IN BEAMS SUBJECTED TO TEANSVEESE STEAIN. 
477 
First, an experiment made by Mr. Hodgkinson, and given in Teedgold’s 
Cast Iron,’ 4th edit. The form of the beam is as shown in the figure. In 
‘ Treatise on 
this case, — 
D =2-5625. 
h = -29. 
V =1-47, mean. 
d =2-1573. 
d! =1-405, mean. 
I =54. 
W=6678. 
♦-• 4 . 77 -—^ 
And employing the formula used for the section No. 16, we have 
2-863I/+2-3476?)=90I53; 
and if <p be taken at nine-tenths of^, 
/=I5086. 
The tensile strength thus computed, accords very closely with the quality of metal 
employed by Mr. Hodgkinson in that and other experiments made by him at that time 
on various forms of girders. 
In the Keports on the ‘ Strength and other properties of Metals for Cannon,’ made 
by the Officers of the Ordnance Department of the United States Government, some 
experiments are given upon the transverse strength of square and round bars of cast iron. 
These experiments were made with very great care by Major Wade, for the purpose of 
testing various qualities of metals and modes of treatment, by frequent re-casting, and by 
keeping the metal for various periods of time under fusion. From each experiment, a 
constant is derived for the purpose of comparing the relative strengths of metal ; and 
in endeavouring to obtain the constant for round iron. Major Wade has employed the 
usually accepted theoiy of the transverse strain. He appears, however, to have found 
that the formula is defective, for he observes at page 21 of the Report, — “A trial was 
made with cylindrical bars in lieu of square bars. These generally broke at a point 
distant from that pressed, and the results were so anomalous that the use of them was 
soon abandoned. The formula by which the strength of the round bars is computed, 
appears to be not quite correct ; for the unit of strength in the round bars is uniformly 
much higher than in the square bars cast from the same kind of iron.” 
The following are the experiments on the round bars, with those on the square bars 
from the same metal ; and it will be seen, that if the tensile strength of the metal be 
computed by the formula here given, including the resistance to flexure, the discrepancy- 
pointed out by Major Wade disappears ; and the tensde resistance, whether obtained 
for the round or the square bars, agrees very nearly with that derived from the experi- 
ments on direct tension under like circumstances. 
