448 
Mil. HODGKINSON’S EXPERIMENTAL RESEARCHES 
Table X. — Uniform Hollow Cylindrical Pillars of Low Moor Iron, No. 3 ; the ends 
being flat, and the lengths less than thirty times the external diameter. Plate XV. 
No. 8 , E, F. 
Number of Ex- 
periment. 
Length of pillar. 
External 
diameter. 
Internal 
diameter. 
1 
Weight of pillar, j 
Breaking weight. 
Value of b. 
Value of c. 
Calculated 
breaking 
weight from 
formula. 
be 
b + t£ 
4 
Remarks. 
i. 
inches. feet. 
30-25 =2-5208 
inch. 
1-26 
inch. 
•767 
lbs. oz. 
6 2 
lbs. 
33679 
lbs. 
38807-6 
lbs. 
86178-5 
lbs. 
32331 
Not perfectly sound. 
2. 
30-25 =2-5208 
1-26 
•781 
6 1 
32867 
38274 
84310 
31790 
f Core not quite in middle, thicknesses of metal 
3. 
26 =2-1666 
1-25 
•768 
5 2 
35302 
48461-7 
83882 
36501 
\ on opposite sides 3:4. 
Air bubbles in casting. 
4. 
26 =2-1666 
117 
•752 
4 7 
31195 
36887 
69283-2 
28764 
Core in centre, T : C : : 43 : 74. 
5. 
23 =1-91666 
116 
•7705 
3 9 
30383 
42633 
64844-7 
30291 
Core in centre, T : C : : 11 : 18. 
6. 
20-166 = 1-6805 
1-21 
•77 
3 9 
41751 
64599-2 
75130-6 
40128 
f Core in centre, broke in middle in many pieces 
I 
7. 
20-166=1-6805 
1-14 
•805 
2 11 
27135 
46408 
56193 
29449 
\ with sharp points. 
Broke in middle in twelve pieces. 
8. 
17 =1-4166 
1-15 
•91 
1 11 
25511 
50927 
42636 
26191 
9. 
16 = 1-3333 
1-15 
•92 
l H 
25105 
54730 
41053 
26273 
Broke in middle in twenty-five pieces. 
10. 
15-125 = 1-2604 
1-16 
•932 
1 8 
26729 
61304-1 
41133-8 
27364 
Core in centre, T : C : : 52 : 64. 
11. 
15-125 = 1-2604 
1-08 
•77 
1 12 
27135 
61570-2 
49457 
30863 
| 12. 
14 =1-16666 
1-15 
•792 
2 0 
37285 
91909 
59953 
40257 
1 13. 
* 
8-8 = -73333 
1-13 
•91 
13§ 
34037 
133000 
38704 
31750 
Broke in middle in ten pieces. 
Most of the pillars, which were under twenty inches long, were turned outside and 
bored within. The whole in this table were (with the exceptions named) very good, 
and the core was nearly in the centre of all, except the 2 nd. By the ratio T : C is 
to be understood the depth of the part extended to that compressed in the section of 
fracture. 
By the values of b in the seventh column is to be understood the breaking weights 
jp^3'55 ^3*55 
calculated from the formula b = 99318 , for long pillars (Art. 51.) ; where 
l is the length of the pillar, and D, d the external and internal diameters. The values 
of c in the eighth column are the weight which would crush, without flexure, a 
mass of iron of the same section as the pillar (Art. 55) ; and the breaking weight in 
the ninth column is computed by the formula (Art. 43.) for short pillars : strength 
be, 
= t — . 3 • It having been shown, I hope satisfactorily, that the strength of short 
b + -%c 
pillars, which break by flexure, depends upon their resistance to crushing (Art. 39-42.), 
I have endeavoured there to show the laws on which it depends ; and the agreement 
between the calculated and the experimental results, in hollow pillars, may be judged 
of from the above results. 
