MAGNETIZATION OF XIcTCKL. 



29?. 



o 



:ill lor ilie particular range of iwist. Tlii.s is .-^Iidwii in Fig. 8, which 

 is the curve for a tension of 782 kgs. weight per sq. cm. 



A study of these from curves (Figs. 5, 6, 7, 8,) sliows the cha- 

 racter of the changes wrought in tiie cycles as tlie load is increased. 

 The symmetry is first lost, the negative loop becoming smaller and 

 smaller. Then, as shown in Fig. 7, it ceases to he a loup, the course 

 i" the return rurve from greatest negative twist lying above the other, 

 and ne\ or rutting it. Then as in Fig. 8, the «/*«'« r«^ course of the 

 curve on the negative side of zero twist vanishes awav altogether ; 

 while at the same time the phennmenon nf reversal of magnetic polar- 

 ity shows itself. Thus the double- looped curve for low tensions 

 passes gradually into a single-looped curse as the tension is increased. 

 And after this single-looped cur\e is obtained, the pheiiomenon of the 

 reversed polarity begins to appear. The passage from the double 

 looped to the single looped <Mn-vç lietokens a peculi;u' alteration in the 

 lag'Jïing'-effect in nickel — :ui alteration wbii-li has no anidoo-ne in the 

 case of ii'on. 



To studv mure carefullv the law ui' ////.s/c/vn/s in nickel — to use 

 Professor F^wing's w<ird — tlie experiment- were repeated in stronger 

 fields. 



Figs. il. 10. 11, 12 show the march of events in a field of 4.94 

 units, the tension- increasing iVuiu 100. V(.v smaller tensions the 

 curves ai'e of tlie apjjroximatelv svmmeti-i<'al form shown already in 

 Fig. .5. an<l do not call for special remark. 1 l(Te then we see how 

 the already diminished loop for negative twisting, as shown in Fig. 9. 

 has vanished altogether in F'ig. 10. At the same time, the curve 

 begins to cross the lines of zero magnetization into the negative region. 

 Fig. 11 is a fui'tber development in the same direction. In both 

 of these cui-ves (10 and 11), the (juantitv , "^ , the rate of change 

 of magnetization with twist, still changes sign at particular twists. 



