50 
CAPTAIN NOBLE AND MR. P. A. ABEL ON EIRED GUNPOWDER. 
collaterally with a series of experiments carried on by a Committee appointed by 
the Secretary of State for War, with the view, among other objects, of determining 
the most suitable description of powder for use in heavy ordnance, which is still con- 
tinually increasing in size ; indeed our main object has been to endeavour to throw 
additional light upon the intricate and difficult subject under investigation by that 
Committee. 
There are perhaps few questions upon which, till within quite a recent date, such 
discordant opinions have been entertained as upon the phenomena and results which 
attend the combustion of gunpowder. As regards the question alone of the pressure 
developed, the estimates are most discordant, varying from the 1000 atmospheres of 
Robins to the 100,000 atmospheres of Rumford; or even, discarding these extreme 
opinions in favour of views which have been accepted in modern text-books as more 
reliable, the difference between an estimate of 2200* and of 29,000f atmospheres is 
sufficiently startling as regards a physical fact of so much importance. The views 
regarding the decomposition of gunpowder are nearly as various ; and we therefore think 
that a description and discussion of our own researches may be usefully preceded by a 
short account of the labours of the previous investigators of this subject and of the 
grounds upon which their conclusions were based. 
In the year 1702, De la Hire, who, according to Robins, was the first writer on the 
force of fired gunpowder, supposed that it was due to the increased elasticity of the air 
contained in and between the grains, the function of the powder itself being merely 
that of a heating agent. Robins (who, however, greatly underrated the temperature of 
explosion) pointed out that the elasticity so acquired would not exceed 5 atmospheres, 
and that such a pressure was not the t.wo-hundredth part of the effort necessary to 
produce the observed effects. 
Robins J, in 1743, read before the Royal Society a paper in which he described expe- 
riments tending to show that gunpowder, when fired, generated permanent gases which, 
at ordinary temperatures and atmospheric pressure, occupied a volume 236 times greater 
than that of the unexploded powder. He made further experiments to show that, at 
the temperature which he conceived to be that of explosion, the elasticity of the per- 
manent gases would be increased fourfold, and hence the maximum pressure due to 
fired gunpowder would be about 1000 atmospheres. 
Robins considered that the whole of the powder (such as he employed) was fired before 
the bullet was sensibly moved from its seat. He argued that, were such not the case, 
a much greater effect would be realized from the powder when the weight of the bullet 
was doubled, trebled, &c. ; but his experiments showed that in all these cases the work 
done by the powder was nearly the same. 
* Bloxam, C. L., ‘Chemistry, Inorganic and Organic,’ 18.67, p. 427. Owex, Lieut.-Col., R.A., ‘Principles 
and Practice of Modern Artillery,’ 1871, p. 155. 
t Piobekt, Gf., ‘ Traite d’Artillerie Theorique et Experimentale,’ 1859, pp. 354-360. 
t New Principles of Gunnery, 1805, pp. 59-74. 
