ELECTRIC CANDLES. 227 



duced by the action of the generator simply, and this is 

 proved in the manner following : 



If in the path of the current from an alternating-current 

 machine capable of giving a spark equal only to that of 6 or 

 8 Bunsen elements, there is interposed a series of condensers 

 of about 500 square metres in surface, a voltaic arc of from 

 15 to 20 millimetres length may be produced^ and carbons 

 of 4 millimetres are made incandescent for a length of 6 or 

 10 millimetres from their extremities. Also, if in the current 

 of an induction coil supplied by an alternating current, and 

 giving a spark of 5 millimetres, there is interposed a con- 

 denser of about 20 square metres of surface, a voltaic arc of 

 30 millimetres may be obtained ; and in this case also car- 

 bons of 4 millimetres in diameter are made incandescent for 

 a length of 6 or i o millimetres from their extremities. Finally, 

 a certain number of condensers being given, if the second 

 surfaces of one or of several of them are joined with the 

 second inducing coil of the machine, or with the earth, there 

 will be produced in the apparatus arranged as before effects 

 much resembling those of static electricity. 



These effects are what might have been expected, and it was 

 by similar means that Plante, with his rheostatic machine, 

 succeeded in transforming voltaic currents into currents of 

 static electricity capable of giving sparks 4 centimetres long. 



Jablochkoff's system of condensers supplies a very simple 

 means of regulating the intensity of the light of the candles 

 while they are in action; for this purpose there is needed 

 merely a commutator by which a greater or less condensing 

 surface may be connected with the circuit. 



Each of these condensers when applied to public lighting 

 is made of 25 separate elements, and corresponds with a 

 group of four candles ; consequently, these four candles are 

 connected with one of the wires proceeding from one of the 

 armatures, and the circuit is of course interrupted at the con- 

 denser. It may therefore be inferred that the current which 

 supplies the candles is only a current of the return discharge 



152 



