42 British Artillery Matériel. {January, 
be employed without these local pressures appearing should 
then be accepted as the battering charge. Experience has 
clearly demonstrated that, by limiting the charge in ac- 
cordance with this rule, the maximum useful effect is attained 
without any risk of undue pressures in the gun; and that if 
the charge thus fixed is exceeded, a portion of the powder is 
wasted, and the gun rendered liable to undue local pressures. 
The charge of 85 lbs. of pebble powder exceeds that which 
the above-mentioned rule would give for this gun, but to no 
dangerous extent, although the maximum useful effect of 
the charge is not obtained. 
In determining the battering charge, a comparison between 
the power of the gun with a calibre of 11 and 12 inches 
came incidentally under the notice of the Committee; the 
results of the experiments clearly demonstrated that a gun 
of 145 inches length of bore is more powerful as a battering 
weapon with a 12-inch calibre than with one of 11-inch, 
and this is still more evident when it is considered that with 
a 12-inch calibre the gun would probably consume 95 lbs. of 
powder with as good useful effect per lb. of powder, and with 
no greater pressure per square inch than it does 85 lbs. of 
powder with an 11-inch calibre. 
The detail has been published of various experiments 
with 35-ton rifled muzzle-loading gun, No. 1. Shot, 700 lbs. 
The pressures were determined by crushers fitted by 
means of a copper cup at the bottom of the bore (A), bya 
screw gauge inserted instead of the vent plug (B), and by 
a gauge screwed into the base of the projectile (C). After 
round 8 the gun was fired by an electric tube placed in the 
cartridge at 12 inches from the bottom, the wires passing - 
through a groove in the shot to the muzzle. 
The following are a few of the points elicited by these ex- 
periments, which appear of the greatest general interest :— 
1. If the powder be burned uniformly in the gun, without 
any indication of wave action, the pressure increases with 
the increase of charge, at first rapidly, but after 20 tons on 
the square inch has been exceeded, then very slowly. In the 
whole course of the Committee’s experiments a uniform 
pressure by crusher gauge of 30 tons in the powder chamber 
has never been attained; this fact appears strongly to 
corroborate the experiments carried out by Captain A. Noble, 
at Elswick, on the pressure produced by ignited powder in 
closed vessels, which indicated that the maximum pressure 
produced by ignited powder in a perfectly closed space is 
somewhat less than 40 tons to the square inch. 
