Our subterranean exploration would be incomplete if it did not illustrate the Vegetable as well as the Animal Life of the ancient world. Let the reader then descend in fancy into the celebrated quarries of Portland on the south coast of England, and he will see the fossilized remains of a long past vegetation exhibited in a very striking manner. In one, of these quarries a vertical section, extending from the surface downward to the depth of about thirty feet, presents the following succession of strata arranged in horizontal layers:--first, a light covering of vegetable soil, beneath which are thin beds of cream-colored limestone, forming a stratum of solid rock ten feet thick; then a bed of dark-brown loam, mixed with rounded fragments of stone, and varying in thickness from twelve to eighteen inches. This is known to the quarrymen by the name of Dirt-bed, and seems, in former ages, to have supported a luxuriant vegetation; for all around are scattered the petrified fragments of an ancient forest. The prostrate stems and shattered branches of great trees are met at every step; but what is most striking and peculiar is, that, in many cases, the petrified stumps are still standing erect, with their roots fixed in the thin stratum of loam, and their trunks stretching upward into the hard limestone rock. Immediately below the Dirt-bed is another thick stratum of limestone, and below this again is a stratum of the famous Portland stone, so highly prized for building purposes. As the quarries of Portland are worked chiefly for the sake of this building stone, little attention is paid to the Dirt-bed and its contents, which are commonly thrown aside by the quarrymen as rubbish. [Illustration: Vegetable soil. Fresh-water Limestone. Clay. Laminated fresh-water Limestone. Dirt-bed with fossil trees and plants. Fresh-water Limestone. Bed of Clay. Portland building-stone full of marine shells. Fig. 23.--Section of a Quarry in the Island of Portland. Total thickness about thirty feet.]