242 ELECTRIC LIGHTING. 



Cost f the Electric Light with Induction 

 chines. We have seen that according to the experiments 

 of Jamin and Roger the electro-motive force of the current 

 from an Alliance magneto-electric machine with 6 discs, 

 having the bobbins arranged for tension and with a speed of 

 200 rotations per minute, is equivalent to that of 226 Bunsen 

 cells; but when the bobbins are arranged for quantity, it is 

 equivalent to the current from only 38 Bunsen cells. We 

 have also seen that the resistance of the generator should be 

 considered fictitiously with regard to Ohm's law as being 

 equivalent to that of 665 Bunsen cells in the first case, and 

 to that of 1 8 cells in the second case. The light produced 

 by that machine was, with the earlier arrangements of it for 

 lighthouses, equal to 230 Carcel lamps; and according to 

 the calculations of Reynaud, Inspector of Lighthouses, the 

 cost of the current was i franc 10 centimes per hour.* 

 If this cost is compared with that of the current from a 

 Bunsen battery of the same power, calculated from the data 

 given by E. Becquerel, the economy of using these machines 

 is in the proportion of i franc 10 centimes to n francs 30 

 centimes, that is to say, more than tenfold; and the cost of 

 the light, compared to that given by ordinary oil in a Carcel 

 lamp, would be only one-seventh. We must, however, observe 

 that the carbons have not been taken into account. 



According to Le Roux's experiments, the cost of the 

 electric light produced by the Alliance machines would, 



* The cost was distributed as follows : 



Francs. 



Interest of capital expended in the purchase of 



the machines ... ... ... ... .., 0*28 



Fuel for steam engine 0*40 



Engineer's wages ... - ... ... ... ... 0*35 



Lubrication, &c 0-07 



Complete data on this question will be found in the Report of Le Roux 

 (Bulletin de les Socittd d Encouragement, tome XIV, page 776), and in 

 Reynaud's Paper on the lighthouses and beacons of the French coast (Paris 

 Imprimerie Nationale, 1864). 



