base. 
ON STRENGTH AND PROPERTIES OF CAST IRON. 347 
represents a wedge broken off from the same cylinder, the 
point of the wedge being flattened by the crushing apparatus 
after the fracture. ‘There is a small crack in this wedge indi- 
cating a disposition to slide off in another direction, or rather 
to form a double wedge, nearly equilateral, having the diameter 
of the end of the cylinder for its base, and its height about 
half that of the former. The operation of this double wedge 
would be to split the cylinder and throw out its two sides. 
Figs. 3 and 4 represent another cylinder before and after 
crushing ; in fig. 4, a double wedge formed at each end threw 
out the opposite sides. Figs. 5 and 6 represent a cylinder 
before and after crushing ; in the latter, as in fig. 4, the ends 
of the figure have formed the bases of imperfectly formed 
cones, whose tendency has been to separate the sides. Fig. 7 
is intended to represent one of these cones, the vertex of 
which is a sharp edge or point. Fig. 8 represents another 
cylinder of rather soft iron; the pressure was removed in the 
commencement of the fracture, and the circumference was 
found to be surrounded with parallel cracks both ways; the 
angle of these cracks with the base being that of the usual 
inclination of the wedge. Fig. 9 represents the appearance 
of a very short cylinder after fracture ; the vertex of the cone, 
formed upon the end not shown, has split the end here repre- 
sented, leaving a part in the middle unbroken; the opposite 
end is sound for a much greater central area than this, but 
its edges are a little broken. 
Fig. 10 represents a rectangle ;* and fig. 11 its appearance 
after fracture. One end of the specimen has been formed into 
a pyramid A, sharp pointed at D, which has split the opposite 
base and thrown off the end B, and the part C very nearly. 
The sides and angular piece at the end are lost. 
Fig. 12 represents a short rectangle before crushing ; figs. 
13, 14, 15, the different appearances of specimens of the same 
size after fracture. In fig. 14 the fracture has been caused 
_ by a sliding off in the way of the diagonal; in fig. 15 the 
specimen slided off in the direction bc, as before, and was 
cracked through its whole length in the direction ad; in fig. 
13, the top of the specimen formed the base of a wedge which 
had split the bottom, and the bottom itself had formed the base 
ofa wedge. Fig. 16 represents a rectangle of the same base 
as the preceding, but of double the height. Figs. 17, 18, 19, 
20, represent its appearances as shewn by different specimens 
after fracture. Fig. 20, in which the parts are separated, 
shows a wedge AC D, which has for its base the bottom of 
* The prism is, in this and many other places, designated by the form of its 
