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



So far I have adverted principally to the means by which a 

 very serious defect in the practical working of the new induction 

 machine was remedied, a defect which many of my friends, who 

 were unacquainted with the efforts which have been made to over- 

 come it, have considered to be fatal to the success of what seemed 

 likely to be a useful invention. But while the difficulty arising 

 from the heating was now obviated, the subdivision of the mate- 

 rials of one large machine into a number of small ones gave rise 

 to another defect which it was also found necessary to overcome; 

 for although the armatures of several machines might be driven 

 nominally at the same speed from the same driving-shaft, by 

 means of straps, yet when the combined direct current from 

 several commutators was required, the want of perfect synchro- 

 nism in the revolution of the armatures operated to produce a 

 diversion of the currents of some of them through the coils of 

 others, which were at the neutral point of their revolution ; and 

 consequently the maximum useful effect of the combined cur- 

 rents could not be obtained. 



As the high speed at which the machines were driven precluded 

 the employment of toothed gearing, the only method which 

 seemed at all feasible for producing the requisite synchronism of 

 the armatures was to place a number of the machines in a straight 

 line, and connect them together by means of a clutch fixed on the 

 end of each armature-spindle. The chief objection to the carry- 

 ing out of this arrangement was the difficulty of providing the 

 requisite means for preserving the synchronism of the system, 

 when any of the intermediate machines were disabled by accident, 

 or stopped for repairs; so that, practically, it would not have been 

 found convenient to work more than two machines geared toge- 

 ther in the manner described. 



It was while experimenting with a pair of machines so geared 

 together, that I first observed the phenomenon which forms the 

 subject of this communication. These machines were arranged 

 for producing the electric light, with a view to their application 

 to lighthouse illumination. The armatures were 4 inches in dia- 

 meter, and each of them was coiled with a copper-wire conductor 

 280 feet long and -J of an inch in diameter. The currents 

 were taken from the armatures by means of copper brushes rub- 

 bing against metal rings connected respectively with the ends of 

 the armature-coils, and were therefore in alternate directions. It 

 has been found that alternating currents are much better adapted 

 for the production of a constant electric light at a fixed point in 

 space than the current which has been rectified by means of a 

 commutator. 



The clutch, by which the armatures were connected, consisted 

 of two iron disks about 4 inches in diameter, having, in the face of 



