The Eocene formation is shown in what is termed the “London Basin,” here illustrated by a section in which we find soft sands without fossils (Thanet Beds), and a kindred kind in Surrey, in which fossils (marine) are found. After these we get the “Reading and Woolwich” beds as we ascend. These are of clay and pebbles, etc., with river fossils. The Oldhaven beds are included on the map; they occur towards Blackheath and Herne Bay. The London clay is very stiff, and in some places blue. It is full of fossils of birds, beasts, fruits, and vegetables, trees, reptiles, and fish, and the variety of the organic remains appears to indicate the fact that at one time the Thames flowed through swampy ground to the sea, in which dwelt, in a warm climate, immense mammalia, such as the megatherium, glyptodon, tapir, etc., and some turtles of enormous size.
It is also on record from late observations that these immense animals were even mixed up, and almost fabulous creatures inhabited the land where England now is. We read of antelope-horses, lion-like bears, and camel-stags. The vegetation was then of a tropical kind, and in the deep forests and jungles these enormous animals—the mammoth dinotherium, and such species—roamed and plunged in the swamps at the mouth of the Thames. At length these types died away, and gave place to the elephant and the hippopotamus, and the climate by degrees became less warm, and still slowly decreased in temperature.
A glance at Sir C. Lyell’s “Principles of Geology” will show us how, as we examine the more modern strata, we find a great increase in the European lands, which may have been compensated by the submersion of the Pacific islands. During the period of the vegetation of the Secondary epochs, our climate (between the lias and the chalk) was favourable to a tropical growth. Enormous rivers flowed through our islands, and gigantic crocodiles, etc., with flying reptiles, were masters of the land. There were numerous fishes, but the reptiles did not appear in such very great numbers.
Fig. 681.—Section across the London Basin (W. Whitaker).
a Lower Bagshot sand (of Hampstead). b London Clay. c Reading and Woolwich beds (including the Oldhaven beds, which occur in the south only). d Thanet sand (crops out on the south only). e Chalk with flints. f Chalk without flints. g Upper Greensand (crops out on the south only). h Gault. i Lower Greensand. k Wealden beds (on the south only). l Oolitic clays (shown only on the north, but proved to occur on the south beyond the range of the section, by the sub-Wealden boring, near Battle, in Sussex). x Old rocks, shown by borings at Kentish Town and at Meux’s Brewery, to pass under the London basin.
These large and elephantine animals must have existed while the climate of Northern Europe underwent some very considerable changes. We read of the woolly rhinoceros, and the hairy elephant, or mastodon, which has been found in Siberia. Reindeer appeared in England, and we know now that these animals inhabit cold countries. The mountains were considerably elevated during the latter Tertiary period; snow fell and ice formed upon the summits of the mountains, while glaciers crept down the sides. The warm, almost tropical climate of the prior ages was gradually but surely giving way to the Ice Age; the earth was slowly dipping, and the sun’s rays had less power.
Professor Ramsay says the “assemblage of fossils found in the London clay point to the fact that the whole of these strata were deposited in the estuary of a great continental river comparable to the Amazon and the Ganges. The palm-nuts and the host of other plants help to prove it, and the remains of river tortoises, crocodiles, snakes, marsupials, and several tapir-like mammals, all point in the same direction. The estuarine conditions begun during the deposit of the Woolwich and Reading beds were still going on when the London clay was thrown down; with this difference, that by sinking of the area the estuary had become longer, wider, and deeper, but still remained connected with a vast continent, through which the Eocene river flowed.”
Fig. 682.—Anoplotherium commune: palæotherium magnum and minus; and crocodile.