The GENERAL STRUCTURE of the district, as now indicated, is determined in the main by the Lammermuirs, a high mountain-range of sedimentary rocks, which formed the northern barrier of an extensive inland basin or sea, and of which the Solway and Tweed occupy the central stretch or depression. The old red sandstone was herein deposited, the strata of which rest unconformably upon the older rocks. The carboniferous beds succeeded, but at a period when the floor of the basin was elevated, and the dimensions contracted; hence these beds, though reposing conformably for the most part on those of the old red and not separable on physical grounds, do not occupy the same extent of surface. Creeks and bays existed around the silurian shores, into which the materials of the sandstone were carried, and thus along the southern slope, from St. Abb’s Head to Portpatrick, the old red is traceable in every opening and indentation, running up in long narrow tongues, or detached stripes, among the mountains. The coal series appear at various intervals in small isolated basins, forming on the west the coal-field of Whitehaven, which dips into the Solway, and on the east occupying from Kelso to Berwick, the valley of the Tweed, where the metals lie in very thin bands, and _underneath_ the mountain limestone. Here are porphyries, which have disrupted and broken through the old red sandstone, and therefore, corresponding in age to those of the Sidlaws, Ochils, and Pentlands; and augite traps and greenstone, scattered over the coal-measures, which are as clearly the product of the movements that issued in the elevation of Arthur’s Seat and the Lomonds.