1908-9.] Load and Vibrations upon Magnetism in Nickel. 39 
Apparatus. 
One end of the annealed nickel wire, 100 cms. long and 092 cm. diameter, 
formerly used, was soldered to the gong of the electric bell, while its other 
end was linked by means of a short length of thread (to prevent torsion) 
to the vertical arm of an L-shaped lever. Its horizontal arm carried a 
light scale pan, counterpoised so that when empty the wire was entirely 
free from load. To prevent vibrations in the ordinary sense when load was 
put “on” or “off,” the scale pan was cushioned with india-rubber, and a 
soft woollen thread was, for the same purpose, wound round the nickel wire 
in a loose spiral. The whole apparatus, which has previously been more 
fully described, || was suspended from the roof by means of india-rubber 
tubing, to prevent external vibrations reaching the nickel wire. The wire 
was in a horizontal position, at right angles to the earth’s magnetic field, 
and coincided with the axis of the magnetising solenoid 41 cms. long. An 
exploring coil and ballistic galvanometer (complete period eleven seconds) 
measured the magnetic intensity at approximately the central position of 
the wire. 
Superposition of Field, Load, and Vibrations. 
The above apparatus- enabled the relative superposition of load, field, or 
cyclic residual magnetisation, as distinguished below, to be performed 
either with or without permanently acting vibrations. In the former case 
the nickel wire was kept in a state of continuous vibration by ringing the 
electric bell. 
A conditions. — Loading, followed by repeated “ offs ” and “ ons ” of 
load, may be superposed at a sufficient number of points on the normal BH 
curve obtained at each point by field reversals increasing from zero (Al), or 
on the normal hysteresis loop (A2). This latter case may, when so stated, 
include the superposition of “ offs ” and “ ons ” of load on a hysteresis loop 
performed with permanent load. Loading and unloading may also be 
superposed, field being zero at all values of cyclic residual magnetisation 
between positive and negative maxima (A3)— the cyclic residual magnetisa- 
tion being produced, as shown in fig. V., by withdrawing the cyclic field 
increasing negatively (positively) always after the positive (negative) cyclic 
extreme has been departed from. Loading and unloading may be per- 
formed in steps. In all these cases each set of observations performed at 
any given point is independent of those performed at any other point. 
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