168 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
Table XXXIV. 
Name of metal. 
“ Rotational coefficient.” 
Temporary alteration of specific 
resistance per unit produced 
by temporary increase of length 
per unit. 
+ signifies increase of resistance 
on application of stress. 
Iron ...... 
+ 78 
+ 2-618 
Zinc. 
+ 15 
+ 2-113 
Lead. 
+ 1-613 
Tin. 
+ 0-2 
+ 1-630 
Brass. 
- 1-3 
Platinum. 
- 2-4 
+ 2-239 
Silver. 
- 8-6 
+ 1-617 
Copper . 
- 100 
+ 1-005 
Aluminium .... 
- 50-0 
-0-420 
Nickel. 
-120-0 
-8-860 
Considering that Hall himself is doubtful about the order of the metals in the 
centre of the list, there seems to be a well-marked relation between the “rotational 
coefficient” and the alteration of specific resistance from temporary mechanical stress. 
This relationship is strikingly apparent in the case of the metals iron, zinc, copper, 
aluminium, and nickel, and there can be but little doubt that results of extreme 
interest might be obtained by observations of the effect of mechanical stress and strain 
on the “ rotational coefficient.” 
The Relation between Electrical Resistance and “Viscosity.” 
Whilst endeavouring to find a relation between the electrical resistances of sub¬ 
stances and their other physical properties, I was struck with the failure which I 
experienced in finding any in the case of those properties which have been already 
examined, except one, and that is one which as yet I have not had time to examine 
with anything like the care which I hope at some future period to be able to bestow 
upon it, namely, that which has been called by Sir W. Thomson, in the case of metals, 
their “ viscosity.” The experiments, however, which have been made show clearly 
that there is in all probability a very close relationship between molecular friction and 
electrical resistance. It is proposed to make extended observations of the diminution 
of amplitude of vibration of wires of considerable length whilst the oscillations of very 
small amplitudes are magnified by a mirror attached to the vibrator; so that small 
vibratory molecular displacement may be obtained, and further to examine the change 
of “ viscosity ” produced by change of temperature. It suffices, however, for the 
present to say that of the pure metals already examined, copper, silver, aluminium, 
zinc, and tin, the order of their “ viscosity ” is the same as that of their specific 
electrical resistance. 
