THE 80-TON GUN. 
478 
throughout, the chamber principle being held in abeyance as a future 
development. 
The projectiles manufactured for the new calibre weighed just 
17031b., including the gas-check, being 237 1b. heavier than those 
fired from the 15-in. calibre. Since the powder-chamber had already 
been enlarged to 16 ins. and a proportionate charge had been fired, it 
was clear that a velocity equal to that previously obtained could not be 
expected with a shot so much heavier. Still, a gain in energy was 
anticipated, on account of the larger base on which the gas would act, 
or, as Captain A. Noble puts it, on account of the greater space within 
the gun in which the gas could expand and do work. The penetrating 
power at 1000 yds. would, it was thought, be diminished by the altera¬ 
tion, unless means could be adopted to obtain a higher velocity than 
calculation showed to be probable if the charges were burnt under the 
same conditions as before. 
Table E furnishes particulars of the rounds fired in the 16-in. calibre. 
In view of the great increase in the weight of the projectile, the 
charges began as low as 250 lb., and were increased by 10-lb. stages 
to 3001b., the results being exactly as anticipated—that is, a less 
velocity, a higher energy, and a lower penetrating power were given 
by round 6 of Table E than by round 45 of Table D; and the same 
may be said of each round capable of comparison. The pressures were 
practically equal in the two calibres. 
It was now thought desirable to try the effect in the enlarged bore 
of increasing the space occupied by the cartridges, and they were 
farther lengthened till the portion of the bore behind the projectile 
contained 32 cub. ins. for each pound of powder instead of 30 cub. ins. 
Rounds 7 to 16 and round 19 show that this addition to the air-space 
permitted a considerable increase to the charge, which rose to 3501b., 
while a farther enlargement of the air-space to 34 cub. ins. enabled the 
Committee to venture on the vast charge of 370 lb.—the largest ever 
fired as yet. A glance at the table will show that the work done by 
350 lb. with 32 cub. ins. volume per pound is about equal to that 
performed by 370 lb. with 34 cub. ins. volume, and an attentive con¬ 
sideration of the successive rounds appears to lead to the conclusion 
that the results rise steadily up to the point of 32 cub. ins. volume, and 
rather exhibit a tendency to fall off in progressiveness after 34 cub. ins. 
A few rounds will probably be fired to determine whether 33 cub. ins. 
and a charge of 360 or 370 lb. will not just reach the top of the curve, 
and give the maximum effect attainable. At any rate, we have now 
arrived at a higher point than w r e had reached previously, and have 
beaten round 48, both in energy and penetration; that is, we can 
drive a bigger shell through a thicker plate than we could before. 
Still, we cannot afford to rest and be thankful, for probably it will not 
be long before farther progress will become inevitable, if we are to 
retain the lead. Sir W. Armstrong's 100-ton M.L. guns, with a 
calibre of 17 ins., firing a shot of 20001b., are guaranteed to yield 
energy equal to 25,000 ft. tons; and as the bores will be of great 
length and the velocity required to produce this effect will be only 
1343 f.s., there is little doubt that the guarantee will be largely sur¬ 
passed. Krupp is said to be constructing a breech-loader to weigh 
61 
