8 Proceedings of the Royal Society of Edinburgh. [Sess. 
respectively in fig. La as compared to fig. I. Fig. I.a also shows a second 
series of experiments, conducted in exactly the same way, in which, by 
means of a smaller steel ball (0252 grams instead of 1*475 grams), nine 
trains of vibrations of increasing intensity are superposed in succession 
between the values of WxD°' 7 = 0*38 and 1*8 for the various values of 
H shown. Had these curves been drawn to the same scale as that adopted 
in fig. I., they would have fallen within the area of the small rectangle 
shown with that figure. Fig. I.a therefore enables the curves to be more 
readily traced closer to the vertical axis, the lowest value of W x D° 7 (038) 
being twenty-seven times less in intensity than the highest value (104). 
Note that the curves for the same values of H in the two series of 
experiments are not in all cases continuous. The conditions are different. 
Thus it is obvious from the discontinuity of the curves when H — T34, 
052, and 0, that the demagnetising effect of nine vibrational trains of 
increasing intensity superposed in succession between the limits of W x D ° 7 
= 0*38 and 1*8 is greater than that of the initial single vibrational train 
W x D 0 ’ 7 = 2*3 of the first series of experiments. On the other hand, when 
H=l*72 and 1*6 the curves appear to be quite continuous, notwithstanding 
the dissimilarity of the conditions. 
The experiments illustrated in fig. I. were repeated for a lower and a 
higher value of cyclic amplitude, and all the results are shown in the 
three diagrams of fig. II., the field and induction at cyclic amplitudes being 
H — 125, 19, 2*7, and B = 1270, 3170, 10,400 respectively. The induction 
changes are in this instance not plotted against W x D 0 " 7 for various 
values of field as in fig. I., but against field (decreasing from the positive 
cyclic extreme) as abscissse for various values of W x D 0 * 7 . The curves 
of the middle diagram are thus derived from the same experimental data 
as those of fig. I. In the latter case each curve represents one series of 
readings obtained consecutively ; in the former case each curve is obtained 
by selecting the same particular values of W x D 0 ' 7 from eight distinct 
series of readings. The curves for the vibrational intensities W x D°‘ 7 — 
3*6, 5 '9, 7'8, and 9*6 have been omitted in these diagrams to avoid unneces- 
sary crowding. The openness of the vertical scale shows clearly the regular 
sequence in which the curves cross each other, and also the shift of the neutral 
points where each curve crosses the horizontal axis ; but it precludes the 
delineation of the complete curves, with the exception of those for the 
lowest vibrational intensity in each case, viz. W x I) 0 ’ 7 = 2*2. It majq 
however, be stated that the curves do not appear to cross each other at 
any other points than those shown in these diagrams, nor do they cross 
each other at any point whatever when induction change is plotted against 
