1 92 



II. XAGAoKA. 



The examination of the curve (Fig. 1, Plate XXYJI.) will shew 

 that on twisting the wire in the positive direction, there is a slight 

 diminution of magnetization till the angle of twist amounts to about 

 10°, then the magnetization gradually increases up to 30? On un- 

 twisting, the magnetization diminishes, but at a somewhat slower 

 rate than it had just been increasing, so that the return curve lies 

 above the other until the wire is nearly all untwisted. The same 

 things happen during negative twisting and untwisting. Thus in 

 the present instance, the course of the change of magnetization is 

 quite different from what was obtained in my former experiments 

 under like circumstances. There I found that when the nickel wire 

 was twisted h 1^5 Tier cm., the magnetization rose gradually till the 

 maximum twist was reached, but on untwisting diminished at a 

 somewhat quicker rate than it had just been increasing, so that the 

 return curve lay below the other.* 



Reversal of hysteresis. — Comparing these two experiments, we lind 

 that there is true lairirinu' or hysteresis in magnetization when the 



* In my former paper, I spoke of Fig. 5 (PI. XVI.) as being exactly the reversa of Thom- 

 son's curve for iron, but I was mistaken ; had the course of the curve been as for the twist of 

 0".86, it would have been so, but not otherwise. 



Compare also Professor Wiedemann's curve (Fig. 1) in his paper HIa(fnctischc i Untei'su- 

 chmujai (Wied. Auu, 13d. XX Vil, L8SG). 



