1872.] Modern Cannon Powder. 7 
Pressure per square inch at 
a aaa ea ———_ “me -—_ra 
Mean of 
2 A B Cc Band C I 4 To. 14 
ie eee eae OOF ———— ————— ce" OX 
ey ee oO o é oO o oO o o 
~ c Qa, Q Qa a a Qa oO, ay 
© Oo is} fo} 5 ° fo} fo} ° fo} fo) 
13) 8 1S) i?) is) is) i=) i?) 
be laa A se oe ieee ee ok a Bee ORS 
eS Ss) 8 2S ee ee Bs ee fe be aie 
= Sy Se ie A ere ee er ee 2S 8 & oY 
o ae Wie 3s oS 5 et Sie, CE ie cS i S| os cS) ea ce 
Yo Ce tS) 48) Se eg Cm OY SY we oe 
Be iS SSS S&S & & S&S SBS SS SS SF S&S |S S&S & 
= B aoanmnmAmn vA a am Q A A aoamara wa 
ee exer Gre 
—6o lbs. } 1327 4824 51°4 — 32°5 — 263 — 294 24°53 — 10°5 124 89 4°8 6°5 3'2 4'5 
D 1742) 
Pellet— 64 
lbs. Ds} x57 5164 25°0 — 22°99 — 20°I — 2I'5 22°2 — 104 II'2 9g'0 5°2 63 — 43 
1677 .- 
eres. | 1344 4947 189 — 17°77 — 180 — 179 193 14'7 123 170 99 7° 70 8'7 49 
—6r lbs. 
W.A. Peb- 
Me Bh 5384 20°9 — 21°3 — 20°0 — 20°7 21'9 160 13°5 12°2 114 g'0 82 4°0 5'0 
T3752), =: 
The letters and numbers refer to the plugs, reading from 
breech to muzzle as in the 8-inch gun Plate II., and it is 
evident that, with the mild kinds of powder the mean 
maximum pressure in the powder chamber, and also the 
pressure at different parts of the gun, arrived at by these 
two perfectly different methods of observation, agree very 
closely; while the intense’ local, or wave, action of the 
violent R.L.G. is also very apparent. The intensity of 
this local action depends, moreover, ina great measure upon 
tnesleneth of the cartridge; if this be- excessive these 
objectionable strains at once begin to appear even in the case 
of pellet or pebble powder, as has been clearly demonstrated 
in the the 11°6-inch 35-ton gun, firing 120 and 130 pounds 
of powder, and also in the ro-inch gun when tried with 
proof-charges of 87°5 pounds. 
The specification upon which pebble powder is received 
mony the trade is very strict. Not only must the 
powder be very uniform in size and density of grain, 
but it is also further tested by firing battering charges 
(35 pounds) of every supply from an 8-inch gun, when 
the pressure in any part of the powder chamber must not 
exceed 20 tons on the square inch, and the variations 
in velocity must be comprised within narrow limits. By 
thus severely testing the whole of our supply of this new 
powder, the committee are able to ensure that it shall never 
depart in any important degree from the required standard. 
The admirable results obtained in the 8-inch and 1o-inch 
guns with pebble powder have been maintained in all the 
heavier natures, insomuch that the use of this powder, 
while materially reducing the strain upon the guns below 
