THE EIGHTY-TON GUN, OR WOOLWICH INFANT. 245 
matters that the powder is exactly burnt up as the shot arrives 
at the muzzle ; and were it so, the pressures, as the projectile 
got near the muzzle, would be very small, because the burning 
surface and quantity of gas generated becomes less and less as 
the grain becomes smaller. Hence it is easy to see the difficulty 
of avoiding the escape from the muzzle of partially burnt grains 
of powder, undesirable as that may be. 
The word “ grain ” has been hitherto used on principle ; but 
the form that the grain takes in the charges of the largest guns 
is that of a rough cube with an edge from 1J to 2 inches in 
length, each single grain, or “ pebble,” as it is called, con- 
taining in itself a considerable charge of powder. So far the 
size of the powder-grain only has been considered. The density, 
and even the glazing, have also to be taken into account. The 
density indeed entirely alters the conditions, for not only does 
powder burn more rapidly as it is less dense, but also, it has 
been recently shown, the assumption that the grain or pebble 
burns evenly from the outside to the centre is quite untrue 
generally, for the pebbles burn through in certain places and 
become honey-combed or sponge-like during combustion, in all 
powders of ordinary density, and are blown out of the gun, and 
may be picked up afterwards in this condition. 
The question of the powder has been discussed at some 
length, because it is necessary to know something of the nature of 
the problem to be worked out, in order to understand the reason 
for the long series of experiments that is being now carried on 
in the Woolwich Arsenal. 
In the design of the ammunition there is nothing differing 
essentially from that of other large guns except the magnitude. 
The projectiles are eventually to be of the same general form as 
our other service projectiles. The armour-punching shot or shell 
have ogival heads and sharp points, and are made of chilled 
iron on Sir W. Palliser’s system. The section of such a head is in 
the form of a rather pointed gothic arch, and the metal in the head 
is chilled white and very dense and hard, while that in the body is 
mottled. Projectiles of this kind have extraordinary powers of 
penetration ; the metal in the head being of the kind to stand 
up under the compression of impact, and to cleave its path into 
the soft iron of which armour is necessarily composed, while 
the base has more tensile strength and holds well together. 
That the head has the qualities of intense hardness is seen in 
the fact that the point never flattens, but remains sharp to the 
end, while the crushing strength of the metal is apparent from 
the fact that it remains quite cool after impact, while the 
pieces^ plate that have suffered compression are for a con- 
siderable time intensely hot. 
The final calibre of the gun is intended to be 16 inches, 
