52 
Proceedings of the Royal Society of Edinburgh. [Scss. 
Discussion and Summary. 
Loading and unloading may be superposed upon magnetisation (A 
conditions) with field increasing from zero (Al), with cyclic field (A2), 
or with zero field, cyclic residual magnetisation (A3) alone being dealt with. 
Reversals of field increasing from zero may also be superposed (B1 con- 
ditions), the nickel wire being either loaded or unloaded. 
Under the A conditions, the magnetic changes following upon load 
changes are compounded of (a) the irreversible vibrational effects due to 
molecular instability and ( b ) the reversible effects of loading and unloading. 
In general, the initial effects (a) are most marked on the first superposition of 
load (or on the first superposition of load “ off” if the nickel wire be already 
loaded). They decrease and finally vanish when “ ons ” and “ offs ” of load 
are sufficiently often repeated, leaving only the final reversible effects ( b ). 
Both effects are clearly distinguishable from each other and traceable 
in regular sequence at all stages of increasing field (Al), cyclic field (A2), 
or cylic residual magnetisation (A3). Permanently acting vibrations 
lessen or eliminate the irreversible effects (a), but increase the reversible 
effects (b). 
The curves representing the first “ on ” of various loads under conditions 
Al are of interest. The irreversible vibrational effect (a) increases the in- 
duction, while the reversible effect ( b ) decreases the induction to a greater 
extent, the greater the load. At low inductions the former predominates. 
Hence the first “ on ” curve falls above or below the normal BH curve as the 
field is low or high, and the neutral points are thrust towards the origin 
the greater the load, from the origin the less the load, just as the Yillari 
critical points are in iron. Under conditions A2 (cyclic field), the first 
“ on ” or the first “off” of load increases the induction at cyclic extremes 
(not unduly increased), decreases the residual magnetisation, and lessens 
those differences to which hysteresis has given rise, irrespective of whether 
“on” is superposed upon a normal loop without load, or load “off” is 
superposed upon a loop performed with load. 
The irreversible changes (a) due to repeated loading and unloading under 
conditions Al (increasing field) accentuate the induction increase due to 
the first superposition of load. This increase is especially well marked in 
low fields, but tends to vanish as field is sufficiently increased. Under con- 
ditions A2 (cyclic fields) also, the results mentioned immediately above as 
due to the first superposition of load “on” or “off” are further increased. 
The vibrational neutral points in the first and third quadrants are where 
the changes due to loading and unloading (induction decrease and increase 
