THE ROYAL ARTILLERY INSTITUTION. 
37 
The number of shot of different rounds fired at these plates is as follows:— 
12-pr. Armstrong. 
25-pr. „ . 
. 5 
. 16 
40-pr. „ ... 
..... 11 
68-pr. ,, . 
. 10 
Total 42 
But the plates are still firm and in good order: and the wall is in as complete 
a state for defensive purposes as before the firing commenced. 
May 16th. 
The experiment was continued with a 100-pr. Armstrong gun, firing for 
the first 10 rounds shell filled with sand: weight empty 95 ^ lbs., full 104 lbs.; 
charge 12 lbs.; then 4 rounds solid cast-iron shot from 68-pr. 95 cwt., with 
a charge of 16 lbs.; then 21 rounds, alternately 8-inch shell and 100-pr. 
Armstrong shell. With the 8-inch shell Pittman's naval fuze was used; with 
the Armstrong shell, the Pillar fuze. Every shell burst on striking. Bange, 
400 yards. 
The 100-pr. shell filled with sand penetrated all the plates, except the 
3J-inch. The first shell that struck this plate did apparently no damage at 
all; it broke up, making a small indent on the plate; another, however, on 
striking near the same place, broke half the plate away and exposed the 
masonry. 
After 10 rounds of 100-pr. blind shell and 4 rounds solid 68-pr. shot 
had been fired the plates were so damaged that live shell were used. 
The live shell did very little damage when they struck the iron plate, not 
nearly as much as the blind shell, owing probably to its bursting before the 
whole of its force was expended on the plate; but when the live shell struck 
where the masonry was exposed they caused great damage, and soon brought 
the wall and surrounding masonry to such a state that a few more shell 
would entirely have destroyed it and the casemate next to it. 
This experiment shews that masonry covered with 2-inch iron plates will 
effectually resist a 12-pr. Armstrong shot at 600 yards. 
Covered with 2^-inch plates, it will effectually resist a 25-pr. Armstrong 
shot, at 600 yards. 
Covered with 3-inch plates, it will effectually resist a 40-pr. Armstrong 
shot, at 600 yards. 
But the 3 \-inch plates are not sufficient to resist the heavier nature of 
projectiles. 
The iron plates were manufactured of rolled iron by Messrs Brown Hughes, 
and Co., Newport. 
6 feet 6 inches by 2 feet 6 inches, 7 n n\ q oi 
4 feet 6 inches by 2 feet 6 inches, ) ’ 25 ’ 2 
inches in thickness. 
Each plate was secured to the masonry by six 2-inch bolts which passed 
through the plate and were secured by double nuts to railway bars buried 
vertically 4 feet in the masonry; the top of these bars were again secured 
by bolts to the rear of the work. 
