200 Proceedings of the Royal Society of Edinburgh. [Sess. 
XX. — Changes of Electrical Resistance accompanying Longitudi- 
nal and Transverse Magnetizations in Nickel. By Professor 
C. G. Knott, D.Sc. 
(Read January 20, 1913. MS. received January 23, 1913.) 
In 1903 I communicated to the Society a paper on the relation between 
magnetization and resistance of nickel at high temperatures (1). In this 
paper the magnetization was along the direction in which the resistance 
was measured. A second paper, in which the magnetization was transverse 
to the direction in which the resistance was measured, was communicated 
in 1906 (2). In these later experiments a flat coil of nickel wire was 
used ; and it was necessary to use very high fields before an appreciable 
change of resistance was obtained. The results indicated that, in a strongly 
magnetic metal like nickel, the magnetization, and not the magnetizing 
force, was the determining factor. It followed that the change of 
resistance accompanying the application of a transverse magnetic force 
must depend, like magnetization, upon the form of the material. In order 
to magnify the resistance effect I resolved to use a fairly broad strip of 
nickel instead of a thin wire. The chief difficulty of measurement would 
then lie in the smallness of the resistance of such a strip. Still, with 
a sufficiently delicate galvanometer this difficulty might be overcome. 
Accordingly, I obtained from Germany a quantity of thin nickel sheeting 
of pure nickel, and proceeded to investigate its properties in exactly the 
same way as had already been applied in the case of nickel wires. 
As I had expected, the change of resistance of a nickel strip when 
magnetized transversely — that is, in the direction of the width of the strip — 
became easily measurable in moderate fields. 
To find how the width influenced the magnitude of the effect I took 
three strips of widths 8, 4, and 2 cm., rolled them into compact coils, and 
placed each axially in turn in the air-gap of an electromagnet. The 
resistance changes due to the action of approximately the same magnetic field 
were as the numbers 62, 47, and 225. These numbers can be accepted only 
as a rough quantitative indication ; for the part of the air-gap occupied by 
the coil varied in length according to the width of the nickel strip which 
formed the coil, and consequently the average field could not be the same 
for all. As is well known, the strength of the field at different points 
