1908-9.] Load and Vibrations upon Magnetism in Nickel. 53 
respectively) assume their final reversible values from the first — the (a) 
effect being zero. These neutral points are thrust towards or from the 
cyclic extremes as the amplitudes are greater or less. Under condition A3, 
a neutral point as above defined (where the changes due to loading and un- 
loading assume their final reversible values from the first) occurs at a 
comparatively large value of cyclic residual magnetisation, which will be 
positive or negative as the cyclic field process has been conducted from 
positive or negative extremes respectively. At all other values the residual 
magnetisation will be either increased or decreased according as these 
values lie between or beyond the limits of the neutral point and the zero 
of cyclic residual magnetisation. Further, the irreversible increase (a) due 
to loading and unloading betiveen these limits will be positive or negative 
according as the immediately preceding field change had been positive or 
negative. But it has been shown in the preceding paper,* read in con- 
junction with this communication, that a phenomenon of this kind can be 
co-ordinated with the shift of the neutral points in a cyclic field from or 
towards the extreme at which the last reversed took place according as the 
vibrational intensity is strong or weak. 
Permanently acting vibrations eliminate the irreversible effects (a) to 
a greater extent under conditions A1 than under conditions A2 where the 
cyclic fields are steepest. 
Under all the above conditions, therefore, the irreversible effects (a) 
are subject to the same laws which govern the superposition of mechanical 
vibrations. They depend in cases A2 (cyclic field) and A3 (cyclic residual 
magnetisation) upon the tendency of different molecular groups of unequal 
stability to rotate in opposed directions, consequent upon the nickel wire 
having been previously subjected to at least one reversal of field change, 
as fully discussed in the paper referred to above.* Under the Al con- 
ditions, the magnetic aeolotropy is less complex, no such opposing tendencies 
having been impressed upon different molecular groups, the field change 
having been in one direction only. 
On the other hand, the reversible effects (b) are such that, under the 
Al conditions (increasing field), loading and unloading sufficiently often 
repeated decrease and increase the induction by equal amounts respec- 
tively. This cyclic load process encloses an area, the curve for loading, as 
pointed out by Ewing, everywhere lying above that for unloading. 
This statement, however, only holds true after the reversible effects (a) 
* “ The Shift of the Neutral Points due to Variation of the Intensity of Mechanical 
Vibrations or Electric Oscillations superposed upon Cyclic Magnetisation in Iron,” pp. 
1-37. Read in conjunction with this paper. 
