474 Royal Society :— 
By using results obtained by Prof. Hodgkinson on the breaking 
weight of inch bars of ten different descriptions of iron, where the 
tensile strength was ascertained by direct experiment, it would ap- 
pear that the ratio between the resistance of tension and the resist- 
ance of flexure varies in different qualities of metal, an inference 
which seems to be confirmed by other experiments on rectangular 
bars given in the Report of the Commissioners on the application of 
iron to railway structures. The mean result, however, accords 
nearly with that of the author’s experiments, and gives the ratio of 
Jf to @ as 1 to *853. Hence, according to these data, the resistance 
to flexure, computed as a force evenly distributed over the section, 
is almost nine-tenths of the tensile resistance. 
This ratio of the values of f and ¢ being applied to the equations 
resulting from the several experiments, gives the tensile strength of 
the metal as derived from each form of section, and the results, 
though not perfectly regular, are found to be within the limits of 
the variation exhibited by the metal as shown by the experiments 
on direct tension in the former paper. Classified and condensed, 
these results are as follows :— 
The mean tensile strength as obtained from 
Pie Upen Srueis, Wi sees see ee ee ee ten 18,282 
The solid rectangular bar of 2 inches ‘sectional area 17,971 
The inch bars—square and round, and square broken 
emetneny. 2. BUNS Ts8 Wes ae wea oe eee 19,616 
The bars of 4 inches sectional ee square and 
round, and square broken diagonally ...... 16,800 
The compound sections in which the metal was 
4 inch thick .. ea PUIMI SEF SA 
Haying thus found that his eaiths fn fe when applied to his own 
experiments, gave consistent and satisfactory results, the author next 
tested them by other known experiments, and especially refers to 
those by Major Wade on the transverse strength of square and round 
bars of cast iron of different qualities, related in the ‘‘ Reports on 
the Strength and other Properties of Metals for Cannon,” presented 
to the United States Government by the Officers of the Ordnance 
Department. The unit of strength, as computed by Major Wade 
from these experiments, came out uniformly much higher in the 
round than in the square bars of the same kind of iron, whence he 
was led to doubt the correctness of the formula employed ; but the 
author shows that when his formula is used, which includes the re- 
sistance of flexure, the discrepancy referred to disappears, and the 
tensile resistance, whether obtained for the round or the square bars, 
agrees very nearly with that derived from the experiments on direct 
tension under like circumstances. 
As to the ratio between the resistance of flexure and the tensile 
resistance, it is remarked that, were the metal homogeneous, the 
former resistance would probably be precisely equal to the latter, in- 
stead of bearing the ratio of nine-tenths, as found by experiment ; but 
the ratio evidently varies in different qualities of metal ; and accord- 
