DISCOVERY BY EXAMINING PECULIAR TRUTHS. 493 



The peculiar effect of a voltaic current decomposing 

 water, first observed by Nicholson and Carlisle, in the year 

 1800, was the origin of the science of electro-chemistry, 

 and of the art of electro-deposition. The unexplained 

 circumstance, noticed by Jenkins, that a strong spark 

 might be obtained by a voltaic battery, if the ends of the 

 battery were connected by a coil of insulated wire, led to 

 the discovery by Faraday, in 1834, of secondary or in- 

 duced currents, and to that of the < extra-current,' or the 

 inductive action of a current upon itself ; and also to the 

 discoveries by Dove in the same subject, made in the 

 years 1839 to 1842. 



The unexplained fact, first noticed by Mr. George 

 Fisher in the year 1818, that the rate of a chronometer 

 was affected by the proximity of a mass of iron ; l and that 

 of Arago, in 1824, that proximity of plates of various 

 substances, especially metals, affected the oscillation of a 

 magnet, originated Faraday's discovery of magneto-elec- 

 tricity. -What is termed 'hydro-electricity' was also 

 discovered in consequence of a peculiar circumstance 

 observed by a workman attending a boiler belonging to 

 the Durham and Newcastle Eailway Co. He reported that 

 the boiler was ' full of fire,' because when he placed his 

 hand near it sparks were emitted. Mr. Armstrong and Mr. 

 Pattison published the facts, and the former investigated 

 them and made known his results, 2 that the electricity was 

 produced at the point where the issuing steam was subject to 

 friction ; and also that similar effects might be produced by 

 a jet of condensed air. He also constructed for the Poly- 

 technic Institution of London a hydro-electric machine 

 of greater electric power than any electric machine pre- 



1 Library of Useful Knowledge, article ' Magnetism,' p. 68. 



2 See Philosophical Magazine, October 1840, and January 1842, 

 dated December 9, 1841. 



