350 Prof. J. A. Ewing. Contributions to the [June 19. 



Fia. 6. 





residual magnetism than was found at the end of stage (6). The 

 ratio of residual to induced magnetism is a maximum about the end 

 of stage (6), and diminishes as stage (c) proceeds. This, again, 

 agrees completely with the observed facts. 



There is some hysteresis during the removal (whether complete or 

 partial) and re-application of magnetic force, because (provided we 

 have enough groups to deal with) there will be some lines of 

 elements which pass to and fro through a condition of instability 

 during the removal and re-application of the force. For certain 

 inclinations of the line the movements are not reversible. 



Suppose, next, that having applied and removed a strong force , 

 leaving strong residual polarity, we begin slowly to reverse >. At 

 first, the effects are slight ; presently, however, instability begins, 

 and, as the force is increased within a narrow range, we find the 

 molecules all upset. This is followed by a stage of nearly elastic 

 deflection as saturation is approached. Thus, the well-known general 

 characteristics of cyclic processes are all reproduced in the model 

 (see fig. 8 below). 



Again, a small repeated cyclic change of superposed upon a 

 constant value of <> produces small changes of resultant moment, 

 which are reversible if the change of > is very small. 1 This, as Lord 



