2 
Proceedings of the Royal Society of Edinburgh. [Sess. 
In a former communication * it was found that the position of the 
neutral points in the first and third quadrants depends not only upon the 
cyclic amplitude, but upon the intensity of the vibrations. To quote : 
“ The smaller the cyclic field ” (amplitude) “ and the greater the vibrational 
intensity, the closer is the neutral point thrust towards the vertical axis ; 
the higher the cyclic field and the less the vibrational intensity, the closer 
is the neutral point thrust towards the cyclic extreme.” For any given 
loop, therefore, the position of the neutral points depends wholly on the 
intensity of the vibrations. 
In a recent paper, Maurain,j* experimenting with electric oscillations, 
obtained a different result. He found that the position of the neutral 
points in the first and third quadrants is where “ la courbe d’ aimantation 
stable ,” as defined, cuts the particular hysteresis loop upon which the 
oscillations are superposed. Their position, thus definitely fixed, is, 
according to these experiments, independent of the intensity of the oscilla- 
tions. On the other hand, Dr Eccles,J also experimenting with electric 
oscillations produced by single minute sparks, obtained yet another result. 
Although the “ spark effect ” increases the induction at both cyclic extremes, 
the first recorded readings, as these positions are departed from, show in all 
cases decrease of induction. There is here no evidence of neutral points, 
and the curves plotted from the observations are discontinuous in the same 
way that dB/dH plotted against cyclic field produces curves discontinuous 
at the cyclic extremes. 
Further, in an earlier series of experiments, Garibaldi found that 
Hertzian waves increased or decreased the permanent magnetism of steel 
according as it had or had not been previously subjected to a demagnetising 
field immediately withdrawn. On the other hand, Maurain, in the paper 
above referred to, obtained a result which he describes as “ presqwe nulle” 
when oscillations are superposed upon residual magnetisation which had 
been reached by the same process of withdrawing a demagnetising field. 
The author of a paper § which I have been unable to refer to wrote me as 
follows : — I found that if a piece of iron or steel is magnetised by a 
direct current , and then demagnetised by reversing the current , the effect 
* “ The Superposition of Mechanical Vibrations (Electric Oscillations) upon Magnetism, 
and conversely, in Iron, Steel, and Nickel,” Trans. R.S.E., vol. xlv., part ii., p. 510. Phil. 
Mag ., Oct. 1907. Electrician , July 5, 1907. 
t “ Les Detecteurs magnetiques et faction des Oscillations electriques sur f aimantation,” 
Journal de Physique , Janvier 1907. 
f Proceedings of the Physical Society of London, vol. xx. Phil. Mag., August 1906. 
§ Note presented at the Meeting of the American Association for the Advancement of 
Science, by G. F. Stradling. (Reports have not been received by the R.S.E. for several 
years.) 
