252 
MINUTES OF PROCEEDINGS OF 
produced by the increased rate of burning of each grain. The direction 
and extent to which altering the size of the grains will affect the rapidity 
of action of the powder, will depend upon the conditions under which 
the powder is ignited—such as whether it is exploded in an open train ; 
in small enclosed charges; in large enclosed charges; whether the 
charge, if large, be thick and short, or long and thin; whether it fits 
the bore closely; which portion of it is first ignited, &c.” 
Now, repeated experiments have shown that with relatively small 
charges, a small-grained powder gives higher velocities than one of 
larger grain: the effect of slow ignition is here but little felt, owing 
to the flame having to traverse a comparatively inconsiderable distance 
to complete the ignition of every grain. But in relatively large charges, 
where the cartridges are necessarily long , the* reverse is the case, and the 
larger-grained powder gives the highest velocities. 
In fact, in the latter case, the effect due to velocity of combustion in 
the smaller grain is more than counterbalanced by the facility given to 
rapidity of ignition by the larger interstices of the larger grain. 
The following table, giving the mean results of an experiment lately 
carried out by the Committee on Explosives, forcibly illustrates this 
reasoning. 
Table IY. 
Showing the mean results of practice from the 9-pr. rifled M.L. gun of 
8 cwt., with gunpowders differing in size of grain, and projectiles 
weighing 9 lb. :— 
Charge, l|lb. 
Charge 
, 14 lb. 
Charge, If lb. 
Nature of 
Tj rH 
<D +3 
Pressure by- 
crusher gauge in 
tons per sq. in. 
Nature of 
i 4 h 
> o 
^ s 
CD 
Pressure by- 
crusher gauge in 
tons per sq. in. 
Nature of 
o 
'Ti pH 
a> J, 
Pressure by- 
crusher gauge in 
tons per sq. in. 
powder. 
Sk 
o| 
At cen¬ 
tre of 
charge. 
At base 
of shot. 
powder. 
Xfl 
°J 
At cen¬ 
tre of 
charge. 
At base 
of shot. 
powder. 
t <S 
pQ-H 
0 | 
At cen¬ 
tre of 
charge. 
At base 
of shot. 
4 to 6* 
ft. 
1156 
6-9 
5-3 
4 to 6* 
ft. 
1263 
8-5 
6-4 
4 to 6* 
ft. 
1366 
10-5 
8-9 
4 to 8, •) 
E.L.G. S 
1169 
7-5 
3-0 
4 to 8, 
R.L.G. j 
1277 
9*6 
7-7 
4 to 8, > 
R.L.G. j 
1368 
10-3 
7-1 
6 to 8, ■> 
L.Gr. J 
1185 
8-4 
6-1 
6 to 8, 7 
L.Gr. S 
1271 
8-9 
6-3 
0 to 8, ■> 
L.G. 5 
1336 
9-5 
7-6 
In the experiments recorded above, the powder was all granulated 
from press cake of the same date of manufacture, and the only variable 
was the size of grain. 
It is apparent that the L.Gr. size gives a lower velocity than the 
E.L.Gr. with large charges and comparatively long cartridges. I think, 
therefore, that instead of a beneficial result being obtained by the 
use of a relatively large charge of small-grained (L.Gr.) powder in a 
* R.L.G., with smaller grains sifted out. 
