312 ELECTRIC LIGHTING. 



to 800 candle-power. In these two instances six lights are 

 used in one circuit, but we have not here the subdivision of 

 the light ; we have, on the contrary, the multiplication of the 

 light, produced by the increased speed of the engine due to 

 the insertion of additional lamps. It is, however, easily 

 shown that if in a circuit where the electro-motive force is 

 constant we insert additional lamps, then when these lamps 

 are joined up in one circuit, t.e., in series, the light varies 

 inversely as the square of the number of lamps in circuit, and 

 when joined up, as in the multiple arc, the light diminishes 

 as the cube of the number inserted. Hence the subdivision 

 of the light is an absolute ignis fatuus. In the first place no 

 machine has yet been produced which is competent or 

 capable to light over 20 lamps ; secondly, no conductor is 

 known but copper that is capable of conveying the current 

 required to light these lamps, and copper is an expensive 

 .material; thirdly, no electric light has yet been produced 

 combining all the criteria of a good light." 



We consider this conclusion somewhat premature, and we 

 must confess that on this point we do not quite agree with 

 the learned English electrician. 



NOTE D. 



ON A NEW ARRANGEMENT OF THE WERDERMANN LAMP. 



The new arrangement of the Werdermann lamp, mentioned 

 on page 209, consists in the addition to the arrangement 

 shown in Fig. 56 of a brake acting on the lateral contact, and 

 put in operation under the influence of the end contact, 

 which is for this purpose adapted to the extremity of a lever 

 attached to the jointed guide that brings the brake into 

 action. So long as the pressure exerted by the movable 

 carbon on the end contact is uniform, the brake does not act, 



