WIEDEMANN EFFECT IN FEKßOMAGNETIC SUBSTANCES. 5 



2. The wire was then stretched by different loads and the 

 above processes were rej^eated. 



3. The longitudinally magnetizing- current was kept 

 constant, and the amount of twist measured by varying 

 the circularly magnetizing current. 



Before each experiment care was taken to demagnetize the wire 

 completely either longitudinally or circularly by passing an alternate 

 current of gradually diminishing intensity. This was found absolutely 

 necessary to secure correct results. 



Twist hi/ varying the loiigitmliiial field. If the direction of the 

 longitudinal field is right-handedly related to that of the circular field, 

 nickel steel is twisted in the direction of the latter. As shown in 

 Figs. 1 and 2, under a given circular field, the amount of twist at 

 first increases till it reaches a maximum, after which it gradually 

 diminishes. But the reversal of the twist is never observed, thousfh 

 the field exceeds 1200 C.Ct.S. units. The position of the maximum 

 twist is slightly displaced in high fields as the longitudinal current 

 increases. The amount of twist is greater in 45% nickel steel than 

 in Sd% nickel steel. Some observed readings are given in the follow- 

 ing tables : — 



