﻿Mr. H. Wilde on a Property of the Magneto-electric Current. 59 



the coils themselves. Now, when the coils D D happen to be 

 at the same moment in that position during their revolution in 

 which they are producing the maximum and minimum amount 

 of current respectively, as must often be the case where there is 

 no synchronism, that current which is at the maximum rushes 

 through the coil which is producing the minimum current, as is 

 shown by the spark at the point where contact is broken be- 

 tween G and H. The effect of this passage of the current from 

 one coil to the other is to accelerate or retard the rotation of the 

 armature (according to the direction of the current) until syn- 

 chronism is established. 



That this influence of one coil upon the other operates in the 

 manner described was easily shown by the following experi- 

 ment : — The driving-strap of one of the armatures was removed, 

 so that only one of the armatures should be producing a current, 

 while the magnetism of the electromagnets of both machines 

 was, as usual, maintained to the same degree. On placing the 

 stationary armature with its coil in a suitable position in relation 

 to the magnet-cylinder for producing electromagnetic rotation, 

 and setting the other armature in motion, the stationary arma- 

 ture with its coil oscillated rapidly in arcs of very small ampli- 

 tude, the oscillations corresponding in number with the alterna- 

 tions of the current. As the amplitude of the oscillations in this 

 experiment was limited by the vis inertia of the armature, and in 

 order that the effect of one pulsation only on the armature might 

 be observed, contact was made and broken suddenly between the 

 plate H and the end G of the coil by a sort of tapping motion, 

 when the stationary armature was suddenly jerked round nearly 

 a quarter of a revolution, sometimes in the direction in which it 

 would have been driven by the strap, and at other times in the 

 opposite direction, according as the alternating electrical wave 

 which happened to be passing at the instant of making contact 

 was positive or negative. 



We have now seen, in the results obtained with the rotating 

 and stationary armatures, a cause sufficient to account for their 

 synchronism when revolving together, — the absence of synchro- 

 nism observed when the terminals F and H were bridged over 

 by a conductor having comparatively little or no resistance being 

 occasioned by the controlling current traversing the short circuit 

 established between the terminals F and H, instead of the 280 

 feet of resistance presented by either of the coils when approach- 

 ing the neutral point of their revolution. The absence of syn- 

 chronism observed when the direct current was taken from the 

 machines by means of commutators, is caused by the direction of 

 the current being coincident with that which they would receive 

 by induction from the electromagnets, and consequently opposite 



