ON THE STRENGTH OF PILLARS. 
419 
ends of the castings were made very strong and rigid, and they were perforated, so 
that links passing through them, to tear the casting asunder by, should act directly 
through the axis. 
square ins. 
1st exp. area of section 1’5330"| ^ ^ 1-540 Breaking weight 21219 
2nd exp. area of section T5470 J Breaking weight 23551 
or strength, per square inch, 14535 lbs. = 6^ tons nearly. 
Mean 22385, 
Compressive Strength of the Iron used above , or that which would crush it without 
Flexure. 
55. The first four experiments on this matter were on rectangular masses, cut out 
of the pieces torn asunder, the sides being rendered smooth and perpendicular to 
each other. The other are from the shortest cylinders in Table II. 
No. of 
Experiment. 
Area of section in inches. 
Height of 
specimen. 
Crushing weight. 
Crushing weight 
per square inch. 
1 
2 
3 
4 
sq. in. 
S j 1-00 x -25 = • 25 
1 1-00 X -25 = -25 
1 f 1-00 x -25 = -25 
£ J 1-00 x *25 = -25 
inches. 
•50 
•50 
1-00 
1-00 
lbs. 
25923] 
25923 
24355 = 
24747, 
> Mean 25923 
■ Mean 24551 
lbs. 
103692 
98204 
5 
6 
7 
8 
9 
- 2123 ? 
U 2 -21237 
|J >-21237 
| -21237 
0 §J -21237 
1-00 
1-00 
1-00 
2-00 
2-00 
23963 ' 
24747 
25139, 
23035 ' 
22699 
fMean 2461 6 
• Mean 22867 
115911 
107675 
When bodies are crushed, as above, they give way by a wedge sliding off in an 
angle dependent upon the nature of the material ; and in cast iron the height of this 
wedge is about 1| the diameter, or thickness of the base of the wedge. If the body 
to be crushed is shorter than would be sufficient to admit a wedge of the full length 
to slide off, then it would require more than its natural degree of force to crush it ; 
because the wedge itself must either be crushed, or slide off in a direction of greater- 
difficulty. If, on the other hand, the height of the body to be crushed be much 
greater than the length of the wedge, then the body will sustain some degree of 
flexure, and fracture will be facilitated in consequence. 
To determine the crushing strength of the iron above used, I shall, for the reasons 
just given, take the results from those specimens which are but little longer than the 
wedge. 
Taking, therefore, a mean from the results of the rectangles half an inch high, and 
the cylinders one inch, we have, 
From the former 103692 
From the latter 115910 
Mean 109801 lbs. = 49-0183 tons per square inch. 
Whence we obtain 86238 lbs. = 38*499 tons, for the weight which would crush a 
3 h 2 
