48. It melts {along with) substances which are dug up and which can be liquefied, just as stone also does. Since all fusible substances, as well as metals which were less easily fusible, were thought to be composed wholly or in part of water, these could logically be as effective as water itself in causing an earth to melt. The melting of a stony material on being heated along with metals is mentioned in section 9 and discussed in the notes on that section.
48. It is softened, and stones are made from it. These include the variegated ones and other composite stones . . . ; for all of these are made artificially when they are fired and softened.
Though it seems necessary to translate λίθους as "stones," the context clearly indicates that artificial stony materials are meant. For the purpose of scientific classification Theophrastus evidently makes little or no distinction between natural stones and materials that are artificially produced. This passage clearly refers to the manufacture of ceramic products of some sort in which an earthy substance such as clay was first "softened" with water and afterwards baked or fired. There are not enough descriptive details in the passage to tell what particular kinds of ceramic products are meank
49. And if glass is also formed, as some say, from vitreous earth, this too is made by thickening.
Though the reading of the text is only 4κ της ύελιπδος, the context indicates that an earth is to be understood. Strabo345 specifically states that a vitreous earth (γη ύαλΐτις) was used in Egypt in the manufacture of colored glasses. He also mentions the use of a special sand (ψάμμος ύαλΐτις) in the manufacture of glass. Some commentators have concluded that Theophrastus meant the sand used in the manufacture of glass, but this does not seem probable. Throughout this part of the treatise he is discussing earths in particular. If he had specifically meant a sand, it is likely that he would have used the special word for it, as he does in sections 21, 40, and 58.
