

The High Lands of the Great Continent (conti7iued) — The Caacasus — 'J'he Western Asiatic Table-land and its Mountains . . .47

CHAPTER IV.

The High Lands of the Great Continent (continued) — The Oriental Table-land and its Mountains . . . . . .52

CHAPTER V.

Secondary Mountain Systems of the Great Continent — That of Scandinavia — Great Britain and Ireland — The Ural Mountains — The Great Northern Plain . . ... . . . 6i

CONTENTS.

(JHAPTICR VI.

'J'he Southern Low l,urijs of the Great Continent, wirh their Secondary Table-lands and Mountains . . • . . .72

CHAPTER Vn.

Africa : Table-land — Cape of Good Hope and Eastern Coast — Western Coast — Abyssinia — Senegambia — Low T^ands and Deserts . .80

CHAPTER VHL

American Continent — The Mountains of South America— The Andes — The Mountains of the Parima and Brazil . . • .88

CHAPTER IX.

'J'he Low Lands of South America — -Desert of Patagonia — The Pampas of Buenos Ay res — The Silvas of the Amazons — The Llanos of the Orinoco and Venezuela — Geological Notice . . . .103

CHAPTER X.

Central America — West Indian Islands — Geological Notice . .110

CHAPTER XL

North America — Table-land and Mountains of Mexico — The Rocky Mountains — The Maritime Chain and Mountains of Russian America . 116

CHAPTER XIL

North America (continued) : — The Great Central Plain or Valley of the Mississippi — The Alleghany Mountains — The Atlantic Slope — The Allantic Plain — Geological Notice . . . . .120

CHAPTER XIIL

Greenland — Spitzbergen — Iceland — Jan May en's Land — Antarctic Lands — Victoria Continent ....... 129

CONTENTS.

CHAPTER XIV.

The Continent of Australia — Tasmania, or Van Diemen's Land — New Zealand — New Guinea — Borneo — Atolls — Encircling Reefs — Coral Reefs — Barrier Reefs — Volcanic Islands — Areas of Subsidence and Elevation in the Bed of the Pacific — Active Volcanoes .... 137

CHAPTER XV.

The Ocean — Its Size, Colour, Pressure, and Saltness^Tides, Waves, and Currents — Temperature — North and South Polar Ice — Inland Seas 157

CHAFFER XVI.

Springs — Basins of the Ocean — Origin, Course, and Floods of Rivers — Hydraulic Systems of Europe — African rivers : The Nile, Niger, «&c. 176

CHAPTER XVII.

Asiatic Rivers — Euphrates and Tigris — River Systems south of the Himalaya — Chinese Rivers — Siberian Rivers . . . .191

CHAPTER XVIII.

River Systems of North America — Rivers of Central America — Rivers of South America, and of Australia ..... 202

CHAPTER XIX.

Lakes — Northern System of the Great Continent — Mountain System of the same — American Lakes . . . . . , 312

CHAPTER XX.

The Atmosphere ....... 220

CHAPTER XXL

Vegetation — The Nourishment and Growth of Plants Classes — Botanical Districts ........ 227

10 CONTENTS.

CHAPTER XXII.

Vegetation of the Great Continent — Of the Arctic Islands — And of the Arctic and North Temperate Regions of Europe and Asia . . 240

CHAPTER XXIII.

Flora of Tropical Asia — Of the Indian Archipelago, India, and Arabia 253

CHAPTER XXIV.

African Flora — Flora of Australia, New Zealand, Norfolk Island, and of Polynesia . . . . . . . . 259

CHAPTER XXV.

American Vegetation — Flora of North, Central, and South America — Antarctic Flora — Marine Vegetation . . . . . 270

CHAPTER XXVI.

Distribution of Insects ...... 288

CHAPTER XXVII.

Distribution of Fishes, and of the Marine Mammalia, Phocae, Dolphins, and Whales . . . ... . . .293

CHAPTER XXVIII.

Distribution of Reptiles — Frogs and Toads — Snakes, Saurians, and Tortoises ........ 306

CHAPTER XXIX.

