CHANGE OF RIGIDITY BY MAGNETIZATION. 



13 



Thus ill nickel, the ratio is rather large compared with other 

 ierroiiKiuneties. In the former experiment, the change of elasticity 

 of tlio same metal, even in a liardened state, was rather large. If we 

 should study the change of elasticity with the present sample, pro- 

 ])orti()iialIy large changes would be observed. That this inference is 

 ])rol)al)Iy correct, may be seen from the results of the method of 

 elongation ; in this case, a well annealed nickel wire was examined, 

 ;uid a large change of elasticity amounting to about 6 % was 

 ol)tained. 



Accordino- to Professor Nao-aoka'^ and Zehnder^^ the mag'netiz- 

 ation of nickel increases by twisting in weak fields ; in strong fields, 

 however, it diminishes by twisting. These results are reciprocally 

 related to ours. 



The change of torsion thus fîxr described for iron, steel, cobalt 

 and nickel is independent of the direction of the magnetizing force. 



From the above result, we may conclude that in ferromagnetic 

 substances, which undergo a large change of elasticity, there is also a 

 proportionally large change of rigidity, and that the natures of their 

 changes are parallel to each other. 



7. In comparing the change of rigidity by magnetization with 

 that of elasticity, we observe the one marked ditference that the 

 change of rigidity is independent of the applied stress, while that of 

 the elasticity is largely inttuenced by it, especially in small stress. 

 Hence it may be suspected that the observed change of elasticity may 



1) Nagaoka. Jour. Coll. Sei., Tokyo 2, 30i, 1888 ; 3, 189, 1889- 



2) Zehnder, Wiecl. Ann. 41, 210, 1890. 



