THE EIGHTY-TON GUN, OR WOOLWICH INFANT. 249 
you hear it. That this might he expected is obvious from the 
fact that the speed at which sound travels is not greatly in ex- 
cess of 1,100 feet per second ; so that for it to overtake the shot 
a very long range and considerable elevation is required. The 
pressure against the base of the projectile would naturally be 
somewhat less than that against the bottom of the bore, because 
the shot is fast moving away from the gas ; but it is a little 
difficult to explain why the difference is quite so great as it is. 
We may run briefly through the succeeding trials of the gun, 
which have been in pursuit of the same ends as the first ; that is 
to say, the object has been gradually to feel the way experi- 
mentally to the condition under which the greatest velocity can 
be given to the shot without subjecting the gun to a pressure 
greatly exceeding 25 tons per square inch. 
On Nov. 18 and 19, and Dec. 9 and 10 last, fifteen rounds 
in all were fired, which concluded the trial of the gun at its 
first calibre of 14J inches. In March it was again fired, when 
the bore had been increased to 15 inches ; and in May, when the 
powder chamber had been increased to 16 inches. The general 
results of these trials have been to show that the powder is 
better, or at all events more uniform, in its effect as the density 
is slightly increased above the average ; that the employment of 
a charge over 250 lbs. was unprofitable and wasteful until the 
calibre arrived at 1 5 inches ; and that the best results, not only 
those which are least injurious to the gun, can be obtained with- 
out increasing the pressure to 30 tons. Of course, as the calibre 
increases, the power of burning powder to advantage does so too. 
Probably a 2-inch cube or grain of powder might be employed 
to greater advantage when the calibre is brought up to the full 
amount of 16 inches, and the chamber still further enlarged. 
At present experiments are being continued with l^-inch cubes, 
but very promising results were obtained with those of If and 
2 inches during the trials. A projectile of 1,460 lbs. weight 
has been fired. The enlargement of the chamber appears to 
have good results, but a sufficient number of rounds have not 
as yet been fired to enable a certain opinion to be given. 
This is the first heavy gun whose chamber has been enlarged ; 
but some successful experiments have been made with field guns 
in the Koyal Arsenal recently. It may be observed we are not 
as yet finally committed to an enlarged powder- chamber, for the 
enlargement has at present been limited to the intended final 
calibre of the gun. 
The greatest velocity that has yet been obtained with the 
80-ton gun is about 1,550 feet per second. 
To pass on to the more interesting question of the probable 
power and uses of the gun on service. 
The most important matter is the power to penetrate armour. 
