THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCI 



[SIXTH SERIES. 



JULY 1912. 



I. On the Magnetic Properties of a Graded Series of Jtftc/ceZ- 

 Manganese Alloys. By James G. Gray, D.Sc, Lecturer 

 on Physics in the University of Glasgow*. 

 [Plate L] 



THE magnetic properties of iron, steel, nickel, and cobalt 

 at moderate and high temperatures have been investi- 

 gated by numerous experimenters, notably by Rowland f, 

 Baur i, Trowbridge §, Perkins ||, Tomlinson IT, and Hop- 

 kinson **. For the above mentioned metals it was shown 

 (for temperatures lying between room-temperature and the 

 so-called critical temperatures of the materials) that the effect 

 of a rise in temperature is to bring about an increase in the 

 susceptibility for low values of the magnetizing force, and a 

 diminution for large values. Thus if we denote the magneti- 

 zation curves corresponding to temperatures ^ and t 2 (t 2 >t 1 ) 

 by A and B respectively, the curve A lies at first below, and 

 finally above, the curve B, provided that the magnetizing 

 force is pushed far enough. 



To account for this result Hopkinson regarded the iron or 

 steel as made up of permanently magnetic molecules, the 

 axes of which become more or less directed to parallelism by 

 magnetic force. The effect of rise in temperature is to 

 diminish the magnetic moment of the molecules, gradually 



* Communicated bv Professor Andrew Gray, F.R.S. 

 t Phil. Mag. xlviii. p. 321 (1874). J Wied. Ann. si. p. 394 (1880). 

 § Proc. Amer. Acad. p. 462 (1885). || Sill. Journ.xxx.p.218(1885). 

 «[ Phil. Mag. xxv. p. 372 (1888). ** Proc. Eoj. Soc. xlv. p. 318 (1889). 



Phil. Mag. S. 6. Vol. 24. No. 139. July 1912. B 



