The author referring, in the introductory part of his paper, to the views taken by Hutton of the structure of the earth's surface around Edinburgh, explained,—That the prevailing rocks are strata of sandstone and shale of the coal formation, with occasional beds of limestone; and interrupted by insulated as well as grouped hills of igneous origin, rising abruptly through them,—That the latter or trap-rocks, seem in many quarters interstratified with the former, as if they had burst while in a state of fusion between the strata of the secondary rocks,—That fragments of the secondary rocks are often seen imbedded in the trap, as if they had been broken away from the strata to which they belonged, and been hurried along by the fused erupted mass,—And that the trap-rocks often present very different appearances in the same hills, shewing that they were erupted under varying circumstances at different periods of time. The author farther explained, that the environs of Edinburgh seem to constitute a Great basin, surrounded by trap-rocks, which dip outwards in all directions from a common centre,—the Pentland Hills, forming the southern boundary, the rocky coast of Fife at Burntisland the northern, and Salisbury Craigs and Corstorphine Hill the eastern and western limits.