Brown — The Subsidence of Torsional Oscillation^ 



525 



From previous work one would have tliought that tlie higher the 

 frequency of the applieil alternating magnetic field the greater would liave 

 been the fatigue of tlie wire ; hut, as the above figures show, a nickel wire of 



a given rigidity can only be fatigued to a certain maximum amount by a 

 magnetic field of a certain frequency ; and the application of a higher 

 frequency magnetic field does not fatigue tlie wire more, but fatigues it to a 

 given maximum in a sliorter period of time. 



In fact, it would appear that the time taken to effect the maximmn fatigue 

 varies iiwersely as the frequeiictj of the applied alternaiing magnelic field. The 

 figures given in Table II for the higher frequency 250 vary slightly from 

 this law ; but in this case the maximum fatigue might have liappened in 2'4 

 instead of 2'5 minutes, which would make it fall in with the rule. As for the 

 figures given for the lower frequency 50, on account of the small quantities 

 observed, a slight error might creep in, and the maximum might easily have 

 been 0'271 taking place in 12 instead of 8 minutes ; in that case this would 

 also fall in with the law above stated. 



Some of the results obtained for the subsidence of torsional oscillations in 

 the same wire are given in Table III ; for the sake of comparison, observations 

 were taken in two longitudinal magnetic fields, D. C, as well as in the five 

 alternating magnetic fields, A. C. 



