The _bowlder clay_ comes first and legitimately within the scope of this estimate; for, whatever theory of its formation be adopted, whether by the sudden submergence of a vast arctic continent and consequent upbreaking of the icy regions of the polar seas, by the sweep of a universal deluge, or a violent upheaval of the bed of the ocean, certain it is that the materials were brought together by rapid spasmodic action. This deposit covers the whole of Northern Europe, much of Asia, and extends over the vast continent of North America, as far as the 42° of latitude: it varies from a hundred to several hundred feet in depth: and thus, so far as quantity and extent of superficial area are concerned, the bowlder clay formation may be compared with any of the older rocky formations of the interior. But no geologist has ventured to speculate about an indefinite cycle of years, as the condition of the planet during the drift and accumulation of these rude and plastic materials. The _sands_ and _gravels_ which succeed are likewise of great depth, spread over extensive valleys, and rise on the acclivities of hills five and six hundred feet above the level of the sea. This may be regarded, all of it, as the collect of the current epoch; and within the period of civilization and history and the arts, what sand-floods have been carried to every quarter of the globe, covering entire regions, devastating cities, and obliterating the very traces of man’s dominion over countries once subject to his use. Nor would fossils be wanting to complete the analogy, as the _dunes_ along the shores of every continent, and especially on the coast of the North Sea in Norway, Denmark, Holland and Belgium, only require consolidation in order to represent with living instead of extinct species, the fossiliferous deposits of anterior times; more particularly the Molasse and Nagelflue of the Swiss Alps. Near Tours, in France, there is a bed of oyster-shells which is twenty-seven miles long, with a corresponding breadth, and twenty feet thick. And in the United States there are beds far exceeding this: a stratum, nearly continuous, has been traced from the Eutaw Springs in South Carolina, to the Chickasaw country—being six hundred miles in length by ten to a hundred miles in breadth.