Michael Faraday, his Life and Works. 425 



Faraday advanced still further in 1831, by discovering that it 

 was sufficient to bring towards, or remove from, a metallic wire 

 forming a closed circuit another parallel wire traversed by an 

 electric current, or simply a magnet, in order to develope in the 

 former wire an electric current. He discovered induction — that 

 phenomenon which so many others had sought in vain, although 

 suspecting its existence, but which he alone had succeeded in 

 producing. 



Let us dwell for a moment upon his fundamental experiment. 

 Two metal wires covered with silk are rolled together round a 

 cylinder of glass or wood; the two wires are thus isolated, and 

 have all their spires approximate and parallel. An electric 

 current is passed into one of these wires; immediately a current 

 is manifested in an opposite direction in the neighbouring wire, 

 the extremities of which are united by a galvanometer ; but this 

 current only lasts for a moment. The current passing through 

 the first wire is interrupted ; immediately another current is de- 

 veloped in the second wire, which is momentary, as in. the former 

 case, but directed in the same way as the producing current, 

 instead of in the contrary direction. The momentariness of these 

 two currents, and the fact of their alternately opposite directions, 

 constitute the two important characters of this new mode of pro- 

 duction of electricity. 



Faraday did not stop at this. Starting from Ampere's idea 

 that a magnet is only an assemblage of electric currents arranged 

 round an axis in a manner very analogous to the circulation of 

 an electric current through a metallic wire rolled into a coil, he 

 tried the replacement, in his fundamental experiment, of the 

 wire traversed by the current by a simple magnet. For this 

 purpose he twisted a single wire instead of two into a coil round 

 a glass or wooden tube; then he introduced a magnet into this 

 tube, and ascertained that at this moment a momentary current 

 is developed in the coil of wire, and that a second, equally mo- 

 mentary but in an opposite direction, is developed at the moment 

 when the magnet is withdrawn. Here, therefore, was realized 

 that production of electricity by magnetism which Faraday had 

 long been seeking, convinced, as he was, that, as electricity pro- 

 duces magnetism, magnetism in its turn must produce elec- 

 tricity. 



Is it necessary to follow Faraday in the multiplied experi- 

 ments by which he demonstrates that the electricity developed 

 by induction possesses all the properties of voltaic electricity, and 

 of the ordinary electricity produced by machines — that it heats 

 fine metallic wires, gives shocks, and even produces the spark ? 

 To produce an electric spark by means of the action of a simple 

 magnet, is one of those striking facts which give to the discovery 



Phil Mag. S. 4, Vol. 34. No. 232. Dec. 1867. 2 F 



