PENETRATION OF EARTH AND MASONRY. 
499 
strike are more or less wasted by not doing all the work of which they 
are capable. 
The instances in actual practice in which shells fired from guns or Comparison 
howitzers produce as great a result as similar shells, buried in favour- ^ e ^ x s e ^ e n. nd 
able positions, and fired by electricity or other means, so as to act as 
deliberately placed stationary mines, are extremely rare, though occa¬ 
sionally what appears to be an increased effect is obtained by a fired 
shell. 
There are several causes, some of which have not been generally Ca^sesof^ 
recognised which tend to this result. effect. 
Powder bursting charges, in shell fired from ordnance, set back from Powder 
their own inertia, in many cases destroying the grain of the powder, sh3i? ed 
and even at times crushing the charge into a solid mass, losing the air 
spacing most favourable to disruptive effect; so that, even supposing 
one of these shell to be burst in a position similar to a shell placed at 
leisure, in the place most favourable to effect, and then exploded, the 
fired shell is at great disadvantage, but not one fired shell in many 
may reach, and be burst in, this desired position for, as will presently 
be shown, the course of a shell in earth, &c. is not regular. 
Even supposing a shell to be dropped vertically into earth and its Difficulty of 
course through the earth to continue straight, the moment of explosion sheii^at the 
would be extremely difficult to arrange, yet there is only one point in right place, 
its course through the earth where a maximum effect could be obtained. 
Again, suppose it is attempted to obtain this maximum of effect by Long fuzes, 
using a long delay faze, to burst this shell after it has come to rest, 
then the exact nature and resistance of the earth would have to be 
known, an almost impossible matter for an attacker, for if the shell 
rests too deep its effect on earth is nil, and of course even on an experi¬ 
mental ground, with every fact available, it would bo most difficult to 
prophesy the exact penetration. 
High explosive filled shell are not so much affected by their contents High expio- 
being set back; in fact with some of the explosives which have been siveshe11, 
used, the setting back and breaking up of the contents of the shell has 
rendered them more violent and effective. If these are burst with 
fuzes with no delay, however, their action is often so quick that they 
make very small craters. They then become, in cases where they 
ricochet, very powerful man-killing projectiles, far more effective than 
shrapnel, as the body of the shell is broken into small pieces which are 
driven with great force and act in all directions; but shell which act 
as man-killing projectiles are never effective in earth. 
There is of course an initial difficulty in firing shell filled with high Difficulties 
explosives, for owing to the enormous rending power of these materials, SpioS? 
if a shell bursts in the gun, the destruction of the gun is almost certain slie11 * 
to follow. This has been entirely got over by the use of compressed 
air as in the Zalinski, Graydon, &c. guns; and there are some high 
explosives of very great power, which appear to be unaffected by the 
shock of discharge. As regards the attack of mere earth, however, 
and particularly of loose earth, high explosives can hardly be expected 
to produce the effect which it is possible to obtain with the slower and 
more sustained action of powder filled shells. The effect which is 
65 
