BOOK XIII 



VOLTAIC ELECTRICITY 



CHAPTER VIII. 



MAGNETO-ELECTRIC INDUCTION. 



"TT^ARADAY'S discovery that, in combinations like those in which a 

 voltaic current was known to produce motion, motior would pro- 

 duce a voltaic current, naturally excited great attention among the 

 scientific men of Europe. The general nature of his discovery was 

 communicated by letter 1 to M. Hachette at Paris, in December, 1831 ; 

 and experiments having the like results were forthwith made by MM. 

 Becquerel and Ampere at Paris, and MM. Nobili and Antinori at 

 Florence. 



It was natural also that in a case in which the relations of space 

 which determine the results are so complicated, different philosophers 

 should look at them in different ways. There had been, from the first 

 discovery by Oersted of the effect of a voltaic current upon a magnet, 

 two rival methods of regarding the facts. Electric and magnetic lines 

 exert an effort to place themselves transverse to each other (see 

 chapter iv. of this Book), and (as I have already said) two ways 

 offered themselves of simplifying this general truth : to suppose an 

 electric current made up of transverse magnetic lines ; or to suppose 

 magnetic lines made up of transverse electric currents. On either of 

 these assumptions, the result was expressed by saying that like currents 

 or lines (electric or magnetic) tend to place themselves parallel ; which 

 is a law more generally intelligible than the law of transverse position. 

 Faraday had adopted the former view ; had taken the lines of mag- 

 netic force for the fundamental lines of his system, and defined the 

 direction of the magneto-electric current of induction by the relation 



Ann. de Chimie, vol. xlviii. (1831), p. 402. 



