322 M. De la Rive's Researches on the Voltaic Arc. 



plied so as to submit to the electrolizing action of the electric 

 current gaseous media, which, from some experiments already 

 made, appear capable of decomposition by this process. 



As a mechanical power, the voltaic arc, by bringing bodies 

 into a state of minute division, and impressing upon them, in 

 this state, a tendency to motion, places them in a favourable con- 

 dition for the study of their molecular constitution, and of the 

 relations which connect this constitution with electricity and 

 magnetism. The struggle that takes place between cohesion 

 and the expansive force of the electric current, the reduction of 

 matter to the molecular state, and the form and nature of the 

 deposits resulting therefrom, are so many phaenomena capable 

 of throwing light on the obscure subject of molecular physics. 



The few preceding remarks suffice to give some idea of the 

 extent of an investigation embracing the whole range of 

 experimental research on the voltaic arc under its various 

 aspects, which I am far from pretending to have attempted. 

 I shall confine myself at present to a few details, and especially 

 to such as exhibit the action of magnetism on the voltaic arc, 

 and on those bodies which transmit interrupted currents. I 

 shall begin by describing some particular phaenomena which 

 I observed during my study of the voltaic arc under various 

 circumstances, while employing different substances as elec- 

 trodes, both in the air and in a vacuum ; I shall then proceed 

 to examine the action of a powerful electro-magnet on this 

 voltaic arc, and I shall conclude by describing some remark- 

 able experiments also illustrating the influence of magnetism 

 on conducting bodies, of whatever nature, traversed by inter- 

 rupted currents. 



§ 1. Some Phccnomena coyicerning the Voltaic Arc. 



Davy was the first who produced the phsenomenon of the 

 voltaic arc with two points of charcoal. More recently, 

 Messrs. Grove-l^ and Danlellf employed with success the 

 points of different metals, and arrived at interesting results: 

 I also published some experiments I made on the voltaic arc J 

 in 184-1. Subsequently, MM. Fizeau and Foucault observed 

 some remarkable facts of the same kind on the occasion of an 

 investigation into the intensity of the light emitted by charcoal 

 in the experinient of Davy §. The researches made up to the 

 present time, have already led to many results, of which I 

 shall consider only the most important. 



1. That the voltaic arc may be produced, a pile of greater 

 tension is required than that which is necessary for the ordi- 



* Bibl. Univ. June 1 840, i. 27. p. 387- 1' ^rck. deV Elect, torn. i. p. AQZ. 

 X Arch, de V Elect, torn. i. p. 262. § Ibid. toni. iv. p. 311. 



