THE ROYAL ARTILLERY INSTITUTION. 
213 
Areas, *6013 and *641. 
Number 
of 
Experi¬ 
ment. 
Crushing 
weight 
in lbs. 
Ultimate 
compression 
in inches. 
Pressure 
per square 
inch in 
lbs. 
Pressure 
per square 
inch in 
tons. 
Remarks. 
1 
73,428 
•120 
122,115 
64'51 
2 
68,052 
•092 
125,787 
56-13 
Both ends flat. 
Mean ...... 
... 
... 
123,951 
55-32 
Areas, *5674 and *7088. 
3 
35,540 
•22 
62,636 
27-96 
4 
40,916 
•24 
57,725 
25-77 
One end rounded. 
Mean...... 
... 
60,180 
26-86 
Areas, *7088 and ■ 
■7088. 
5 
38,260 
•25 
53,978 
24-09 
6 
37,580 
•25 
53,030 
23-67 
Both ends rounded. 
Mean . 
37,920 
•25 
53,504 
23*88 
Mr Fairbairn goes on to state,— 
“ In the foregoing experiments it will be observed, by reference to the two first 
Tables, that the resistance of cast-iron flat-ended shot to crushing is about 55 tons 
per square inch, whilst in the two following, we find that the 
round-ended specimens of the same material gave way, and 
were crushed with only 26 \ tons, rather less than one-half the 
load required to crush the flat-ended ones. This may be 
accounted for as under:— 
“ Taking for example, the cylinder a, with a rounded end 
forcibly pressed against a steel plate 6, it is crushed by (a 
fixed law observable in every description of crystalline substance) 
the part s forming itself into a cone, which, acting as a wedge, 
splits off the parts ( cc ) at the angle of least resistance, and 
these, sliding over its sides, are broken in pieces on the 
surface of the plate.” (Fig. 9.) 
These cones ( 5 ) have been obtained from cast-iron shot of all sizes, and in 
the collection of specimens in the model-room of the Ordnance Select 
Committee may be seen a cone of a 5J oz. cast-iron bullet which has been 
fired from a wall-piece, and also a cone of precisely similar form of a MF' 
spherical cast-iron shot which has been fired from a 12-ton gun. 
Mr Fairbain found that the indentation made by a round-ended punch is 
nearly 3^ times as great as that made with a flat-ended punch, and deduced :— 
“ That the work done is twice as great in the case of the round-ended shot as 
compared with those of the flat-ended.” 
Numerous experiments have been made since 1861 in order to determine 
the form of head best suited for penetration. 
Shot with flat heads, hemispherical heads, spike heads, stepped heads, 
&c., have been tried. 
No advantage was found from stepping the head of the shot, either with 
one or two steps; with the former the step was broken off, and with the latter 
the first step was generally broken off, and the second was formed into a cone. 
Mr Fairbairn made some experiments on statical pressure with stepped 
punches, and found that a plain flat-ended punch is more effective for 
Fig. 9. 
