THE HOYAL ARTILLERY INSTITUTION. 
195 
RESULTS OE EXPERIMENTS WITH PROJECTILES 
AGAINST 
IRON ARMOUR. 
[Extracted from the Transactions and Reports of the Special Committee on Iron. 1861-1864.] 
BY CAPTAIN A. HAERISON, B.A. 
Service cast-iron shot being comparatively useless for attacking either 
ships or forts which are protected with iron armour, it has become necessary 
to employ for this purpose projectiles of a harder and tougher nature, and 
numerous experiments have been made in order to determine the requisite 
material; it may, therefore, be of interest to give a short account of these 
experiments, showing the results which have been obtained. 
In a memorandum by Mr Pole, 1 * in reference to the action of shot upon 
plate armour, an explanation is given, which I shall here quote, regarding 
the power lost in using cast-iron shot 
“ The damage caused to a plate by a certain amount of work stored-up in an 
impinging shot, may be modified by three distinct qualities in the shot itself, namely, 
its material , its weight , and its form . It was evident at an early period of our 
investigations, that, unless the shot could be supposed perfectly hard and coherent, (a 
condition unattainable in practice) a portion of the work it contained would, if the 
resisting power of the plate was great, be expended upon the shot itself—that is, in 
distorting its form, or in breaking it to pieces. and it was also evident that 
the power thus applied must be so much wasted, or deducted from the effective 
action on the plate struck. The late trials of shot made of steel more carefully and 
efficiently tempered than heretofore, have afforded the opportunity of comparing its 
effects with those of simple cast and wrought-iron, and the difference has been very 
marked; for, in proportion as the material of the shot has offered greater resistance 
to fracture or distortion, the damage to the plate has been so considerably increased 
as to show that the power lost by the weaker materials has been greater than was 
before suspected. 
“These results have led to some interesting experiments, with the view of 
ascertaining the amount of power lost. It was observed by the Committee that 
the shot, or fragments of shot, after striking the plate, were considerably heated; 
and Sir W. Armstrong, acting on this hint, has endeavoured, by the application of 
the dynamic theory of heat, to solve this problem. He fired shots of various 
* A Member of the Special Committee on Iron. Appendix C. Report 1862. 
