THE DEVELOPMENT OF ARMOUK. 
515 
Attack on Pxate No. 6,559. 
No of Round. 
Weight of 
Projectile in 
Strikiug 
Velocity in 
Striking Energy 
in Foot-Tons. 
Energy per ton of 
Plate in Foot-Tons. 
Perforation through 
Iron by Tresidder 
Formula in Inches. 
Relation of Calcu¬ 
lated Perforation 
to thickness of 
Plate. 
Depth of Indent 
in Inches. 
Kg. 
Lb. 
Metre- 
Seconds. 
Foot- 
Seconds. 
I. 
45-5 
100-3 
608-4 
1996 
2771 
549-1 
14-0 
1-62 
4-9 
II. 
45-7 
100-8 
638-9 
2096 
3070 
608-2 
15-0 
1-78 
5.3 
III. 
45‘5 
100-3 
677-3 
2222 
3434 
680-5 
16-4 . 
1*89 
4-3 
IV. 
45-55 
100-4 
677-3 
2222 
3438 
681-3 
16-4 
1-89 
5-3 
Fig. 21. 
The first two rounds 
produced no bulges 
or cracks. The third 
struck nearer to the 
second than was in¬ 
tended, and horizontal 
and vertical through 
cracks were made to 
the plate edge, appar¬ 
ently starting from 
round II (see Fig. 21). 
A fourth round furth¬ 
er developed the 
cracks, but no bulges 
were made (see Fig. 
22 ). 
The plates were 
good, but the attack 
is not severe. The 
gun employed was 
only a 15-c.m. (5*9- 
in.) piece, which is 
small for a plate 8*66 
in. thick. The homo¬ 
geneous plate had a 
great deal of bone 
and stiff resistance in 
it, but judging from 
the way the cracks 
appear to start from 
the second point of 
impact, the metal was 
becoming strained and 
Fig . 22. 
