CH. XIII] 



LIGHT FROM THE ARC 



551 



Most of the light from the arc, and all of the light which is useful 

 for projection comes from the craters of the arc ; from the positive 

 crater, if a direct current arc. 



753a. Table showing the proper size of cored-carbons for 

 different amperages, and the rate of wear in millimeters per 

 hour; also the relative rate of burning in length and in weight. 



(For the small carbons to be used on the house electric light- 

 ing system see 123, 131, 417-418.) 



Direct Current, Right-Angled Carbons. 



AUTOMATIC LAMP 



HAND-FEED LAMP 