Distribution of Birds in the Arctic Regions — In Europe, Asia, Africa, America, and the Antarctic Regions ..... 316

* CONTENTS. 11

CHAPTER XXX.

Distribution of Mammalia throughout the Earth . . : . 336

bHAPTEE XXXI.

The Distribution, Condition, and Future Prospects of the Human Race 356

PHYSICAL GEOGRAPHY.

CHAPTER I.

GEOLOGY.

The change produced in the civilized world within a few years, by the application of the powers of nature to locomotion, is so astonishing, that it leads to a consideration of the influence of man on the material world, his relation with regard to animate and inanimate beings, and the causes which have had the greatest effect on the -physical, moral, and intellectual condition of the human race.

The former state of our terrestrial habitation, the successive convulsions which have ultimately led to its present geographical arrangement, and to the actual distribution of land and water, so powerfully influential on the destinies of mankind, are circumstances of primary importance.

The position of the earth with regard to the sun, its connexion with the bodies of the solar system, together with its size and form, have been noticed by the author elsewhere. It was there shown that our globe forms but an atom in the immensity of space, utterly invisible from the nearest fixed star, and scarcely a telescopic object to the remote planets of our own system. The increase of temperature with the depth below the surface of the earth, and the tremendous desolation hurled over wide regions by numerous fire-breathing mountains, show that man is rerpoved but a few miles from immense lakes or seas of liquid fire. The very shell on which he stands is unstable under his feet, not only from those temporary convulsions that seem to shake the globe to its centre, but from a slow almost imperceptible elevation in some places, and an equally gentle Subsidence in others, 2 as if the internal molten matter were subject to secular tides, now heaving and now ebbing, or that the subjacent rocks were in one place expanded and in another contracted by changes of temperature.

The earthquake and the torrent, the august and terrible ministers of Almighty power, have torn the solid earth and opened the seals of the most ancient records of creation, written in indelible characters on " the perpetual hills, and the everlasting mountain's." There we read of the changes that have brought the rude mass to its present fair state, and of the myriads of beings that have appeared on this mortal stage, have fulfilled their destinies, and have been swept from existence to make w^ay for new races which, in their turn, have vanished from the scene till the creation of man completed the glorious work. Who shall define the periods of those mornings and evenings when God saw that his work was good ? and who shall declare the time allotted to the human race, when the generations of the most insignificant insect existed for unnumbered ages? Yet man is also to vanish in the ever-changino- course of events. The earth is to be burnt up, and the elements are to melt with fervent heat — to be again reduced to chaos — possibly to be renovated and adorned for other races of beings. These stupendous changes may be but cycles in those great laws of the universe, where all is variable but the laws themselves and He who has ordained them.

The earth consists of a great variety of substances, some of which occur in amorphous masses, others are disposed in regular layers or strata, either horizontal or inclined at all angles to the horizon. By mining, man has penetrated only a very little w^ay, but by reasoning from the dip or inclination of the strata at or near the surface, and from other circumstances,' he has obtained a pretty accurate idea of the structure of our globe to the depth of about ten miles. All the substances of which we have any information are divided into four classes, distinguished by the manner in which they have^TTeen formed, namely — Plutonic and Volcanic rocks, both of igneous origin, though produced under different circumstances ; Agueous or Stratified rocks, entirely due to the action of water, as the name implies ; and Metaraorphic rocks, deposited also by water, according to the opinion of many eminent geologists, and consequently stratified, but subsequently altered and crystallized by heat. The Aqueous and Volcanic rocks are formed at the surface of the earth, the Plutonic and Metamorphic at great depths, but all of them have originated simultaneously during every geological period, and are now in a state of slow and constant progress. The antagonist principles of fire and water have ever been and still are the cause of the perpetuaTvTcissitudes to which the crust of the earth is liable.

