Theory of Induced Magnetism. 213 



ratio of residual to induced magnetism is a maximum about 

 the end of stage b, and diminishes as stage c proceeds. 

 This, again, agrees completely with the observed facts. 



Fig. 5. 



There is some hysteresis during the removal (whether com- 

 plete or partial) and reapplication 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 con- 

 dition of instability during the removal and reapplication of 

 the force. For certain inclinations of the line, the movements 

 are not reversible. 



Suppose, next, that having applied and removed a strong 

 force <!J5, leaving strong residual polarity, we begin slowly 

 to reverse ^. At first, the effects are slight ; presently, how- 

 ever, 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 deflexion as saturation is 

 approached. Thus, the well-known general characteristics of 

 cyclic processes are all reproduced in the model (see fig. 8 

 below). 



