MA CHINES WITH AL TERN A TE RE VERSIONS. 1 05 



magnets, B B, which move inside of the cylinder, as in the 

 foregoing apparatus, and which, being of contrary polarities, 

 successively supply in each section of the induced coil cur- 

 rents alternately reversed. This inducing system is excited 

 by a Gramme generator like that described on page 74. 

 It is this system of machines which supplies the currents 



FIG. 34. 



required for the lighting of the Place de r Opera, the Avenue 

 de P Opera, and the Place du Theatre- Francis. Four machines 

 are employed for this purpose ; one is placed in the cellars 

 of the opera-house, two others in cellars near the middle of 

 the Avenue de P Opera, and the fourth is set up in one of the 

 houses adjoining the Place du Theatre-Fran^ais* 



