394 



Professor J. A. Eiving 



[May 22, 



At first, the group, if it has been shuffled by any casual disturbance, 

 arranges itself at random in lines that give no resultant polarity. A 

 weak force produces no more than slight quasi-elastic deflections ; a 

 stronger force breaks up the old lines, and forms new ones more 

 favourably inclined to the direction of the force (Fig. 10). Avery 

 strong force brings about saturation (Fig. 11). 



In an actual piece of iron there are multitudes of groups lying 

 variously directed to begin with— perhaps also different as regards 

 the spacing of their members 



Some enter the second stage while 



Fig. 10. 



Fig. 11. 



others are still in the first, and so on. Hence, the curve of mag- 

 netisation does not consist of peifectly sharp steps, but has the 

 rounded outlines of Fig. 1. 



Notice, again, how the behaviour of these assemblages of ele- 

 mentary magnets agrees with what I have said about residual mag- 

 netism. If we stop strengthening the field before the first stage is 

 passed — before any of the magnets have become unstable and have 

 tumbled round into new places — the small deflection simply dis- 

 appears, and there is no residual effect on the configuration of the 



