460 



FERREE AND RAND— LIGHTING 



the pressed Sudan; Reflector V. the pressed Sudan toned brown; 

 and Reflector VI. the prismatic. The size and type of the first five 

 of these reflectors have already been given. Reflector VI. is of the 

 extensive type, 8^:4 in. in diameter and sH in. deep. Reflectors I., 



Chart V. (Translucent Direct Reflectors Differing in Density.) Show- 

 ing the tendency of the six types of translucent direct reflectors to cause loss 

 of power to sustain clear seeing. In A, power to sustain clear seeing before 

 and after work is represented on the ordinate and hours of work on the 

 abscissa; and in B, percentage drop in power to sustain clear seeing after 

 work for the different reflectors is plotted along the ordinate and highest 

 brightness of reflector in candlepower per square inch along the abscissa. 



IV., V. and VI. are commercial products, but II. and III. are experi- 

 mental products inserted in the series to give gradations in density. 

 The blown Veluria used in the former series of experiments was 

 omitted from this series because the illumination efifects obtained and 



