54 Proceedings of the Royal Society of Edinburgh. [Sess. 
producing induction increase are over. Permanently acting vibrations 
increase the range of magnetic change due to load change, but decrease 
the area of the loops formed during the cyclic load process. The 
load effect is thus negative if the induction be regarded as positive, 
and when plotted against the latter as abscissae the resultant curve is 
concave upwards. Consequently Villari critical points have been looked 
for at very small and very large values of induction.* Hydweiller,f 
contrary to the almost universally accepted view, claimed to have found 
such a result at low values of field with various small loads, essentially 
similar to the Villari reversal in iron. Messrs Honda and Shimizu J have, 
however, recently repeated these experiments, and they find that no such 
reversal exists. They maintain that Hydweiller never reached a magnetic 
zero, the necessary initial starting-point from which such experiments 
must be conducted. In any case, the experiments described under A2 and 
A3 conditions show that the latter’s method of demagnetisation by a 
combined process of field reduction and tapping might itself create a 
molecular condition favourable to the occurrence of a Villari reversal in 
nickel, even although a magnetic zero, as measured by magnetometer 
methods, had been reached. 
The results of: the comparisons instituted between the curves repre- 
senting the final reversible effects of “ ons ” and “ offs ” of load and those 
obtained under the Bl conditions with and without permanently acting 
vibrations need not be repeated in detail. They may, however, be shortly 
summarised as follows-. The curves obtained under the Bl conditions 
without vibrations exhibit magnetic but not load hysteresis ; those under 
the A1 conditions exhibit load hysteresis, but eliminate to a large extent 
magnetic hysteresis ; while the curves with permanently acting vibrations 
eliminate both magnetic and load hysteresis. The load curve always falls 
below the corresponding curve without load. 
The reversible effects ( b ) under conditions A2 and A3 are more complex. 
At points in the second and third quadrants where induction and field 
oppose each other, loading and unloading produce, after the irreversible 
changes due to molecular instability are over, no induction change 
whatever. Thereafter, until zero induction is reached, loads “ on ” and 
“ off” increase and decrease induction respectively. There is thus in 
cyclic fields well-marked Villari reversals in nickel. With cyclic residual 
magnetisation (A3 conditions, zero field) essentially similar phenomena are 
* Kelvin ( loc . cit.). 
t Wied. Ann., lii. 1894, p. 462. Phil. Mag., (5) xxxv., 1893, p. 469. 
f Physikalische Zeitschrift, 5, 1904, p. 254 and p. 631. 
