236 ELECTRIC LIGHTING. 



two poles capable of attracting soft iron armatures. These 

 armatures are provided with stops and with opposing springs, 

 and are each attached to a jointed arm placed in a different 

 direction, and connected on either side with one of the 

 carbon-holders. Now it follows from this arrangement that 

 each current sent out of the machine produces a double 

 attraction, and gives rise to a movement that becomes vibra- 

 tory by reason of the rapid succession of the currents, and 

 this movement, by bringing the carbons nearer to and further 

 from each other, keeps them continuously lighted. This move- 

 ment may moreover be more or less marked by means of the 

 stops and springs of the armature. (See, for details of this 

 arrangement, the journal La Nature of the 2oth September, 

 1879.) 



The company which manufactures the De Meriten's ma- 

 chines now devotes some attention to fabricating carbons 

 for the electric light, and candles of a new form invented by 

 Soligniac, which, it seems, yield very good results. These 

 candles have four carbons of unequal diameter, separated 

 from each other by an interval of half a millimetre, are 

 connected together in the same plane by two insulating 

 and volatilizable bands. The two outside carbons have a 

 larger diameter than the others (4 millimetres), which are 

 only 2\ millimetres in diameter; the outside carbons are, 

 moreover, fitted into copper sockets, by which the electric 

 communication is made with the lamp. Finally, the four 

 carbons are at their bases connected by plaster of Paris, 

 which occupies all the space between the two sockets. It 

 appears that candles on this plan can only work well with 

 four carbons, and that those in which only three are used 

 must be abandoned. 



We have seen (p. 139) that Alkelmer sought to -diminish 

 the resistance of electric carbons by introducing metallic 

 plates between the sides of the insulator and the carbons. 

 Now these plates also possess, according to him, the very 

 great advantage of enabling the candle to be automatically 



