196 TT. XAGAOTCA. 



nickel wire. Out of the many curves obtained in this series, I give 

 only three, those namely which correspond to fields of 2.8, 15. 3, 21.1 

 units respectively. The first two curves (Fig. 9 and Fig. 10) have 

 the some characteristics as those obtained for nickel twisted through 

 ± 0°.S6 per cm. There is still true lagging on untwisting. But the 

 third curve (Fig. 11) for §=21.1 is not similar to the corresponding 

 curves represented in Fig. 7 and Fig. 8. The curve in its general 

 form is like those obtained for smaller twists, hut the nature of the 

 hysteresis has been changed. The hysteresis which has been positive 

 for the two former curves becomes negative for this strength of the 

 magnetizing force. The magnetization diminishes on twisting till 

 the extreme limit of torsion is attained, and on untwisting it gra- 

 dually increases. If the magnetization had tended to lag behind, as 

 was found to be the case for the smaller twist, the return curve would 

 have been the lower. But this is no more the case : the curve on 

 untwisting passes above that of twisting, and thus there must have 

 been reversal of hysteresis for this strength of the magnetizing force. 

 It is at once apparent that the strength of the magnetizing field is 

 one of the principal factors affecting the phenomenon of the reversal 

 of hysteresis. 



In order to investigate this change more thoroughly, a new wire 

 was taken from the same bundle, and examined in fields §=16 

 (Fio-. 12) and «0=20.8 (Fig. 13). The former curve shows that there 

 is decrease of magnetization up to a certain amount of twist, but on 

 further twisting there is increase. This increase, however, is so 

 small that it is barely sufficient to attain the original intensity even 

 at the extreme limit of twist. On untwisting, the magnetization 

 gradually diminishes but increases again, passing through a minimum 

 value before the wire is completely brought back to its initial posi- 

 tion. This peculiarity of a minimum on untwisting had never been 



