We must now pass on to the stones that are employed for handicrafts, and, first of all, whetstones for sharpening iron. Of these stones there are numerous varieties; the Cretan stones having been long held in the highest estimation, and the next best being those of Mount Taygetus, in Laconia; both of which are used as hones, and require oil. Among the water-whetstones, the first rank belonged to those of Naxos, and the second to the stones of Armenia, both of them already[2776] mentioned. The stones of Cilicia are of excellent quality, whether used with oil or with water; those of Arsinöe,[2777] too, are very good, but with water only. Whetstones have been found also in Italy, which with water give a remarkably keen edge; and from the countries beyond the Alps, we have the whetstones known as “passernices.”[2778]
To the fourth class belong the hones which give an edge by the agency of human saliva, and are much in use in barbers’ shops. They are worthless, however, for all other purposes, in consequence of their soft and brittle nature: those from the district of Laminium,[2779] in Nearer Spain, are the best of the kind.
CHAP. 48.—TOPHUS.
Among the multitude of stones which still remain undescribed, there is tophus;[2780] material totally unsuited for building purposes, in consequence of its perishableness. Still, however, there are some localities which have no other, Carthage, in Africa, for example. It is eaten away by the emanations from the sea, crumbled to dust by the wind, and shattered by the pelting of the rain: but human industry has found the means of protecting walls of houses built of it, with a coating of pitch, as a plaster of lime would corrode it. Hence it is, that we have the well-known saying, “that the Carthaginians use pitch[2781] for their houses and lime[2782] for their wines,” this last being the method used by them in the preparation of their must.
In the territories of Fidenæ and Alba, in the vicinity of Rome, we find other soft kinds of stone; and, in Umbria and Venetia, there is a stone[2783] which admits of being cut with the teeth of a saw. These stones are easy to be worked, and are capable of supporting a considerable weight, if they are only kept sheltered from the weather. Rain, however, frost, and dew, split them to pieces, nor can they resist the humidity of the sea-air. The stone[2784] of Tibur can stand everything except heat, which makes it crack.
CHAP. 49.—THE VARIOUS KINDS OF SILEX.
The black silex[2785] is in general the best; but in some localities, it is the red, and occasionally the white; as in the Anician quarries at Tarquinii, near Lake Volsinius,[2786] for example, and those at Statonia,[2787] the stone of which is proof against fire even.[2788] These stones, sculptured for monumental purposes, are subject to no deterioration by lapse of time: moulds, too, are made from them, for the purpose of fusing copper. There is a green silex, also, which offers a most powerful resistance to the action of fire, but is never found in any large quantities, and, in all cases, in an isolated form, and not as a constituent part of solid rock. Of the other kinds, the pale silex is but rarely used for erections: being of globular form, it is not liable to injury, but at the same time it is insecure for building purposes, unless it is well braced and tightly held together. Nor yet does river silex offer any greater security, for it always has the appearance of being wet.
CHAP. 50.—OTHER STONES USED FOR BUILDING.
When the nature of stone is doubtful, the proper precaution is, to quarry it in summer, and not to use it for building before the end of a couple of years, leaving it in the meantime to be well seasoned by the weather. The slabs which have been damaged will be found to be better suited for the foundations under ground: while those, on the other hand, which have remained uninjured, may be employed with safety, and exposed to the open air even.