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IV. Quelques recherches sur I' Arc Voltaique, et sur V influence quexerce le Magnetisme 
soit sur cet arc soit sur les corps qui transmettent les Courants Electriques Bis - 
continus. 
Researches on the Voltaic Arc, and on the influence 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, 
8fc. 85c. 
Received November 26, 1846, — Read January 7, 1847. 
THE luminous voltaic arc occurring between two conducting bodies, each commu- 
nicating with one of the poles of the pile, is not merely one of the most brilliant 
phenomena in physics, but, from the numerous aspects under which it may be re- 
garded, it is also one of the most important. 
As a source of light, this phenomenon, when exhibited in a vacuum, enables us to 
examine what influence this particular origin of the light Employed may have in 
various optical experiments. Compared with the solar light, the light of the voltaic 
arc presents some curious differences and also resemblances. If, on the one hand, 
we find in it the seven coloured rays of the spectrum, on the other the black streaks 
are replaced 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 solidifica- 
tion of even the most refractory bodies in vacuo, and consequently under circum- 
stances exempting them from oxidizing action and other chemical influences, which 
usually result from the application of a high temperature in atmospheric air. It like- 
wise 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 composition 
of atmospheric air, and at different degrees of density. 
As an electro-chemical power, the voltaic arc may be applied so as to submit to 
the electrolizing action of the electric current gaseous media, which, from some ex- 
periments 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 condition 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 
