36 
Proceedings of the Royal Society of Edinburgh. [Sess. 
thereby made to those points of the loops where the last reversal of field 
change took place. It may therefore be repeated, that residual magnetisa- 
tion is not necessarily decreased by vibrations. The sign of the induction 
change cannot be determined apart from the direction of the path by which 
points on the vertical axis (cyclic residual magnetisation) have been reached,, 
nor apart from the vibrational intensity. 
In this short summary of deductions from the molecular theory of 
magnetisation and of the experimental results the word “ vibrations ” 
refers both to mechanical vibrations and electric oscillations (co-directional 
and transverse). In the former case the intensity of the mechanical 
vibrations was found to be proportional to a definite function (W x D 0 ' 7 ) of 
the weight (W) of the steel ball and the distance (D) through which it fell. 
The accuracy of this experimental method is obvious, and no difficulty was 
experienced in obtaining as many as twenty distinct curves between the 
limits of W x D 0 ' 7 = 038 and 104 (measured in gram-centimetres), from 
which the conclusions are drawn. 
Although, in the latter case, a similar definite signification would be 
less readily obtained, the same general conclusions are equally applicable 
to both. With damped electric oscillations the experimental results are 
necessarily more complex. The induction changes due to superposed 
oscillations are the resultant of the irreversible * (vibrational) effects, and 
the reversible effects of the oscillatory current, just as the induction 
changes due to loading and unloading (or vice versa), are the resultant of 
the irreversible (vibrational) effects (due to a complex molecular seolotropy 
in cyclic field) and the reversible effects of the “ ons ” and “ offs ” (or 
vice versa) of the load.f The irreversible effects are subject to the same 
laws which govern the induction changes due to superposed mechanical 
vibrations in cyclic fields. In fact, these results may be taken to be general, 
not only applying to electric oscillations, weak alternating currents, and the 
* This compounding of the irreversible with the reversible effects may very easily be 
lost sight of. The following appears to be worth further consideration. Professor 
Rutherford, 1 in his determination of the damping of oscillations by the magnetic method, 
assumes that if the initial phase of the oscillation train be such as to increase the magnetisa- 
tion of the bundle of steel needles, it will produce no magnetic effect, because these have 
been magnetised to saturation. That is to say, as the initial phase increases to a maximum 
the magnetisation will increase, and as the initial phase falls to zero the decrease of 
magnetisation will not exceed the previous increment. But the irreversible (vibrational) 
effect opposes the increase and assists the decrease, hence the residual magnetisation may 
fall below its original value. The proof as stated would therefore appear to be incomplete. 
t “The Effect of Load and Vibrations upon Magnetism in Nickel,” pp. 38-56. Read 
in conjunction with this paper. 
l “ On a Magnetic Detector of Electric Waves, and some of its Applications,” Phil. Trans. Roy. Soc., 
London, A., 1897, vol. clxxxix., p. 1. 
