.A. -AT 



Intelligence and Miscellaneous Articles. 



I place vertically two carbons AB, A'B',. d 

 communicating with the poles of a pile or a 

 Gramme machine ; I light the arc in C by 

 means of a small carbon introduced between 

 the first two and then taken away. I then 

 place behind the south pole of a magnet pro- 

 jected in C, or the north pole in front, or both 

 at the same time. We know that, according to 

 Biot and Savart's law, the element of current c 

 must be displaced toward its right, looking at 

 the south pole ; and experiment shows that the 

 arc immediately moves as far as the base B B' of 

 the carbons ; it reascends, on the contrary, to 

 to the summit A A' if the magnet be turned. It then becomes 

 fixed at the summit, but changes shape : it curves, and spreads out 

 into a sheet with pretty intensely loud hummings. If the magnet 

 is powerful, the arc is as it were blown upwards, and finally dis- 

 appears after taking the shape of an elongated flame. 



The same thing happens if we surround the two carbons with a 

 rectangle, CDEF, traversed by the same current. Each of the 

 parts of this rectangle cooperates in raising the arc if the direction 

 of the current is the same in the carbons and in the rectangle, and 

 in causing it to descend if the directions are contrary. The action 

 is multiplied by the number of turns given to the outer wire. 

 Four turns are sufficient to fix the arc in A A'; and it remains 

 there, whatever be the position given to the apparatus, even when 

 the points are directed downwards. 



It is evident that in this experiment the arc can be kept in A A' 

 and all insulating material omitted between the carbons. "When 

 the operation takes place with a continuous current of constant 

 direction, the positive carbon burns more brightly, is more quickly 

 consumed, and diminishes in length ; the arc is maintained at and 

 descends with its extremity. The negative carbon burns only in 

 its interior ; it diminishes in thickness, but keeps its length entire, 

 and may serve for another time. When machines with alternating 

 currents are employed, of which the direction changes at the same 

 time in the carbons and in the rectangle, the action keeps the same 

 sign; in spite of the inversions, the arc is always kept at A A' ; 

 and the carbons undergoing equal wear, their points remain always 

 at the same level, as in the Jabloschkofi: candle. 



It remains to know how the arc can be lighted at the beginning, 

 and relighted if it happens to be extinguished. For this purpose I 

 render the carbons movable about two joints A' and B', with a 

 spring to reunite them at their summit, and two buttresses to pre- 

 vent too wide separation between them. Under these conditions 

 the carbons repel one another, being traversed by opposite currents. 

 Moreover C D attracts A B, and repels A' B', while E E performs 

 the inverse action. All these effects concur to separate the 

 carbons, which recede spontaneously. They ignite immediately the 

 current commences, keep apart as long as it continues, to rejoin cne 



