ILLl'UIXATIOX AM) /'//O7VM/AT/,T 



429 



voltage will exist across <S 2 and will cause it to pull up its end of 

 the lever and so close the cut-out .-witch. The circuit is then 



1 through the resistance" A*. Upon starting, the cut-out 

 switch is normally closed. More current passes throjugh the low 



nice path formed by N, and the carbons than through R. 

 Hence N! immediately pulls the carbons apart. This action ceases 

 when the voltage across No becomes sufficient to counteract the 

 effect of Si. The feeding mechanism is 

 connected to a dashpot which prevents 

 any sudden movement of the plungers. 

 The mechanism of the multiple lamp, 



'.s). i< very simple. The current 



s through the ballast in which 

 about 30 to 50 per cent, of the power 

 i- tost, The current then passes through 

 two solenoids connected in series, each 

 of which operates on one of the legs 

 of a U-shaped plunger. Should the 

 current become too great, the pi linger 

 raises the upper carbon by means of 



hitch and thereby increases the 

 the arc. This causes the 

 current to decrease to its normal value. 

 When the power is turned off, the 

 upper carbon drops and closes the 

 circuit so that the lamp is ready for 

 operation. 



195. Flame Arcs. Approximately 



eighty-five per cent, of the light in 



the direct-current arc come- from the incandescent crater 



in the positive carbon. In the enclosed arc the percent 



lower than this. In either 0886, probably not more than 10 to 20 



nt. of the light come- from the air flame it-elf. In flame 



! l the light comes from the flame. It i- found that 



by imprcirnating the carbons with certain salts, the arc itself 



ief luiiiine-eent due to the \ i<ni of these salts and 



the lumr they attain at the hmh arc tern; 



The color of ; trolled by the kind of salt 



I nr example, calcium salts produce a yellow color, 



FlO. 386. Mechanism :unl 

 i-oiiiHM-tioii-i <>f multiple arc 

 lamp. 



