194 



H. NAGAOKA. 



of zero twist. The curve of magnetization for stronger field« (Fig. 5) 

 are similar to the aboves, the range of the change of magnetization 

 becoming 1 apparently greater as the magnetizing field is increased. 



oil JO o o 



Reversal of polarity for the. twist of ± 0°,86. — The next wire used 

 was taken from the same specimen as before. A weight of 5 kgs. (881 

 kg. cmr' ; ) was strung to the end of the brass wire attached to the 

 lower extremity of the nickel wire. After the wire was brought to 

 the cyclic condition by repeated torsion and detorsion in a field of 

 0.34 unit, the following deflections were taken. 



These readings shew that, in the given field, the amount of lon- 

 gitudinal stress was sufficient to produce the phenomenon of reversed 

 polarity. The magnetization curve (Fig. G) when compared with the 

 corresponding curve for the twist of ± 4°.5 again indicates how the 

 changes of magnetization differ in these two cases. In former expe- 

 riments, there was always increase of magnetization on first twisting, 

 and decrease on untwisting, the hysteresis being negative. In the 

 present instance, there is steady decrease of magnetization during 

 positive twisting, and increase during untwisting. Besides, as the 

 twist at either extremity begins to be undone, the magnetization lags 

 behind, so that the hysteresis is positive. 



These experiments sufficiently prove that the reversal of polarity 



