ON THE MECHANICAL: PROPERTIES OF IRON PROJECTILES, 183 
The difference of form does not, however, lessen the quantity of mechanical 
force (the weights being the same), as each ball has the same work stored in it 
when delivered from the gun at the same velocity, and the blow upon the 
target ought to be the same in effect but for the difference of shape in the case 
of the round ends, which break to pieces with one-half the pressure. 
It is difficult to estimate the difference of force or work done upon the target 
by the two balls; it. is. certainly not in the ratio of their relative tenacities 
(the metal being the same), but arising from form, as the one would strike 
the target with its whole sectional area in the shape of a punch adapted for 
perforation, whilst the other, although much easier fractured, would effect a 
deeper indentation upon the plate. 
The same law of defective resistance is observable in wrought iron and 
steel as is indicated in cast iron, but not to the same extent. On com- 
paring the mean of twenty-six experiments on wrought iron with those 
on cast iron, it is evident that the difference between the two is considerable 
in their respective powers of resistance to compression. In the experiments 
on cast iron the specimens were invariably broken into fragments, and those 
of wrought iron, although severely crushed, were not destroyed. The same 
law, however, appears to be in operation in regard to the flat- and the round- 
ended specimens, although less in that of wrought iron, as both forms were 
squeezed so as to be no longer useful, the ratios being as 75 : 50 nearly, or 
100: 67-4. The round-ended shot, as might be expected, supported con- 
siderably more than one-half the pressure applied to the flat-ended one before 
it was finally distorted, whilst the cast iron was broken with less than one- 
half the pressure required to crush the flat-ended specimens. . From these 
and the experiments on impact, there cannot exist a doubt as to the damaging 
effects of wrought-iron projectiles. 
The experiments on steel indicate similar results to those on cast and 
wrought iron, as may be seen from the mean of nineteen experiments given 
in the following summary of results :— 
No. of Breaking Ultimate Pressure Pressure 
Ad weight in {| compression | per square per square Remarks. 
Experiments. Ibs. in inches. inch in lbs. | inch in tons. 
L 145,756 04 269,419 120°27 Flat-ended. 
10 114,980 “21 202,643 90°46 Round-ended. 
Here the same law of defective resistance is present in the round-ended 
cylinders as in those of cast iron, and doubtless the same ratio would have 
been obtained, provided the apparatus had been sufficiently powerful to have 
fractured the flat-ended specimens; we may therefore conclude that, instead 
of the above ratio of 100 : 75, it would-have been 100 : 50 or thereabouts. 
From these facts, and those on wrought iron, we are led to the conclusion 
that the power of resistance to fracture of a cylindrical shot with both ends 
flat is to that with its front end rounded as 2: 1 nearly. 
_ The experiments of which the above is an abstract were extended to lead, 
as well as cast and wrought iron, and steel; but those on lead were of little 
value, as the compression was the same whether the ends were rounded or flat. 
This is accounted for by the extreme ductility of the metal and the facility 
with which it is compressed. As regards the wrought-iron specimens it may 
be observed that no definite results were arrived at, excepting the enormous 
statical pressure they sustained, equivalent to 78 tons per square inch of 
