228 
STEEL AS APPLIED TO ARMOUR. 
its energy on tlie plate; tlie smaller pieces scatter themselves about 
the face of the plate, and so much of the energy is frittered away. A 
hard plate that will break up the shell at the moment of striking 
appears, therefore, to be the desideratum. But intimately allied with 
hardness we find brittleness—as indicated by the cracking of the 
cast-iron—and if these cracks are serious, or developed by continuous 
firing, the armour will fall off in large flakes and leave the structure 
we wish to protect bared to the fire of the enemy; as noticed, with 
wrought-iron such a result would not be possible, and our object must 
be then to find an alloy that will combine, as far as possible, the 
ductility of wrought-iron with the hardness of cast. 
Such an alloy is steel. 
By attention to its chemical constitution, combined with certain 
mechanical measures, which will be noticed presently, steel can be 
made either to approach wrought-iron or cast-iron in these special 
properties of extreme hardness or ductility. Intermediate between 
these two we find steel combining, in a greater or less degree, both 
these properties, i.e., a steel which approaches cast-iron in hardness, 
and yet possesses some of the ductility of wrought-iron. 
But if our armour-plate is made all through of one sort of steel, 
we should expect to find it either too soft, and therefore yielding to 
perforation ; or else, if hard, too brittle. 
It therefore seems as if the ideal armour-plate, if made of steel, 
should have a hard face that will stand up to and break the projectile 
at the moment of impact, supported by a softer steel foundation, that 
will assist the hard surface to resist the shock through its mass, and 
so prevent the cracking and peeling off. 
Having thus considered the problem for the steel-maker, a glance 
at some of the principal properties of steel may prove of interest, 
before passing on to an indication of some of the methods that have 
been tried for its solution, followed by a brief notice of some recent 
armour-plate trials, for which I am indebted to The Engineer and 
Engineering . 
Steel for our purpose may be considered as an alloy of iron, with 
carbon, silicon, manganese, sulphur, etc., some of which elements it is 
the object of the steel-maker to get rid of, whilst others he introduces 
in certain proportions, and by certain methods, to attain certain ends. 
Phosphorous and sulphur are his two chief enemies, and with these 
we will not concern ourselves, being content to know that their injurious 
effect is minimised by their nearly complete removal. 
Carbon, we may say, is the element whose effect we have chiefly to 
consider. When it is present in only small proportions, such as 0*1 
per cent., the steel is soft and assimilates to wrought-iron : the higher 
percentage of carbon there is the harder is the steel, and the more 
nearly it assimilates to cast-iron in its properties. The method of 
introducing it in the various amounts is outside the limits or objects 
of this letter in which, I suppose we have satisfactorily produced our 
steel and are only considering its after treatment. Carbon, then, is an 
element of great importance, and we shall see how it has recently 
been introduced in larger quantities to get the hard-face plate. Silicon 
