24 Proceedings of the Royal Society of Edinburgh. [Sess. 
Figs. IX. and X. show the results obtained when the secondary 
terminals of the oscillation transformer were connected directly with the 
ends of the single steel wire (transverse oscillations). In these experi- 
ments the length of a single spark is increased from 1 mm. to 11 or 12 
mms. by increments of 1 mm. Fig. IX. shows for the following values of 
decreasing positive cyclic field, viz. H = 133, 0'9, 0’65, 048, 0*3 and 0, the 
results when the induction change due to superposed transverse oscillations 
increasing in intensity by the means above indicated are plotted against 
the length of the spark as abscissae. Table YI. shows the experimental 
data from which two of the curves, viz. H — 09 and 065, have been plotted. 
Observe that the galvanometer readings are very small, and have been read 
to 0‘25 of a mm. division of the scale ( i.e . to B — 06). Notwithstanding 
this, the readings obtained with positive and negative fields are nearly the 
same throughout (as a rule identical), so that with transverse oscillations it 
is unnecessary, for obvious reasons, to reverse the oscillation connections to 
obtain similar curves differing only in sign, as was found absolutely neces- 
sary with co-directional oscillations. 
Fig. X. shows from the same experimental data the induction changes 
plotted against the decreasing cyclic field as abscissm for various oscillation 
intensities corresponding to spark lengths of 1, 2, 3, 5, 8 and 11 mms. In 
these experiments the cyclic amplitude is H = 1‘9, B = 3l70 and the residual 
magnetisation B — 2000 when H = 0. 
Figs. IX. and X. for transverse oscillations exhibit differences when zero 
field is approached, not observed either with co-directional oscillations or 
mechanical vibrations, but not such as to affect the general results. Compare 
these two figures with figs. VII. and VIII. for co-directional oscillations, 
and with figs. I. and II. for mechanical vibrations. 
Results . — When damped trains of electric oscillations are superposed 
upon magnetisation, it is necessary to distinguish between co-directional 
and transverse oscillations. In the latter case the oscillation phase neither 
directly assists nor directly opposes the magnetisation change, and the same 
results are obtained if the secondary oscillation connections are reversed 
relative to either positive or negative magnetisation. In the former case 
the oscillation phase must either directly assist or directly oppose the mag- 
netisation change. If it could be assumed that L1 \e initial amplitude of 
each damped train of secondary oscillations was invariably greater than 
that of succeeding amplitudes, it might be anticipated that the curves 
representing the induction changes due to oscillations superposed upon that 
arm of the hysteresis loop decreasing from the positive extreme would fall 
above or below each other according as the phase of the first amplitude 
