THE MAGNETO-ELECTRIC CURRENT. 105 



heating was now obviated^ tlie subdivision of the materials 

 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 drif ting-shaft, by means of straps, yet when the 

 combined direct current from several commutators was 

 required, the want of perfect synchronism in the revolution 

 of the armatures operated to produce a diversion of the 

 currents of some of them through the coils of others 

 at the neutral point of their revolution ; and consequently, 

 the maximum useful eflPect of the combined currents 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 

 requsite 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 together 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 diameter, and each of 

 them was coiled with a copper-wire conductor 280 feet 



