466 FERREE AND RAND— LIGHTING 



periments by lining the reflector to a depth of 9.5 cm. (3.7 in.) with 

 a mat surface of low reflection coefficient. This lining formed all 

 of the surface that was visible in the openings of the four reflectors 

 at Outlets A and B, and cut out the image of the lamp in the two 

 reflectors at Outlet B. In the two reflectors nearest the observer, 

 however, some of the bright lining and image were still visible, but 

 the angle of presentation was here great enough that comparatively 

 little effect on the comfort of the eye and its power to sustain clear 

 seeing was had or was to be expected. Two sets of lining were 

 used, one a very dark gray (reflection coefficient of about 4 per 

 cent.) ; the other a lighter gray (reflection coefficient of about 38.5 

 per cent.). Reflector IV. provided with the first of these linings is 

 designated in the charts as Reflector I., and with the second, as 

 Reflector II. Still another modification was made of this reflector 

 to lessen the effect of the opening on the eye. The apparent or 

 physiologic brightness of this opening, as was the case with the other 

 opaque reflectors, was enhanced by induction from the dark green 

 coating or backing on the outer surface of the reflector. This effect 

 is quite noticeable on inspection where a comparison with a reflector 

 presenting less or no induction is afforded, but does not register in 

 the photometer because the surroundings are not included in the 

 photometric field. In case of Reflectors I. and II. this induction was 

 lessened a great deal by covering the outside of the reflector with a 

 closely fitting cap of mat white paper. 



Because of the favorable results obtained with these modified 

 reflectors, a similar modification of Reflector V, was made by the 

 manufacturer for the purpose of reducing the brilliancy of its open- 

 ing. In this case the band was made permanent by sand-blasting the 

 corrugated glass surface of the reflector. The coefficient of re- 

 flection of the surface thus prepared was approximately 52 per cent. 

 The band was made 5 cm. in width. While considerable improve- 

 ment in the effect on the eye was produced by this modification, not 

 nearly so good results were gotten as in the other case because (a) 

 the coefficient of reflection was not sufficiently reduced by the sand 

 blasting; and (b) Reflector V. was not deep enough to give the best 

 results with this type of modification. The tip of the lamp, for 

 example, was visible to the observer in case of four out of the six 



