1902 - 3 .] Mr J. Bussell on Molecular Conditions of Iron. 545 
(Second) To change sign if either the direction of H he reversed 
or the direction of ab he rotated through an angle of 90°. 
If both these changes be made simultaneously, the sign of 
this theoretical effect ought to remain unaltered. 
The experimental results have fully confirmed the above deduc- 
tions. They further show a distinct and increasing difference 
between the curves of transverse induction, according as ab is 
rotated more and more in opposite directions, from the position 
which was formed to give the maximum effect. Corresponding to 
this, the theoretical diagrams indicate different conditions of zero 
molecular balancing (at right angles to H) according as the angle 
which ab makes with H approximates to 0° or 90° respectively. 
A comparison is also instituted between the changes involved in 
the process by which iron passes from the molecular condition in 
which it is left demagnetised by decreasing reversals and by 
annealing , as increments of residual magnetisation are superposed 
upon both of these conditions respectively. 
If the residual magnetisation impressed by ab (making, say, an 
angle of 45° with H) he strong, the application of H shows that 
the various changes which take place in the induction component 
at right angles to itself are practically the same for both methods 
of demagnetisation. But the essential differences in the two cases 
become more and more apparent as the residual magnetisation is 
taken less and less. In the case of demagnetisation by annealing 
the curves are seen to coincide ultimately with the horizontal axis. 
On the other hand, in the case of demagnetisation by reversals, 
they coincide ultimately with those symmetrical curves which 
change sign with H. But if, after demagnetisation by reversals, 
sufficiently small increments of residual magnetisation be super- 
posed by means of ab , the symmetrical nature of the curves 
gradually vanish, and the further changes which then occur 
become less and less dependent on the previous demagnetisation 
process as the residual magnetisation increases. 
The opening out of the neutral closely packed equatorial belt, 
distinctive of demagnetisation by reversals, into narrowing zones 
of opposite polarities is traced, and the molecular rotations involved 
are, as before, illustrated by theoretical diagrams. 
Mechanical tapping is shown very considerably to disturb the 
