Experimental Researches in Electricity. 1 7 



magneto-electric combinations producing their daily effects 

 unseen, amid the beautiful and complex mechanism of the 

 Calcutta Mint, or during the extensive and varied operations 

 in metals, in constant progress in the Foundry at Cossipore ! 



A farther consideration of the effects of terrestrial mag- 

 neto-electricited action, appeared to Faraday to lead irresis- 

 tibly to the conviction that inductive action must be produced 

 by the earth on its own mass, in consequence of its diurnal 

 rotation, and a curious and interesting series of experiments 

 were undertaken, with the view of verifying this impression. 

 Conceiving it not impossible that certain natural differences 

 might exist between bodies as to the intensity of the cur- 

 rent produced in them by terrestrial induction, especially 

 as Messrs. Babbage, Herschell, and Harris had found great 

 differences between metals and other substances, as well as 

 between metals and each other, he inferred these differences 

 might be rendered sensible by opposing the bodies to each 

 other. This view was however not confirmed by experi- 

 ment, for although he opposed copper to iron, and copper 

 to a large mass of pure still water, being the lake in the 

 gardens of Kensington Palace, he could procure no decisive 

 galvanometrical effects ; and it appeared that when cutting 

 the magnetic curves with equal velocity, even such dissimilar 

 bodies as copper and water exactly neutralised each other's 

 effects. He then examined the curious and interesting 

 results obtained by Mr. Fox of Falmouth, relative to the 

 electricity of metalliferous veins, with the view of discovering 

 whether any of these were due to magneto-electric induc- 

 tion, but believes, although not able to speak strongly, 

 that they are not. As increased length of the substance 

 acted upon increases the intensity of the current, Faraday 

 hoped to obtain, with large masses of moving water, sensible 

 effects, although quiescent water gave none. He therefore 

 experimented on the Thames at Waterloo Bridge, by stretch- 

 ing a copper wire nine hundred and sixty feet in length along 



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