1908-9.] Load and Vibrations upon Magnetism in Nickel. 47 
obtained by simply withdrawing the field H — ±111. Intermediate values 
of residual magnetisation are, however, obtained by withdrawing the negative 
(or positive) cyclic field at a sufficient number of points of the loop descend- 
ing from the same positive (or negative) induction amplitude. The six small 
diagrams show the changes which take place between the first and fortieth 
“on” and “off” of the same load (11 ozs. = 0‘5 kilos per mm. 2 ), as if the 
cyclic field had always started from the positive extreme, as illustrated 
in the large central reference diagram. The value of the induction given 
with each diagram is obtained by measuring the induction change when, 
after the fortieth “off” of load, a single step is taken to the opposite cyclic 
extreme to that from which the cyclic process started. Between each 
set of observations, thirty or forty reversals of the highest field used 
intervene. 
Results . — The initial irreversible and final reversible effects of loading 
CYCLIC RESIDUAL MAGNETISATION. A3 CONDITIONS. 
and unloading at the extreme values d= 2800 of residual magnetisation, shown 
in fig. V., must, for reasons of symmetry, be each the reflection of the 
other in the horizontal axis. In each case the irreversible vibrational 
effect lowers the induction from 2800 to 1900, while the reversible 
effects of loads “on ” and “off” many times repeated decrease and increase 
respectively the residual magnetisation. But when these positions are 
departed from, the symmetry of the curves between the first and fortieth 
“ ons ” and “ offs ” of load disappears. This is well illustrated in the next 
pair of curves, where, quite accidentally, the residual magnetisation is 
B = + 800 and B = — 800 respectively. At the former positive value of 
induction there is practically no irreversible vibrational effect, loading and 
unloading taking their final values almost at once. At the latter negative 
value of induction, however, the initial lowering of the residual magnetisa- 
tion which marks more especially the first “ on ” of load is still largely in 
