THE DEVELOPMENT OF ARMOUR. 
477 
Fig. 10. 
results of an experiment made to ascertain if hair furrows, wrinkles 
or surface cracks, 26 in all in a 5*75 in. Krupp nickel plate 
acted injuriously. The plate was 2*73 ra x T5 m (8 ft. 1T1 in. x 4 ft. 
11 in.) and weighed about 4^ tons. The following table shows the 
attack made. 
No. of round. 
Calibre in 
Weight of shot 
Striking 
velocity. 
Perforation through iron. 
Fairburn. 
Tresidder. 
e.m. 
in 
lbs. 
f.8. 
inches. 
inches. 
1 
15 
59 
112-4 
1560 
10-4 
10-2^ 
2 
15 
5-9 
112-4 
1891 
12-8 
13-6 
3 
15 
5-9 
112-4 
1734 
11-7 
11-8 
4 
21 
8-27 
209-4 
1431 
10-9 
10-3 
5 
21 
8-27 
209-4 
1641 
12-7 
12-6 
It will be seen by the figures that only rounds 2 and 5 perforated. 
The shot most nearly matching the plate is No. 3. This gives the 
plate a figure of merit of 2*05, that is it equals 2*05 times its thickness 
of wrought iron. This is not near so good as the above mentioned 
Carnegie 6-in. plate as to perforation, but it is a very tough plate as 
shown by the absence of cracks. Another 5*75-in. plate gave a much 
better result, defeating a 21 cm (8’27 in.) shot with 13*5 in. calculated 
perforation and striking energy of 7,424 foot tons, implying a figure of 
merit of 2*35 and 1,584 foot tons energy per ton of plate. 
42 
