1912-13.] Magnetic Induction in Ferric Oxide. 
69 
VII. — Preliminary Observations on Magnetic Induction in Ferric 
Oxide at Various Temperatures and in Different States, and on 
the Possible Chemical Changes indicated by the Observations. 
By G. E. Allan, D.Sc., Lecturer on Electricity, Pure and Applied, and 
Assistant to the Professor of Natural Philosophy in the University 
of Glasgow; and John Brown, M.A., B.Sc., Houldsworth Research 
Scholar in the University of Glasgow. Communicated by Professor 
A. Gray, F.R.S., LL.D. 
(Read July 1, 1912. MS. received December 8, 1912.) 
Magnetic Induction in Ferric Oxide. 
In a previous paper by one of us,* it was shown that a certain part of 
rock magnetism was variable and uncertain under the influence of raised 
temperature. In some instances the rock specimen became permanently 
more magnetic after it was heated in air, whereas, in the majority of cases, 
heating caused great loss of magnetic quality. It was suggested that the 
increase of magnetism observed was caused by the transformation of 
haematite into a more magnetic iron oxide. 
In order to obtain material which might support this assumption, and 
also to amplify the work of previous investigators, experiments were 
undertaken with artificial and natural ferric oxide, in which the trans- 
formation of ferric oxide from a non-magnetic into a magnetic condition 
was observed, while some of the conditions which assist or impede this 
change were also studied. 
The magnetic properties of crystalline haematite have been described 
by Westman and Kunz, and Abt has given an account of those of the 
compact ore. 
J. Westman,]- dealing with specular iron ore (Eisenglanz) , subjected it 
to magnetic fields up to 70 C.G.S., and found that the mineral possesses 
considerable coercive force, also that the magnetic property is confined 
chiefly to the base plane of the crystal. The susceptibility of crystalline 
haematite amounts to only one- to two-thousandths of that of ordinary 
iron. 
J. Kunz, l from tests of over a hundred specimens from different sources, 
* Phil. Mag., April 1909. 
t Upsala Universitets Arsskrift, 1896 ; Mat. och Naturv., ii. 1, 1897. 
X Neues Jahrb.f. Miner alogie, vol. i. pp. 62-88, 1907. 
