at a temperature from 38 deg. to 41 deg.  C., until they do not contain more than 0.1 per cent. of moisture.  The calcium carbonate is also finely pulverised and dried, and is added to the mixed nitro-celluloses after they have been sifted through a 16-mesh sieve.  The nitrates are next weighed out and dissolved in hot water, and to this solution is added the mixture of nitro-celluloses and calcium carbonate with constant stirring until the entire mass becomes a homogeneous paste.  This pasty mass is next spread upon trays and re-dried at a temperature between 38 deg. and 48 deg.  C., and when thoroughly dry it is transferred to the kneading machine.  The ether-alcohol mixture is now added, and the process of kneading begun.  It has been found by experiment that the amount of solvent required to secure thorough incorporation is about 500 c.c. to each 500 grms. of dried paste.  To prevent loss of solvent due to evaporation, the kneading machine is made vapour light.  The mixing or kneading is continued until the resulting greyish-yellow paste is absolutely homogeneous so far as can be detected by the eye, which requires from three to four hours.  The paste is next treated in a preliminary press (known as the block press and is actuated by hydraulic power), where it is pressed into a cylindrical mass of uniform density and of such dimensions as to fit it for the final or powder press.  The cylindrical masses from the block press are transferred to the final press, whence they are forced out of a die under a pressure of about 500 lbs. per square inch.  As it emerges from the final press the powder is in the form of a ribbon or sheet, the width and thickness of which is determined by the dimensions of the powder chamber of the gun in which the powder is to be used.  On the inner surface of the die are ribs extending in the direction of the powder as it emerges from the press, the object of these ribs being to score the sheets or ribbons in the direction of their length, so that the powder will yield uniformly to the pressure of the gases generated in the gun during the combustion of the charge.  The ribbon or sheet is next cut into pieces of a width and length corresponding to the chamber of the gun for which it is intended, the general rule being that the thickness of the grain (when perfectly dry) shall be fifteen one-thousandths (.015) of the calibre of the gun, and the length equal to the length to fit the powder chamber.  Thus, in case of the 6-inch rapid-fire gun the thickness of the grain (or sheet) is 0.09 of an inch and the length 32 inches.  The sheets are next thoroughly dried, first between sheets of porous blotting-paper under moderate pressure and at a temperature between 15 deg.  C. and 21.5 deg.  C. for three days, and then exposed to free circulation of the air at about 21.5 deg.  C. for seven days, and finally subjected for a week or longer to a temperature not exceeding 38 deg.  C. until they cease to lose weight.

[Footnote A:  Lieut.  W. Walke, “Lectures on Explosives,” p. 330.]