40 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Either demagnetisation by decreasing reversals intervenes, or under condi- 
tions (A2) and (A3) and only where expressly stated many reversals of 
high amplitude alone may intervene. 
B conditions. — After demagnetisation by decreasing reversals, the 
nickel wire being loaded, field reversals increasing from zero may be 
superposed (Bl). When the loading is zero the normal BH curve is 
obtained. 
In this paper the A and B conditions refer exclusively to the relative 
superposition of load and field. Mechanical vibrations are never super- 
posed ; they either are or are not permanently acting. 
Diagrams. 
Field (H), induction (B), and induction change (dB) are in C.G.S. units 
in all the diagrams. The curves are either obtained from the average 
readings taken with both positive and negative fields increasing from zero ; 
or in the case of cyclic fields, the results plotted for each arm of a hysteresis 
loop are obtained from the average results taken with both arms ; the same 
method being adopted for cyclic residual magnetisation. 
The occurrence of Yillari reversals, found to exist with cyclic fields and 
with cyclic residual magnetisation, appears to offer the explanation that 
results not so easy of satisfactory repetition obtained in very low fields in- 
creasing from zero may be fully accounted for by the difficulty of reaching 
in every case an absolutely neutral position by the method of demagnetisa- 
tion by decreasing reversals in nickel. For this reason the data and 
conclusions relating to cyclic fields and cyclic residual magnetisation will 
be taken first ; fields increasing from a neutral magnetic zero last. 
Cyclic Fields. 
Experimental Data. — Fig. I. shows the effects of the first “ on ” and of 
the seventh “on ” and “off” of a load of 11 ozs. (05 kilos per square mm. 
of sectional area), superposed under the A2 conditions, at a sufficient 
number of points, upon the normal hysteresis loop without load. Fig. II. 
shows the effects of the first “off” and of the seventh “off” and “on” of 
the same load, superposed under the same conditions, upon the hysteresis 
loop performed with load “ on.” In both cases the value of the field 
H = T23 at cyclic extremes is the same. In both cases nearly final results 
are reached with the seventh “on” and “off” of load. The series of small 
diagrams show the inductive changes (dB) which occur between the first 
