"Journal of Researches," &c., by Charles Darwin, 2nd ed,, p.B 8i.B

inhabitants. In its burning temperature, Pachyderms of monstrous forms, but of peaceful habits, traversed the tall vegetation, composed of grasses of all sorts. Deer of gigantic size, their heads ornamented with enormous horns, escorted the heavy herds of the Mammoth; while the Horse, small in size and compact of form, galloped and frisked round these magnificent horizons of verdure which no human eye had yet contemplated. Nevertheless, all was not quiet and tranquil in the landscapes of the ancient w^orld. Voracious and formidable carnivorous animals waged a bloody war on the inoffensive herds. The Tiger, the Lion, and the ferocious Hyaena; the Bear, and the Jackal, there selected their prey. On the opposite page an endeavour is made to represent the great animals among the Edentates which inhabited the American plains during the Quaternary epoch (Plate XXIX). We observe there the Glyptodon, the Megatherium, the Mylodon, and, along with them, the Mastodon. A small Ape (the Orthopithecus), which first appeared in the Miocene period, occupies the branch of a tree in the landscape. The vegetation is that of tropical America at the present time.

The deposits of this age, which are of later date than the Crag, and of earlier date than the Boulder Clay, with its fragments of rocks frequently transported from great distances, are classed under the term " pre-glacial." After the deposition of the Forest Bed, which is seen overlying the Crag for miles between high and low-water mark, on the shore west of Cromer, in Norfolk, there was a general reduction of temperature, and a period of intense cold, known as the "glacial period," seems to have set in, during which a great part of what is now the British Islands was covered with a thick coating of ice, and probably united with the Continent.

At this time England south of the Bristol Channel (the estuary of the Severn), and the Thames, appears to have been above water. The northern part of the country, and the high-ground generally of Britain and Ireland were covered with gliding glaciers, by whose grinding action the whole surface became moulded and worn into its present shape, while the floating icebergs which broke off at the seaside from these glaciers, conveyed away and dropped on the bed of the sea those fragments of rocks and the gravel and other earthy materials which are now generally recognised as glacial accumulations.

In all directions, however, proofs are being gradually obtained that, about this period, movements of submersion under the sea were in progress, all north of the Thames.

XXIX.—Ideal American Landscape in the Quaternary Epoch.

POST-PLIOCENE PERIOD.

Ramsay points out indications, first of an intensely cold period, when land was much more elevated than it is now; then of submergence beneath the sea; and, lastly, re-elevation attended by glacial action. "When we speak of the vegetation and quadmpeds of421 Cromer Forest being pre-glacial," says Lyell, "we merely mean that their formation preceded the era of the general submergence of the British Isles beneath the waters of the glacial sea. The successive

deposits seen in direct superposition on the Norfolk coast,'' adds Sir Charles, " imply at first the prevalence over a wide area of the Newer Pliocene Sea. Afterwards, the bed of the sea was converted into dry land, and underwent several oscillations of level, so as to be, ■irst, dry land supporting a forest; then an estuary; then again land; and, finally, a sea near the mouth of a river, till the dov.-nward movement became so great as to convert the whole area into a sea of considerable depth, in which much floating ice, carrying mud, sand, and boulders melted, letting its burthen fall to the bottom. Finally, over the till with boulders stratified drift was formed; after which, but not until the total subsidence amounted to more than 400 feet, an upward movement began, which re-elevated the whole country, so that the lowest of the terrestrial formations, or the forest bed, was brought up to nearly its pristine level, in such a manner as to be exposed at a low tide. Both the descending and ascending movement seem to have been very gradual."

Fig;. 193. — Palaeophognos Gcsncri. Fossil Toad.

422

EUROPEAN DELUGES.

The Tertiary formations, in many parts of Europe, of more or less ejctent, are covered by an accumulation of heterogeneous deposits, filling up the valleys, and composed of very various materials, consisting mostly of fragments of the neighbouring rocks. The erosions which we remark at the bottoms of the hills, and which have greatly enlarged already existing valleys; the mounds of gravel accumulated at one point, and which is formed of rolled materials, that is to say, of fragments of rocks worn smooth and round by continual friction during a long period, in which they have been transported from one point to another — all these signs indicate that these denudations of the soil, these displacements and transport of very heavy bodies to great distances, are due to the violent and sudden action of large currents of water. An immense wave has been thrown suddenly on the surface of the earth, making great ravages in its passage, furrowing the earth and driving before it debris of all sorts in its disorderly course. Geologists give the name of diluvmvi to a formation thus removed and scattered, which, from its heterogeneous nature, brmgs under our eyes, as it were, the rapid passage of an impetuous torrent — a phenomenon which is commonly designated as a deluge. / To what cause are we to attribute these sudden and apparently temporary invasions of the earth's surface by rapid currents of water? In all probability to the upheaval of some vast extent of dry land, to the formation of some mountain or mountain-range in the neighbourhood of the sea, or even in the bed of the sea itself The land suddenly elevated by an upward movem.ent of the terrestrial crust, or by the formation of ridges and furrows at the surface, has, by its reaction, violently agitated the waters, that is to say, the more mobile portion of the globe. By this new impulse the waters have been thrown with great violence over the earth, inundating the plains and valleys, and for the moment covering the soil with their furious waves, mingled with the earth, sand, and mud, of which the devastated districts have been

