Rigidity of Ferromagnetic Substances by Magnetization. 545 



In a given field the change of rigidity is independent of 

 the twisting couple. It is also a proof of the same fact that 



Fig. 8. 



the curves corresponding to different couples pass through a 

 point on the axis of the field. The ratio of the change to the 

 modulus itself for different fields is given in the following 

 table and in fig. 4. 



H 20. 40. 80. 100. 200. 400. 600. 800. 



— xlO 2 . .-0-96 -1-68 -0-67 0-12 263 5-32 6-67 7*48 

 K 



Thus in nickel the change of rigidity is considerably larger 

 compared with other ferromagnetics. The nickel rod used 

 in the preceding experiment was turned into a square rod 

 from a plate, and the mechanical process, which the specimen 

 underwent, hardened it in magnetic quality. If we study 

 the change of elasticity with the present sample the propor- 

 tionally large change would be observed. 



According to Profs. Nagaoka* and Zehnderf the mag- 

 netization 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 twist so far described for iron, steel, nickel, 

 and cobalt is independent of the direction of the magnetizing 

 field. 



9. In comparing the change of rigidity by magnetization 

 with that of elasticity, we observe one marked difference that 

 the former is independent of the applied stress while the 

 latter is largely affected by it, especially with small stress. 



* Nagaoka, Journ. Coll. Sci. Tokyo, ii. p. 304 (1888) ; iii. p. 189 

 (1889). 

 f Zehnder, Wied. Ann. xli. p. 210 (1890). 



