2 ART. 14.— K. HOXDA AND S. SHIMIZÜ : 



examined by C. O. Knott who found tliat the tension diminished the 

 angle of twist in these metals. 



Tlie present paper consists of two parts : firstly we deal with the 

 influence of tension on the Wiedemann effect in nickel steels, and 

 secondly with the same effect in ferromagnetic bars and the effect of 

 torque on it. AVe lately published a paper relating to the effect of 

 tension on the mao;netic chansre of leng'th ; in this we found that the 

 magnetic elongation of nickel steels is largely affected by tension, and 

 that when the tension exceeds a certain value, the contraction is 

 accompanied by magnetization. From Maxwell and Crystal's ex- 

 planation as well as from that of Kirchhoft' for the Wiedemann effect, 

 it seems probable that the direction of twist in nickel steels is reversed, 

 when the suspended weight exceeds the said limit. We therefore 

 studied this point particularly and found that the above inference is 

 not correct. 



So far as we are aware, AYiedemann effect m cobalt has not yet 

 been studied, perhaps because it is difficult to obtain a specimen in 

 the form of a wire on account of its brittleness. It was therefore 

 desirable to have an experiment for the metal. Our apparatus used 

 in studying the change of rigidity by magnetization was conveniently 

 used for examininfr the Wiedemann effect of ferromao^netic bars. We 

 had two cobalt bars, one in the cast state and the other in the annealed. 

 The observations showed that the torsion in cobalt was opposite to 

 that of iron, as was to be expected from the change in length by 

 magnetization. 



