110 



HENRY A. EOWLAND 



These experiments show in the most positive manner the effect we 

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

 cation introduced into magnetic distribution by the variable 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 



TABLE IX. 



5 10 15 20 



FIG. 3. Plot of Table IX, showing surface-density for different values of the 



magnetizing force. 



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 surface-density to decrease; and Table 

 VIII shows this even better. Should we calculate Q", however, we 

 should always 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 



