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COMMENTARY
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and more brittle than stone. Plato53 also attempted to explain why an admixture of some water with earth was necessary in order to produce a material fusible by fire. He considered that if a body were composed of earth alone, not compacted by any unusual force, the interstices in it would be larger than the fire particles, which could therefore pass in freely without exerting any force that would tend to break up the mass. On the other hand, he considered that, if some water were present, the fire particles could force their way into the smaller pores of the water particles and thus break up or disturb these; and they in turn then acted on the earth, so that the entire mass was broken up and fusion was finally effected. But Plato believed that when the mass of earth was forcibly compacted, as was supposed to happen to earthenware, the pores were smaller and only fire particles could find an entrance. Theophrastus seems to imply here, as a logical extension of this argument, that the reason pottery and certain stones fly apart on the application of heat is that the fire particles force their way into the small pores of such bodies, which are thereby fractured owing to their inherent brittleness.
The negative ούδ' should be bracketed in the text; the meaning ought to be that many stones, like pottery, fly into pieces owing to the action of fire. It seems most unlikely that Theophrastus intended to make an exception of pottery.
11. they are useless unless they are . . . wetted again. It is not obvious why the denser stones which harden on drying are supposed to become useless. Possibly the allusion is to their availability for cutting or carving; for some absorbent stones are definitely easier to work when wet. With sandstone, for example, this is certainly true; for it is cut much more easily when it is impregnated with water, as it often is in the quarries, than when it is completely dry. The statement that certain stones become softer and more brittle when they are dry is also somewhat obscure. There is a strong probability that the allusion is to native asphalt and related substances, which were well known and extensively used in ancient times.54 These soften in a characteristic way when
53 Timaeus, 61A-B.
54 R. J. Forbes, Bitumen and Petroleum in Antiquity (Leyden, 1936).
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