4 Mr. R. L. Wills on the Effects of Temperature 



Sectional area . . . . =1*50 sq. cms. 



No. of turns in primary coil ... 75 



„ „ secondary coil ... 50 



Mean value of magnetizing force per ampere of current 

 = 4'3 c.G.s. 



The induction corresponding to a ballistic throw of one 

 scale-division on reversing the current when there was no 

 additional resistance in the secondary circuit was 9*334. 



The specimen was first demagnetized by reversals of 

 current, by passing currents successively diminishing in 

 amount to zero and rapidly alternating iu direction through 

 the primary, any initial magnetism the ring may have 

 possessed was thus got rid of. 



Magnetizing currents were next passed through the primary 

 circuit while the ring was at the ordinary temperature of the 

 room ; each current was reversed several times and the kicks 

 in the galvanometer noted. 



The results, reduced to c.G.s. units, were : — 



H. 



p. 



H. 



/*• 



H. 



301 



3129 



H. 

 12 9 



fi. 



1124 



0-086 



379 



172 



3084 



0-344 



543 



1-935 



3245 



4-30 



2608 



17-2 



858 



0-688 



814 



2-15 



3273 



602 



2089 







1-075 



1299 



2-58 



3231 



8-60 



1581 







where H represents the magnetizing forca and fi the per- 

 meability. 



The passage from one stage of the magnetizing process to 

 another is gradual, taking place through a definite range of 

 magnetic force. Nagaoka* has shown for nickel that the 

 passages from stage to stage can be made much more abrupt 

 by applying torsion with a longitudinal pull. 



For the present purpose it will be more convenient to 

 represent the results of experiment by plotting permeability 

 as ordinates instead of induction, showing the relation between 

 permeability and magnetic force. 



Fig. 1 represents the curve thus obtained from the data 

 given above. The permeability reaches a maximum with a 

 magnetizing force of about 2 C.G.s., and when the third stage 

 of the magnetizing process is entered upon the permeability 

 falls very rapidly. 



Corresponding curves for higher temperatures are very 



* Journal of the College of Science of the University of Tokio, vol. ii. 

 p. 304 (1888). 



