72 
MINUTES OF PKOCEEDINGS OF 
secured to a strong iron girder frame the base of which turned back horizon¬ 
tally, and was strongly attached by nuts to vertical bolts let into the 
granite. 
The total thickness of this shield was 21 inches. 
The left or west embrasure was finished in a flat arch, height 6 feet, 
width 6 feet. 
It was closed by an iron shield, having an opening or port hole 28 x 42 
inches. 
The shield consisted of a solid rolled iron plate 13^ inches thick, manu¬ 
factured by Messrs Brown & Co. It was secured at top and bottom by 
iron railway bars, let into the granite in the course of construction, and these 
horizontal bars were again tied by transverse bars cramped at each end and 
built into the granite. 
The above dimensions are given in general terms. 
3. The guns selected for the trial of the casemate were, in respect to calibre 
and weight, of a class that may be expected sooner or later to enter largely 
into the general armament of ships of war; none of them exceeded 12J tons 
in weight. In these respects, therefore, they were fair representations of the 
power of an offensive fleet, and the effects produced by them on the structure 
may be taken as reliable data on which to base an opinion with regard to the 
comparative advantages of iron and granite (considered as to their powers 
of resistance only), as material for the construction of works of defence. 
The guns, projectiles, and charges were as follows - 
Calibre. 
Weight. 
Charge. 
Weight 
of shot. 
Striking velocity. 
600 
yds. 
1000 
yds. 
600 
yds. 
1000 
yds. 
ins. 
tons. 
cwt. 
lbs. 
lbs. 
lbs. 
lbs. 
ft. 
ft. 
10*0 
12 
2 
67 
41-3 
36-0 
280 
1273 
1209 
9-22 
12 
2 
66 
39'5 
30-25 
220 
1395 
1322 
8-00 
6 
19 
60 
26-0 
22-0 
150 
1369 
1292 
7*00 
6 
19 
72 
180 
— 
115 
1370 
4. The battery was placed at 200 yards from the casemate, but the charges 
were reduced to give a striking velocity equivalent to 1000 yds. and 600 yds. 
range, with the full service charges. 
The fire was opened on the 16th November, commencing with one round 
of solid steel shot from each gun against each shield. 
5. The results, so far as they can be traced before the debris are cleared 
away, may be stated in general terms as follows: 
The compound iron and wooden shield in the east embrasure was 
struck fair by 13 shots, viz. 
