What is common to the two countries, among the primary and crystalline rocks, occupies the whole western line of coast. The eastern shores of Ireland, correspond in mineralogical character with the opposite shores of Scotland, England, and Wales, where a great silurian belt covers, almost continuously, both lines of coast. These districts have thus all a common origin, are all of the same geological epoch, and were probably at one period more united than appearances now indicate. The Cumbrian group is isolated from the other portions of the system, and, as described by Professor Sedgwick, comprehends the lowest fossiliferous beds in the island, or perhaps as yet known in the crust of the globe. The elaborate work of Sir R. I. Murchison on “THE SILURIAN SYSTEM,” has made every one acquainted with the extensive deposits in Wales and Cornwall, in which the divisions of the system are fully pointed out, their fossil contents amply detailed, and their relations to analogous deposits in other parts of the world satisfactorily demonstrated. Through all these regions, therefore, we are again carried back among the earlier records already noticed. Coincident with the same are the old red sandstone deposits which stretch along the base of the more highly-inclined silurians, covering the greater portion of Herefordshire and Devonshire; and here, as in Scotland, the sandstones and conglomerates are immediately succeeded by the rich treasures of the carboniferous age. In the rocks of the three families lie, in profuse abundance, the organic remains of the epochs which produced them—cast like wreck among the silts and sands now hardened and upheaved into mountains—the peaks of Skiddaw and Snowdon, of Plinlimmon and Helvellyn, once the beaches or floors of our ancient seas.