hly dried, are of a uniform yellowish-grey colour,
and of the characteristic colloidal consistency; they possess a perfectly
smooth surface, and are free from internal blisters or cracks. The
temperature of ignition of the finished powder should not be below 172 deg.
C., and when subjected to the heat or stability test, it is required to
resist exposure to a temperature of 71 deg. C. for thirty minutes without
causing discoloration of the test paper.

~W.A. Powder.~--This powder is made by the American Smokeless Powder
Company, and it was proposed for use in the United States Army and Navy.
It is made in several grades according to the ballistic conditions
required. It consists of insoluble gun-cotton and nitro-glycerine,
together with metallic nitrates and an organic substance used as a
deterrent or regulator. The details of its manufacture are very similar to
those of cordite, with the exception that the nitro-glycerine is dissolved
in a portion of the acetone, before it is added to the gun-cotton. The
powder is pressed into solid threads, or tubular cords or cylinders,
according to the calibre of the gun in which the powder is to be used. As
the threads emerge from the press they are received upon a canvas belt,
which passes over steam-heated pipes, and deposited in wire baskets. The
larger cords or cylinders are cut into the proper lengths and exposed upon
trays in the drying-house. The powder for small arms is granulated by
cutting the threads into short cylinders, which are subsequently tumbled,
dusted, and, if not perfectly dry, again placed upon trays in the drying-
house. Before being sent away from the factory, from five to ten lots of
500 lbs. each are mixed in a blending machine, in order to obtain greater
uniformity. The colour of the W.A. powder is very light grey, the grains
are very uniform in size, dry and hard. The powder for larger guns is of a
yellowish colour, almost translucent, and almost as hard as vulcanite. The
powder is said to be unaffected by atmospheric or climatic conditions, to
be stable, and to have given excellent ballistic results; it is not
sensitive to the impact of bullets, and when ignited burns quietly, unless
strongly confined.

Turning now to the smokeless powders, in which the chief ingredient is
nitro-cellulose in some form (either gun-cotton or nitro-lignine, &c.),
one of the first of these was Prentice's gun-cotton, which consisted of
nitrated paper 15 parts, mixed with 85 p