1905-6.] Electric Oscillations and Magnetic Properties of Iron. 39 
It might thus appear that even under the B conditions the 
'effect of oscillations is to reduce residual magnetisation. Such a 
statement, however, cannot he regarded as correct, because by- 
plotting against maximum induction one of the most important 
effects of oscillations has been eliminated, viz., that of increased 
permeability. 
In fig. 4 residual magnetisation is plotted against field, and we 
0 5 500 5000 7500 10000 
see that it is only at high values of induction — where per- 
meability is, so to speak, naturally eliminated — that the effect of 
oscillations is to reduce retentivity. For lower fields, and through- 
out a wide range, oscillations increase retentivity. A comparison 
with fig. 3 shows that the greater the permeability in the three 
cases, the greater is the residual magnetisation. The residual 
magnetisation curves with co-direction al and transverse oscillations 
also cross each other — as w T as found to be the case for permeability, 
— and greatly exceed in value the normal retentivity curve without 
