VITRUM

( ὕαλος ), gla . A story has been preserved by Pliny, that gla was first discovered accidentally by some merchants who, having landed on the Syrian coast at the mouth of the river Belus, and being unable to find stones to support their cooking-pots, fetched for this purpose from their ships some of the lumps of nitre which composed the cargo. This being fused by the heat of the fire, united with the sand upon which it rested, and formed a stream of vitrified matter. No conclusion can be drawn from this tale, even if true, in consequence of its vaguene ; but it probably originated in the fact, that the sand of the district in question was esteemed peculiarly suitable for gla -making, and exported in great quantities to the workshops of Sidon and Alexandria, long the most famous in the ancient world. Alexandria sustained its reputation for many centuries: Rome derived a great portion of its supplies from this source, and as late as the reign of Aurelian we find the manufacture still flourishing. There is some difficulty in deciding by what Greek author gla is first mentioned, because the term ὕαλος unquestionably denotes not only artificial gla but rock-crystal, or indeed any transparent stone or stone-like substance. Thus the ὕελος of Hero dot us, in which the Ethiopians encased the bodies of their dead, cannot be gla , for we are expre ly told that it was dug in abundance out of the earth; and hence commentators have conjectured that rock-crystal or rock-salt, or amber, or oriental alabaster, or some bituminous or gummy product, might be indicated. But when the same historian, in his account of sacred crocodiles, states that they were decorated with ear-rings made of melted stone, we may safely conclude that he intends to describe some vitreous ornament for which he knew no appropriate name. Gla is, however, first mentioned with certainty by Theophrastus, who notices the circumstance alluded to above, of the fitne of the sand at the mouth of the river Belus for the fabrication of gla . Among the Latin writers Lucretius appears to be the first in which the word vitrum occurs; but it must have been well known to his countrymen long before, for Cicero names it along with paper and linen, as a common article of merchandise brought from Egypt. Scaurus, in his aedileship ( B.C. 58), made a display of it such as was never witne ed even in after-times; for the scena of his gorgeous theatre was divided into three tiers, of which the under portion was of marble, the upper of gilded wood, and the middle compartment of gla . In the poets of the August an age it is constantly introduced, both directly and in similes, and in such terms as to prove that it was an object with which every one must be familiar. Strabo declares that in his day a small drinking-cup of gla might be purchased at Rome for half an as, and so common was it in the time of Juvenal and Martial, that old men and women made a livelihood by trucking sulphur matches for broken fragments. When Pliny wrote, manufactories had been established not only in Italy, but in Spain and Gaul also, and gla drinking-cups had entirely superseded those of gold and silver; and in the reign of Alexander Severus we find vitrearii ranked along with curriers, coach makers, goldsmiths, silversmiths, and other ordinary artificers whom the emperor taxed to raise money for his thermae. The numerous specimens transmitted to us prove that the ancients were well acquainted with the art of imparting a great variety of colours to their gla ; they were probably le succe ful in their attempts to render it perfectly pure and free from all colour, since we are told that it was considered most valuable in this state. It was wrought according to the different methods now practised, being fashioned into the required shape by the blowpipe, cut , as we term it, although ground ( teritur ) is a more accurate phrase, upon a wheel, and engraved with a sharp tool like silver. The art of etching upon gla , now so common, was entirely unknown, since it depends upon the properties of fluoric acid, a chemical discovery of the last century. The following were the chief uses to which gla was applied:—1. Bottles, vases, cups, and cinerary urns. 2. Gla pastes, presenting fac-similes either in relief or intaglio of engraved precious stones. 3. Imitations of coloured precious stones, such as the carbuncle, the sapphire, the amethyst, and, above all, the emerald. 4. Thick sheets of gla of various colours appear to have been laid down for paving floors, and to have been attached as a lining to the walls and ceilings of apartments in dwelling houses, just as scagliuola is frequently employed in Italy, and occasionally in our own country also. Rooms fitted up in this way were called vitreae camerae , and the panels vitreae quadraturae . Such was the kind of decoration introduced by Scaurus for the scene of his theatre, not columns nor pillars of gla as some, nor bas-reliefs as others have imagined. 5. Gla was also used for windows. [ Domus , p. 144 .]