64 THE PRODUCTION AND USE OF LIGHT 



FIG. 53, A library lighted by indirect lighting, 



the surface to be illuminated. The lamps are placed within a 

 reflector which diffuses and reflects the light against the ceiling 



(Figs. 52 and 53), which in turn 

 reflects the light downward to 

 the surfaces which are to be 

 illuminated. The efficiency of 

 such lighting depends largely 

 upon keeping the reflector free 

 of dust (Fig. 54) and upon the 

 -character and color of the ceil- 

 ing finish. At best, however, 

 not more than about 70 per 

 cent/ of the light is reflected by 

 the ceiling; generally the effi- 

 ciency pf the indirect systems 

 of lighting is much lower than 



FIG. 54. Removing the dust from .i- r\ , ^ m 



the indirect lighting bowl. tms ; Owm S to lts low efficiency, 



indirect lighting is frequently 



regarded as a luxury although its superior quality is recognized 

 by everyone. Bright spots, such as bright, exposed, unshaded 



