I. THE MINERAL INGREDIENTS, POSITION, AND ARRANGEMENT OF THE CARBONIFEROUS SYSTEM.—The rocks belonging to this formation, in the order of superposition, succeed the old red sandstone, consisting of a series of deposits of great thickness, of an infinite number of alternations and varieties, and nearly the same in every coal-field all over the earth. They constitute one great group of marked physical characters, formed under similar conditions, and produced during the same epoch or period of time. The out-crop of the beds meets the eye along the ridge of which the Lomonds may be taken as the center, ranging eastward by St. Andrews to Fifeness Point, and extending indefinitely westward by Stirling, Campsie Hills, Port-Glasgow, to the coast of Arran. The southern lip of the great coal basin of Scotland stretches from the German Ocean, near Dunbar, to the Ayrshire coast in the North Channel, flanked by the old red sandstone and Silurian rocks almost continuously throughout. And within the space now indicated are situated all the principal coal-fields of the northern part of the empire. The lower beds of the formation consist generally of coarse-grained sandstone, termed by the English geologists millstone grit, and inclose a few thin unworkable seams of coal. Bands of ironstone, shale, and sandstone are superimposed in repeated alternations. A thick massive limestone lines the edges, feathering in and out through the area of the basin which contains the coal metals. This is the mountain limestone, the most of which is supposed to have once existed as coral reefs, raised on the bottom of shallow seas, so subdivided as to form suitable compartments for receiving and retaining the matter of the coal. Accordingly, corals, encrinites, and shells everywhere prevail in the rocks of this deposit, and, in some instances, present the appearance of a homogeneous, agglutinated mass of the remains of these marine animals—the first of living creatures which the waters were charged to bring forth, and with which they were now swarming. The bituminous beds, the true coal, generally occupy a central position in the group, firmly caked and inclosed between the arenaceous and shaly strata. The number of seams vary in different basins, ranging in Scotland from eleven to thirty-two or thirty-three, and comprising an average thickness of the useful mineral of a hundred and twenty feet. The varieties of coal—as anthracite or blind-coal, cannel or parrot, and the common house or glance-coal—are occasioned chiefly by the different proportions of the bituminous elements which enter into their composition. Compared with Scotland, the coal-measures of England and Wales are of a greater average thickness, lie far beneath the surface, and contain in general a greater proportion of bitumen.