238 ELECTRIC LIGHTING. 



ened by their combustion, the luminous point will remain 

 at the same elevation, and the electric candle may thus be 

 used for projecting images on a screen like the electric lamp 

 with clockwork movements. Lavaud de 1'Estrade points out 

 yet another arrangement for obtaining the same effects with 

 Wilde's candle, but these apparatus are not yet sufficiently 

 practical for us to dwell upon them. 



Other systems of electric lights have been proposed, and 

 we should never have done if we considered all the more or 

 less fanciful ideas which have been advanced. To give a 

 notion of their value, we need but allude to the method men- 

 tioned in certain newspapers, of covering the walls of rooms 

 with fluorescent and phosphorescent substances, which, 

 according to these projectors, will in the daytime store up 

 light sufficing to illuminate the rooms by night. This simple 

 notice will serve to show how far the imagination will run 

 when it is not controlled by a wise theory. 



At the exhibition of electric light in the Albert Hall, at 

 London, in 1879, more than 25 different electric lamps were 

 on view. There were, in the first place, specimens of all that 

 we have described ; and besides, there was a new form of 

 incandescent lamp, contrived by Higgin, which was very 

 similar to that of Ducretet, and in which use was made of 

 mercury to push on the movable carbon in proportion to its 

 rate of consumption. 



