1912-13.] Electrical Resistance and Magnetization of Nickel. 217 
enhanced effect is greater as the steady longitudinal magnetization is 
increased. 
Each curve, it will be noticed, is a kind of iso-magnetic curve. Along 
each H curve the transverse magnetic field is constant ; and along each T 
curve the longitudinal magnetic field is constant. 
With these graphs in view, we may summarise the phenomena in these 
words : 
1. When a nickel strip is conveying a current, its conductance is 
diminished in a longitudinal magnetic field, increased in a transverse 
magnetic field. 
2. Reversal of either magnetic field does not change the accompanying 
effect on the conductance. 
3. When a cyclic longitudinal field is superposed upon a steady trans- 
verse field of magnitude less than a certain critical value, the diminution in 
the conductance is less marked as the transverse field increases and 
practically vanishes when this critical value of transverse field is reached. 
4. When the steady transverse field exceeds this critical value, the 
superposed cyclic longitudinal field causes an increase in the conductance ; 
and this increase in conductance becomes more marked as the longitudinal 
field is taken greater. 
5. When a cyclic transverse field is superposed upon a steady 
longitudinal field, the increase in the conductance is augmented. Not only 
does the increase of conductance grow greater with the stronger transverse 
field, but it also grows greater as the steady longitudinal field is increased. 
It may be noted in passing that it is not possible to connect in any 
way the change of resistance with the changes of length and volume which 
nickel experiences when magnetized. In a longitudinal field of 50 units 
nickel is shortened by about 5 in 1,000,000, and expands linearly at right 
angles by about 2 in 1,000,000 (6). These small changes would produce a 
diminution of resistance of about 9 in 1,000,000. This is quite negligible 
in comparison with the measured changes, and besides is in the opposite 
direction. 
It is evident that we are dealing with a remarkable molecular and 
intermolecular effect. Now the one fundamental theory in electricity 
which at present can claim any success in getting behind electrical and 
magnetic phenomena is that which exploits the negatively charged electron. 
As early as 1900, Sir J. J. Thomson (7), in his memoir presented to the 
Congres International de Physique, showed how, on certain plausible 
assumptions, the electron theory of conductance established a relation 
between magnetic force and electrical resistance. His conclusion was that 
