468 



FERREE AND RAND— LIGHTING 



these features were plotted against the results of the tests. As com- 

 pared with the corresponding charts given for the previous experi- 

 ments, these charts show great irregularity unless separate curves 



1 I 3 



Chart VII. (Opaque Direct Reflectors Diff^ering in Lining, Dimensions 

 and Design.) Showing the tendency of the seven types of opaque direct re- 

 flectors to cause loss of power to sustain clear seeing. Loss of power to 

 sustain clear seeing before and after work is represented on the ordinate and 

 hours of work on the abscissa. 



are plotted for the reflectors similar in design. Reasons for the 

 irregularity are, perhaps, (a) the method of specifying brightness. 

 We are inclined to believe that if the surfaces of high brilliancy 

 which vary considerably in extent for the series of reflectors se- 



