1908-9]. Load and Vibrations upon Magnetism in Nickel. 49 
VI. and VII., plotted against induction. When “ ons ” and “ offs ” are repeated 
a sufficient number of times, equal magnetic changes occur in either case. 
The full and faint dash line curves of fig. X. show respectively for all 
values of field the induction reached when load is put “off” and “on” for 
the fortieth time, without vibrations. These curves represent the final 
reversible results with a load of 11 ozs. (0*5 kilos per sq. mm.) under the A 
conditions. The other two pairs of curves in this diagram are obtained 
under the B conditions, the load used being the same. The full and faint 
continuous lines are respectively the normal BH curve without load and 
the BH curve with load. The full and faint dotted lines show the 
corresponding curves without and with load respectively, but with 
permanently acting vibrations. 
The ordinate differences between each of the above three pairs of curves 
with and without load are in fig. XI. plotted against induction. The dash 
line curves show this load effect under the A conditions without mechanical 
vibration, while the continuous line curve represents within the limits 
of experimental error the load effects under the B conditions irrespective 
of whether vibrations are or are not permanently acting. 
Fig. XII., without vibrations, shows for three different values of induction 
the changes due to loading and unloading which take place between the 
first and fortieth “ ons ” and “ offs ” of load, plotted from the experimental 
data from which the dash line curves of fig. X. were obtained. The 
remaining diagrams of the fig. show for three very similar values of 
induction the corresponding changes under the same A conditions, but with 
permanently acting vibrations. The induction values given with each 
figure are obtained after the fortieth “off” of load by taking a single step 
to a sufficiently high value of field, as already explained. 
Results . — In fields increasing from zero, the effect of the first “ on ” 
of load superposed under the A conditions is to increase or decrease 
induction as field (induction) is low or high ; within the experimental 
limits, the less the load the greater is the increase in low fields ; the greater 
the load, the greater is the decrease in high fields. The neutral points 
are thrust towards the origin the greater the load, from the origin the less 
the load (fig. VI.). Although in this respect the initial irreversible effect 
of load in nickel is similar to the final reversible effect of load in iron, 
the resemblance is in appearance only. With permanently acting vibra- 
tions the initial effects nearly vanish, the first superposition of load 
decreasing the induction (almost) from the origin (fig. VII.). It thus becomes 
apparent that these initial effects of load are at all stages the result of 
the vibrational effect due to the first superposition of load which is always 
VOL. xxix. 4 
