﻿Mr. H. Wilde on a Property of the Magneto-electric Current. 57 



me, two iron pins which could be guided into two corresponding 

 holes in the face of the other. These disks could be engaged or 

 disengaged either when the machines were at rest or in motion. 

 The relative positions of the pins and holes in the disks were 

 such that the armatures might be engaged in reversed positions 

 of half a revolution when required. 



Each of these 4-inch machines, when making about 2000 re- 

 volutions per minute, was of itself capable of producing a very 

 efficient electric light ; and when the two armatures were clutched 

 together in such a position that the united positive currents 

 from both machines proceeded from one polar terminal simulta- 

 neously with the united negative currents from the other polar 

 terminal, the sum of the currents of the two machines was ob- 

 tained. On the other hand, when the armatures were clutched 

 together in the reverse position without any change being made 

 in the armature connexions, no current was produced outside the 

 two machines. 



These experiments, besides exhibiting the necessity of syn- 

 chronous rotation, further showed that the armatures must also 

 occupy the same relative position in the magnet-cylinders in 

 order that the combined current from the two machines might 

 be obtained. It now occurred to me to see to what extent the 

 want of synchronism in the armatures would affect the magni- 

 tude of the current. The armatures were therefore unclutched 

 and allowed to revolve independently of each other, in the same 

 manner as when the attempt was made to take the combined 

 direct current from the commutators. After the alternating 

 current had beeu transmitted through the electric lamp for some 

 time, I was surprised to find that there was no perceptible dimi- 

 nution in the amount of light produced from the carbon points, 

 and that the current would melt very nearly the same quantity 

 of iron wire as when the armatures were clutched together. On 

 examining into the circumstances attending this unexpected phe- 

 nomenon, I first observed that, whenever the machines were 

 stopped, the pins and holes in the respective disks were exactly 

 opposite each other, and that, while the armatures were revol- 

 ving, the two disks could at all times be engaged and disengaged 

 with the greatest facility. Moreover, even when, before starting 

 the machine, the disks were set a quarter or half a revolution 

 out of the position in which the maximum amount of current 

 was obtained, it was found that, after the armatures had been 

 revolving for a few moments, the disks resumed their normal 

 position with respect to each other (as indicated by the action of 

 the clutch) — thereby exhibiting not only the synchronous rota- 

 tion of the armatures, but also that the machines contained a 

 principle of self-adjustment to the position in which the maxi- 



