328 H. NAGAOKA. 



be taken in discriminating the untwistings due to magnetization and 

 to after-effect in nickel is greatly lessened as compared with the pre- 

 cautions necessary in the case of iron. If sufficient care be taken to 

 wait till the after-effect l^ecomes very small, we may use thin nickel 

 wires in the investigation of the effect of magnetization on torsion. 

 Generally I waited an hour after the cessation of torsional oscillation, 

 but if the wire was loaded, it was left for a night. 



The thicknesses of the wires used in the present investigation varied 

 from 0.34 to 0.72 mm. Most of the experiments were tried with 

 the thinnest, for with it the effects were greatest. The wire was 

 always carefully annealed by means of a Bunsen flame. It so happen- 

 ed, that when the twist was very large, the wire once used assumed 

 a spiral aspect as was observed by Himstedt.* Such wires were rejected, 

 and other wires cut from the same specimen were used instead. 



The experiment was first tried with the wires aljove mentioned, 

 when the permanent twist was very small, and the wire was subjected 

 to weak longitudinal stress. The following gives the readings of 

 untwistino- due to man-nctization when the load was the weio^ht of the 

 cross only. 



* Wied. Ann. 17. pg. 712. 



