35 
1908-9.] Vibrational Neutral Points in Magnetised Iron. 
will be assisted in the direction of their last rotations, which may or may 
not coincide with that of the immediately preceding field change, the 
stronger the vibrational intensity. On the other hand, the rotation of the 
molecules of the least stable groups, to the exclusion of those of greater 
stability, will be assisted in the direction of their last rotations the weaker 
the vibrational intensity. But as these are the first to rotate in the direc- 
tion of the cyclic field change after reversal, it follows that the induction 
change due to superposed vibrations will coincide in directional with that 
of the immediately preceding field change throughout a wider range of 
cyclic field the less their intensity. According to this hypothesis, neutral 
points occur where the rotations of the molecules in opposite directions 
balance, and these positions must be thrust towards the cyclic extreme at 
which the last reversal of field change took place the weaker the vibrational 
intensity. 
The above deductions due to a complex magnetic seolotropy produced 
by reversals of field change are thus in harmony with the experimental 
results obtained for cyclic field and cyclic residual magnetisation with 
mechanical vibrations and electric oscillations, and summarised in terms of 
the immediately preceding field change in Section III. of this paper. 
In cyclic fields symmetrical about the origin there are higher and lower 
limiting values of the decreasing cyclic field between which the neutral 
points may shift. These vanish in the origin or the cyclic extremes accord- 
ing as the amplitude is sufficiently decreased (zero amplitude at the origin) 
or sufficiently increased (saturation values of induction at the extremes). 
The locus of the lower limiting value of the neutral points may 
approximate to the stable curve of Duhem (theoretical) or Maurain 
(experimental). The locus of the higher limiting value of the neutral points 
approximates to the cyclic extremes, but can only vanish there when the 
effect of the vibrations superposed at the extremes is zero. Between these 
loci, which may thus cover a very wide range of the decreasing cyclic field, 
neither unduly increased nor decreased, superposed vibrations may either 
increase or decrease the induction according as the vibrational intensity is 
sufficiently strong or sufficiently weak. 
With cylic residual magnetisation (zero field) there are also lower and 
higher limiting values between which the neutral points may shift. The 
direction of shift is towards the higher limiting values, which may occur 
close to but not at one or other of the extremes of residual magnetisation, 
the less the vibrational intensity. It will be towards the positive extreme 
if the slope of the unsymmetrical loops by which points on the vertical 
axis were reached be positive, and vice versa, because a nearer approach is 
