36 
Proceedings of Royal Society of Edinburgh. [sess. 
relatively small increase of induction. For low values of field the 
increase is greater for co-directional than for transverse oscillations ; 
for high values of field, this relationship is reversed. 
After leaving cyclic extremes there are points when the field 
is decreasing where co-directional and transverse oscillations 
respectively produce neither an increase nor a decrease of 
induction. In low fields they are thrust from the cyclic extremes, 
in high fields, towards the cyclic extremes. 
When these points are passed, oscillations produce a decrease of 
induction, and this for all values of field is greater for co-directional 
than for transverse oscillations. This decrease passes into 
increase in the opposite sense, and the first conditions are 
reverted to at the other end of the cycle. 
In all cases the induction change is greatest when oscillations 
are superposed on an increasing field. For low fields this occurs 
