ARMOURED DEFENCES. 
331 
The use of these compound plates will involve a new mode of 
fastening them, because bolt-holes passing through the steel would be 
inadmissible; but we hope we have got over all difficulty in this 
respect by screwing into the wrought-iron back a seat for a spherica 
nut to hold the armour bolt without confining it laterally. 
A plate, on a novel principle, made by Sir J. Whitworth, deserves 
notice, notwithstanding that it did not succeed very well. It was 
composed of a mass of fluid-compressed steel, pierced all over, at 
regular intervals, by screwed plugs of an extremely hard steel, so 
arranged that, wherever a shot might strike, it would have to cut into 
one of the hard plugs. 
Perhaps I shall now be expected to say a few words as to the effect 
of the different kinds of armour upon battering projectiles of various 
makes and forms. 
First, then, it may be said that although chilled cast-iron shell nearly 
always break up on striking wrought-iron armour directly at high 
velocities, yet in doing so they seem to lose very little of their useful 
energy, and in both direct and oblique fire against this armour chilled 
cast-iron shells hold their own fairly well against other kinds of 
projectile. 
The only instance in which I have seen any kind of projectile strike 
thick iron armour obliquely (angle from normal 30°) at a velocity of 
over 1500 ft. per second, and remain entire, was that of a 9-in. forged 
steel shell made by Whitworth. 
The following are the most noticeable instances of chilled cast-iron 
projectiles remaining entire after doing good work upon wrought- 
iron armour hitting directly :— 
Round. 
Calibre. 
Weight, 
lb. oz. 
Plate. 
Striking velocity. 
2332 ... 
... 10 4 .... 
.. 4iins. .. 
.... 1699 f.s. 
2165 ... 
... 6 „ .... 
... 80 0 .... 
.. 5 „ .. 
.... 1026 „ 
2249 ... 
... 8 „ .... 
... 182 8 ..., 
... 8 „ .. 
.... 1108 „ 
2260 ... 
... 8 „ ... 
... 182 8 .... 
... 10 „ .. 
.... 1337 ,, 
Both forged and cast steel shell, well tempered, have been passed 
through great thicknesses of wrought-iron in direct hitting without 
being injured; the same 9-in. forged shell of Whitworth fluid-pressed 
steel has been passed three times through 12 in. wrought-iron armour 
plates without breaking up, and a forged steel shell, hardened in oil, 
from the 8-in. long gun (Rd. 2284) remained entire and very slightly 
altered in form in a 16^-in. iron plate which it struck with a velocity of 
over 2200 ft. per second. The chief advantage to be gained by the 
use of these very costly steel projectiles over the simple chilled cast-iron 
projectiles appears to lie in the possibility of their being used for 
carrying a bursting charge of gun-cotton, or some such violent explosive, 
through thick iron armour before explosion. This the chilled iron shell 
can never do. 
As to the effect of chilled cast-iron armour upon projectiles, there is 
not sufficient known at present to admit of much being said about it. 
On steel-faced armour the best effect has been obtained with cast- 
steel shell in direct fire, and perhaps rather the best effect with 
Behaviour of 
battering 
projectiles 
of various 
kinds. 
