after the parts have been properly shadowed; and, as soon as the outlines are dry, the glass ought to be varnished with a solution of gum copal, and the spangles strewed on while it is wet; when they are perfectly dry, it is necessary to varnish them over two or three times.
Glass is so remarkably elastic, that if the force with which glass balls strike each other, be computed at 16, that with which they recede, from their elasticity, will be nearly 15. Hence we have seen glass wigs, and even glass brushes, manufactured by Bohemian artists.—If glass be exposed to the influence of dew, it becomes moist, which does not happen either with silver or any other metal. And if a goblet, or other drinking-glass, be filled with water, and rubbed on the brim with a wet finger, it will impart musical notes, higher or lower, in proportion as the glass contains more or less of that fluid: it likewise possesses considerable electrical properties, and is therefore frequently employed in experiments on electricity.
Before we conclude this article, we cannot omit to take notice of the numerous accidents that frequently happen in consequence of person inadvertently, or adventurously, swallowing fragments of broken glass. In such case, the safest remedy is to administer, as speedily as possible, large draughts of olive or other demulcent oils, by which the membranes of the stomach and intestines may be lubricated, and thus the injurious effects of the glass timely counteracted. If children, or other improvident persons, have cut themselves with glass, it is of the first importance to ascertain whether any particles of it have remained in the wound: these should, at all hazards, be immediately extracted by a skilful operator; as, without such precaution, the most dangerous consequences are to be apprehended, in parts thus injured.
For different methods of uniting broken glass, we refer to the articles Cement, vol. i. p. 476; and Garlic, vol. ii. p. 366.
Glass-wort. See Salt-wort.
GLAUBER's-SALT, a chemical composition, which is usually prepared by adding to sea-salt an equal quantity of oil of vitriol diluted with water, distilling off the marine acid, and dissolving and crystallizing the remainder.
These salts may also be obtained by mixing four ounces of borax with one ounce and one dram of oil of vitriol; the whole of which, when sublimed, affords what is by chemists called Sedative Salt; and if the remainder be exposed to a strong fire, it will yield Glauber's-salts. They were first prepared by John Rhodolphus Glauber, a celebrated chemist of the 17th century; and are of considerable use in medicine as cooling purgatives, when taken in doses from six to twelve drams: they also prove excellent aperients in various chronical disorders, such as habitual costiveness, for which small doses of one dram of this salt, with two scruples of cream of tartar, and one scruple of sal-ammoniac dissolved in water, may be given with advantage, three or four times a day.
GLAZING signifies the coating or enamelling of earthen ware with any vitreous substance, the basis of which consists of lead. It is one of those familiar arts with which the ancients were doubtless better acquainted than our modern potters. The Roman urns discovered
