66 Prof. Nagaoka and K. Honda on Magnetostriction 



the direction of the induced current is opposite to that in iron, 

 and the total quantity of the current attains a maximum, 

 whence it continually diminishes, but not to such an extent 

 that the current ultimately changes its direction. 



Fig. 15. 



These experiments show that the twist produced by the 

 combined action of the longitudinal and circular magneti- 

 zations, the circular magnetization produced by twisting a 

 longitudinally magnetized wire, and the longitudinal mag- 

 netization caused by twisting a circularly magnetized wire, 

 are characterized by having various peculiarities, which are 

 common to all of them. This cannot be a mere chance 

 coincidence ; we shall have to ascribe these allied phenomena 

 to the same common cause. 



In these experiments we were assisted by Mr. S. Shimizu, 

 a post-graduate in physics, to whom our best thanks are due. 



(d) Application of Kirchhoff's Theory to Wiedemann Effect. 



In our last paper on magnetostriction, we noticed that 

 Kirchhoff's theory can be extended to the study of the relation 

 between torsion and magnetization, exactly in the same 

 manner as was done by Maxwell and Chrystal to explain the 

 Wiedemann effect. There we found that the mean circular 

 magnetization called into play by twisting a ferromagnetic 

 wire of radius B, through an angle co amounts to 



_ 1 



\a>k J '£B.. 



(A) 



