152 
MR, H. TOMLINSON ON THE INFLUENCE OF STRESS 
The Effect of Longitudinal Magnetization on the Electrical Resistance 
of a Bar of Cobalt. 
Experiment LXX. 
A bar of cobalt, 8 ‘5 centims. long and 75 centim. in diameter, was provided with 
stout copper terminals, and balanced against a similar bar. The precautions taken 
and the mode of experimenting were exactly the same as with the nickel bar. 
Table XXXII. 
Deflection of 
tangent galvanometer 
= $*>• 
Tan 0 + *00840 sec 0 
= c. 
Increase of resistance 
due to magnetiza¬ 
tion in terms of 
divisions of galvano¬ 
meter scale = a. 
c 
Cl 
c-’ 
4-00 
T04 
1-40 
13-5 
130 
6-25 
163 
3-90 
24-0 
147 
13-00 
•343 
8'50 
24-8 
72 
In this case the values of - agree quite as well as and if we take the mean of 
the former, namely 21'1, we obtain an increase of resistance per unit attending mag¬ 
netization by a unit force =628 XlO -8 ; a number, it will be noticed, only about 
one-seventh of that obtained in the case of the nickel. The cobalt was, like the nickel, 
unannealed, and annealing would have caused the effect of a moderate magnetizing 
force to be greater, though not so much greater as would be the case with nickel. 
In both the nickel and cobalt bars there was a permanent increase of resistance 
produced by magnetization, the maximum alteration amounting in nickel to about 
•125 per cent., and in cobalt to '025 per cent.; so that the maximum permanent 
alteration of resistance which is caused by magnetization is much greater with nickel 
than cobalt. 
With both bars the M.C. was found to produce very nearly the same alteration of 
resistance, whether passed in one direction or the other through the coil. 
The Effect of Longitudinal Magnetization on the Electrical Resistance 
of a Bar of Bismuth. 
Experiment LXXI. 
As it seemed desirable to ascertain whether diamagnetic substances would have 
their resistances altered in the same direction as paramagnetic ones, some experiments 
were made with bars of bismuth, but as the magnetization which can be imparted by 
