NO. 2 



HISTORY OF ELECTRIC LIGHT SCHROEDER 



77 



increases when a magnet, in shunt with the arc, becomes sufficiently 

 energized to close the contacts in the circuit of the starting magnet 

 causing the electrode to pick up and start off again. 



MERCURY ARC RECTIFIER FOR MAGNETITE ARC LAMPS 



As the magnetite arc requires direct current for its operation, the 

 obvious way to supply a direct constant current for series circuits is 

 to rectify, by means of the mercury arc, the alternating current ob- 



r 



m 



Mercury Arc Rf.ctifier Tube for Series Magnetite 

 Arc Lamps, 1902. 



The mercury arc converted the alternating constant current into direct 

 current required by the magnetite lamp. 



tained from a constant current transformer. The terminals of the 

 movable secondary coil of the constant current transformer are con- 

 nected to the two arms of the rectifier tube. One end of the series 

 circuit is connected to the center of the secondary coil. The other 

 end of the series circuit is connected to a reactance which in turn is 

 connected to the pool of mercury in the bottom of the rectifier tube. 

 One-half of the cycle of the alternating current goes from the 

 secondary coil to one arm of the rectifier tube through the mercury 

 vapor, the mercury arc having already been started by a separate 



