824 
MR, H. TOMLINSON ON THE INFLUENCE OF STRESS AND 
concerned.* We might, perhaps, be inclined to infer that, because the internal 
friction is independent of the load, so also will be the torsional elasticity, but my own 
experience had taught me that it was by no means safe to do so. It is true that 
Experiments VIII. and IX. had shown that the torsional elasticity must be nearly 
independent of the load when the latter is at all large, inasmuch as the period of 
vibration was nearly the same for all the loads. There were, however, slight 
differences in the vibration-period for the different loads, which I felt inclined to 
attribute to the fact that the boxes might not always bang quite vertically. The 
following experiments seem to show conclusively that for loads ranging from moderate 
amounts to great ones the period of vibration is independent of the load. 
Experiment XII. 
A pan made of brass was suspended by two hooks, H, H (fig. 3); the bottom of the 
pan was circular, and the two suspenders HA, HA, made of drawn brass, were 
soldered into A. The lead cylinders before-mentioned were in the first instance 
placed on the pan, so that their centres were in the same line as the axis of the wire. 
The brass cylinders, C 2 , were placed near the ends of the bar YV, at equal distances 
from the wire, and had in consequence of their position and mass a very considerable 
moment of inertia as compared with the rest of the vibrator. After the arrangements 
had been completed the apparatus was allowed to remain suspended for several days, 
and was during this period frequently vibrated. The vibration-period was then 
determined, and, two of the lead cylinders having been removed, a further rest of 
24 hours was given,f when again the vibration-period was determined ; and so on, 
until all the lead cylinders had been removed. In this experiment the same piano- 
steel wire as before was used. The temperature ranged from 9 o, 30 C. to 13°'40 C. 
Vibration-period in 
seconds. 
Load on the wire in 
kilos. 
Couple in dyne 
centime, required to 
twist the wire 
through one radian. 
16 : 658 
1-208 
5713 
18T06 
5-208 
5738 
19-889 
9-208 
5758 
2F331 
13-208 
5766 
22-720 
17-208 
5754 
24-003 
2F208 
5756 
* G. Wiedemann has shown in his paper already quoted that for moderate loads the torsional 
elasticity is independent of the load. 
t Rest should always be given either after putting on or taking off load, as, though the torsional 
elasticity is not so much affected by shocks as the internal friction, it is affected. 
