402 Sig. Nobili and Antinori on the Electro-motive Force 



any other preamble than the same notice which has served as 

 the point of departure in our j-esearches. 



" The memoirof Mr.Faiaday,"so says the notice, "is divided 

 into four pai'ts. In the first, intitled ' Production of Voltaic 

 Electricity* ', is found the following important fact, — that a 

 voltaic current which traverses a metallic wire produces an- 

 other currentin a neighbouring wire, that the second current is 

 in a direction contraiy to the first, and continues but for a 

 moment; that if the producing current is removed, a second 

 current is manifested in the wire submitted to its action con- 

 trary to tiuit which was first formed in it, i. e. in the same di- 

 rection as the producing current. 



" The second part of the memoir treats of electric currents 

 produced by the magnet. On causing helices to approach to 

 magnets, Mr. Faraday has produced electric currents ; on 

 removing the spirals, cui'rents in the contrary direction were 

 formed. These currents act powerfully on the galvanometer ; 

 pass, though feebly, through brine and other solutions, and in a 

 particular case Mr. Faraday /las obtained a sj)a7-k. Hence it 

 follows that this philosopher has by using a magnet only pro- 

 duced the electric currents discovered [studied] by M. Ampere. 



" The third part of the memoir is relative to a particular 

 electric state, which Mr. Faraday calls electromo state\. He 

 intends to write of this another time. 



" The fourth part speaks of the experiment not less cu- 

 rious than extraordinary ofM, Arago, which consists, as is 

 known, in making a magnetic needle revolve under the in- 

 fluence of a rotatory metallic disc, and vice versa, Mr. Fara- 

 day considers this phaenomenon as intimately connected with 

 that of the magnetic I'otation, which he had the fortune to dis- 

 cover about ten years ago. He has ascertained that by the 

 rotation of the metallic disc under the influence of a magnet, 

 there may be formed electric currents in the direction of the 

 rays of the disc in sufficient number to render the disc a new 

 electrical machine." — Le Temps, Dec. 28, 1831. 



1 . Ordinary Magnetism, Phil. Trans. 1 832. Part I. ( Experimen- 

 tal Resea)c/ies in Electricity, 27 to 59 : 83 to 138: 217 to 26't). 



We had no occasion to make trials before we succeeded in 

 the experiment of Mr. Faraday. The first spirals which we 

 brought near to the pole of a magnet quickly manifested their 

 influence on the galvanometer. We observed three facts in 

 succession {Exp. Res. 30. 37. 4'7.)- Whilst approaching the 



[* This should be induction of voltaic electriciti/. — M. F.] 

 (t This should be electrotiic stale. I said I should write to my friend 

 about it another time. — M. F.] 



magnet, 



