114 
MINUTES OF PROCEEDINGS OF 
will appear from the following remarkable result of proof of powder with the 
8-in. gun:—^__ 
Description of powder. 
Density. 
Corrected 
Corrected pressures. 
M. Y. 
A. 
B. 
C. 
W.A. pebble, 19-20. 10. 74 
n 2-inch cubes, 9.6.74 
1-797 
1-75 
1412 
1414 
15*9 
16-7 
16-0 
17-0 
15- 0 
16- 0 
The old theory of grains of powder burning uniformly from the surface to the 
centre would utterly fail to account for such results as these, and even when 
combined with the density theory it is difficult to give a satisfactory explan¬ 
ation where the densities differ so little. If, however, the porosity of the 
grains be taken into consideration, the difficulty to a great extent disappears; 
for when once it is admitted that the flame may burroAV itself into the mass 
of the grain, it becomes a mere question of how far it does so in order to 
account for a violence of explosion even greater than was exhibited by the 2A 4 
grains referred to in the beginning of this paper. 
Another important element in its influence on the rate of combustion of 
gunpowder, is the nature of the charcoal used. In a great many respects this 
is very obscure. Prom an observation of the consistent manner in which the 
pebble-powder supplied by Messrs. Hall and Son gave low pressures with 
high velocities, the author was led to infer that the charcoal was the main 
cause. The density of the powder was low, but Messrs. Hall burn their 
charcoal rather hard, the effect of which is to make it, when ground, gritty, 
or more of the nature of fine-grain than dust. Each particle of charcoal 
must take time to burn, and the larger the particles the slower will be the 
combustion. This cause more especially affects the initial stages of com¬ 
bustion, where the modification is most required, while the low density gives 
all the advantage of a quick-burning powder aftenvards. 
It is thus evident that out of the various methods which are open in powder- 
making for the purpose of moderating the rate of combustion and rendering 
it suitable to any size of gun, many choices may be made, so long as the 
applicability of the powder to the gun is kept in view, and uniformity is 
secured. The most recent experiments of the Committee on Explosives lead 
them to infer that cubes of 1J or u ins. with a density of about 1*75 will 
prove most suitable ; and thus a muzzle velocity of about 1400 f.s. may be 
obtained with a projectile of 800lbs. from the 88-ton gun with a pressure 
of less than 25 tons in the bore of the gun. The following are given as 
samples—the charge being 130 lbs., and weight of shot 800 lbs.:— 
Description of powder. 
* CQ 
0 
O) 
p 
W.A. 1^-inch cubes, 13.4.74 
1-75 
W.A. 14-inch cubes ...... ^ 
It 
1-75 
EYDPvirrmnf 
M. Y. 
Pressure in tons per square inch. 
Date. 
No. 
Axis of 
bore. 
Centre oi 
charge. 
Base of 
shot. 
Feet 
travel. 
A. 
B. 
C. 
1. 
2. 
QQ ft ft A 
(13 
1380 
22-9 
21-6 
17-3 
19-9 
15-6 
do* / • / 41* 
f 14 
1380 
25-0 
24-6 
22-7 
20-2 
16-1 
f 0 to ftA 
(79 
1393 
vent 
23-7 
23-3 
19-7 
14-2 
f o. id. 
181 
1386 
. u 
23-6 
23-1 
19-0 
13-6 
f 89 
1403 
24-3 
246 
22-9 
18-7 
14-9 
1 
f QA 1 Q ftA 
3 91 
1398 
22-5 
24-3 
22-5 
20-5 
14-7 
V,oU. id. 
1 92 
1406 
23-7 
22-9 
22-6 
21-7 
— 
193 
1414 
23-2 
23-3 
23-3 
20-0 
— 
