We descend to the river side. The incessant action of the current has worn a deep channel through the leaden-colored silt; the banks stand up perpendicularly over the water, and downwards, for twenty feet together,--for such is the depth of the deposit,--we may trace layer after layer of reeds, and flags, and fragments of driftwood, and find here and there a few fresh-water shells of the existing species. In this locality, six thousand years are represented by twenty feet. The depth of the various fossiliferous formations united is at least fifteen hundred times as great. We pursue our walk, and pass through a morass. Three tiers of forest trees appear in the section laid open by the stream, the one above the other. Overlying these there is a congeries of the remains of aquatic plants, which must have grown and decayed on the spot for many ages after the soil had so changed that trees could be produced by it no longer; and over the whole there occur layers of mosses, that must have found root on the surface after the waters had been drained away by the deepening channel of the river. The six thousand years are here represented by that morass, its three succeeding forests, its beds of aquatic vegetation, its bands of moss, and the thin stratum of soil which overlies the whole. Well, but it forms, notwithstanding, only the mere beginning of a formation. Pile up twenty such morasses, the one over the other; separate them by a hundred such bands of alluvial silt as we have just examined a little higher up the stream; throw in some forty or fifty thick beds of sand to swell the amount; and the whole together will but barely equal the Coal Measures, one of many formations.