It has been ascertained by observation that the Plutonic rocks, consisting of the granites and some of the porphyries, were formed in the deep and fiery caverns of the earth, of melted matter, which crystallized as it slowly copied under enormous pressure,, and was then heaved in unstratified masses by the elastic force of the internal heat even to the tops of the highest mountains, or forced in a semifluid state into fissures of the superincumbent strata, sometimes into the cracks of previously formed granite ; for that rock, which constitutes the base of so large a portion of the earth's crust, has not been all formed at once ; some portions had been solid while others were yet in a liquid state. This class of rocks is completely destitute of fossil remains.

Although granite and the volcanic rocks are both due to the action of fire, their nature and position are very different : granite, fused in the interior of the earth, has been cooled and consolidated before coming to the surface ; besides, it generally consists of few ingredients, so that it has nearly the same character in all countries. But as the volcanic fire rises to the very surface of the earth, fusing w^hatever it meets with, volcanic rocks take various forms, not only from the different kinds of strata which are melted, but from the different conditions under which the liquid matter has been cooled, though most frequently on the surface — a circumstance that seems to have had the greatest effect on its appearance and structure. Sometimes it approaches so -nearly to granite that it is difficult to perceive a distinction : at other times it becomes glass : in short, all those massive, unstratified, and occasionally columnar rocks, as basalt, greenstone, porphyry, and serpentine, are due to volcanic fires, and are devoid of fossil remains. -

There seems scarcely to have been any age of the world in which volcanic eruptions have not taken place in some part of the globe. Lava has pierced through every description of rocks, spread over the surface of those existing at the time, filled their crevices, and flowed between their strata. Ever changing its place of action, it has burst out at the bottom of the sea as well as on dry land. Enormous quantities of scoriae and ashes have been ejected from numberless craters, and have formed extensive deposits in the sea, in lakes, and on the land, in which are imbedded the remains of the animals and vegetables of the epoch. Some of these deposits have become hard rock, others remain in a crumbling state ; and as they alternate with the aqueous strata of almost every period, they contain the fossils of all the geological epochs, chiefly fresh and salt water testacese.

According to a theory now generally adopted, which originated with Mr. Lyell, whose works are models of philosophical investigation, the metamorphic rocks, which consist of gneiss, micaschist, clay-slate, statuary marble, &c., were formed of the sediment of water in regular layers, differing in kind and colour, but, having been deposited near .the places where plutonic rocks were generated, they have been changed by the heat transmitted from the fused matter, and in cooling under heavy pressure and at great depths they have become as highly crystallized as the granite itself, without losing their stratified form. An earthy stratum has sometimes been changed into a highly crystallized rock to the distance of a quarter of a mile from the point of contact by transmitted heat, and there are instances of dark-coloured limestone full of fossil shells, that has been changed into statuary marble from that cause. Such alterations may frequently be seen to a small extent in rocks adjacent to a stream of lava. There is not a trace of organic remains in the metamorphic rocks ; their strata are sometimes horizontal, but they are usually tilted at all angles to the horizon, and form some of the highest mountains and most extensive table-lands on the face of the globe. Although there is the greatest similarity in the plutonic rocks in all parts of the world, they are by no means identical ; they differ in colour, and even in ingredients, though these are few.

Aqueous rocks are all stratified, being the sedimentary deposits of water. They originate in the wear of the land by rain, streams, or the ocean. The debris carried by running water is deposited at the bottom of the seas and lakes, where il is consolidated, and then raised up by sirbterraneous forces, again to undergo the same process after a lapse of time. By the washing away of the land the lower rocks are laid bare, and, as the materials are deposited in different places according to their weight, the strata are exceedingly varied, but consist chiefly of arenaceous or sandstone rocks, argillaceous or clayey rocks, and of calcareous rocks composed of sand, clay, and carbonate of lime. They constitute three great classes, which, in an ascending order, are the primary and secondary fossiliferous strata, and the Tertiary formations.

The primary fossiliferous strata, the most ancient of all the sedimentary rocks, consisting of limestone, sandstones, and shales, are entirely of marine origin, having been formed far from land at the bottom of a very deep ocean ; consequently they contain the exuviae of marine animals only, and after the lapse of unnumbered ages the ripple marks of the waves are still distinctly visible on some of their strata. This series of rocks is subdivided into the Cambrian and the upper and lower Silurian systems, on account of differences in their fossil remains.'

