30 
Proceedings of the Royal Society of Edinburgh. [Sess. 
expanded 100 times in comparison with that usually adopted for 
hysteresis loops. 
Maurain, commenting on Eccles’ results, says : “ Les courbe qui, dans 
le memoire de M. Eccles representent V action des oscillations anx diff events 
points d’une des branches d’un cycle d’aimantation, paraissent comporter 
une discontinuity dans les valeur de cette action autour du sommet d’un 
cycle ; je nai pu me rendre compte de la cause de cette difference entre ses 
resultats et les miens.” 
Between the upper and lower limiting values of the neutral points, 
which, as has been shown in this paper, may cover a very wide range of 
decreasing cyclic field, Eccles obtains only induction decrease when 
oscillations of very weak intensity are superposed ; Maurain, experimenting 
in all cases with oscillations of much greater intensity, only induction 
increase. In the former case the neutral points are thrust towards their 
upper limiting values, which may occur quite close to the cyclic extremes, 
and the curves are discontinuous, because readings do not appear to have 
been taken between these two positions. In the latter case the neutral 
points are thrust from the cyclic extremes towards their lower limiting 
value, where the curves crowd together as the intensity of the oscillations 
are more and more increased. The lower limiting value of the neutral 
point may correspond to “ la courbe d’aimantation stable.” 
In the view of the author, the molecular theory of magnetism lends no 
support to the possibility that the positions of the neutral points (where 
vibrations or oscillations superposed upon cyclic fields produce no induction 
change) are independent of their intensity, nor that within definite limits 
vibrations or oscillations may not, when superposed at the same point, pro- 
duce induction change in opposite directions, according as their intensities 
are sufficiently weak or sufficiently strong. 
V. Molecular Theory. 
It now remains to be shown whether the whole of the experimental 
results obtained with mechanical vibrations (Section I.) and with electric 
oscillations (Section II.), and restated in terms of field change irrespective 
of the presence (cyclic field) or absence (cyclic residual magnetisation) of 
the field (Section III.), are not only in harmony with, but a necessary 
deduction from, the molecular theory of magnetisation. 
It will be convenient that the word vibrations when used alone signifies 
in the remainder of this paper either mechanical vibrations or electric 
oscillations. 
