When finely pulverized chalk is stirred into a solution of soluble glass of 30° B. until the mixture is fine and plastic, a cement is obtained which will harden in 6 or 8 hours, possessing an extraordinary durability, and alike applicable for domestic and industrial purposes. It may be used for uniting stone, brick, etc, and for filling up cracks. In short, it seems to be applicable to about the same purposes for which plaster-of-Paris is used, but it is much harder and stronger. If for' part of the chalk some colouring matter be substituted, differently coloured dements of the same general character are obtained. The following materials give good results: - (1) Finely pulverized or levigated stibnite (grey antimony, or black sulphide of antimony) will produce a dark cement, which, after burnishing with an agate, will present a metallic appearance. (2) Pulverized cast iron, a grey cement. (3) Zinc dust (so-called zinc grey), an exceedingly hard grey cement, which, after burnishing, will exhibit the white and brilliant appearance of metallic zinc.

This cement may be employed with advantage in mending ornaments and vessels of zinc, sticking well to metals, stone, and wood. (4) Carbonate of copper, a bright green cement. (5) Sesquioxide of chromium, a dark green cement. (6) Thenard's blue (cobalt blue), a blue cement. (7) Minium, an orange-coloured cement.

(8) Vermilion, a splendid red cement.

(9) Carmine red, a violet cement.