24 Magnetic Properties of Alloys of Nickel and Iron. [Dec. 12, 



non-magnetic at 13° C, is now decidedly magnetic at the same tem- 

 perature. On heating the material it remained magnetic until it 

 reached a temperature of 580° C. At this temperature it became non- 

 magnetic, and, on cooling, remained non-magnetic to the ordinary 

 temperature of the room. Eig. 2 shows the inductions at various 



Fig. 2. 



temperatures, the abscissa? being temperatures for a magnetising 

 force 6' 7, whilst fig. 3 shows the induction in terms of the tempera- 



EiG. 3. 



4000 



-r 



V 































\ 



























° 2000 





X 































4 



Mt 



7/VM 



2 t'LS 





fir, 















i 







A 









trig 















temp 



i 



zrature 







IC 



0° 



21 



)0° 











E 



5 





ture to a different scale for a force of 64. These curves show that, for 

 a range of temperature from somewhat below freezing to 580° C, this 

 material exists in two states, either being quite stable, the one being 

 non-magnetic, the other magnetic. It changes from non-magnetic to 

 magnetic if the temperature be reduced a little below freezing ; the 

 magnetic state of the material does not change from magnetic to non- 

 magnetic till the temperature is raised to 580° 0. 



The same kind of thing, in a much less degree, can be seen with 

 ordinary steel. Over a small range this can exist in two states, but 

 in changing its state from non-magnetic to magnetic a considerable 

 amount of heat is liberated, which causes a rise of temperature of the 

 steel. Whether any material quantity of heat is latent in the nickel 

 steel I do not know. 



