On the Production of Transient Electric Currents. 121 



JMagnetlSing 



current. 



Torsion. 





magnetisation. 



(VTolra A 



OLccttl^ ah T \J\J 



+ 39 



+ 39 





)} 5> J> 



— 78 



— 39 



T> f „ A 



J5 5> JJ 



4- 78 



T / O 



T OC7 





4- fn fiO° 



^ OU L 'J UV7 



— 72 



QQ 



— OO 





After several "J 









+ and — twists, I 



-64 



-32 





+ 60° to -60° J 









-60° to +60° 



+ 64 



+ 32 



Then, Reverse A to B. 



at +60° 



-71 



-39 



B to A. 





+ 78 



+ 39 



Also, starting from a neutral state — 





0° to + 60° 



+ 35 



+ 35 





at +60° 



-74 



-39 



„ B to A 



33 33 



+ 78 



+ 39 



These figures show that if we call +39 the normal circular magneti- 

 sation proper to the given torsion (60°) and the given longitudinal 

 magnetising force, then the first application or reversal of the mag- 

 netising force while the wire is held twisted developes the full normal 

 value of the circular magnetism, whereas the first application or 

 reversal of the torsion under constant magnetising force does not 

 produce the normal value, but something less. Also that this defect 

 of circular magnetism is increased by successive back and forth twist- 

 ings, which finally cause the circular magnetism to oscillate between 

 two considerably reduced values. After this steady state has been 

 reached, a single reversal of the longitudinal magnetising force, the 

 torsion being kept constant, suffices to produce the full normal value 

 of the circular magnetism proper to the state so arrived at. 



§ 10. If after being circularly magnetised by applying longitudinal 

 magnetising force whilst it is held twisted, the wire be relieved of 

 torsion by allowing the twisting arm to return suddenly, but without 

 shock, to zero, a portion of the circular magnetism survives the 

 removal of the stress which gave rise to it. Thus : — 



Magnetising 

 current. 



Torsion. 



Transient 

 current. 



Circular 

 magnetisation. 





At +60° 



+ 39 



+ 39 





+ 60° to 0° 



-24 



+ 15 



Also, „ „ 



to -60° 



-48 



-33 



From the last observation it will be seen that the second step 



