To this glowing description we might add what we ourselves have witnessed on the coast of South America, where the great Amazon, the Orinoco, and the Essequibo, roll their mud-laden waters into the Atlantic, and form vast accumulations of alluvial deposit all along its northern coast; indeed, the coast line of all the Guianas of South America, averaging some five to ten miles in width, and at least 1,000 miles in length,—Venezuela, British Guiana, Surinam, and Cayenne,—are nothing more than the deposit formed at the base of the mountains by these and other rivers of smaller note. Buried in this mud are pebbles, trunks of trees, animal remains, and so on; and if these in process of time should be elevated and afterwards hardened, or submerged and pressed into clayey slate or sandy stone, the fauna and the flora of these deltas would then be brought to light, just as the leaves of plants are exhibited between the pages of a botanist’s collecting book. In some such method as this was once formed a delta, now constituting the Wealden formation in our own country. What is now the south-east of England, including the Weald clay, the Hastings sand, and the Purbeck beds of limestone and marls, in short, the greater part of the counties already named, with part of Dorsetshire, was once the delta of a mighty river, that so long and so uninterruptedly flowed through this then uninhabited part of the planet, that its accumulated deposits average 1,000 feet in thickness. We have but to pause over those words—_one thousand feet thick_;—once mud, or rather fluviatile deposits of mud and sand, a thousand feet thick in order to receive fresh evidence of the high antiquity of the globe, and of the recent creation of man. We have but for a moment to remember that these deposits consist of innumerable layers of mollusks and crustaceans, a prodigious accumulation of the bones of reptiles and fishes, and of the trunks, branches, and foliage of a long extinct vegetable world, all quietly brought down by “the rivers of waters” of that era, and carefully and without injury deposited in what were then the bottoms of bays or the rising land of deltas, in order to appreciate the evidence which this one deposit alone affords of the immense period of time occupied in its accumulation. Our next section, the cretaceous division of the secondary rocks, presents us with an exclusively marine deposit. The Wealden, as we have said, is a fresh-water deposit. “Many a long and weary journey,” says Dr. Mantell, “have I undertaken to examine the materials thrown up from a newly-made well, or the section exposed by recent cuttings on the roadside, in the hope of obtaining the data by which this problem is now completely settled.” The data referred to are such as these—the absence of all ammonites, encrinites, corals, terebratulæ, and other marine organisms, which form so large a portion of the cretaceous and other sea deposits.