7I have described the different species of lime and sand, and their qualities. Stone quarries, from which square and rubble stones are procured and prepared for the purposes of building, will now be considered. The qualities of these differ very much. Some stone is soft; the red, for instance, found in the neighbourhood of Rome, in the countries of the Pallienses, Fidenates, and Albanæ. Some moderately so, as the Tiburtine, Amiternine, Soractine, and those of that sort. Others are hard, even as flints. There are many other species, as the red and black sandstone (tophus) of Campania, and the white sort of Umbria, Picenum, and Venice, which is cut with a saw like wood.
2The soft species have this advantage, that when recently taken from the quarry they are easily worked, and answer well under cover; but when used in open and exposed situations, and subjected to the action of the frost and rain, they soon become friable, and moulder away. They are also much affected by the salt near the sea-shore, and are not capable of preserving their strength when exposed to great heat. The Tiburtine stones, and those of a similar nature, resist great weights no less than the action of the weather, but are easily injured by fire. The instant they are exposed to that they are ruined, from their possessing so small a quantity of moisture; their earthy particles, also, are few, and the quantity of air and fire in them considerable. Hence, from the small portion of earth and water which they contain, the fire easily acts upon them, and, occupying the interstices, drives out the air with accumulated violence, and communicates its own hot quality to them.
3There are many quarries on the borders of the Tarquinienses, called the Anician quarries, in colour much resembling the Alban stone. They are worked in most abundance in the neighbourhood of the Volscinian lake, and in the prefecture of Statonia. This stone has numberless good qualities; neither frost nor fire affects it. It is hard and durable, from its containing but little air and fire, but a moderate quantity of moisture, and much earth. Close in texture, it is not injured by the weather nor by heat.
4The monuments about Ferentinum, which are built of this stone, prove its durability; among these may be observed large statues well executed, bas-reliefs on a smaller scale, and acanthus leaves and flowers elegantly carved, which, though long since wrought, appear as fresh as though they were but recently finished. From the stones of the above quarries the metal founders make their casting moulds, for which they are well calculated. If this stone were to be had near Rome, it would be used in all works about the city, to which it is indeed worthy to be applied.
5But as necessity, on account of proximity to the quarries, obliges us to use the red sort of stone, that of the Pallienses and other species in the immediate vicinity of the city, in order to find that which is least defective, let it be selected as follows. Two years before the commencement of the building, the stones should be extracted from the quarries in the summer season; by no means in the winter; and they should then be exposed to the vicissitudes and action of the weather. Those which, after two years’ exposure, are injured by the weather, may be used in the foundations; but those which continue sound after this ordeal, will endure in the parts above ground. These rules apply equally to squared as to rubble or unsquared stone work.