458 



FERREE AND RAND— LIGHTING 



of the greatest and Reflector VI. is of the least density. In this 

 connection it is scarcely needful to mention that the greater is the 

 density of the reflector, the lower is the brilliancy of the surface 

 which it presents to the eye. The results of this series of experi- 

 ments are represented in Chart III. 



80 



40 



YI 



80 



40 



B 



16 



70 



170 



270 



80 



40 



80 



40 



002 0.04 0.06 



m 



80 



40 



80 



40 



200 500 1000 20 40 60 



Chart IV. (Semi-indirect Reflectors Differing in Density.) Showing 

 the tendency of the six types of semi-indirect reflector to cause loss of power 

 to sustain clear seeing. In Curve A, percentage drop in power to sustain 

 clear seeing after work for the different reflectors is plotted against ratio of 

 average brightness to brightness at point of work; in B, against ratio of light- 

 est surface to brightness at point of work; in C, against average brightness; 

 in D, against ratio of lightest surface to average brightness ; in E, against 

 ratio of lightest surface to darkest surface; and in F, against ratio of average 

 brightness to darkest surface. 



