COST OF ELECTRIC LIGHTING. 



241 



by Lacassagne and Thiers, for the lighting of the Rue Impe- 

 rial, which required a battery of 60 Bunsen cells, the cost 

 amounted to about 3 francs per hour for a light equivalent 

 to a mean of 50 Carcel lamps (75 at the beginning, 30 at the 

 end), and this cost was distributed as follows : 



This cost of 36*. 55 c. per hour is nearly the same as that 

 calculated by Becquerel from the actual expenditure. 



According to new and very interesting investigations under- 

 taken by Reynier, the cost of the electric light with incan- 

 descence lamps may be reckoned as follows for each Carcel 

 lamp per hour : 



With a Bunsen battery (Ruhmkorff 's form) 



a Thompson battery (large size) 



., a bichromate of potassium battery, with 

 porous vessels, chloride of ammonium 

 and mercury (Goarant and Tromelin's 

 form) 



Fr. c. 

 0*122 



0062 



0*180 



In order to obtain a current equivalent to that from 

 8 Bunsen cells (RuhmkorfFs form), giving a light of from 

 6 to 12 Carcel lamps, 45 Thompson cells, or 24 Goarant 

 and Tromelin cells, would be required. 



It will be seen from these figures that the economical 

 solution of the problem of electric lighting is not to be 

 found in batteries with liquids. 



16 



