196 
MINUTES OF PEOCEED1NGS OF 
materials against iron plates, and, by measuring carefully the quantity of heat 
generated in them by the concussions, obtained an approximate estimate of the 
work lost. He found that, with hard-tempered steel shot, the power expended on 
the projectile was about one-tenth of that stored-up in it at the moment of striking; 
while with softer shot it was two-tenths, and with soft wrought-iron it amounted to 
more than one-half of the whole. Cast-iron has hitherto eluded observation, on 
account of the difficulty of collecting the fragments, and measuring the heat in 
them. 
** These experiments are very rough, and the investigation of the subject is, yet, 
very incomplete; but still enough has been done to warrant the conclusion, that, in 
firing at plates of strong resisting power, considerable loss of effect takes place when 
cast or wrought-iron shot are used.” 
Mr Eairbairn, also a member of the Special Committee on Iron, arrived 
at the same conclusion, after making a series of experiments to ascertain the 
resistance of different kinds of shot to a force tending to crush them. The 
specimens experimented on were a portion of some shot of cast-iron, wrought- 
iron, and steel, which were manufactured at Enfield for the purpose of 
being fired from a wall piece against iron plates. The results obtained by 
Mr Eairbairn are thus described in his Report:—- 
fc It has been correctly stated, that it requires a considerable amount of force to 
break up shot when delivered with great velocity against an unyielding object, such 
as the side of an iron-cased ship, and it may be thence concluded that the force 
expended in thus breaking up the shot must be deducted from that employed in 
doing work on the plate. This is confirmed by experiment, which shows that 
though the whole of the force contained in the ball, when discharged from a gun at 
a given velocity, must be delivered upon the target, the amount of work, or damage 
done to the plate, will depend on its weight and the tenacity of the material of which 
the shot is composed. 
“ If, for example, we take two balls of the same weight, one of cast-iron and 
the other of wrought-iron, and deliver each of them upon the target with the 
same velocity, it is obvious that both balls carry with them the same projectile 
force as if they were composed of identically the same material. The dynamic 
effect, or work done, however, is widely different in the two cases, the one being 
brittle and the other tough; the result is that the cast-iron is broken in pieces 
by the concussion of the blow, whilst the other either penetrates the plate, or 
what is more probable, flattens its surface into a greatly increased area, and inflicts 
greater punishment upon it. In this instance, the amount of work done is in 
favour of the wrought-iron shot; but this does not alter the condition in which the 
force was in the first instance delivered upon the target, but is entirely due to the 
superior tenacity of the wrought-iron shot to that of cast-iron, which yields to the 
blow, and is broken to pieces, in consequence of its inferior power of resistance. The 
same may be said of steel in a much higher degree.” 
The following table shows the summary of results of Mr Eairbairn's 
experiments:— 
