THE ROYAL ARTILLERY INSTITUTION. 
215 . 
Wrought-iron is an excellent material in most respects for ordnance; it is 
exceedingly tough, and although not so hard as cast-iron or steel, and 
therefore less able to resist injury from the action of powder and shot in the 
bore of a gun, it is not liable to snap like the far more tenacious material 
steel, and will withstand a greater moving or percussive force. Soft iron is 
preferable to the harder qualities, for, as Kirkaldy remarks, “ Although the 
softness of the material has the effect of lessening the amount of the 
breaking strain, it has the very opposite effect as regards the working 
strain. This holds good for two reasons : first, the softer the iron the less 
liable is it to snap; and second, fine or soft iron, being more uniform in 
quality, can be more depended upon in practice.” It is difficult to obtain 
large masses of wrought-iron without slight flaws, caused by the cinder and 
impurities not thoroughly got rid of in the working of the metal; but such 
flaws are generally of far less consequence than cracks of equal size in cast 
metals, and do not, like the latter, indicate the speedy destruction of the 
material; flaws across the fibre of the metal are necessarily dangerous. 
Wrought-iron, in consequence of its toughness, possesses another great 
advantage over cast-iron or steel; when fractured it does not, like those 
brittle' metals, fly into a number of destructive pieces, but its failure is 
gradual, it may be easily noticed, and so injury to the gunners may be 
avoided.* 
Cast steel being exceedingly hard and elastic, is well adapted for the 
bores of guns; but although its tensile strength is very great, it is liable to 
snap without warning when exposed to strain suddenly exerted. However, 
the steels now made for ordnance, both in England and on the Continent, 
are much softer and tougher than ordinary cast steel of good quality. The 
steel used for the bores of our large guns is tempered in oil, by which means 
it is rendered both harder and tougher. 
Great difficulty is still experienced in obtaining large masses of cast steel 
of uniform quality, but since the successful productions of Krupp and some 
of our own manufacturers, it is to be hoped that this objection will be 
before long overcome. There remain, however, two other rather formidable 
objections to the employment of steel alone, viz. the great cost of the metal, 
and its tendency, when fractured, to fly into a number of destructive pieces, 
which render it less suitable than wrought-iron for the exterior of a gun. 
By hooping steel with wrought-iron, the endurance of the former is doubtless 
much increased, and its destruction is less dangerous.t 
In the above remarks on wrought-iron and steel, I have not attempted an 
inquiry into the best methods of producing these materials; I will only 
remark that by the adoption of the Bessemer process of conversion, the cost of 
wrought-iron and steel would be much reduced, but that further experiments 
are required before the Bessemer metals could be safely employed in the 
manufacture of ordnance. 
* “ Out of nearly 3000 guns made on this principle no one gun has hurst explosively.”—Sir W. 
Armstrong’s Evidence, Report on Ordnance, p. 134. 
f That wrought-iron hoops will prevent dangerous results when the inner steel tube gives way 
has been shown in many of the late trials of ordnance. 
