'3 



•THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE 



[FIFTH SERIES. 



SEPTEMBER 1897.. 



XXXII. On the Magnetic Properties and Electrical Resistance 

 of Iron as dependent upon Temperature. By David 

 K. Morris, Ph.D., formerly 1851 Exhibition Scholar, 

 University College 3 London*. 



[Plates II. & III.J 



rff^HE changes brought about by heating in the various 

 JL physical properties of iron have been, since the first 

 investigations into the nature of the phenomenon of recales- 

 cence by Gore and by Barrett, the subject of much experimental 

 work, which, during the last ten years, has been largely upon 

 the relation of the magnetic properties of iron to temperature. 

 As long ago as 1879, however, Baur of Zurich f described 

 experiments on an iron bar inserted while hot into a long- 

 magnetizing helix, which served to determine its permeability 

 at any instant, the temperature being estimated from a 

 knowledge of the law of cooling. This method, although 

 rough, enabled him to show that in weak magnetic fields the 

 permeability of iron rises, and that in strong ones it falls, with 

 rise of temperature ; and that as the critical point is reached 

 the magnetic qualities of iron in fields of all strengths very 

 rapidly disappear. 



These results have been confirmed and extended by the 



* Communicated by the Physical Society : read May 14, 1897. In- 

 augural Dissertation for the Degree of Ph.D. at the University of Zurich. 



t C. Baur, " Neue Untersuchungen iiber den Magnetismus," Wied. 

 Ann. 1880, p. 394. 



Phil. Mag. S. 5. Yol. 44. No. 268. Sept. 1897. R 



