1908-9.] Load and Vibrations upon Magnetism in Nickel. 55 
observed. The reversals occur at somewhat lower values than the vibra- 
tional neutral points where “ons” and “offs” of load assume their final 
values from the first, just as the Villari critical points occur at lower 
values of induction (second and fourth quadrants) than the vibrational 
neutral points (first and third quadrants) with cyclic fields. Permanently 
acting vibrations increase the irreversible effects (b) under the A2 as under 
the A1 conditions. The Villari critical points remain. 
These Villari reversals, occurring as they do under both the A2 and A3 
conditions, depend therefore upon the molecular condition impressed upon 
the nickel by the cyclic field process, independent of the presence of the 
field itself. To distinguish from the Villari critical points which occur 
in iron and cobalt in opposite senses, apart altogether from cyclic con- 
ditions, these phenomena may more appropriately be called the cyclic 
Villari reversals in nickel. 
Obviously, the effects of loading and unloading under cyclic conditions 
must be more complicated in iron and cobalt than in nickel. 
Just as the initial irreversible effects (a) can be co-ordinated under the 
A2 and A3 conditions with molecular groups of unequal stability tending to 
rotate in opposite directions, see p. 53, so may the reversible effects (b) of 
loading and unloading be co-ordinated with the molecular groupings which 
have, in continuation of this process, actually assumed opposite polarities, 
as Professor Hughes * found to be the case when zero magnetisation was 
reached or approximated to. In comparison with so essentially an isotropic 
process (isotropic co-directionally, not transversely, in reference to the field) 
as that of demagnetisation by decreasing reversals, the methods of reaching 
a magnetic zero by a reduced field reversal under the A2 conditions, or by 
subsequently withdrawing a slightly greater value of reduced field reversal 
under the A3 conditions, do not differ essentially from those adopted by 
Hughes, who reached a position of neutrality or approximate neutrality by 
tapping or by heating to redness an iron wire left residually magnetised. 
He showed that as the surface was dissolved away by means of nitric acid 
the successive longitudinal layers were of opposite polarities, and that it is 
the summation of these opposing layers which under such conditions 
constitute magnetic neutrality. Under both the A2 and A3 conditions 
the demagnetising process precludes perfect symmetry of the molecular 
groupings of opposite polarities. It therefore follows that the conditions 
constituting magnetic neutrality will not be such that the final effects 
(6) of loading and unloading can possibly be zero. Such a condition — 
where the summation of the positive and negative magnetic changes due to 
* “Magnetic Neutrality and Polarity,” Proc. Roy. Soc., London, xxxvi., 1883-4, p. 405. 
