34 
Proceedings of the Royal Society of Edinburgh. [Sess. 
symmetrical loop will be positive throughout a wider range of either the 
less the vibrational intensity, but never quite throughout the whole range. 
The direction of the shift of the neutral points represented by the large 
arrows will be towards the negative extreme H x of the horizontal axis and 
towards the positive extreme R of the vertical axis the less the vibrational 
intensity, because a nearer approach is in both cases made to the negative 
cyclic extremes of the unsymmetrical loops at which the last reversals of 
field change took place. These deductions relative to cyclic residual 
magnetisation (vertical axis-zero field) and what may similarly be called 
cyclic zero induction (horizontal axis) are inseparably connected with each 
other. In the former case residual magnetisation is not necessarily 
decreased by vibrations. In neither case can the sign of the induction 
change due to superposed vibrations be determined apart from (1) the 
direction of the path by which the points on either axis have been reached, 
nor apart from (2) the vibrational intensity. 
The experimental results with cyclic residual magnetisation show the 
wide range throughout which these conclusions deduced from the molecular 
theory of magnetisation are applicable. Vibrations may increase the residual 
magnetisation within the limits of B = 0, and a point, B — 8700, not far 
removed from the extreme possible limit under the conditions, viz. B = 9100. 
Conclusion. 
The above deductions from the molecular theory of magnetisation depend 
primarily, therefore, upon the molecular condition in which the iron is left 
when the cyclic field process is arrested at any point, and not upon the 
actual values of the induction or field, either or both of which may be zero. 
If the cyclic field change be large enough a preponderance of the molecules 
must be rotating in the direction of the field change as the cyclic amplitudes, 
not necessarily symmetrical about the origin, are approached. On a 
reversal of field change the most favourably placed molecules of the least 
stable molecular groups must be the first to experience a reversal of their 
rotation, followed by those of more and more stable groups as the field 
change is taken greater and greater. Finally, the opposite cyclic extremes 
will be reached. 
The intensity of vibrations superposed at any point will necessarily 
differentiate between molecular groups of various degrees of stability whose 
molecules have been arrested in their passage from positions of less to 
positions of greater stability under the conditions. The rotation of the 
molecules of a greater number of molecular groups of all degrees of stability 
