GLASS. and burn, afterwards carrying the ashes to the glassmakers of Hebron. 1 The Phoenicians, too, must have made use of the materials thus prepared for them by these marine vegetables, but they were not content with that. Those who believe that the Phoenicians were the first to substitute a mineral base for these vegetable ashes, and to make use of nitre or saltpetre, as it is vulgarly called, nitrate of potash, as a chemist would say may be in the right. 2 We do not know whether this step in advance was actually made by Egypt or not, although we know that she possessed the materials. 3 It has been ascertained, however, that the Phoenicians made use of saltpetre, which is, perhaps, worked more economically and at least gives a finer quality of glass. 4 Glass in which vegetable soda is used is never so limpid as that made only with potash. The superiority of Phoenician glass was also attributed to the fineness of the sand collected on the coast, at the mouth of the river Belus, near Ptolemais. 5 Glass may be divided into three classes ; colourless and quite transparent glass ; coloured and transparent glass, which tints the rays passing through it with its own colour ; and opaque glass, resembling porcelain. The Phoenicians manufactured all three kinds. The first is chiefly represented in our collections by those urns, of comparatively recent date, which are found in abundance in the Greek and Roman sepulchres of Cyprus. The wonderful iridescence shown by some of them arises from molecular action going on through so many centuries. 6 But no such importance 1 LORTET, La Syrie d'Aujourd'hui, 2 FROEHNER, La Verrerie antique, p. 26. 3 In the natron lakes, to the west of the Nile. 4 "The river Belus," says TACITUS (Hist, v., 7), " falls into the sea of Judaea. Round its mouth glass is produced by submitting a mixture of sand and nitre to the action of fire. The coast, though of moderate extent, is inexhaustible in this respect." PLINY (xxxvi., 191), also speaks of glass as composed of nitre and sand. 5 The fame of this stretch of sand is attested by several writers. See STRABO, xvi. ii. 25. JOSEPHUS, De Bella Judaico, n. x. 12. PLINY, xxvi. 190. Strabo, after mentioning the heaps of sand collected for the manufacture and the virtues attributed to it, says very sensibly that equally good material is to be found elsewhere. 6 This iridescence has been studied by more than one chemist. The following works maybe consulted with advantage : SIR DAVID BREWSTER, Notes on the Decay of Glass, especially upon that of t/ie Ancient Glass Found at Nineveh (Appendix to LAYARD'S Nineveh and Babylon 1853) ; and On the Decomposed Glass Found at Nineveh and other Places (in the Transactions of the British A ssocia tion,. 1860, p. 9) ; J. FOWLER, On the Process of Decay in Glass, and, incidentally, on the Composition and Texture of Glass at Different Periods, and the History of its Manufacture (Archaologia 1880, vol. xlvi. pp. 65-162).
