1913-14.] Resistance of Iron in Crossed Magnetic Fields. 259 
XX. — Changes of Electrical Resistance accompanying Longi- 
tudinal and Transverse Magnetizations in Iron and Steel. By 
Professor C. Gr. Knott, D.Sc. 
(Read May 4, 1914. MS. received October 1, 1914.) 
In t January 1913 I communicated a paper on the changes of resistance of 
nickel when subjected to a combination of longitudinal and transverse 
magnetic fields (1). The following paper contains an account of exactly 
similar experiments with iron and steel. 
Each steel or iron strip formed the core of an anchor-ring coil which 
was double-wound, with two exactly equal coils of copper wires. When 
the current was passed through the two contiguous coils in series in the same 
direction the metal cores were magnetized longitudinally. When the current 
was passed in opposite directions through the two coils there was no 
magnetization produced in the cores, but the heating effect was the same 
as in the first case. At the beginning of each experiment the current was 
applied in the latter or unmagnetizing arrangement, and was sustained for a 
sufficient time to permit the temperature to become practically constant. 
With reversal of the current in the one half of the enveloping coil a longi- 
tudinally magnetizing force was established within the region occupied 
by the iron or steel core. By means of a succession of reversals and re- 
reversals the core could be subjected to a cyclical variation of magnetizing 
force, while the temperature remained practically constant. 
Six layers of the magnetizing coil were wound round each core, the 
number of windings in each layer being in accordance with the following 
table. 
Layer. 
Number of Windings 
in Magnetizing Coil. 
Steel Core. 
Iron Core. 
I. 
156 
184 
II. 
130 
176 
III. 
120 
184 
IV. 
128 
180 
V. 
112 
186 
VI. 
160 
180 
Total Windings 
806 
. 
1090 
