VOLTAIC ARC LAMPS. l8l 



lamps and obtained a gold medal. This honour compels us 

 to give some details of this new apparatus, which, it appears, 

 acts remarkably well. 



The apparatus is, like the preceding, based upon the 

 attraction of solenoids acting directly on the carbon-holders 

 by means of chains passing over pulleys of unequal diameter, 

 and this action can be regulated by a counterpoise which 

 acts on the antagonistic force.' But the improvement in the 

 original apparatus consists in this : the lower carbon acts on 

 a rod with a piston which moves freely in a tube filled with 

 mercury, and produces two useful effects. In the first place, 

 it prevents any abrupt movement of the carbon holders, for 

 the mercury being able to pass but slowly through the 

 narrow space between the piston and the interior surface 

 of the tube, resists a too rapid rise or descent ; in the second 

 place, it affords an excellent contact for the negative rod. 



The small counterpoise serving as antagonistic force has 

 also a happy arrangement. It slides on a small rod jointed 

 horizontally, with one end connected with the free extremity 

 of the chain of the lower carbon-holder ; so that, by moving 

 backward or forward an externally projecting stud, its effect 

 may be increased or diminished. 



Experiments made with this lamp have proved very satis- 

 factory. It is now applied at Sautter and Lemonnier's, in 

 the workshops of Cockerill and Seraing, in Denayer's paper 

 manufactory at Willebroek, at the Gare du Midi at Brus- 

 sells, &c. 



Rapieff's Lamp. This system is only an extension of 

 Bailhache's, in which the carbons are kept always at the 

 same relative distance in spite of their consumption, by 

 means of a spring pressing on them like the candle springs 

 uf carriage lamps. In Bailhache's system the carbons were 

 kept at a distance suitable for the formation of the arc, by 

 two hollow cones of calcined magnesia in which their points 

 were placed, and which formed a kind of stop-collar. As 



