At Siphnos,2761 there is a kind of stone2762 which is hollowed and turned in the lathe, for making cooking-utensils and vessels for keeping provisions; a thing too, that, to my own knowledge,2763 is done with the green stone2764 of Comum2765 in Italy. With reference, however, to the stone of Siphnos, it is a singular fact, that, when heated in oil, though naturally very soft, it becomes hard and black; so great a difference is there in the qualities of stone.
There are some remarkable instances, too, beyond the Alps, of the natural softness of some kinds of stone. In the province of the Belgæ, there is a white stone2766 which admits of being cut with the saw that is used for wood, and with greater facility even. This stone is used as a substitute for roof-tiles and gutter-tiles, and even for the kind of roofing known as the pavonaceous2767 style, if that is preferred. Such are the stones that admit of being cut into thin slabs.