1876.] 
459 
The Constants of Colour. 
prismatic tints. (See Fig. 2.) The general effect of this 
proceeding will be to diminish the adtion of the coloured 
light ; the resultant light will indeed present to the eye 
Fig. 1. 
more light, but it will appear paler ; the colour-element will 
begin to be pushed into the background. Conversely, if we 
now should subject our mixture of white and coloured light 
Fig. 2. 
Spettrum crossed by Band of Superimposed White Light. 
to analysis by a second spectroscope, we should infallibly^ de- 
tect the presence of the white as well as of the coloured light ; 
