444 



ALTERNATING CURRENTS 



lamp, but they increase the light in the direction in which it 

 is utilized. 



HORIZONTAL SECTION 

 OF REFRACTOR 



VERTICAL SECTION 

 OF REFRACTOR 



FIG. 399. Magnetite arc lamp with prismatic refractor. 

 135* 150 165 180 165 150 135* 



80 15' 15" 30 



Fro. 400. Candlepower distribution curves of lamp with and without reflector. 



204. Interior Illumination. Interior illumination is a very big 

 subject and requires considerable space for a comprehensive 

 treatment. It is more or less complicated by the number of 

 lamps that it may be necessary to use, by the reflection from 

 ceilings, walls, etc. The more involved problems require the 

 services of an illuminating engineer who has had considerable 



