GUNPOWDER: its manufacture and conyetance. 
45 
generally it is allowed to lie in store for a much longer time. 
Some wood has been kept for twenty years, protected from the 
weather by a roof of thatch, and is still perfectly sound. 
Strange to say, comparatively little dogwood is used in the 
powder factories of Giermany, though it is quite certain that it 
supplies the best charcoal for the purpose.* The old plan for 
charring wood was to burn it in pits, and this is still the prac- 
tice abroad, but for many years the charcoal at Waltham has 
been manufactured by sawing the wood into short lengths, and 
packing it into iron cylinders called “ slips,” which are placed 
on a small carriage, and run into a retort very like those used 
in gasworks. Here the slip is exposed to the flames for a period 
varying from two and a-half to three and a-half hours, the gas 
issuing from the wood in the process being utilised as fuel; and 
the superintendent of the work knows when the wood is com- 
pletely charred, by the peculiar colour with which the combus- 
tion of the gas tinges the fire. As soon as this appears, the slip 
is withdrawn and cooled. The charcoal when taken out is 
ground in a machine like a colossal coffee-mill, and then, like 
the sulphur, sifted in a slope-reel. 
The three ingredients are now ready for the regular process 
of manufacture to be commenced. Up to a certain point (the 
formation of the u press-cake ”) the process is the same for 
whatever purpose the gunpowder is intended, but at that point 
it divides into two branches, according as it is to be used for 
heavy guns or smaller weapons. We shall, therefore, first trace 
the various stages of the manufacture up to the press-house, and 
then explain the method of making the various kinds of gun- 
powder, and the objects desired to be obtained by these modifi- 
cations. 
The first process is that of simply mixing the ingredients. 
For this purpose the proper quantities of each are accurately 
weighed out, allowance being made for a certain amount of 
moisture in the saltpetre. The proportions vary in different 
countries, and according to the purpose for which the gun- 
powder is to be used. For English Grovernment powder of every 
kind it is — saltpetre 75 parts, sulphur 10, charcoal 15, the 
sulphur being reduced almost to a minimum, as its chief use is 
only to ignite the charge and accelerate its action. In France 
* M. Proust’s experiments on charcoal, made from various woods, give 
the following results : — 12 grains of charcoal of each wood, mixed with 60 
grains of saltpetre and ignited, yielded the following proportions of gas in 
cubic inches: Dogwood, 80-84; willow, 76-78 ; alder, 74-75; filbert, 72 ; 
fir, 76 ; elm, 62 ; oak, 61-63. The importance of not overheating the wood 
is shown by the fact, that when the charcoal consisted of overheated willow, 
the yield of gas was only from 59-66 cubic inches. 
