1908-9.] Load and Vibrations upon Magnetism in Nickel. 43 
where the curves are obtained by the summation of a series of readings as 
in figs. I. and II., but also the effects of magnetic viscosity. The same 
results, however, are obtained in both cases. 
In figs. Xll.a and IV.a the induction changes (dB) are plotted as 
ordinates; the number of times the load has been put “on” and “off” as 
abscissae. The curves of these figs., and those of figs. La and Il.a, are 
merely introduced to show the general nature of the sequence of changes 
which occur when “ons” and “offs” of load (in the case of Il.a “offs” 
and “ ons ” of load) many times repeated are superposed at all stages of 
that arm of the loops descending from the positive to the negative cyclic 
extreme. 
Results. — The effects of the first “ on ” and the first “ off” of load super- 
posed at all points of hysteresis loops not unduly increased, without (fig. I.) 
and with (fig. II.) load respectively, are essentially vibrational in character. 
In other words, induction at cyclic extremes is increased, residual magnetisa- 
tion decreased, neutral points occur in the first and third quadrants, and, 
generally speaking, those differences to which magnetic hysteresis gives 
rise are reduced, irrespective of whether “ on ” is superposed upon a normal 
loop without load, or load “off” superposed upon a loop performed with 
load. The differences between the curves representing the first “ on” (fig. I.) 
and the first “off” (fig. II.) might have been anticipated from the known 
effects of load in nickel. Load “ on ” (tig. I.) increases the induction to a 
less extent, decreases the residual magnetisation to a greater extent, than 
load “ off” (fig. II.). Load “ on ” therefore thrusts the neutral point towards, 
load “ off ” from, the cyclic extreme. These neutral points are not Villari 
critical points due to load, but irreversible vibrational effects inseparable 
from the putting “ on ” or “off” of load. 
Although it is the first “ on ” (figs. I.a, Ill.a) or the first “ off” (fig. Il.a) 
superposed upon hysteresis loops without and with load respectively which 
produces the most marked irreversible induction changes, repeated loading 
and unloading, as these figures show, also produce irreversible effects by no 
means negligible. These, however, gradually disappear, leaving finally 
equal and opposite induction changes due to “ ons ” and “ offs ” when the 
process is sufficiently often repeated. A study of these diagrams shows that 
these combined changes occur at all stages of the loop in orderly sequence, 
and that both effects consequently may readily be distinguished from each 
other. Repeated loading and unloading therefore accentuate all the 
vibrational effects already mentioned due to the superposition of the first 
“on” (fig. I.) or the first “off” (fig. II.). The induction at cyclic extremes 
is further increased, and the differences due to magnetic hysteresis 