denuded by their abrupt invasion. The phenomenon has been sudden but brief, like the upheaval of the mountain or chain of mountains, which is presumed to have been the cause of it; but it was often repeated: ^vitness the valleys which occur in every country, especially those in the neighbourhood of Lyons and of the Durance. These strata indicate as many successive deposits. Besides this, the displacement of blocks of minerals from their normal position is proof, now perfectly recognisable, of this great phenomenon.

There have been, doubtless, during the epochs anterior to the Quaternary period of which we write, many deluges such as we are considering. Mountains and chains of mountains, through all the ages we have been describing, were formed by upheaval of the crust into ridges, where it was too elastic or too thick to be fractured. Each of these subterranean commotions would be provocative of momentary irruptions of the waves.

But the visible testimony to this phenomenon — the living proofs of this denudation, of this tearing away of the soil, are found nowhere so strikingly as in the beds superimposed, far and near, upon the Tertiary formations, and which bear the geological name of diluvium. This term was long employed to designate what is now better known as the "boulder" formation, a glacial deposit which is abundant in Europe north of the 50th, and in America north of the 40th, parallel, and re-appearing again in the southern hemisphere; but altogether absent in tropic-al regions. It consists of sand and clay, sometimes stratified, mixed with rounded and angular fragments of rock, generally derived from the same district; and their origin has generally been ascribed to a series of diluvial waves raised by hurricanes, earthquakes, or the sudden upheaval of land from the bed of the sea, which had swept over continents, carrying \vith them vast masses of mud and heavy stones, and forcing these stones over rocky surfaces so as to polish and impress them \vith furrows and strice. Other circumstances occurred, however, to establish a connection between this formation and the glacial drift. The size and number of the erratic blocks increase as we travel towards the Arctic regions; some intimate association exists, therefore, between this formation and the accumulations of ice and snow which characterise the approaching glacial period.

As we have already stated at the beginning of this chapter, there is very distinct evidence of two successive deluges in our hemisphere during the Quaternary epoch. The two may be distinguished as the Eu7'opca)i Deluge and the Asiatic. The two European deluges occurred prior to the appearance of man; the Asiatic deluge

happened after that event; and the human race, then in the early-days of its existence, certainly suffered from this cataclysm. In the present chapter we confine ourselves to the two cataclysms which ovenvhelmed Europe in the Quaternary epoch.

The first occurred in the north of Europe, where it was produced by the upheaval of the mountains of Norway. Commencing in Scandinavia, the wave spread and carried its ravages into those regions which now constitute Sv/eden, Norway, European Russia, and the north of Germany, sweeping before it all the loose soil on the surface, and covering the whole of Scandinavia — all the plains and valleys of Northern Europe — with a mantle of transported soil. As the regions in the midst of which this great mountainous upheaval occurred — as the seas surrounding these vast spaces were partly frozen and covered with ice, from their elevation and neighbourhood to the pole — the wave which swept these countries carried along with it enormous masses of ice. The shock, produced by the collision of these several solid blocks of frozen water, would only contribute to increase the extent and intensity of the ravages occasioned by this violent cataclysm, which is represented in Plate XXX.

The physical proof of this deluge of the north of Europe exists in the accumulation of unstrati«fied deposits which covers all the plains and low grounds of Northern Europe. On and in this deposit are found numerous blocks which have received the characteristic and significant name of erratic blocks, and which are frequently of considerable size. These become more characteristic as we ascend to higher latitudes, as in Norway, Sweden, and Denmark, the southern borders of the Baltic, and in the British Islands generally, in all of which countries deposits of marine fossil shells occur, which prove the submergence of large areas of Scandinavia, of the British Isles, and other regions during parts of the glacial period. Some of these rocks, characterised as erratic^ are of very considerable volume; such, for instance, is the granite block which forms the pedestal of the statue of Peter the Great at St. Petersburg. This block was found in the interior of Russia, where the whole formation is PermiiVi^ and its presence there can only be explained by supposing it to have been transported by some vast iceberg, earned by a diluvial current. This hypothesis alone enables us to account for another block of granite, weighing about 340 tons, which was found on the sandy plains in the north of Prussia, an immense model of ^vhich was made for the Berlin Museum. The last of these erratic blocks deposited in Germany covers the grave of King Gustavus Adolphus, of Sweden, killed at the battle of Lutzen, in 1632. He was interred beneath the

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