ON THE APPLICATION OF GUN-COTTON TO WARLIKE PURPOSES. 29 
Mere affusion, however, does not suffice to get rid of all the adherent acid, 
hence the cotton must remain for a yet longer period in a stream of water, 
natural or artificial. 
g. Impregnation of gun-cotton with soluble glass—The object of this process 
is to close the pores of the gun-cotton fibre by silica precipitated within them, 
by which the velocity of explosion of gun-cotton is hereafter retarded ; 
moreover any lingering traces of acid that may remain are neutralized by 
combination with soda liberated from the soluble glass. This operation is 
performed by means of a centrifugal machine, into which a central tube 
passes for supplying the glass solution. By this arrangement the liquid is 
driven in very minute division through the gun-cotton ; the glass solution 
employed has a density of 12° Baumé. The material having been treated 
as described, has next to be dried by atmospheric exposure: as drying pro- 
ceeds, decomposition of the soluble glass goes on. Atmospheric carbonic acid 
uniting with soda, forms carbonate of soda, whilst silica is precipitated. 
The carbonate of soda thus produced being soluble in water, can be got 
rid of hereafter by washing, whereas the precipitated silicic acid not being 
soluble, remains attached to the cotton fibres, protecting them from de- 
composition under atmospheric influences, however high the temperature 
may be. 
h. Dreatment with soap.—F or many purposes it is desirable to retain the 
fibres of gun-cotton soft, in order to guard against the contingency of explo- 
sion from very violent friction, gun-cotton being somewhat harsh to the touch. 
This is readily effected by dipping the material, already treated with 
soluble glass and washed, previous to final drying, into a soap ley, the excess 
of which is to be hereafter squeezed out, and the gun-cotton finally dried. 
22. Have you any special information to give the Committee respecting the 
practical applications of gun-cotton? 
a. In general.—The proper utilization of gun-cotton presupposes a thorough 
knowledge of the nature of its energy and the bearing of its mechanical ad- 
vantages, in order that the object proposed may be gained through a favour- 
able choice of circumstances. These influences are more perceptible with 
gun-cotton than with gunpowder, inasmuch as gun-cotton admits of variation 
from a point of inefficiency to one of highest energy. 
Ignited in an open space (i. ¢. not under pressure), the explosive effect of 
gun-cotton is trifling, very much less than that of gunpowder. Ignited in 
spaces more or less closed, then in proportion as the closure is perfect does 
the explosion assimilate itself to that of gunpowder, the force of which under 
certain circumstances it considerably surpasses ; 7. ¢. it is dependent on the re- 
sistance met with. The maximum of the explosive effect of gun-cotton is 
attamed when the charge is so regulated, as to dimensions and form, that 
the whole of it becomes ignited before the yielding of any side of a vessel in 
which it is enclosed. 
The products of combustion of gun-cotton are wholly gaseous, whereas 
gunpowder by combustion yields only 31 per cent. of gas, whence it would 
seem that the energy of a charge of gunpowder should be nearly equalled by 
a charge of gun-cotton only one-third of its weight. The available power 
of one part of gun-cotton by weight, may, under certain circumstances, be 
raised to the effect of six parts by weight of gunpowder. 
b. Application of gun-cotton as a charge for smooth-bore guns.—The 
standard of reference was furnished by experiments conducted with a twelve- 
pounder bronze field piece, which gaye results as follows ;— 
