470 FERREE AND RAND— LIGHTING 



found to obtain in each case between the tendency to produce ocular 

 discomfort and to cause loss in power to sustain clear seeing. 



As was stated earlier in the paper a marked characteristic of the 

 effects produced by the dense and completely opaque direct reflectors 

 was the low illumination of the ceiling and the upper part of the 

 room, and the high and in some cases almost glaring illumination 

 of the floor and objects in the working plane. So far as effects on 

 the eye of the kind registered by our tests are concerned, how- 

 ever, these irregularities of illumination and of the low surface 

 brightnesses extraneous to the lamp and reflector seem to be of com- 

 paratively little consequence so long as the higher brilliancies of lamp 

 and reflector are themselves taken care of. In this series of experi- 

 ments, including the translucent direct reflectors, we have had quite 

 wide variations in the distribution of illumination, ranging from 

 well-illuminated ceilings and comparatively evenly illuminated walls 

 and working plane for the direct reflectors of medium density to 

 the dark ceilings and upper parts of the room and highly illuminated 

 lower half in case of the opaque reflectors. And considering this 

 work in connection with the preceding work, by means of the opaque 

 and translucent reflectors turned both up and down, and reflectors 

 of the distributing and focusing types, we have had the greatest 

 amount of light first in the upper half of the room, then in the lower 

 half, and within limits lanes of light have been produced ; still it has 

 been possible to get in all of these cases comparatively good eff'ects 

 on the eye so long as no excessive brilliancies were introduced into 

 the field of view. Table I., for example, has been prepared to show 

 the difference in the evenness of the illumination on the working 

 plane for Reflector I. of the series of translucent direct re- 

 flectors (designated in the table as Reflector A) and Reflectors 11. 

 and IV. of the present series of opaque reflectors ; and Chart VIII., 

 Fig. I, to give a graphic representation of the eye's ability to sustain 

 clear seeing for these reflectors and Reflector I. of the present series. 

 (The distribution of illumination for Reflector I. was so similar to 

 that for Reflector II. that it has been omitted from Table I.). A 

 comparison of this table and chart shows the following points. Re- 

 flector A gives a comparatively even illumination not only of the 

 working plane but of the entire room, and Reflectors I. and II. a very 



