THE DEVELOPMENT OF ARMOUR. 
557 
If Tresidder’s slide rule be used, 12 (the d) is set to about 721*5 (w), 
and opposite to 1861 will be found 23*6 (for t). 
For shock or fracture strain there is nothing to guide us beyond 
the energy per ton of plate and the relation of the diameter of the 
shot to the width of the plate respectively. 
In the above case this will be as follows :— 
■nr , • n i < \ 10 ft. X 7 ft. X llji , —1 — 
W (weight of plate) = 1 8 x log 1-3422 
1 ta 
That is the dimensions of the plate in cubic feet multiplied by the 
factor for the weight of a cubic foot of steel in tons. 
log (10 X 7) = 1*8451 
log 187 = _2*2718 
log for steel = 1*3422 
3*4591 
log (12 x 16) 2*2833 
W = 14*99 tons 1*1768 
For energy. 
2 log v (1861) = 13'2697 
log W (721.5) = 2*8682 
log (g x 2240) 
9*3976 
5*1590 
E = 17320 
log W (14.99) 
4*2386 
1*1758 
Shock or energy per ton of plate — = 1155 
w 
3*0628 
The diameter of the shot is | the width of the plate which is a 
function of the fracture strain. 
(To be Continued.) 
