EFFECT OF TWIST OX THE MAGNETIZATION OF NICKEL ANi> IKON. -05 



lîy examining the curve (i ig'. 35) we see that on twisting the 

 wire, there is constant decrease of magnetization, while on untwist- 

 ing, the magnetization rises steadily till it reaches a maximum, after 

 which it returns to its original value at the initial position of zero 

 twisting'. Thus in the returning branch the curve is no more 

 lower than in the going 1 branch, so that the course of the magnetiza- 

 tion curve is opposite to that for the twists smaller than and up to 

 ± 9°.0. As was already noticed in nickel, there is also reversal of 

 hysteresis in iron. So far as my experiments go, the strength of the 

 field or the amount of longitudinal stress does not seem to produce 

 ;iii\ remarkable variation on hysteresis, as the curves (Fig. 3o*, 37, 

 38) will shew. 



It is thus established that the hysteresis in iron becomes reversed 

 when the range of twist exceeds a certain limit. This must evidently 

 lie between the twists of± 9° and ± 13°^ per cm. Bui ii is not easy 

 to determine the exact critical twist, even by experimenting for twists 

 intermediate between the two. For a twist of \'2° per cm. the 

 difference between the going and returning branches of the curve 

 diminishes to a certain extent as will be seen from Fig. 39. For 

 a twist of 10. °4 (Fig. 40) the two brandies of the curve are separated 

 by a still smaller interval ; but still the former lies below the latter, 

 so that the hysteresis is opposite in character to that for the twist of 9° 

 per cm. Judging from these experiments, it can safely be inferred 

 that the curious phenomenon of the reversal of hysteresis in iron 

 takes place when the range of twist amounts to about ± 10° per cm. 



Comparison of results for iron and nickel. — Comparing these results 

 for iron with those obtained for nickel, we find some analogy between 

 the two. As was formerly remarked, the changes in magnetiza- 

 tion in nickel due to cyclic twistings are opposite in character 

 to those of iron. But when the amount of twist as well as the 



