Complete Works, Vol. V (1890) - Page 28

not, are more comminutable than hewable, because by constriction or baking, the pores in them have been constricted and drawn tight, so that their cleavage and division is taken in different directions. Whosoever, however, are not constricted or hardened beyond the temperament of the stone, are well hewable and cuttable to a rule; although they cannot be cut like wood, but rather by parts extracted bit by bit, with the remaining body of the stone staying together. This, therefore, is the mode of the hewability and unhewability of stone. The very instruments of the stonemason's art show this; for masons hew hewable stones to a rule according to the entire surface of the stone. Those that are unhewable, which are comminutable, are not hewn on the entire surface, but it suffices that several corners of the non-flat but rough surface reach the line, just as the Lesbian masons are said to do, because in the island of Lesbos only comminutable stones are found.

CHAPTER VI.

On the cause of the porosity and compaction of stones, and of their gravity and levity.

According to this method, it is also determined regarding the cause of the porosity of stones and the cause of their compaction. For some stones are found to be of such porosity that they swim upon water, just like the stones that Vulcan mythological reference to volcanic activity casts forth, and some pumice stones are found to be most compact, like precious stones and genera of marbles; others, however, are found to be almost in the middle between these. And indeed the cause of porosity is no other than that the moisture was not all mixed with the earthy part, but stood in its diverse parts, as in a vessel, which, when it was consumed by baking, left

holes, and the stone was made porous, swimming on water due to the air included in those holes. Compaction, however, is chiefly the making of parts by moisture penetrating the stone's matter from all sides; for which reason it makes any part of it flow to any other part; and therefore the stone is made compact. This moisture, however, is corporeal and watery, or spiritual, or airy. And because the airy is more subtle than the watery, stones mixed from vapors are of more compact substance than those from other watery or earthy substance. Concerning the cause of the gravity or levity of stones, it is superfluous to intend here, since this has been sufficiently treated in the book On the Heaven and the World original: "De Cælo et Mundo", where it was shown why lighter stones are submerged under water, while heavier woods swim on the water. These, therefore, are things said in common about stones.

CHAPTER VII.

On the cause of the multitude of small stones along the shores, and on the order of bricks which are sometimes found along the shores as if placed artificially.

Beyond all things already said, it sometimes happens along the banks of rivers and seas that a great multitude of small stones are found connected as if by very strong mortar, as if they were taken from some wall; for which reason some think that the works of the Ancients had been there and destroyed by water. And what is more wonderful, along the entire length of the shore, there is sometimes found an order of bricks, as if they were placed there artificially; although this does not seem to be the work of art, because it is very thin, not having the mode of any wall, but only brick next to brick, with nothing above or below it of