THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



JULY 1900. 



I. Effects of Temperature on the Magnetic Properties of Iron 

 and Alloys of Iron. By R. L. Wills, A.R.C.Sc.L, 1851 

 Exhibition Scholar, St. Johns College, Cambridge *. 



THE experiments of Baur f, Hopkinson i, Morris §, and 

 others on the effects of temperature on the magnetic 

 quality of iron show that as the temperature is raised the 

 magnetization for small magnetizing forces increases, at first 

 gradually, but beyond a temperature of about 600° C. the 

 permeability increases very rapidly until the critical tem- 

 perature is approached, when the magnetization suddenly 

 disappears. 



The maximum permeability obtained by Hopkinson was 

 about 11,000 with a magnetizing force of 0"3 c.G.S. at a 

 temperature of 775° C. The rise in permeability is less and 

 less as the magnetic force is increased ; with a force of 

 4 c.G.s. the permeability remains practically constant as the 

 temperature is raised till about 700° C. is reached, then the 

 permeability falls, but much more gradually than with lower 

 magnetizing forces. 



To explain these results Professor Ewing || has applied a 

 modification of Weber's molecular theory, in which the con- 

 straint of the molecules is supposed due to their mutual 

 action as magnets. 



* Communicated by Prof. J. J. Thomson, F.Pv.S. 

 t Wied. Ann. xi. p. 407 (1880). 

 % Phil. Trans, vol. clxxx. A. pp. 443-465 (1889). 

 § Phil. Mag. September 1897, pp. 229-230. 



|| Proc. Roy. Soc. vol. xlviii. pp. 215-216 (1890). See Ewing's 

 ' Magnetic Induction in Iron and other Metals,' chap. xi. 



Phil. Mag. S. 5. Yol. 50, No. 302. July 1900. B 



