105. TO MAKE A BEAUTIFUL SOFT GLASS FOR JEWELRY.--Take six ounces of clean fine white sand, three ounces of red lead, three ounces of pure sub-carbonate of potass, one ounce of nitrate of potass, half an ounce of borate of soda, and two drachms of arsenic; mix and pound them all together. Put the compound in a crucible, and set it in a common fire, often stirring it with an iron rod, till it is well melted, and becomes transparent. This compound will liquify very easily without any great heat, if the sand is fine, (which sometimes requires to be ground or pounded in a glass or flint mortar,) and if it be kept melted awhile, will become beautifully transparent, and may be cast or blown in the manner of other glass. This glass may be changed to a red or ruby colour, by adding and fusing together with it, a small quantity of finely powdered precipitate of gold, (gold precipitated from solution in nitro-muriatic acid by the addition of tin.) It may be also changed to blue by the addition of zaffre, (an ore of cobalt,) and magnesia: a green colour may be given by a precipitate of copper; and yellow by calcined iron, and white by calcined bones. This subject is treated of largely in the _Handmaid of the Arts_, to which, for further information on the subject, the reader is referred. 106. COMPOSITION OF VARIOUS KINDS OF GLASS.--The best flint glass is composed of 129 lbs. of white sand, 50 lbs. of red lead, 40 lbs. of sub-carbonate of potass, 20 lbs. of nitrate of potass, and 5 oz. of magnesia. The best crown glass is composed of 60 lbs. of white sand, 30 lbs. of sub-carbonate of potass, 15 lbs. of nitrate of potass, 1 lb. of borate of soda and 1/2 lb. of arsenic. The composition of common green window glass, is 120 lbs. of white sand, 30 lbs. of sub-carbonate of potass, 60 lbs. of wood ashes, 20 lbs. of muriate of soda and 5 lbs. of arsenic. The composition for looking glass plates, is 60 lbs. of clean white sand, 25 lbs. of purified sub-carbonate of potass, 15 lbs. of nitrate of potass, and 7 lbs. of borate of soda. Common green bottle glass is made from 200 lbs. of wood ashes, and 100 lbs. of sand. The materials for making glass, is first reduced to powder; then mixed and exposed to a strong heat, in suitable pots and furnaces, till the whole mass liquifies and becomes thoroughly commixed and transparent.