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Proceedings of the Royal Society of Edinburgh. [Sess. 
axis (figs. I. and I.a), and when the hysteresis loop is performed with load 
“ on ” apparently closer still (figs. II. and Il.a). 
Results with permanent vibrations . — The great differences which occur 
between the curves representing the effects of “ ons ” and “ offs ” of load 
superposed upon a normal loop (fig. I.), and “offs” and “ ons ” superposed 
upon a loop performed with permanent load (fig. II.), to a large extent dis- 
appear when the nickel wire is kept in a state of continuous vibration 
(irrespective of whether the experiments are repeated for the same field 
amplitude, or approximately for the same induction amplitude). This is 
immediately apparent on comparing figs. I. and II. without vibrations with 
figs. I.v and II. v with vibrations. The latter figures, taken in conjunction 
with the text, show that loading and unloading decrease and increase re- 
spectively both the induction at cyclic extremes and the residual magnetisa- 
tion from the first. Nevertheless, the irreversible vibrational effects have not 
entirely been eliminated. The relation of the fourth “off” curve (fig. I.v) 
and of the fourth “ on ” curve (fig. II. v) to the normal loop and to the loop 
performed with load upon which they are respectively superposed is 
obviously vibrational. The induction at cyclic extremes is in both cases 
slightly increased, the residual magnetisation decreased. At higher induction 
amplitudes, however (figs. III. and IV.), the irreversible vibrational effect of 
repeated loading and unloading entirely vanishes at the cyclic extremes when 
mechanical vibrations are acting — see fig. IV.a, H = 11T. This is not quite 
the case without vibrations, fig. Ill.a, H = 11T. As the cyclic extremes are 
departed from the irreversible effects in both cases reassert themselves, 
reaching maximum values, which may be opposite in sign to the final effect 
of load, where the slope of the cyclic curves is great. At all stages the 
initial irreversible effects with vibrations (fig. IV.a) are much less than 
without vibrations (fig. Ill.a), and in the former case are confined to a 
much narrower range of low field. 
While this is so in reference to the initial effects, the final reversible 
effects of load, i.e. the ordinate difference between the “on” and “off” 
curves, are much greater with (figs. IV. and IV.a) than without (figs. III. 
and Ill.a) permanently acting vibrations. Also the Villari reversals in the 
second and fourth quadrants remain practically unchanged although they 
occur at much lower values of the cyclic field. 
t / 
Cyclic Residual Magnetisation. 
Experimental Data. — Fig. V. shows the results obtained with what may 
be called cyclic residual magnetisation between the limits of B = dt 2800 
