1912-13.] Electrical Resistance and Magnetization of Nickel. 201 
along the axis of an air-gap of the length required to admit all the coils is 
not by any means uniform. 
It then occurred to me that some interesting results might be obtained 
if the nickel were subjected to a combination of the two fields — the one 
along the direction in which the resistance was measured, and the other 
at right angles thereto. A few rough experiments towards the end of 
July 1905 convinced me that the investigation was worth following up. 
Accordingly, in December of the same year, with an improved form of 
apparatus, I began the first series of experiments. Experience suggested 
further improvements ; and the experiments which are now to be described 
were carried out between May 14 and June 27, 1906. 
My intention was to carry out similar experiments with iron strips. 
Unfortunately, the arrangement had to be taken to pieces in consequence of 
the removal of the Natural Philosophy and Applied Mathematics Depart- 
ments from the Old University to the new quarters in Infirmary Street, 
an event which involved so many readjustments and developments that 
it was never found possible to continue the present research on the lines 
originally laid down. 
As the results obtained with the nickel seemed to be both novel and 
interesting, I propose to discuss them now by themselves, with the hope, 
however, that further results in the same line of study may be obtained 
before long. 
© 
As already indicated, the main idea of the experiments is to subject the 
magnetic metal to a combination of magnetic fields acting in mutually 
perpendicular lines, and to measure the associated change of resistance 
for each combination. 
A strip of nickel of width 2T cm. and of resistance 0*0378 ohm was 
doubled over and rolled up like a tape measure so as to form an anchor- 
ring core for a transformer-wound coil. The neighbouring turns of the nickel 
were insulated by interleaved asbestos sheeting, and the magnetizing coil was 
wound round in two layers, there being 57 turns in the inner layer and 
51 in the outer. In its final form the coil formed a roughly elliptical 
anchor ring, whose external diameters were 4 and 3*5 cm., and interior 
diameters 1*7 and 1*3 cm. 
If we regard this as electromagnetically equivalent to a circular anchor 
ring of radius 131 cm., we find in accordance with the usual formula that 
one ampere passing through the magnetizing coil will produce in the 
interior an average field of 16*5 gauss. 
This coil was then placed axially in the gap of a solenoid consisting of 
six large coils placed end to end, three on each side of the gap. The field 
