Stresses on the Elastic Properties of Steel. 217 
knife-edge A inserted. The downward force P x at the end 
of the shaft indicated by A was obtained by allowing the 
desired weight to hang from the end of the arm. The up- 
ward force P 1? at the same end A, was obtained by allowing 
the desired weight to hang from a bicycle chain which ran 
over a suitably mounted bicycle wheel and fastened to the other 
end of the arm, in such a way as to give the required vertical 
upward pull. The friction of the wheel and chain were 
negligible. The arm at the end C was the fixed arm. The 
specimens were tested in flexure by applying the loads P at 
the centre by means of the testing-machine. Torsional 
deformations were measured on a gauge-length of 4 feet 
9 inches by means of an Olsen troptometer. Flexural deforma- 
tions were measured with an Olsen deflectometer. After the 
torque had been applied the beam of the testing-machine was 
balanced, eliminating from consideration the weight of the 
cross-beam and the weights used in applying the torsion. 
Results. — The lowering of the torsional elastic limit of steel 
tubing due to the various tensional loads is shown by PL XI. 
fig. 2. Curve 1 shows the results of simple torsion tests, Curve 2 
the results of torsion tests while the material was under tension 
to 2/6 the elastic limit in tension. Curves 3, 4, 5, and 6 
show the results of torsion tests while the material was under 
tension of 3/6, 4/6, 5/6, and 6/6 respectively the elastic limit 
in tension. Each curve represents, at least, an average of 
two tests. The results of the compression-torsion tests 
are shown by fig. 3. Curve 1 shows the results of simple 
torsion tests of the material. Curve 2 shows the results of 
torsion tests while the material was under a compression of 
2/6 the elastic limit in compression. Curves 3, 4, and 5 
show the results of torsion tests while the material was under 
compression to 3/6, 5/6, and 6/6 respectively the elastic limit 
in compression. Each curve represents an average of two or 
more tests. The values of 2/6, 3/6, &c. of the elastic limit were 
not in every case exactly noted, but the results used in the tables 
and curves show a discrepancy in only one or two cases. 
The results of the torsion-flexure tests of nickel- and carbon- 
steel are shown by figs. 4 & 5 (PI. XL). Fig. 4 shows the 
results of the tests of mild carbon-steel shafting. Curve 1 
shows the result of a flexure test of a piece of the shafting 
when no torsion is applied. Curve 2 shows the results of a 
flexure test of a similar piece of shafting while it was under 
a fibre stress of 22,800 lbs. per sq. inch on the outer fibre. 
Curves 3 and 4 show the results of flexure tests of shafting- 
while under a stress on the outer fibre, due to torsion, of 
30,400 and 38,000 lbs. per sq. inch respectively. Fig. 5 
shows the results of tests of nickel-steel shafting. These 
