CHANGE OF ELASTIC CONSTANTS OF FERJIOMAGNETICS. 07 



•wire traversed by an electric current/^' The change of magneti- 

 zation by the longitndiual current is considerably greater, in the 

 case of magnetizing the wire traversed by the current, than in 

 the case of passing the current through the magnetized wire. 

 All these jihenomena may perhaps arise from the hysteresis effect 

 of magnetization ; i.e. the final states attained by a magnetic sub- 

 stance differ according to the order of applying the field and the 

 stress, or the field and the longitudinal current. 



In conclusion, it may be remarked that, since the change of 

 the elastic constants by magnetization is not so small as is gener- 

 ally believed, in any theory of magnetostriction aiming at the 

 <piantitative agreement between the theory and the experiment, 

 these changes must necessarily be taken into account. In addition 

 to this, an equality such as 



dxd// H/jüx ' 



in which § is a quantity which depends upon two apparently 

 independent variables x and y, can not be used without experi- 

 mental verification. These facts make the development of the 

 theory very difficult. 



In passing, the following remarks may be added. If we con- 

 sider, in the above equation, Q as the length of a specimen, :c 

 the temperature and y the magnetic force, we have 



provided I is independent of the order of applying the field and 

 the temperature. Integrating, we get 



Khr-lg) 



m 



(^ m. )h \ m Jo 



*) K. Honda, Ibid. 11, p. 284, 1899. 



