RESEARCHES IN MAGNETISM. 
605 
reversals, a new field applied, and the operation of loading and unloading resumed. 
The results are shown in Plate 63, fig. 42, and it would lengthen this paper needlessly 
to give all the recorded numerical values. The effects of the first loading after the 
application of each magnetising field are shown in dotted lines : the effects of a cycle 
0 — 18'5 — 0 after several repetitions had brought about a nearly cyclic state of matters, 
are shown in full lines. The wire was demagnetised by reversals before the applica¬ 
tion of each new magnetising field. The fields were :— 
Curve 
Magnetising field 
(in fig. 42). 
(in c.g.s. units.) 
I. 
0-34 
II. 
2'49 
III. 
575 
IV. 
8-6 ’ 
V. 
11-6 
VI. 
20-1 
VII. 
34-0 
One kilo, of total load corresponds to 2'3 kilos, per sq. mm. 
This series of curves shows well the gradual transformation which occurs as we 
increase the intensity of magnetisation, before applying cyclic changes of stress. 
As the region of magnetic saturation is reached the maximum points on the on and 
off branches occur with lower and lower values of the load, and the descending 
branch of the on curve (to the right of the maximum ) becomes a more and more 
important part of the whole. In the highest curve (No. VII.) it constitutes, in 
fact, nearly the whole action, and the off maximum point comes very near the zero 
of load, with the result that the subsequent on curve starts from so high a point 
as to exhibit no maximum at all. To the last, however, the initial curve of loading, 
after the field has been applied, shows a maximum point, though that also comes 
nearer the zero of load as the wire becomes more strongly magnetised. The 
resultant effect of the first loading passes a maximum, but remains positive in 
all but the highest curve ; and after the cyclic state is established the general effect 
of on load is positive up to curve V., and has its maximum in curve II. The 
following table shows some of the results declucible by a comparison of the curves :— 
4 I 
MDCCCLXXXV. 
