504 
PENETRATION OP EARTH AND MASONRY. 
Difficulty iu 
obtaining 
effective 
hits. 
Any task can 
be perfor¬ 
med. 
Best way of 
attacking 
escarp. 
Large shell. 
Casemates. 
Tables of 
penetration. 
It is most difficult to obtain a reasonable proportion of effective bits 
with high angle fire for the first form of attack. If the gun is placed 
fairly close to the work small charges must be used in the gun, and the 
shell is apt to strike with such feeble velocity that it fails to penetrate 
and does little more than roughen the surface of good masonry. Light 
shells are almost useless for, when firing at hard masonry where a 
given falling angle is common to a large and a small shell, the lesser 
may have so little momentum that it would hardly scratch the sur¬ 
face, where the big shell penetrates and utilises its bursting charge. 
Another reason for using the heaviest possible shell. 
If, on the other hand, the gun is taken to a distance with a view to 
the use of a larger firing charge and an increased striking velocity, 
rather a larger proportion of shell are wasted by not striking at all. 
Any required task ccm be performed. It is a mere question of ex¬ 
penditure, but many practical artillerymen agree that, if very large 
howitzers are not available, and unless some great advantage is to be 
gained by breaching an escarp, it is better to leave it alone. A good 
masonry escarp wall, protected by a fine earth, sand, or shingle covering 
mass, would need an expenditure of ammunition which would, otherwise 
applied, effect the destruction of everything that the escarp protected. 
If such a task is set, then by far the most effective plan is to shoot 
from a fairly long range, chosen with reference to the quality of the 
masonry attacked, so as to ensure each shell that strikes burying itself 
in the masonry and there exploding, when a few shell, striking fair, 
may do a great deal. Make the crest of the covering mass the mean 
point of impact; that is, see that during the firing, half the shells go 
over and half strike the mass, using such an elevation that shells that 
just go over will strike the masonry some little way down; while those 
that are short will not ricochet but will blow away the covering mass, 
gradually permitting a less angle of elevation to the guns until the 
defences are reduced to a dead level. 
For such work none but the largest shell can be economical. A 
large remaining velocity is a necessity. 
Another form of masonry is met with in defences, namely, casemates 
and overhead cover of various kinds. These, whether protected by 
earth or not, are best attacked by large shell filled with high explosives, 
fired at very high angles of elevation, and fitted with delayed fuzes. 
If such can be got down through the earth covering, on or into the 
masonry, or through the masonry into the casemate, the latter must be 
wrecked. A large mine of a high explosive properly tamped, as such 
a shell would be, is irresistible. Excavations, such as galleries, might 
be attacked in the same way, but it is difficult to see how their presence 
could be made known, except by the accident of a shell getting into 
them, when their debris blown into the air would tell a tale. 
I do not append any tables showing penetration into earth or masonry. 
Nothing practical appears to be deducible. Shells will sometimes, 
under favourable conditions, penetrate 40 feet of earth, but so much 
depends on the nature of the earth, and on varying circumstances that 
it is difficult to lay down any law. Each target that offers itself must 
be taken on its merits, 
