56 
CAPTAIN NOBLE AND ME. E. A. ABEL ON FIEED GUNPOWDEK. 
strain on the gun, by the use of powder properly adapted in size of grain to the calibre 
and length of bore proposed to be used. 
Rodman’s conclusions on this head are extremely valuable, although, as has been 
elsewhere pointed out*, some of his experimental results are open to grave criticism. 
His experiments on the relation between the tension and density of powder (the powder 
being placed in a strong shell and fired through a small vent) were not carried far enough 
to be of much value ; but on Plate 13. fig. 2 we have represented his results in comparison 
with those of Rumfokd. 
Rodman also made an attempt to determine the pressure that would be exerted when 
powder was exploded in its own space. He fired the charges, as before, through a vent 
in a strong shell, and considered that the maximum pressure would be realized before 
the shell burst. His results were very various, ranging from 4900 to 12,400 atmo- 
spheres, the highest tension being obtained with the smallest charge. These anomalous 
results were probably due to the distance from the charge at which his instrument was 
placed, the products of combustion doubtless attaining a very high velocity before acting 
on the piston. 
In 1857 Bunsen and Schischkoff publishedf their very important researches on 
gunpowder. Their experiments were directed, first, to determine the nature and pro- 
portions of the permanent gases generated by the explosion of gunpowder ; secondly, 
to determine the amount of heat generated by the transformation. With the aid of 
these experimental data they deduced, from theoretical considerations, the temperature 
of explosion, the maximum pressure in a close chamber, and the total theoretical work 
which gunpowder is capable of performing on a projectile. 
The powder in these experiments was not exploded, but deflagrated, by being allowed 
to fall in an attenuated stream into a heated bulb in which, and in the tubes connected 
with it, the products were collected. 
The transformation, according to these experimenters, experienced by gunpowder in 
exploding, is shown in the following scheme. It will be observed that the permanent 
gases represented only about 31 per cent, of the weight of the powder, and occupied at 
0° C. and 760 millims. only 193 cubic centims. — that is, approximately, 193 times the 
volume occupied by the unexploded powder. 
* Noble, “Tension of Fired Gunpowder,” Proc. Eoyal Institution, vol. vi. p. 282. 
t Poggendokff’s ‘ Annalen,’ vol. cii. p. 325. A translation of Bunsen and Schischkoff’s memoir appeared 
in the occasional papers of the Eoyal Artillery Institution, vol. i. p. 297 ; see also, at p. 312 of the same 
volume, Mr. Abel’s remarks on Bunsen and Schischkoff’s results. 
