on the Magnetic Properties of Iron. 5 



similar to one another, the maximum permeability in each 

 case occurring at values of the magnetic force depending 

 on the temperature. 



Plotting the curves for different temperatures and observ- 

 ing the force at which the maximum permeability occurs in 



Fiar. 1. 



4000 



3000 



a. 2000 



1000 











































10 12 14 16 18 



H 



each case, we may obtain some idea as to how much earlier 

 in the magnetizing process the successive stages are brought 

 on by heating to any temperature, and from this ascertain the 

 rate of transition from stage to stage as the temperature 

 is raised. 



The ring was next very slowly heated and the following 

 results obtained with a constant magnetizing force of 

 6*45 c.g.s. : — 



Temp. 



in deg. C 



Induction 



per sq. cm 



.} 



15° 



12991 



223° 



391° 



577° 



712° 743° 



766° 



12991 



12883 



12233 



8877 3247 



93 



It will be seen the induction remains practically constant 

 as the ring is heated until the temperature reaches about 

 400° C. ; then the induction falls, at first slowly, but more 

 rapidly when a temperature of about 700° C. is passed, and 

 the specimen becomes practically non-magnetic at about 

 776° C. The ring was heated slightly above the critical 

 temperature and a very slight movement in the galvanometer 

 on reversing the magnetizing current observed. 



Readings were taken at various temperatures as the gas 

 was lowered with the same magnetizing force; the magnetic 

 quality returns as rapidly as it disappeared, but at a slightly 

 lower temperature. 



