ILLUMINATION 369 



Loss by Absorption, 



Color of Glassware. Per Cent. 



Medium opalescent globes 25 to 40 



Heavy opalescent globes 30 to 60 



Flame glass globes. . . . 30 to 60 



Signal green globes 80 to 90 



Ruby glass globes 85 to 90 



Cobalt blue globes 90 to 95 



FIG. 259. Each of these two little rooms receives the same light. Dark 

 walls absorb most of the rays of light in the left-hand room. 



Color of Walls. The color of the walls of a room is a very 

 important matter. If the color is one that reflects light, instead 

 of absorbing it, less illumination will be required and the cost of 

 the lighting will be lessened. 



In school rooms the wall space occupied by blackboards causes 



