472 



FERREE AND RAND— LIGHTING 



uneven illumination; yet Reflectors I. and II., from which all high 

 brilliancies have been eliminated, give very much better results for 

 the eye than Reflector A so far as the povv'er to sustain clear and 

 comfortable seeing is concerned; and Reflector IV., which gives the 

 same general type of distribution of illumination as Reflectors I. 

 and II. but has not had the brilliancy of its opening cut down, gives 



Chart VIII. 



Fig. I. Showing a comparison of the effects of unevenness of illumina- 

 tion and unevenness of surface brightness on the power of the eye to sustain 

 clear seeing for a period of work. Reflectors I., II. and IV. give a very un- 

 even illumination (dark upper walls and ceiling and lanes of light in the 

 working plane) ; but the brightness of the openings of Reflectors I. and 11. 

 have been reduced by lining Reflector IV. to a depth of 9.5 cm. with surfaces 

 of low reflection coefficient, 4 per cent, and 38.5 per cent, respectively. A is 

 a translucent reflector giving a comparatively even illumination of walls, 

 ceiling and working plane. All are installed pendant in accord with the prin- 

 ciples of direct lighting. 



poorer results for the eye than Reflector A. The results for Re- 

 flectors I., II. and IV. were taken from a series in which an attempt 

 was made to find the maximum brightness of opening which the eye 

 could stand without much loss in power to sustain clear and com- 

 fortable seeing with the types of reflector and installation used. 

 The efifect on the eye of Reflector I. (coefficient of reflection of 



