227 
STEEL AS APPLIED TO ARMOUR. 
BY 
LIEUTENANT J. H. MANSELL, B.A. 
As an introduction to tlie consideration of wliat we want in an ideal 
armour-plate, we will consider how wrought, and cast-iron armour, 
respectively, resist the attack of projectiles. 
Wrought-iron, when struck by a projectile, yields locally and 
destroys the energy of the blow in the act of its own destruction. It 
is perforated by the projectile in a greater or less degree, and the 
protection afforded by it depends on whether the energy of the pro¬ 
jectile is destroyed before the armour is completely perforated. 
None of the shock of impact is transferred into its mass, and 
obviously, as the ballistics, etc., of guns improved, so must the thick¬ 
ness of the wrought-iron protection against their fire be increased. 
The question of weight alone would determine a maximum thickness 
in the case of ships of war. 
On the other hand, wrought-iron, however hard it is struck, does 
not crack, all the damage being confined to the immediate vicinity of 
the point of impact. 
Cast-iron has never yet been perforated to any appreciable extent, 
only slight gouges in it being formed. 
As compared with wrought-iron it is hard. The cast-iron stands 
up to the shell and breaks it up or deflects it, but the shell cannot get 
through. The shock of the blow it transfers through its mass, and 
we therefore find cast-iron developing cracks at a distance from the 
point of impact. Cast-iron is, however, unsuited for the protection of 
ships, though it has been applied to some forts on the Continent, 
notably at Spezia and near Antwerp. Here, then, we have two 
extreme cases :—Wrought-iron is soft and ductile, it suffers a maxi¬ 
mum amount of injury at the point of impact, and a minimum in its 
mass. Cast-iron is hard and brittle, it suffers a minimum amount of 
injury at the point of impact, and a maximum in its mass. To com¬ 
pare these two forms of resistances :—Obviously a system in which 
resistance is only offered in the act of self-destruction is unsatisfactory, 
but there is more than this to be said in favour of the hard surface oi 
cast-iron. An ogival-headed projectile, when it first strikes a plate, is 
in the position of greatest disadvantage as regards its own resistance to 
breaking up or deformation. As it gets its nose into the plate, the 
plate itself surrounds and supports the walls of the projectile, and 
assists it in its work of destruction. And in addition, if a projectile 
is broken up at the instant of striking, it has not time to impress all 
6. YOL. XIX. 
