344 H. SAGAOKA. 



Professor Ewing has remarked that the production of a transient 

 current by twisting an iron wire in a magnetizing held is a natural 

 consequence of Sir William Thomson's discovery that aeolotropic 

 stress gives rise to aeolotropic magnetic susceptibility in iron. The 

 stress on twisting the wire is equivalent to compression and stretch- 

 ing along lines perpendicular to the radius, and inclined at 45° to the 

 normal plane section. The susceptibility along the lines of com- 

 pression is different from that in the direction of stretching. The 

 consequence is that the lines of induction originally parallel to the 

 axis of the wire are changed into helices which are inclined toward 

 the direction of the relatively increased magnetic susceptibility. 

 These considerations lead to the conclusion that in nickel, the direc- 

 tion of the current is determined by that of compression while in iron 

 it is determined by that of stretching. Thus the direction of the 

 transient current in iron and nickel should be in opposite directions, 

 and in fact this was found to be the case. 



It ma}', however, be doubted whether the effect of twisting is 

 even approximately equivalent to compression in one direction and 

 extension in the other. It is not at all improbable that twist gives 

 rise to changes in the molecular configuration of the wire. As we 

 are absolutely ignorant of the ultimate structure and arrangement of 

 the molecules, nothing definite can be stated. But if there is any 

 change produced among the polarized molecules of the magnetized 

 wire, it is quite probable that the displacement of the molecules will 

 give rise to changes in the transient current, which will be quite 

 inexplicable in terms of aeolotropic susceptibility as generally as- 

 sumed. Although such aeolotropy ma)' be one of the chief causes of 

 the transient current, yet other causes ma) 7 exist whose effects can 

 not be neglected. In fact, I have reason to believe that aeolotropy 

 does not sufficiently explain all the phenomena observed in 



