LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



NOVEMBER 1847. 



lA. Researches on the Voltaic Arc, and 07i the iiifluence which 

 Magnetism exerts both on this Arc and on bodies transmitting 

 interrupted Electric Currents. By M. Auguste De la Rive, 

 Professor in the Academy of Geneva, Foreign Member of 

 the Royal Society, Corresponding Member of the Academy 

 of Sciences at Paris, 8cc.^ 



rilHE luminous voltaic arc occurring between two conduct- 

 J- ing bodies, each communicating with one of the poles of 

 the pile, is not merely one of the most brilliant phaenomena in 

 physics, but, from the numerous aspects under which it may 

 be regarded, it is also one of the most important. 



As a source of light, this phaenomenon, when exhibited in 

 a vacuum, enables us to examine what influence this particular 

 origin of the light employed may have in various optical ex- 

 periments. Compared with the solar light, the light of the 

 voltaic arc presents some curious differences and also resem- 

 blances. If, on the one hand, we find in it the seven coloured 

 rays of the spectrum, on the other the black streaks are re- 

 placed by brilliant ones, and these are differently interspaced. 

 In this field of inquiry, much, or rather all, yet remains to be 

 investigated. 



As a source of heat, the voltaic arc enables us to study the 

 fusion and solidification of even the most refractory bodies in 

 vacuo, and consequently under circumstances exempting them 

 from oxidizing action and other chemical influences, which 

 usually result from the application of a high temperature in 

 atmospheric air. It likewise allows us to determine the effects 

 produced upon bodies at a high temperature, by various gases 

 or vapours, distinct from those which enter into the composi- 

 tion of atmospheric air, and at different degrees of density. 



As an electro-chemical power, the voltaic arc may be ap- 



* From the Philosophical Transactions for 1847, part i. ; having been 

 received by the Royal Society Nov. 26, 1846, and read Jan. 7, 1847. 

 Phil. Mag. S. 3. Vol. 31. No. 209. Nov. 184.7. Y 



