The Commissioners of the Northern Light-houses, as before noticed, having finally resolved that the erection upon the Bell Rock should be of stone, constructed upon principles similar to the Edystone Light-house, it became a question of importance in the economy of the work, to fix the quality and description of stone to be used. Considering this subject in reference to the Edystone Light-house, it appears that the hearting or interior of the solid part is of sandstone from Portland Island, and that the exterior of that building is of Cornish granite, both of which were highly suitable in quality, and were fortunately procurable from quarries the most contiguous to Plymouth, where these works were situate. [Sidenote: Mineralogy of the southern and eastern shores of Britain.] It may farther be noticed, that granite is perhaps the only stone upon the coast of England, which possesses durability for withstanding the effects of the weather in a situation so exposed, or strength sufficient for undergoing the process of landing the stones when in their prepared state. In Scotland, however, the case is widely different, for here, the country abounds with excellent building materials of almost every description; and excepting in those districts which produce granite, that stone is rarely had recourse to for buildings of any description. It is curious to observe, and it may here not be out of place to remark, in looking into the mineralogy of the British coast, on the great scale, that we find the shores of the whole southern parts of the kingdom, or from Portland Island in Dorsetshire, to Flamborough Head in Yorkshire, consist chiefly of chalk, limestone, clay, and beds of gravel. But if we continue our course from thence northward, to Stonehaven in Kincardineshire, including the Firth of Forth, the strata, with little exception, are sandstone, greenstone, limestone and coal. The Aberdeenshire coast is chiefly of granite, syenite, and gneiss, while a part of Banffshire consists of serpentine and porphyry: but here the sandstone again makes its appearance, and stretches along the northern shores of the Moray Firth , Caithness and Sutherland, nearly as far to the westward as Cape Wrath. To this great extent of sandstone country, may also be added the islands of Orkney and Shetland, with some considerable exceptions, however, in so far as regards Shetland; but, in Orkney, these are confined to comparatively small portions of gneiss with granite veins, which occur in Pomona or the Mainland, and in the Island of Græmsay.