THE 80-TON GUN. 
465 
The results obtained in the 14^-in. calibre are shown in italics, 
underneath the similar ones obtained in the 15-in. calibre. We have 
here six pairs of rounds which are comparable in all respects; and it 
will be seen that the increase of calibre has so facilitated the com¬ 
bustion of the charge and added to its effect upon the projectile, that a 
higher velocity accompanied by a lower pressure has in every case 
been gained. These advantages are due to the shortening of the 
cartridge, which thus burns up more uniformly, and to the enlargement 
of the base of the shot, so that a greater surface is exposed to the 
action of the gas. On the other hand, the enlargement of the diameter 
of the shot causes it to be more retarded during flight by the air, and 
also enables the armour-plate to present greater resistance to pene¬ 
tration. Owing to these two causes, then, we see from the last column 
of Table A that when equal charges are employed a positive loss in 
penetration at 1000 yds. results from boring up the gun. This, how¬ 
ever, is not the right way to calculate the powers of the respective 
calibres. The object of the artillerist is to get the best ratio of 
penetration to pressure, not to charge; and if an increase of calibre 
enables him to use larger charges without increased pressures, and 
so to obtain additional penetration, his object will have been gained. 
Thus, if round 2 in the table be compared with round 13, it will be 
seen that 230 lb. of l*5-in. cubes can be fired in the 15-in. bore 
without giving quite so much mean pressure as is given by 220 lb. of 
the same powder in the 14|-in. bore, while a higher penetrating power 
is obtained. Again, comparing rounds 7 and 20 in the table, fired 
with the 2-in. cubes, it appears that with exactly the same penetrating 
power, at 1000 yds., a considerable reduction in pressure is obtained by 
the increase of calibre. Rounds 3 and 19 also exhibit a good increase 
of penetration, but at the expense of some additional pressure.- 
This portion of the experiment may be briefly summed up in the 
statement that increasing the diameter of the bore by half-an-inch 
simply made a bigger gun of the piece ; and, as might be expected, 
the big gun proved more powerful than the small one—the difference 
being obvious, even with so small an enlargement. 
We now come to something more novel. The science of explosives, 
though it has made rapid progress during the last few years, is far 
from being thoroughly understood yet, and still possesses the charm of 
offering its votaries much untrodden ground to explore and many new 
facts and combinations to discover. No matter how simple the con¬ 
ditions, how thoroughly ascertained the component variables, a new 
experiment with gunpowder almost always yields some unexpected 
results; and I have now to relate how the power of the 80-ton gun 
was suddenly increased in a very remarkable degree. 
As was pointed out in the previous paper on this subject, the great 
object of the artillerist is to diminish the maximum pressure of the gas 
on the surface of the bore to the lowest point consistent with good 
results as regards velocity, but to sustain this low maximum as long 
as possible. In fact, a gunner acquainted with his art would like a 
uniform pressure in the gun up to the moment of the shoffs quitting 
the muzzle* When a cartridge is rammed home, and the projectile 
60 
