M. DE LA RIVE’S RESEARCHES ON THE VOLTAIC ARC. 
37 
of resemblance in the phenomena presented by the two electrodes, although placed 
in conditions entirely symmetrical, deserves to be taken into serious consideration, for 
it may throw light upon the nature of the electric current, and upon the link which 
unites it with the molecular state of the bodies through which it is transmitted. 
§ 2. Influence of Magnetism on the Voltaic Arc. 
Davy was the first who observed that a powerful magnet acts upon the voltaic arc 
as upon a moveable conductor, traversed by an electric current ; it attracts and 
repels it, and this repulsion and attraction manifests itself by a change in the form of 
the arc. Even the action of the magnet may, as I have found, break the arc by too 
great an attraction or repulsion exerted upon it, causing the communication which 
the transmitted particles establish between the electrodes to cease. 
The action which I have just mentioned is not the only one which magnetism 
exerts on the voltaic arc. I have already stated the curious fact, that if two 
points of soft iron acting as electrodes, be both placed within a helix formed of thick 
copper wire of several coils, the voltaic arc developed between the two points of iron 
ceases the moment a strong current is passed through the wire of the helices, and 
reappears if this current be arrested before the points have become cold. The arc 
cannot be formed between the two iron points when they are magnetized, whether 
by the action of the helices, or by that of a powerful magnet, unless they be brought 
much nearer to one another, and the appearance of the phenomenon is then entirely 
different. The transported particles appear to disengage themselves with difficulty 
from the positive electrode, sparks fly with noise in all directions, while in the former 
case, it was a vivid light without sparks, and without noise, accompanied by the 
transfer of a liquid mass, and this appeared to be effected with the greatest ease. It 
is of little moment with respect to the result of the experiment, whether the two rods 
of magnetized iron present to that part of their extremities between which the lumi- 
nous arc springs, the same magnetic poles or different poles. 
The positive electrode of iron, when it is strongly magnetized, produces, the moment 
that the voltaic arc is formed between it and a negative electrode of whatever nature, 
a very intense noise, analogous to the sharp hissing sound of steam issuing from a 
locomotive engine. This noise ceases simultaneously with the magnetization. 
For the purpose of better analysing these different phenomena, I placed an electro- 
magnet of large dimensions and great power in such a manner as to enable me to 
place on each of its poles, or between them, different metals destined to form one of 
the electrodes of the pile,, while one point of the same metal, or another substance, 
acted as the other electrode. I have alike employed as electrodes, placing them in 
the same circumstances, two points of the same metal or of different metals. The 
following are the results which I have obtained. A plate of platinum was placed on 
one of the poles of the electro-magnet, and a point of the same metal was placed ver- 
tically above it ; the voltaic arc was produced between the plate and the point, the 