The Cambrian rocks, sometimes many thousand yards thick, are for the most part destitute of organic remains, but the Silurian rocks abound in them more and more as the strata lie higher in the series. In the lower Silurian group are the remains of shell-fish, almost all of extinct genera, and the few that have any aflfinity to those alive .are of extinct species ; Crinoidea, or stone-lilies, which had been fixed to the rocks like tulips on their stems, are coeval with the earliest inhabitants of the deep ; and the trilobite, a jointed creature of the crab kind, with prominent eyes, are almost exclusively confined to the Silurian strata, but the last traces of them are found in the coal-measures above. In the upper Silurian group are abundance of marine shells of almost every order, together with Crinoidea, vast quantities of corals, and some sea-weeds : several fossil sauroid fish, of extinct genera, but high organization, have been found in the highest beds — the only vertebrated animal that has yet been discovered among the countless profusion of the lower orders of creatures that are entombed in the primary fossiliferous strata. The remains of one or more land-plants, in a very imperfect state, have been found in the Silurian 2* rocks of North America, which shows that there had been land with vegetation at that early period. The type of these plants, as well as the size of the shells and the quantity of the coral, indicate that a uniformly warm temperature had then prevailed over the globe. During the Silurian period an ocean covered the northern hemisphere, islands and lands of moderate size had just begun to rise, and earthquakes with volcanic eruptions from insular and submarine volcanos, were frequent towards its close.

The secondary fossiliferous strata, which comprise a great geological period, and constitute the principal part of the high land in Europe, were deposited at the bottom of an ocean, like the primary, from the debris of all the others carried down by water, and still bear innumerable tokens of their marine origin, although they have for ages formed part of the dry land. Calcareous rocks are more abundant in these strata than in the crystalline, probably because the carbonic acid was then, as it still is, driven off from the lower strata by the internal heat, and came to the surface as gas or in calcareous springs, which either rose in the sea, and furnished materials for shell-fish and coral insects to build their habitations and form coral reefs, or deposited their calcareous matter on the land in the form of rocks.

The Devonian or old red sandstone group, in many places ten thousand feet thick, consisting of strata of dark red and other sandstones, marls, coralline limestones, conglomerates, &c., is the lowest of the secondary fossiliferous strata, and forms a link between them and the Silurian rocks by an analogy in their fossil remains. It has fossils peculiarly its own, but it has also some shells and corals common to the strata both above and below it. There are various families of extinct sauroid fish in this group, some of which were gigantic^ others had strong bony shields on their heads, and one genus, covered with enamelled scales, had appendages like wings. The shark approaches nearer to some of these ancient fish than any other now living.

During the long period of perfect tranquillity that prevailed after the Devonian group was deposited, a very warm, moist, and extremely equable climate, which extended all over the globe, had clothed the islands and lands in the ocean then covering the northern hemisphere with exuberant tropical forests and jungles. Subsequent inroads of fresh water or of the sea, or rather partial sinkings of the land, had submerged these forests and jungles, which, being mixed with layers of sand and mud, had in time been consolidated into one mass, and were then either left dry by the retreat of the waters, or gently raised above their surface.

These constitute the^emarkable group of the carboniferous strata, which consists of numberless layers of various substances filled with a prodigious quantity of the remains of fossil land-plants, intermixed with beds of coal, which is entirely composed of vegetable matter. In some cases the plants appear to have been carried down by floods and deposited in estuaries, but in most instances the beauty, delicacy, and sharpness of the impressions show that they had grown on the spot where the coal was formed. More than three hundred fossil plants have been collected from the shale where they abound, frequently with their seeds and fruit, so that enough remains to show the peculiar nature of thisflora, whose distinguishing feature was the preponderance of ferns : among these there were tree-ferns which must have been forty or fifty feet high. There were also plants resembling the horse-tail tribe, of gigantic size ; others like the tropical club mosses : an aquatic plant of an extinct family was very abundant, besides many others to which we have nothing analogous. Forest-trees of great magnitude, of the pine and fir tribes, flourished at that period. The remains of an extinct araucaria, one of the largest of the pine family, have been found in the British coal-fields ; the existing species now grow in very warm countries: a few rare instances occur of grasses, palms, and liliaceous plants. The botanical districts were very extensive when the coal-plants were growing, for the species are nearly identical throughout the coal-fields of Europe and America. From the extent of the ocean, the insular structure of the land, the profusion of ferns and firtrees, and the warm, moist, and equable climate, the northern hemisphere during the formation of the coal strata is thought to have borne a strong resemblance to the South Pacific, with its fern and fir clothed lands of New Zealand, Kerguelen islands, and others.

