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THEOPHRASTUS ON STONES
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Not only the descriptions of its properties given by ancient writers but also the localities that they mention as its source show beyond doubt that it was a natural bituminous material of some kind. The clearest description is that of Dioscorides, who says: "One should select the black kind, which resembles long pieces of pine charcoal, and is splintery and somewhat shiny, and which, furthermore, does not dissolve slowly when it is ground fine and some oil is poured over it." As Forbes363 rightly pointed out, this is a description of a pure bitumen or asphaltite. In particular, it corresponds closely to what is now called glance pitch, a kind of bitumen which is known to occur in small deposits in the very localities where the ancient material is said to have been found. The Seleucian Syria named by Dioscorides as the source was next to Cilicia, the district which Theophrastus names, and it included the Pierian Seleucia, which, according to Strabo,364 was the source named by Posidonius. Even though these localities are all in the same general region, the identity of the material cannot be fixed, since small deposits of various other bitumens also occur in the coastal districts at the extreme northwestern corner of the Mediterranean.
It may be objected that Theophrastus would not classify a compact material like glance pitch as an earth, especially since he has previously classified other compact bitumens as stones. Nevertheless, he might have regarded it as an earth in a special sense, for Galen365 remarks that such a material was called an earth only because it could be resolved into a "mud" with water. There are positive indications, however, that the material used on vines at the time of Theophrastus was only a clay or sand impregnated with asphalt, which clearly could have been called an earth, and that in later times a pure bitumen came into use; this was still called an earth because it was used for the same purpose as the earlier material and was of the same general nature. When Theophrastus speaks of boiling the earth that was applied to vines, this is an indication that it was not glance pitch, for this bitumen has a high softening or melting point and a very high boiling
3es Bitumen and Petroleum in Antiquity, p. 19. 8β* VII, 5, 8.
365 De simplicium medkamentorum temperamentis ac jacultatibus, IX (Kiihn ed., XII, 186).
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