83G 
MR, H. TOMLINSON ON THE INFLUENCE OF STRESS AND 
The mean of the two last values of the logarithmic decrement is ’001972, and here 
it remained very fairly constant, further oscillation not diminishing the internal fric¬ 
tion. When, however, rest for one or more days w^as now given, the internal 
friction would rise again until once more repeated oscillations would reduce it to 
’001972 or thereabout. No doubt the increase of internal friction attending 1 on 
rest in this case is owing to changes of temperature which occur in the interval, such 
changes, as we have seen, tending to disturb the molecular arrangements wffiich 
existed at the end of the frequent oscillations. 
Summary. 
1. The proportionate diminution of amplitude due to internal molecular friction in 
a torsionally vibrating wire is independent of the amplitude, provided the deforma¬ 
tions produced do not exceed a certain limit. This limit varies with the nature of the 
metal, and is, for nickel wire, very low. 
2. The logarithmic decrement of amplitude increases with the length of the vibra¬ 
tion-period, but in a less proportion than the latter, and in a diminishing ratio. The 
amount of increase of the logarithmic decrement attending on a given increase 
through a given range of the vibration-period varies with the nature of the metal, 
and with those metals in which the internal friction is small becomes nearly 
insensible. 
3. It follows from 2 that the internal friction of a solid does not resemble the 
viscosity of fluids. 
4. Permanent molecular strain resulting from loading, not carried to a sufficient 
extent to produce sensible permanent extension, diminishes the internal friction 
and increases the torsional elasticity. 
5. Considerable permanent longitudinal extension and permanent torsion produce 
increase of internal friction and diminution of torsional elasticity. The effect of 
torsion is much greater than that of extension, and the increase of internal friction is 
much greater than the decrease of torsional elasticity. 
6. The internal friction of a metal is independent of the temporary load. 
7. Annealing a hard-drawn wire may enormously diminish the internal friction, 
especially if, after annealing, the wire be kept suspended for some days and frequently 
vibrated. 
8. Pest after suspension, aided by not too large oscillations at intervals, diminishes 
the internal friction of a wire which has been recently suspended, or which, after 
suspension, has been subjected to considerable molecular agitations by mechanical or 
thermal agency. 
9. “ Fatigue of elasticity ” is not felt, provided the deformations produced do not 
exceed a certain limit. This limit varies considerably with the nature of the metal, 
