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



difference of conductibility between them, then the develop- 

 ment of heat, instead of being uniform, as it might appear it 

 ought to be, is much greater on the positive side. This im- 

 portant fact evidently proves that this portion of the circuit 

 has to resist a much more energetic action than that which the 

 other side experiences ; a fact which is confirmed by the mo- 

 lecular segregation accompanying this action at the positive 

 electrode. This want of resemblance in the phaenomena pre- 

 sented by the two electrodes, although placed in conditions 

 entirely synmietrical, deserves to be taken into serious consi- 

 deration, 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 ()f 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, tra- 

 versed 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 re- 

 pulsion 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 cop- 

 per 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 phaenomenon is then 

 entirely different. The transported particles appear to dis- 

 entxage 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, accom- 

 panied by the transfer of a liquid mass, and this appeared to 

 be effected with the greatest case. 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 luminous arc springs, the same magnetic 

 poles or different poles. 



The positive electrode of iron, when it is strongly magnet- 



