188 CG. KNOTT 



magnetised circularly by a current passing along it. the positive lag is 

 eliminated if the wire is tapped or kept in a state of forced vibration. 

 Thus it may be that the tendency of cyclic twisting is to produce 

 negative magnetic lag ; but that the eifect is modified by the mag- 

 netic retentiveness of the undisturbed wire, a retentiveness which 

 is generally explained in terms of molecular friction. 



The two explanations suggested are not altogether rivals. It is 

 quite possible indeed, that both may be true, being simply somewhat 

 different ways of looking at the phenomena involved. 



