40 Proceedings of Royal Society of Edinburgh. [sess. 
oscillations, with the exception already mentioned, where the 
induction is great. 
Coercive Force. — For low fields of the order of a few hundreds, 
oscillations likewise increase coercive force, but with slightly 
higher fields this effect soon disappears, and thereafter oscillations 
decrease coercive force. 
Hysteresis Loss for Constant Induction. — When under normal 
conditions the maximum cyclic induction is of the order of one to 
five hundred, co-directional oscillations for constant maximum 
induction diminish the energy loss in the iron about four times, 
transverse oscillations about three times. But as the induction is 
increased this difference gradually lessens, and after B under 
normal conditions has reached 5000 it is apparent that transverse 
oscillations diminish the loss in the iron to a greater extent than 
co-directional oscillations. In all cases for constant induction, 
oscillations cause a diminution of the energy loss ; hut when the 
induction is high (say, B = 12,000), the diminution, although 
sufficiently w^ell marked, has become a relatively small effect. 
Hysteresis Loss for Constant Field. — When under normal 
conditions the maximum cyclic induction is of the order of 
a few hundreds, oscillations for constant maximum fields increase 
the energy loss in the iron about four times relative to the loss 
when no oscillations are acting. As the induction is increased to 
some thousands, the energy loss becomes very approximately the 
same with and without oscillations. When, however, the induc- 
tion is higher still — say, B= 12,000 — a sufficiently well-marked 
but relatively small decrease of hysteresis loss is caused by the 
oscillations. The energy loss for co-directional and transverse 
oscillations does not differ greatly relative to each other for 
constant maximum fields. The greater relative retentivity and the 
lower permeability at low fields (where the difference is so much 
greater than under normal conditions), under transverse relative 
to co-directioual oscillations are in harmony with this result. 
The curves exhibited are not here reproduced. Fig. 6, however, 
may be referred to, where the full line curve shows the normal 
hysteresis loop without oscillations, the dotted line curve, the 
greatly increased hysteresis loop with co-directional oscillations. 
They do not differ in type from each other. The phenomena of 
