If the old Egyptian, by quarrying the nummulite limestone, bore unconscious testimony to the recent origin of man (whose remains are wholly absent from the Tertiary deposits), so did the ancient Britons and Gauls, when they laid the first rude foundations of future capitals on the banks of the themes and of the Seine. Both cities lie in basins of Eocene Tertiary, occupying hollows in the chalk. Under London there is principally a thick bed of clay, the "London clay" attaining a thickness of five hundred feet. This bed is obviously marine, containing numerous species of sea shells; but it must have been deposited near land, as it also holds many fossil fruits and other remains of plants to which we shall refer in the sequel, and the bones of several species of large animals. Among these the old reptiles of the Mesozoic are represented by the vertebrae of a supposed "sea snake" (Palæophis) thirteen feet long, and species of crocodile allied both to the alligators and the gavials. But besides these there are bones of several animals allied to the hog and tapir, and also a species of opossum, These remains must be drift carcases from neighbouring shores, and they show first the elevation of the old deep-sea bottom represented by the chalk, so that part of it became dry land; next, the peopling of that land by tribes of animals and plants unknown to the Mesozoic; and lastly, that a warm climate must have existed, enabling England at this time to support many types of animals and plants now proper to intertropical regions. As Lyell well remarks, it is most interesting to observe that these beds belong to the beginning of the Tertiary, that they are older then those great nummulite limestones to which we have referred, and that they are older then the principal mountain chains of Europe and Asia. They show that no sooner was the Cretaceous sea dried from off the new land, then there were abundance of animals and plants ready to occupy it, and these not the survivors of the flora and fauna of the Wealden, but a new creation. The mention of the deposit last named places this in a striking light. We have seen that the Wealden beds, under the chalk, represent a Mesozoic estuary, and in it we have the remains of the animals and plants of the land that then was. The great Cretaceous subsidence intervened, and in the London clay we have an estuary of the Eocene. But if we pass through the galleries of a museum where these formations are represented, though we know that both existed in the same locality under a warm climate, we see that they belong to two different worlds, the one to that of the Dinosaurs, the Ammonites, the Cycads, and the minute Marsupials of the Mesozoic, the other to that of the Pachyderms, the Palms, and the Nautili of the Tertiary.