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CHAPTER VIII: 



DISCOVERY OF THE LAWS OF MAGNETO-ELECTRIC 

 INDUCTION. FARADAY. 



IT was clearly established by Ampere, as we have 

 seen, that magnetic action is a peculiar form 

 of electromotive actions, and that, in this kind of 

 agency, action and reaction are equal and opposite. 

 It appeared to follow almost irresistibly from these 

 considerations, that magnetism might be made to 

 produce electricity, as electricity could be made to 

 imitate all the effects of magnetism. Yet for a long 

 time the attempts to obtain such a result were 

 fruitless. Faraday, in 1825, endeavoured to make 

 the conducting-wire of the voltaic circuit excite 

 electricity in a neighbouring wire by induction, as 

 the conductor charged with common electricity 

 would have done, but he obtained no such effect. 

 If this attempt had succeeded, the magnet, which, 

 for all such purposes, is an assemblage of voltaic 

 circuits, might also have been made to excite elec- 

 tricity. About the same time, an experiment was 

 made in France by M. Arago, which really involved 

 the effect thus sought; though this effect was not 

 extricated from the complex phenomenon, till Fara- 

 day began his splendid career of discovery on this 

 subject in 1832. Arago's observation was, that the 

 rapid revolution of a conducting-plate in the neigh- 



