CHAP. VIII.] 



THE ELECTRIC LIGHT. 



631 



electric lighthouse such as those of the Heve only costs two francs 

 seventy-nine cents with a machine of four discs ; and for an equal 

 intensity the net cost is only one-seventh. This, however, is for a 

 service in which there must be no interruption. In industrial appli- 

 cations the net cost would be certainly still less, provided always that 

 the light was employed not less 

 than ten hours a day. In the 

 cases where the motive force can 

 be borrowed from powerful engines 

 which are working for other pur- 

 poses, as in many manufactories, 

 the electric light as M. Koux 1 

 also has remarked would scarcely 

 cost any more than the original 

 outlay for the magneto-electric 

 machine and the regulator. 



In the new opera-house in 

 Paris the electric light is thrown 

 upon the stage by means of a 

 Bunsen battery of 360 elements 

 which is established in a room on 

 the ground-floor. M. Dubosq has 

 here arranged six tables, each 

 supporting a Bunsen battery of 

 sixty elements. This battery is 

 placed upon the table, which is 



made of very thick unpolished glass that cannot be injured by the 

 acids. The elements are arranged in four rows of fifteen each. The 

 table is provided underneath with a board which supports a large 

 rectangular basin, in which the plates are placed after they have 

 been used. The jars of the battery, rilled with nitric acid, are, 

 after being used, placed in a tub containing the acid, and closed 

 with a wooden lid. 



In order to work a battery of such power under favourable 

 conditions, M. Dubosq has had to make special arrangements for the 



1 Les Machines Magneio-electriques Franpaises, et V Application de TEhctricite d 

 TEclairage dts Phares, two lectures delivered before the Society for the Encourage- 

 ment of National Industries, 



FIG. 444. Electric light apparatus in the 

 lighthouses of the Heve. 



