202 H. XAGAOKA. 



curve becomes double looped simultaneously with the vanishing of 

 the opposite polarity. The newly formed loop gradually widens as 

 the magnetizing force is further increased, as will be seen from Fig. 

 28. The experiments made for the twists of ± 0.°86, ± 1°.7, ± 4°.o 

 all show that the cyclic curve of magnetization is gradually trans- 

 formed from a double looped to a single looped curve, when the wire 

 begins to shew opposite polarity. 



Large twists applied to nickel do not seem to affect the pheno- 

 menon of reversal of polarity. After observing the changes in mag- 

 netization as shown in Fig. 22, I loaded the wire with 1 kgrm. 

 weight. The longitudinal stress thus applied was already sufficient 

 to cause the reversal of polarity and the curve as shown in 

 Fisr. 29 was obtained. It is single looped and similar in character 

 to those observed for the twist of ± 4°. 5. The results thus 

 far obtained by varying the amount of twist from ± 0°.86 to ± 9° 

 per cm. prove that the phenomenon of the reversal of polarity always 

 takes place however the twist may vary, provided sufficient longitu- 

 dinal stress be applied. To examine more particularly into these 

 intricate relations between twist, longitudinal stress, and magnetization 

 would mean an amount of labour, whir-h the importance of the subject 

 hardly seems to merit, 



Effect of Twist on the Magnetization of Iron. 



This subject was first investigated by Sir William Thomson, and 

 t ho experiments to be described are to a great extent merely a repeti- 

 tion of his. The effect of twist on the magnetization of iron is not 

 of so complex a character as it is in the case of nickel. In iron, 

 the effect of the longitudinal stress combined with twist does not 

 produce any reversal of polarity, nor are the changes of hysteresis 

 so intricate as in nickel. But when the twist exceeds a certain limit, 



