INTO THE STRENGTH OF WROUGHT-IRON PLATES. 
719 
The values of S and S,, as determined by these calculations, being less for the beam 
in experiment 13 than they are for the beam in experiment 12, it follows that the 
latter has a better distribution of the material than the former. And at the same 
time the difference of the value of these constants is so small as to lead us to infer 
that the form of the beam in experiment 12 approaches to that of maximum strength 
with a given quantity of material. The sectional areas of the top and bottom flanches 
are to each other as 28 : 30 or 14 : 15, which is very nearly a ratio of equality. 
APPENDIX. 
Experiments by Thomas Loyd, Esq., Inspector of Machinery, to ascertain the effect 
of a tensile strain upon bars of wrought iron under varied conditions. Twenty pieces 
of If S C bar iron, each 10 feet long, were cut out of the middle of twenty rods of 
iron. These 10-feet lengths were cut into two parts of 5 feet each, and marked with 
the same letter. A, B, C, &c. were first broken so as to get the average breaking 
strain. Al, B®, Q were subjected to the constant action of three-fourths of the break- 
ing weight for five minutes. The load was then taken off, and they were afterwards 
broken. It will be seen that the breaking strain was about the same as before, thus 
proving that the previous strain had not weakened them. 
Experiment 1. 
First. 
Second. 
Mark on 
the bars. 
Dimensions 
of the bars. 
Breaking 
weight 
in tons. 
Ultimate 
elongation 
of bar in 
inches. 
Mark on 
the bars. 
Dimensions 
of the bars. 
Breaking 
weight 
in tons. 
Ultimate elongation of bars in 
inches with 25 tons. 
A. 
1-37 
33-75 
9-12 
A 
2. 
33-75 
1-56 
B. 
1*37 
30-00 
9-12 
B 
2. 
33-00 
1-61 
C. 
1-37 
33-25 
9-75 
C 
2. 
33-25 
1-56 
D. 
1*37 
32-75 
9-22 
D 
2. 
32-25 
1-75 
E. 
1-37 
32-50 
9-22 
E 
2. 
32-50 
1-75 
F- 
1-37 
33-25 
10-50 
F 
2. 
33-00 
1-56 
G. 
1-37 
32-75 
8-50 
G 
2. 
33-00 
1-61 
H. 
1-37 
33-25 
10-61 
H 
2. 
33-50 
1-50 
I. 
1-37 
33-50 
8-37 
I 
2. 
32-75 
1-67 
J. 
1-37 
33-30 
9-22 
J 
2. 
33-25 
1-67 
K. 
1-37 
32-25 
8-00 
K 
2. 
32-50 
1-86 
L. 
1*37 
32-25 
7-30 
L 
2. 
31-30 
2-00 
M. 
1-37 
30-25 
9-12 
M 
2. 
32-75 
Broke mark 1-75 in s. c. 
N. 
1-37 
34-25 
9-22 
N 
2. 
34-00 
1-12 
0 . 
1-37 
31-75 
7-61 
0 
2. 
32-50 
1-75 
P. 
1-37 
29-73 
10-00 
P 
2. 
31-00 
1-75 
Q. 
1-37 
33-50 
9-22 
Q 
2. 
33-75 
1-50 
R. 
1-37 
33-73 
9-75 
11 
2. 
3.3-75 
1-56 
S. 
1-37 
33-00 
9-12 
S 
2. 
33-25 
1-12 
T. 
1-37 
32-25 
8-75 
T 
2. 
31-00 
2-18 
Mean ... 
32-87 
9-09 
32-81 
1-64 
