426 
MINUTES OF PROCEEDINGS OF 
This is one of the most important points Bodman has drawn attention to, 
for in this way the maximum pressure can be reduced, and yet the initial 
velocity maintained. 
As, however, there is a danger of carrying even this advantage to an 
extreme, I shall premise another set of experiments made by Bodman, which 
will serve to illustrate the point I refer to. 
He tried statical pressure through the medium of soft wax in cylinders 
bored out like a gun on a small scale (see Big. 5). Yarious lengths of the 
bore were filled with the w r ax and the bursting pressures obtained. The 
calibre was B128 ins., and the thickness of metal one calibre. The follow¬ 
ing are the results :— 
Length pressed. 
Mean bursting 
pressure. 
Length pressed. 
Mean bursting 
pressure. 
ins. 
tons. 
ins. 
tons. 
6 
24-0 
7 
27-1 
5 
26-8 
2 
33-0 
4 
32-0 
2 
29-4 
3 
34*8 
2 
40*3 
2 
39*1 
2-6 
42-0 
Bodman considers that these pressures are high, owing to the want of 
perfect fluidity in the wax. They serve, however, to show a law which is 
represented in Big. 6, where the horizontal and vertical co-ordinates of the 
curve = represent the lengths of bore and bursting pressures respectively. 
The benefit to be derived from the operation of this law may be shortly 
stated thus: with two calibres the circumferential strength is increased by 
one-half, while beyond five calibres no advantage is gained by it. It will be 
noticed, that if the powder burn very slowly, the shot will move during the 
first and most important part of its course under a much smaller pressure 
than the gun is capable of sustaining, with a corresponding loss of velocity. 
The maximum pressure should be obtained as soon as possible, and should 
not be allowed to subside too rapidly, but should be continued as nearly as 
possible in accordance with the curve given above. The maximum pressure 
ought not, however, to be obtained so rapidly as to partake of the nature of 
a sudden pressure, i.e., it should not be obtained so rapidly as not to give 
the metal of the gun time to expand before it has reached its maximum. 
The law above given has also a very important bearing on the size of the 
bore of the gun; for, in addition to giving a smaller pressure per square 
inch, a larger bore will not throw the pressure so far forward with the same 
charge of powder. 
Committee on 'Explosives. 
Somewhat tardily in our own country this Committee has been appointed 
to consider, amongst other things, the question of most pressing importance 
before proceeding with the manufacture of very heavy guns, viz., to find a 
powder which, in the monster ordnance we are about to construct, will give 
the greatest initial velocity of projectile with the least strain on the gun. 
In our heavy service guns, when B.L.G. powder is used, we find the 
initial velocities .decreasing with the size of the gun; thus— 
Nature of gun. 7-inch, 8-inch, 9-inch, 10-inch, 600-pr. 
Initial velocity.. 1458, 1368, 1386, 1298, 1180. 
