﻿126 



Mr. J. S. Dow on Colour 



however, was distinctly the brighter, even in the case of the 

 very large screen. 



Fig. 3. 



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The illumination was now weakened by introducing re- 

 sistance in series with the glow-lamp, and the blue began to 

 appear brighter. A point was soon reached, when, for the 

 very large screen, the blue was unquestionably brighter than 

 the red. At this stage the difference in appearance of the 

 different sized screens was much more marked than at the 

 higher illumination, and, in the case of the smaller screens, 

 the red was still much brighter than the blue. 



As the light was still further weakened the colours began 

 to disappear until, eventually, the red appeared as black, 

 while the blue shone out with a phosphorescent white 



