434 



Dr. Silvanus Thompson on 



loops is specially marked in those beaked forms which are 

 obtained when the magnetization has been pushed to high 

 degrees of saturation : the diminished permeability of the 

 material resulting in a diminished reactance, and therefore 

 in a disproportionate increase in the magnetizing current. 

 This is well seen on examination of the analysis of figs. 14, 

 15, and 16. Cosine terms of the higher orders are responsible 

 for the distortion of the ellipse into the characteristic two- 

 beaked form. Fig. 25 shows the result of superposing a 

 negative third cosine-constituent upon the ellipse. But this 

 particular figure, resembling a capital S, could not result 

 from any experiment, as neither the ascending nor the de- 

 scending half is single-valued. No experimental curve* could, 

 on ascending from the point where it crosses the ?^ axis, 

 curve backwards toward the 33 axis, and then recurve from 

 that axis. Such a curve would be unstable ; and the 

 ascending branch could, at most, ascend parallel to the 38 

 axis before turning to the cusp. Is it too remote to speculate 

 that the vertical portions of the loops experimentally found 

 for soft iron really do represent instabilities, and mask the 

 true forms of the loops ? 



The superposition of a negative fifth-order constituent is 

 shown in fig. 26 ; but, again, the only possible cases must be 

 such as to yield single-valued resultants. 



Fie-. 26. 



It will have been noticed that in the analyses of some of 

 the loops the amplitudes of the negative cosine terms appear 

 in a descending set of values. If these amplitudes are of 

 relative magnitudes as 1 : \ : \ : \ &c, the resultant curve 

 will have its middle portion truly vertical. Fig. 27 gives a 



* See, for example, P. Holitscher {lnaug. Diss., Zurich, 1900), 

 " Experimented Untersuchungen iiber den remanenten Magnetism us 

 des Eisens," plate 6. 



