159 
In this case 
I = 30.75, 
b = 15, 
b'= 1.5, 
d = 24.25, 
d' = 22.03, 
which gives 62.19 tons as the breaking weight of the beam. 
The actual breaking weight being 58 tons, it would appear 
that the constant coefficient assumed is in each instance too 
high for the quality of iron of which these beams were cast. 
This result appears to have been anticipated by Professor 
Hodgkinson in the case of large beams; and in one of his 
experiments, art. 147, on a beam cast for Messrs. Marshall 
and Co., of Leeds, he gives .625 as the coefficient, which 
agrees wdth the result of this experiment. 
Applying this coefficient to Professor Hodgkinson’s 
formulae, they will be as follows : — 
2.05 a d 
birst lormula, IV =. 
Second formula, JV= (bd^ — (6 — b')d'^'^ 
The first of these would give 58.2 tons, and the second 
58.31 tons, as the breaking weight; either of which calcula- 
tions would be sufficiently correct for any practical purpose. 
