ILU'MIXATION AND PIluTnM l-.TUY \ 17 



throughout the room. This method of lighting conceals the 

 source and insures a fairly uniform distribution. The method is 

 inefficient and the complete hiding of the source of light is 

 considered objectionable by many persons. 



An improvement over the indirect is the semi-indirect system. 

 The opaque bowl is replaced by a translucent bowl, allowing a 

 considerable portion of the light to be transmitted through the 

 fixture. As in the indirect system, a large amount of light is 

 directed to the ceiling and then reflected through the room. 

 This system is more efficient than the indirect and is more pleas- 

 ing because the source of light is not entirely concealed. Both 

 us require clean, light-colored ceilings for their most effec- 

 tive use. 



Factory 1 and shop lighting is a field in itself. Individual machines, 

 where fine work is being done, may require 1 individual lamps. 

 The-e lamps should be provided with reflectors which concentrate 

 the light on the work. Overhead belting militates against good 

 illumination and this fact constitutes a good argument for indi- 

 vidual and group drives. Cranes often necessitate lamps being 

 placed much higher than is efficient from the standpoint of 

 illumination. Where units are placed high above the floor, large 

 units are more efficient than small ones. The cost of lighting a 

 factory is a very small percentage of the total cost of operation. 

 over, good illumination results in increased production. 

 more accurate work, and fewer accidents. Particular care should 

 be taken to provide good illumination in factories, mills, etc. 



205. Street Illumination. Street illumination differs materi- 

 ally from interior illumination. Interior illumination must be 

 such that small details can be clearly seen. This requires intens- 

 ities of from 1.25 to 8.0 foot-candles. When this high int. 

 is obtained, there is no difficulty whatever in seeing and ,-,-,, 



i.jects. On the other hand, the purpose of street lighting 

 is not. to show details but to enable one to see and 

 objects and persons. Obviously this must be accomplished with 

 very much less than those used in interior illumination. 

 In a room, th- ills, paper, etc. an- nearly always light 



in color and considerable light is obtained by reflection 



See Electrical World Vol. 70, l'H7 V:moua articles <m Illumination by 

 Prof. C. K. 



