Electromagnetic Induction Machines. 447 



machine may be so diminished that it may be driven directly 

 from the crank of a steam-engine, concurrently with an increase 

 of electric power proportionate to the number of electromagnets 

 and armatures in the electromagnetic circles. 



While the excitation of the electromagnets of the machine by 

 the current from several of its armatures is attended with some 

 advantages where portability is required, yet, as provision has to 

 be made for keeping the major and minor currents separate from 

 each other, the commutator arrangements become somewhat 

 complicated, and faults in either of the circuits are not so readily 

 localized as when a separate exciting machine is employed. In 

 those cases, therefore, where conveniences for driving separate 

 machines are at hand, and when the power of several of them is 

 required simultaneously, as in large electro-depositing establish- 

 ments, some advantage will be gained by using a separate ma- 

 chine of suitable power to excite the electromagnets of several 

 machines, when the currents from the whole of them may be 

 utilized, and a commutator on the axis of each machine will be 

 dispensed with. 



In my paper " On a Property of the Magneto-electric Current 

 to control and render Synchronous the Rotations of the Armatures 

 of a number of Electromagnetic Induction Machines "*, I stated 

 that this property would be available when the machines were 

 used for the electro-deposition of metals from their solutions. 

 It has, however, been found that the small resistance presented 

 by depositing solutions to the passage of the currents prevents 

 this property from manifesting itself (in accordance with what I 

 stated in my paper respecting the effect of joining the poles with 

 a good conductor) ; and it is only when the machines are em- 

 ployed for the production of electric light or other purpose 

 where the external resistance is considerable, that this electro- 

 mechanical function of the current comes into useful operation. 



Before concluding my description of this further development 

 of the principle of electromagnetic accumulation, I consider it 

 a duty I owe to myself as well as to science that I should not 

 allow to pass unnoticed the views and statements of certain 

 writers respecting the place and value of my investigations in 

 the history of natural knowledge. The peculiar good fortune 

 which enabled me to follow up the discovery of a great principle 

 to such brilliant results has contributed, accidentally in some 

 instances, to establish the idea that these results are an expan- 

 sion of Faraday's discovery of magneto- electricity rather than a 

 distinct step in electrical science. A brief glance at the history 

 and progress of electricity and magnetism will suffice to show 



* Proceedings of the Literary and Philosophical Society of Manchester, 

 December 15, 1868. Phil. Mag. S. 4. vol. xxxvii. p. 54, 



