r/8 ELECTRIC LIGHTING. 



a rod / fixed to the magnetic core acts on the detent of the 

 clockwork. The motion of the wheels causes a forward 

 movement of the two racks in the proper proportion for 

 keeping the point of light stationary. The light current 

 passes through the two coils, and according as its intensity 

 is greater or less, the iron core is more or less attracted 

 within the coils, a sufficient enfeeblement causing a release 

 of the detent, whereupon the approach of the carbons ensues. 



In this system, as in those of Archereau, Gaiffe, Jaspar, 

 Loiseau, c., the increase of the current has the effect of 

 separating the carbons from each other, and the clockwork 

 brings them nearer together ; but as under these conditions 

 the path of the movable piece in the electro-magnetic system 

 is considerable, and as the attractive effect is much less 

 sudden than in the case of electro-magnets with turning 

 armatures, the separations of the carbons are produced freely 

 and without oscillations, which is an advantage.* 



These are the regulators which, during the whole duration 

 of the Exposition, have worked with the machines of the 

 Alliance Company. With alternately reversed currents, they 

 offer real advantages, for J. Van Malderen has shown that 

 with these currents an iron rod is almost as strongly drawn 

 into a coil as with direct currents, only there is a much 

 greater heating of the electro-magnetic system ; but to com- 

 pensate for this there is much less residual magnetism, and 

 therefore greater sensitiveness. 



Brush's Lamp. The report of the American Commis- 

 sion appointed to examine magneto-electric machines having 

 bestowed great praise on this lamp, we have considered it 

 our duty to give a description of it here, although it appears 

 to us inferior to those we have in France. 



This lamp, which is represented in Fig. 46, is, like the pre- 

 ceding, based on the attraction of solenoids. The electro- 



* See the laws of the attractions of solenoids in tome II. of my Expose des 

 applications de rtlectriciU, p. 132. 



