THE ROYAL ARTILLERY INSTITUTION. 
135 
ignited. There is no doubt that the products of decomposition of the gun¬ 
powder, obtained under these circumstances, differ greatly from those which 
result from its explosion in confined spaces or in the open air under 
ordinary atmospheric conditions. In all the experiments conducted in the 
most highly rarefied atmospheres (at pressures of 0*5 to 1*5 in inches of 
mercury), the contents of the vessel, after the final deflagration of the powder, 
always possessed a very peculiar odour, similar to that of horseradish, due 
to the production of some sulphur-compound; nitrous acid was also very 
generally observed among the products. It is readily conceivable that the 
chemical action established between the constituents of gunpowder, under 
the circumstances described, must be of a very imperfect or partial character, 
the conditions under which it is established being unfavourable to its 
energetic development. 
In describing the phenomena which accompany the ignition of gun-cotton 
in atmospheres of different rarefaction, I have pointed out that, at pressures 
varying from one to twenty-four in inches of mercury a pale yellow flame 
was observed, which increased in size with the pressure of the atmosphere; 
and that a flame of precisely the same character was produced in rarefied 
atmospheres of nitrogen. The experiments instituted in nitrogen show that 
the explosion of loose tufts of gun-cotton in atmospheres of that gas, even at 
normal pressures, was always attended with a pale yellow flash of flame, 
quite different from the bright flash produced by igniting gnn-cotton in air. 
The same result was observed in atmospheres of carbonic acid, carbonic oxide, 
hydrogen, and coal-gas. In operating with pieces of gun-cotton-twist or 
thread of some length instead of employing the material in loose tufts, the 
results obtained in the two last-named gases were very different from those 
observed in atmospheres of nitrogen, carbonic acid, and carbonic oxide. 
When ignited by means of a platinum wire (across which it is placed) in 
vessels filled with either of those two gases, and completely closed or open 
at one end, the piece of twist burned slowly and regularly, the combustion 
proceeding much more deliberately than if the same piece of gun-cotton had 
been ignited in the usual manner in air, and being accompanied by only a 
very small jet or tongue of pale yellow flame, which was thrown out in a line 
with the burning surface when the gun-cotton was ignited. The same result 
was obtained in currents of those gases when passed through a long, wide glass 
tube, along which the gun-cotton-twist w r as laid, one end being allowed to 
project some distance into the air. The projecting extremity being ignited, 
as soon as the piece of twist had burnt up to the opening of the tube through 
which the gas was passing, the character of the combustion of the gun-cotton 
was changed from the ordinary to the slow form above described. On 
repeating this form of experiment in currents of hydrogen and of coal-gas, 
the ignited gun-cotton burned in the slow manner only a very short distance 
inside the tube, the combustion ceasing altogether when not more than from 
half an inch to one inch of the twist had burnt in the tube. The same 
result was observed when the current of gas was interrupted at the moment 
that the gun-cotton was inflamed. It was at first thought that this 
extinction of the combustion of gun-cotton by hydrogen and coal-gas might 
be caused by the very rapid abstraction of heat from the burning surface of 
gun-cotton in consequence of the diffusive powers of those gases; but when 
the experiments were made in perfectly closed vessels, the piece of gun- 
[vol. iv.] 18 
