446 FERREE AND RAND— LIGHTING 



We have avoided, therefore, as far as possible, making any com- 

 parison of results in different series or years ; but wherever this has 

 been done, the comparisons are based on the results of the same 

 observer with sufficient check experiments to show that the error 

 of observation is safely within the variation in result upon which 

 the conclusion is based. The following are some of the results that 

 have been obtained. 



1. Of the lighting factors that influence the welfare of the eye, 

 those we have grouped under the heading distribution are appar- 

 ently fundamental. Thus far in the work they seem to be the most 

 important we have yet to deal with in our search for the conditions 

 that give us the minimum loss of efficiency and the maximum com- 

 fort in seeing. If, for example, the light is well distributed in the 

 field of vision and diffuse and there are no extremes of surface 

 brightness, our tests indicate that the eye, so far as the problem of 

 lighting is concerned, is practically independent of intensity of light. 

 That is, when the proper distribution effects are obtained, intensities 

 high enough to give the maximum discrimination of detail may be 

 employed without causing appreciable fatigue or discomfort to the 

 eye. The work on composition or color value of light is still in 

 progress. While, therefore, we are not in a position to conclude 

 fully on this point, our belief based on the work which has been 

 done is that the color differences that are ordinarily present in ar- 

 tificial light are not nearly so important as are, for example, the 

 differences in the precautions that are being used to exclude high 

 brilliancies from the field of view. The defects with regard to color 

 value are, however, as a practical problem harder to remedy. 



2. For the type of control of distribution factors given by the 

 semi-indirect reflectors of low and medium density and the direct re- 

 flectors which present, as many of them do, excessive brilliancies due 

 to opening, surface of reflector, or wholly or partially exposed 

 sources, our results show that often too much light is used in ordi- 

 nary work for the comfort and welfare of the eye. That is, with 

 these reflectors, means have not yet been found to produce this 

 amount of light without introducing harmful brilliancies into the 

 field of view. 



3. The angle at which the light falls on the object viewed is an 