The animal remains of this period are in the mountain limestone, a rock occasionally nine hundred feet thick, which, in some instances, lies beneath the coal-measures, and sometimes alternates with the shale and sandstone. They consist of crinbidea and marine testacese, among which the size of the chambered shells, as well as that of the corals, shows that the ocean was very warm at that time, even in the high northern latitudes.

The coal strata have been very much broken and deranged in many places by earthquakes, which frequently occurred during the secondary fossiliferous period, and from time to time raised islands and land from the deep. However, these and all other changes that have taken place on the earth have been gradual and partial, whether brought about by fire or water. The older rocks are more shattered by earthquakes than the newer, because the movement came from below; but these convulsions have never extended all over the earth at the same time — they have always been local: for example, the Silurian strata have been dislocated and tossed in Britain while a vast area in the south of Sweden and Russia still retains a horizontal position. There is no proof that any mountain-chain has ever been raised at once; on the contrary, the elevation has always been produced by a long-continued and reiterated succession of internal convulsions, with intervals of repose. In many instances the land has risen up or sunk down by an imperceptible equable motion continued for ages, while in other places the surface of the earth has remained stationary for long geological periods.

The magnesian limestone, or permian formation, comes immediately above the coal-measures, and consists of breccias or conglomerates, gypsum, sandstone, marl, &c. ; but its distinguishing feature is a yellow limestone rock, containing carbonate of magnesia, which often takes a granular texture, and is then known as dolomite. The permian formation has a fossil flora and fauna peculiar to itself, mingled with those of the coal strata. Here the remnant of an earlier creation gradually tends to its final extinction, and a new one begins to appear. The flora is, in many instances, specifically the same with that in the coal strata below. Certain fish are also common to the two, which never appear again. They belong to a race universal in the early geological periods, and bear a strong resemblance to saurian reptiles. A small number of existing genera only, such as the shark and sturgeon, make some approach to the structure of these ancient inhabitants of the waters. The new creation is marked by the introduction of two species of saurian reptiles: the fossil remains of one have been found in the magnesian limestone in England, and those of the other in a corresponding formation in Germany. They are the earliest members of a family which was to have dominion in the land and water for ages.

A series of red marls, rock-salt, and sandstones, which •have arisen from the disintegration of metamorphic slates and porphyritic trap containing oxide of iron, and known as the trias or new red sandstone system, lies above the magnesian limestone. In England this formation is particularly rich in rock-salt, which, with layers of gypsum and marl, is sometimes six hundred feet thick ; but in this country the muschelkalk is wanting, which in Germany is so remarkable for the quantity of organic remains. At this time creatures like frogs of enormous dimensions had been frequent, as they have left their footsteps on what must then have been a soft shore. Forty-seven genera of fossil remains have been found in the trias in Germany, consisting of shells, cartilaginous fish, encrinites, &c., all distinct in species, and many distinct in genera, from the organic fossils of the magnesian limestone below, and also from those entombed in the strata above.

