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



to that which tends to impart an accelerating or retarding im- 

 pulse to the armatures. 



Having obtained the full effect of the combined alternating 

 currents from the two machines without any mechanical gearing, 

 it yet remained to obtain the combined direct currents from the 

 machines in the same manner. A pair of rings and a commu- 

 tator were therefore fitted upon one of the armature-spindles, 

 which was made sufficiently long for the purpose, and metallic 

 connexion was established between the rings of each machine 

 and the commutator on the prolongation of the armature-axis. 

 As the commutator necessarily revolved synchronously with the 

 two armatures, it was found that the combined alternating cur- 

 rents were rectified just as if they had proceeded from only one 

 machine, and were consequently available for electrodeposition, 

 or for any other purpose for which a direct current might be 

 required. 



Although this property of synchronous rotation has as yet 

 been observed only in the case of several pairs and a triple com- 

 bination of machines, yet there is no reason for supposing that 

 it may not be extended to any number of machines that may be 

 conveniently worked together from the same prime mover. It is 

 necessary, however, to observe that as the controlling power of 

 the current is only calculated to correct such minute deviations 

 from synchronism as it is beyond the power of mechanical skill 

 to prevent, the driving and driven pulleys should be respectively 

 as nearly as possible of the same diameters, as the correction of 

 any considerable difference in the number of the revolutions of 

 the armatures, caused by differences in the diameters of the 

 pulleys, must necessarily be attended by a corresponding dimi- 

 nution of the useful effect of the current outside the machines. 



Before concluding this communication I wish to direct atten- 

 tion to an important property of the magneto-electric circuit 

 which renders the commonly accepted theory, by which the ge- 

 neration and propagation of the electric influence in voltaic cir- 

 cuits is explained, inapplicable to those circuits which are entirely 

 metallic. Reference to this property is all the more called for 

 at the present time, as I find that a want of acquaintance with 

 it has given rise to no small amount of misconception on the 

 part of several eminent mathematicians and electricians who 

 have examined my experiments on the electric condition of the 

 earth, and the method by which I have thought proper to esti- 

 mate the magnitude of powerful induction-currents*. 



The intensity of a voltaic current, as represented by the ma- 

 thematical theory of Ohm, is equal to the electromotive force di- 



* Philosophical Magazine, August 1868. 



