350 Mr. H. A. Rowland on Magnetic Distribution. 



Table IX. 





C. 



B. 



A. 



X. 



•257. 



•363. 



1-303. 



o, 









• 



4 J 



5 



6 



7 



8 



10 

 12 



2-5 



31 



11 

 1-3 



72 



41 



5-9 



21 

 40 



61 



8-2 



9-6 



77 



109 



18-6 



7-9 



11*5 



213 



65 



90 



16-8 



100 



150 



274 



6-2 



10-9 



20-9 



5-0 



9-8 



215 



18 

 30 



20 



4-7 



148 



20 



3-6 



165 



Fig. 3. 



Plot of Table IX., showing surface-density for different values of the 

 magnetizing force. 



These experiments show in the most positive manner the effect 

 we are considering ; and we are impressed by them with the great 

 complication introduced into magnetic distribution by the vari- 

 able character of magnetic permeability. 



In fig. 3 I have represented the distribution on half the bar, as 

 given in Table IX., the other half being of course similar. Here 

 the greatest change is observed in the part covered by the helix, 

 though there is also a great change in the other part. These 

 Tables show that, as the magnetization of the bars increases, at 

 least beyond a certain point, the curves on the part covered by the 

 helix increase in steepness ; and the figure even shows that near 

 the middle of the helix an increase of magnetizing force may cause 

 the surf ace-density to decrease-, and Table VIII. shows this even 

 better. Should we calculate Q", however, we should alw r ays find 

 it to increase with the magnetizing force in all cases. These 

 effects can be shown also in the case where the bar does not ex- 

 tend beyond the helix, but not nearly so well as in this case, 

 seeing that here Q" can obtain a greater value. 