During a long period of tranquillity the oolite or Jurassic group was next deposited in a sea of variable depth, and consisted of sands, sandstones, marls, clays, and limestone. At this time there was a complete change in the aqueous deposits all over Europe. The red iron-stained arenaceous rock, the black coal, and dark strata were succeeded by light blue clays, pale yellow limestones, and, lastly, white chalk. The water that deposited the strata must have been highly charged with carbonate of lime, since few of the formations of that period are without calcareous matter, and calcareous rocks were formed to a prodigious extent throughout Europe; the Pyrenees, Alps, Apennines, and Balkan abound in them, and the Jura mountains, which have given their name to the series, are formed of them. The European ocean then teemed with animal life; whole beds consist almost entirely of marine shells and corals. Belemnites and ammonites, from an inch in diameter to the size of a cart-wheel, are entombed by myriads in the strata ; whole forests of that beautiful zoophite, the stone-lily, flourished on the surface of the oolite, then under the waters ; and the encrinite, one of the same genu§, is embedded in millions in the enchorial shell marble, which occupies such extensive tracts in Europe. Fossil fish are numerous in these strata, but different from thoae of the coal series, the permian formation, and trias. Not one genus of the fish of this period are now in existence. The newlyraised islands and lands were clothed with vegetation like that of the large islands of the intertropical Archipelagos of the present day, which, though less rich than during the carboniferous period, still indicates a very moist and warm climate. Ferns were less abundant, and they were associated with various genera and species of the cycadeae, which had grown on the southern coast of England, and in other parts of northern Europe, congeners of the present cycas and zamia of the tropics. These plants had been very numerous, and the pandanae, or screw-pine, the first tenant of the new lands in ancient and modern times, is a family found in a fossil state in the inferior oolite of England, which was but just rising from the deep at that time. The species now flourishing grows only on the coasts of such coral islands in the Pacific as have recently emerged from the waves. In the upper strata of this group, however, the confervse and monocotyledonous plants become more rare — an indication of a change of climate.

The new lands that were scattered in the ocean of the oolitic period were drained by rtvers, and inhabited by huge crocodiles and saurian reptiles of gigantic size, mostly of extinct genera. The crocodiles came nearest to modern reptiles, but the others, though bearing a remote similitude in general structure to living forms, were quite anomalous, combining in one the structure of various distinct creatures, and so monstrous that they must have been more like the visions of a troubled dream than things of real existence; yet in organization a few of them came nearer to the type of living mammalia than any existing reptiles do. Some of these saurians had lived in the water, others were amphibious, and the various species of one genus even had wings like a bat, and fed on insects. There were both herbivorous and predaceous saurians, and from their size and strength they must have been formidable enemies. Besides, the numbers deposited are so. great that they must have swarmed for agesin the estuaries and shallow seas of the period, especially in the lias, a marine stratum of clay the lowest of the oolite series. They gradually declined towards the end of the secondary fossilifefous epoch, but as a class they lived in all subsequent eras, and still exist in tropical countries, although the species are very different from their ancient congeners. Tortoises of various kinds were contemporary with the saurians, also a family that still exists. In the stonefield slate, a stratum of the lower oolitic group, there are the remains of insects; and the bones of two small quadrupeds have been found there belonging to the marsupial tribe, such as the opossum ; a very remarkable circumstance, because that family of animals at the present time is confined to New Holland, South America, and as far north as Pennsylvania at least. The great changes in animal life during this period were indications of the successive alterations that had taken place on the earth's surface.

The cretaceous strata follow the oolite in ascending order, consisting of clay, green and iron sands, blue limestone, and chalk, probably formed of the decay of coral and shells, which predominates so much in England and other parts of Europe, that it has given the name and its peculiar feature to the whole group. It is, however, by no means universal ; the chalk is wanting in many parts of the world where the other strata of this series prevail, and then their connection with the group can only be ascertained by the identity of their fossil remains. With the exception of- some beds of coal among the oolitic series, the Wealden clay, the lowest of the cretaceous group in England, is a fresh-water formation, and the tropical character of its flora shows that the climate was still very warm. Plants allied to the zamias and cycades of our tropical regions, many ferns and pines of the genus araucaria, characterized its vegetation, and the upright stems of a fossil forest at Portland show that it had been covered with trees. It was inhabited by tortoises approaching to families now living in warm countries, and saurian reptiles of five different genera swarmed in the lakes and estuaries. This clay contains fresh-water shells, fish of the carp kind, and the bones of wading birds. The Wealden clay is one of the various instances of the subsidence of land of which there were others during this period.