1 908-9 J Vibrational Neutral Points in Magnetised Iron. 27 
neutral points, therefore, is from or towards the jDositive extremes according 
as the vibration or oscillation intensity is strong or weak. In both cases 
the neutral points may occur close to the positive extremes if the intensity 
is sufficiently reduced, towards the lower limiting value of the neutral 
points if the intensity is sufficiently increased. 
On the other hand, the direction of the induction change due to 
superposed vibrations or oscillations is at all corresponding points reversed 
for cyclic residual magnetisation as compared with cyclic field. This 
reversal can neither be co-ordinated with the induction nor with the 
presence or absence of the field. It can, however, be directly co-ordinated 
with the field change immediately preceding the superposition of vibrations 
or oscillations, which is of opposite sign in the two cases. 
The results in both cases may now be stated as follows : — When 
vibrations or oscillations are superposed at the cyclic field amplitudes or at 
the extreme values of cyclic residual magnetisation, the direction of the 
induction change due to superposed vibrations or oscillations corresponds 
with that of the immediately preceding field change. As these extreme 
positions are departed from, the direction of the induction change is first 
opposed to, afterwards corresponds with, that of the immediately preceding 
field change, and continues to do so until the opposite extremes of cyclic 
field amplitude or cyclic residual magnetisation are reached. The position 
of the neutral points depends upon the intensity of the vibrations or 
oscillations, and it is thrust from the extremes the greater their intensity, 
but reaches a lower limiting value before zero field in the one case or 
zero magnetisation in the other case is reached. On the other hand, the 
neutral points are thrust towards an upper limiting value the weaker the 
intensity of the vibrations or oscillations, which may occur close to but not 
at the cyclic field amplitude in the one case, or close to but not at the 
extreme value of cyclic residual magnetisation in the other case, provided 
always the vibrations or oscillations are sufficiently weak. Within the 
upper and lower limiting values of the neutral points, the directional of the 
induction change may either correspond with or be opposed to the 
immediately preceding field change according as the intensity of the 
vibrations or oscillations are weak or strong. In both cases, also, the 
direction of the induction change therefore will correspond with that of the 
immediately preceding field change throughout a wider and wider range 
the weaker the vibrational or oscillational intensity, but never quite 
throughout the whole range. 
