GLASS, (from the Saxon, glues) a hard, brittle, transparent lactitions substance, formed by the fusion of silicious matter, such as powder flint or fine sand, blended with alkaline ealth, metallic oxide, and other substances. In building, glass is used in thin transparent plates for windows, which admit light, while they exclude wind and rain.
The time at which glass was invented, is very uncertain. " It was known," says Dr. Lure, " to the Phenicians, anti constituted for a long time an exclusive manufficture of that people, in consequence of its ingredients, (natrou, sand, and fuel,) abounding upon their coasts. It is probable that the more ancient Egyptians were unacquainted with glass, we find no mention of it in the writings of Moses. But according to Pliny and Straho, the glass-works of Sidon and Alexandria were funOus in their times, and produced beautiful articles, which were cut, engraved, gilt, and stained of the most brilliant colours, in iinitation of precious stones. The II,oinans employed glass fir various Ifni-poses; and have It-ft specimens in lIerculanctun. of NV ow-gl tis, which must have been blown by methods analogous to the modern. The Phenician processes seem to have been learned by the Crusaders, and transferred to Venice in the 13th century, where they were long held secret, and formed a lucrative commercial monopoly. Soon after the middle of the I7th century, Colbert enriched France with the blown mirror glass manufacture." The application of glass to the glazing, of windows, is of comparatively modern introduction, at least in northern and western Europe. In 674, artists were. brought to England from abroad to glaze the church at Wearmouth in Ihn-ham ; and even in the year 1567, this mode of excluding cold from dwellings was confined to large establishments, and by no means universal even in them. An entry then made, in the minutes of a survey of Alnwiek Castle, the residence of the Duke of Northumberland, informs us that the glass-casements were taken down during the absence of the thirdly to preserve them from accident. A century after that time, the use of was so small in Scotland, that only the upper rooms in the royal palaces were furnished with it, the II )wer part having wooden shutters to admit or exclude the air.
At an early period of its history in this conntry, the glass manuffieture became an object of taxation, and duties were from time to time imposed on it, which operated most inju riously, not only on the manufacture itself, lint on building generally, by preventing the more extensive use of so orna mental an article. Within the last few years, however, a more enlightened policy has prevailed ; and so great a reduction of the duties on glass has been granted, that an enormous increase in the manufacture and use of it has taken place. The result is seen in the improved appearance of our dwelling-honses, in the great superiority of the quality of the glass used at present. and in the magnificent plate-glass windows now so generally adopted in shop-fronts.
Of the glass used in building, there are three qualities in common 1st, denominated best, second, and third. The best is that which is of the purest metal, and free of blemishes, as blisters, specks, streaks. &c. The second is inferior, from its not }wing so free of these blemishes. The third is still inferior, both in regard to quality and colour, being of a greener hue. They are all sold at the same price per crate, lint the number of tables is diffi.rent, according to the quality : best, 12 tables; second, 15 tables ; third, 15 tailless These tables are circular when manuffictured, and about four feet in diameter ; in the centre is a knot, to which, in the course of the process, the flashing rod was fixed, but, for the safety of carriage and convenieney of handling, as well as utility in practice, a segment is cut offi about four inches from the knot : the large piece with the knot, still retains the name of tulle, the smaller piece is technically termed a slab. From these tables hieing of a given size, it is reason able to suppose that when the dimensions of squares are such as chit the glass to waste, the price should be advanced.