470 
]ME. W. H. BAELOW ON THE EESISTANCE OE ELEXTEE 
Compound Sections. 
Eorm of section. 
Length 
Breaking 
T alue oif, or the 
of bearing. 
■weight. 
calculated resistance 
in. 
lbs. 
at the outer fibre. 
No. 15. 
I Section, flanges horizontal 
. 48 
4008 
37,508 
No. 16. 
M Section, flanges vertical . 
. 48 
2569 
43,358 
Solid bars of 4 inches sectional area and 
upwards. 
No. 11. 
Square bar broken on its side 
. 60 
3478 
39,094 
No. 12. 
Round bar 2^ inches diameter 
. 60 
4143 
39,560 
No. 13. 
Round bar 2^ inches diameter 
. 60 
3132 
44,957 
No. 14. 
Square bar broken on its angle 
. 60 
2988 
47,746 
It will be seen from these results, that the apparent resistance at the outer fibre, com- 
puted on the principles of this theory, varies from 25,271 lbs. to 53,966 lbs. ; while the 
tensile strength of the metal, as obtained by experiments on direct tension, averages only 
18,750 lbs. This discrepancy and variation will be found to arise from the omission of 
the resistance consequent on the molecular disturbance accompanying curAature. 
In my former paper a formula was given by which the difference between the tensile 
strength and the apparent resistance at the outer fibre could be computed, approximately, 
in solid rectangular beams and open girders. I now propose to trace the operation of 
the resistance of flexure, considered as a separate element of strength, and to show its 
effect in each of the above forms of section. 
The theory at present acted upon, proceeds on the assumption that there ai’e only- 
two resistances in a beam, namely, tension and compression ; but this supposition fails 
to account, not only for the strength, but also for the visible changes of figui'e which 
arise under transverse strain. 
If abdc (fig. 3) represent the centre portion of a solid rectangular beam before any 
Eig. 3. 
strain is applied, kghi is the figure which this portion wiU assume when subjected to 
