834 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS AND 
It will be noticed that the logarithmic decrement begins to fall very rapidly as soon 
as the range of arc has become 230 - 8 — 201'5. Immediately, therefore, that the 
calculations necessary for obtaining the above results bad been finished, the vibrator 
was again started, but now with only an initial arc of about 300 scale-divisions. 
Range of arc. 
Logarithmic decre¬ 
ment due to internal 
friction. 
299-2-16.3-8 
•004038 
165-8- 67-5 
-003713 
67‘5- 34‘8 
•002687 
34-8- 190 
•002438 
19-0- 11-2 
•002106 
By this time the vibration-period had diminished to 5’900 seconds. 
After a rest of five hours the vibrator was started with an initial arc of just over 
100 scale-divisions. 
Range of arc. 
Logaiith nic decre¬ 
ment due to internal 
friction. 
100-2-57-8 
•002200 
57-8—36-8 
•001771 
36-8-22 0 
•002044 
Mean .... 
•002005 
Remarks on Experiment XXIII. 
In the first place, we may direct our attention to the diminution of the vibration- 
period produced by rest after repeated vibrations ; this seems to be almost, if not 
quite, as pronounced as it is in the case of iron, the vibration-period gradually 
diminishing from 6'010 seconds to 5 - 900 seconds, and this, too, in spite of the fact 
that the same vibrator had been used several times previously with the wire, and had 
been carefully adjusted at the commencement of the experiment. # 
In the second place may be noticed the diminution of the logarithmic decrement 
which attends the above-mentioned diminution of the vibration-period, and that the 
former of the two is very much greater than the latter. This last is easily accounted 
for if we assume with Wiedemann that the internal friction is due to the to-and-fro 
rotation of the molecules about their axes, and not, as is the torsional elasticity of 
the wire, mainly upon the force necessary to alter the distances separating the centres 
of the molecules. 
Thirdly, the effect of “ elastic fatigue” becomes less and less apparent as the ampli- 
* It should be understood that the bar of the vibrator was not changed in any of the alterations of 
the mass of the vibrator, but only the cylinders. 
