It is evident that Theophrastus had no first-hand knowledge of the way in which glass was made. Though glass objects of many kinds were well-known objects of commerce at the time, his ignorance is perhaps excusable, since there is apparently no literary346 or archaeological evidence that glass was manufactured in ancient Greece.
Although the process of thickening (πάχννσ-ις) may seem to have no connection with the processes of softening or firing, in the Aristotelian sense of the word it was closely related to these other processes and was often a necessary consequence of them. According to Aristotle,347 "thickening" was the compacting of dry matter by the removal of moisture, and this moisture could be removed by the agency of fire. Thus firing was a means of thickening. Moreover, the phenomenon of softening might occur in the course of thickening an earthy substance by the action of fire. Theophrastus apparently believed that glass was made by subjecting a particular eartli to the action of fire, which compacted it to form glass. Here again, Theophrastus is clearly following the doctrines of Aristotle.
49. The most unusual earth is the one mixed with copper; for in addition to melting and mixing, it also has the remarkable power of improving the beauty of the color. Since it is not certain what noun should be understood with the feminine article ή, this passage as a whole has been explained in very different ways. Hill348 evidently believed that Theophrastus was still alluding to glass manufacture, and he therefore concluded that the article referred to ΰελο? ("glass"), which is mentioned in the preceding sentence. Furthermore, Hill concluded from a suggestion of De Laet that the word χαλκω ("copper") was originally χαλίκι ("gravel"), and he not only made this unwarranted alteration in the text but translated it incorrectly as "flints." Hence his translation of this passage is radically different from the one given here. Various scholars have accepted Hill's view that the passage refers to glass, but most of them have not
346 Mary L. Trowbridge, "Philological Studies in Ancient Glass," doctoral dissertation (University of Illinois, 1922), p. 133.
347 Meteorologica, IV, 6, 383a.
848 Theophrastus's History of Stones, pp. 118-19.
