hen
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.]

The sheets, when thoroug