The Cave of Fingal is accessible only by sea, and is formed by ranges of massive basaltic columns, fifty feet and upwards in height. The stone of which these columns are formed very much resembles that of the Giants’ Causeway.
In several parts of the world large masses of basalt are discovered, composing entire insulated mountains, of somewhat conical form. They are considered by some writers as volcanic productions, but the proofs of this are by no means satisfactory.
Amongst the uses to which basalt has been applied, two of the most important are as materials of an excellent and durable kind for building and paving. When burned and pulverized, these stones impart to mortar with which they are mixed the property of hardening under water. They easily melt, without any addition, into an opaque and black glass; and from them, under a certain modification, bottles of olive-green colour, and of extreme lightness, but great strength and solidity, have been formed. Some of the kinds have been advantageously employed as millstones. Basalt is occasionally used by artists for touch or teststones, to ascertain the purity of gold and silver; and goldbeaters and bookbinders, on the Continent, usually make their anvils or beating blocks of it.
Basalt, though harder, more brittle, and less pleasing in its colours than marble, was in considerable esteem among the sculptors of antiquity, on account of its great durability. Many fine works were consequently executed by them in this stone. Pliny, who has described several, states that the columns of it were sometimes so large as to admit of several figures being wrought out of them. The Emperor Vespasian had an entire statue, accompanied by the figures of sixteen children, cut out of a single column of basalt; this statue he placed in the Temple of Peace, and dedicated it to the Nile. The famous statue of Minerva, at Thebes, is described by travellers to have been formed of basalt. Antiques of basalt are always in a much better state of preservation than those of marble. Even such as are dug out of the earth still retain their original polish; and the finest touches of the chisel upon them are still unimpaired.
ORDER III.—SALINE STONES.
LIME, OR CALCAREOUS FAMILY.
139. Lime, after it has been freed from extraneous matters by burning, is a mineral of whitish colour, and pungent, acrid, and caustic taste. It has the property of changing vegetable blue colours to green, and of corroding and destroying animal substances.