16 
Proceedings of the Royal Society of Edinburgh. [Sess. 
not considered necessary, with the high induction amplitude alone used, viz. 
B = 8000, that demagnetisation by decreasing reversals should follow upon 
the completion of each series of readings. In no case, however, were 
further trains of oscillations of increasing intensity superposed at the same 
or any other point until about forty reversals of field at the cyclic 
amplitude had intervened. 
The superposed trains of damped secondary electric oscillations were 
increased in intensity by progressively increasing either the number of 
1 mm. spark gaps in series or the length of the single micrometer spark 
gap. In the former case, oscillation solenoids No. 1 and No. 2 were used, 
which subjected the bundles of fine iron wires to oscillations co-directional 
with the magnetising cyclic field; in the latter case the steel wire ’092 cms. 
diameter was subjected to transverse oscillations, its ends being directly 
connected with the secondary of the air transformer. 
With co-directional oscillations it was found necessary to reverse the 
connections between the secondary of the oscillation transformer and 
either of the oscillation solenoids. Under these conditions the Wimshurst 
machine did not reverse its polarity during any series of continued 
experiments, although it might do so from day to day. The results 
obtained by reversing the connections between the oscillation primary and 
the Wimshurst could only be explained by the polarity of the latter 
reversing in an erratic manner. This method was therefore discarded 
from the first. 
