182. BALLICHULISH MARBLE.—On the north side of the ferry of Ballichulish, in Lochaber, there is a rock of marble, of beautiful _ash─grey colour_, and of a fine, regular, and uniform grain, which is capable of being wrought into blocks or slabs of any size, and is susceptible of a fine polish. This marble is finely sprinkled throughout with grains and specks of pyrites (236), and with grains and specks of a beautiful lead ore, which to the eye appears to be rich in silver. If used for ornamental purposes, it would be a bright and beautiful metallic marble. 183. BLAIRMACHYLDACH MARBLE.—In the bed of a river, at the farm of Blairmachyldach, about three miles south of Fort William, is a singular marble, consisting of _a black ground, flowered with white_. It is of fine close grain, but not very hard. The flowering in it is light, and beautiful, like fine needle─work, or rather resembling the frosty fret─work upon glass windows, in a winter morning. The cutting and polishing of marble appear to have been performed by the ancients nearly in the same manner as it is with us. In polishing, the first substance employed is a sharp, coarse─grained sand. Afterwards a finer sand is used, then emery (58) in different degrees of fineness. These are followed by a red powder called tripoli (119): and the last polish is given with putty. 184. _BLACK MARBLE is a species of limestone, of uniform black colour, and easily distinguishable, by an excessively disagreeable smell, which is emitted on rubbing two pieces of it together, or striking it with a hammer._ Few minerals are susceptible of a more beautiful polish than this. It is consequently much used for chimney─pieces, small columns, vases, and other ornamental work. There are two quarries of black marble near Bakewell, in Derbyshire: and it is manufactured to a considerable extent by Messrs. Brown and Co. at Derby, who have fixed up in their ware─rooms a large slab of it as a looking─glass. By the ancients it was much prized. Marcus Scaurus is said to have ornamented his palace with columns of black marble, each thirty─eight feet high; and many of the monuments of ancient Persepolis were executed in it. M. D’Avejan, Bishop of Alais, used a kind of black marble for paving the apartments of his palace; but the friction and heat rendered it so fetid that his successors were compelled to substitute another species of stone in its place.—The pavements, however, of many churches, and of the porticos of several galleries, on the Continent, are of black marble. 185. _CALCAREOUS ALABASTER is a species of limestone of somewhat whitish or yellowish colour, translucent, and internally splendent or shining._ _It is nearly a pure carbonat of lime; and occurs in masses, hanging, like immense icicles, from the roofs of lime─stone caverns, and also coating the sides of such caverns._