All these formations show distinct evidence of their having been deposited from still or slowly-flowing deep waters. Thus the eocene appears in the Paris basin,--formed clearly at an estuary, in which are mingled some interesting fresh-water deposits;--in the lacustrine formations in Auvergne; also at Aix; and in the north of Italy. It appears probable that, in the formations generally termed eocene, both fresh-water and marine deposits have been confounded, and several formations of widely-different eras regarded as the result of one. We have not yet been furnished with any distinct and clear evidence to show that the deposits of the Paris basin, and those of Auvergne, are of the same age. At all events, it is sufficient for our present purpose to know that they are the result of actions which are now as general as they were when the plastic clay of Paris, and its sulphate of lime, or the London clay, were slowly deposited. As a general conclusion, we may decide that, at the eocene period, existing continents were the sites of vast lakes, rivers, and estuaries, and were inhabited by quadrupeds, which lived upon their thickly-wooded margins. Many remains, allied to those of the hippopotamus, have been found in the subsidences of this period. Examples of the miocene or middle tertiary era are to be found in Western France, over the whole of the great valley of Switzerland, and the valley of the Danube. In these deposits we find the bones of the rhinoceros, elephant, hippopotamus, and the dinotherium, an extinct animal, possessing many very distinguishing features.[243] The pliocene period has been termed the age of elephants, and is most remarkable for the great mastodons and gigantic elks, with other animals not very unlike those which are contemporaneous with man. In the superficial layers of the earth, the diluvium, alluvium, peat and vegetable soil, we have a continuation of the history of the mutations of our globe and of its inhabitants, which has been here so briefly sketched. They bring us up to the period when man appeared in the world, since whose creation it is evident no very extensive change has been produced upon the surface. We have viewed the phenomena of each great epoch, marked as they are by new creations of organized beings, and it would appear as if, through the whole series, from the primary rocks up to the modern alluvial deposits, a progressive improvement of the earth’s surface had been effected, to fit it at last for the abode of the human race.