292 Proceedings of the Royal Society of Edinburgh. [Sess. 
XXI. — Transverse Induction Changes in Demagnetised and Partially 
Demagnetised Iron in relation to the Molecular Theory 
of Magnetism. By James Russell. 
(Read March 4, 1912. MS. received March 26, 1912.) 
In a former communication * the seolotropy of iron, demagnetised by the 
method of decreasing reversals, was shown. During the early stages of 
induction the permeability is greater to the re-application of a magnetising 
force in the same direction — whether positive or negative — as that used in 
the immediately preceding demagnetising process, than to a transverse 
force. The demagnetisation is complete in the sense that there is no 
external polarity, and also in the sense that perfect symmetry exists to 
the subsequent application of the same positive or negative directional 
field. This symmetry being uni-directional, seolotropy immediately appears 
if the subsequent magnetising force contains a transverse component. 
The hypothesis was advanced that on the completion of the demagnetis- 
ing process by decreasing reversals of a directional force ab, a preponderance 
of the molecules might set equatorially in reference to this force. If the 
subsequent magnetising field makes an angle other than zero with ab, the 
number of molecules lying in the most advantageous position — i.e. at right 
angles to the new field — is reduced and the deflecting moment becomes less 
and less as the angle approximates to 90°. A general explanation is thus 
afforded, in terms of the theory of rotatable molecular magnets, why iron 
in the early stage of induction is not isotropic to a magnetising field having 
a component at right angles to that used in the immediately preceding 
demagnetising process. 
It follows as a deduction, either from the above hypothesis or from the 
fact of the molotropy of demagnetised iron,-|* that, when the angle between 
the demagnetising force and that subsequently applied is other than 0° and 
90° the application of the latter ought 
First. — To develop a transverse induction component which will tend 
to disappear as saturation values are reached ; and which ought 
Second — To change sign if either the direction of the subsequently 
*“ Magnetic Shielding in Hollow Iron Cylinders,” Trans. Boy. Soc. Edin ., vol. xl. pp. 
649-654 (on “ Magnetic iEolotropy ”). 
+ “ The Molecular Condition of Iron demagnetised by Various Methods,” Proc. Boy. Soc. 
Edin., vol. xxiv. p. 544. 
