RESEARCHES BASED UPON THE THEORY 



231 



numbers which gave the curves in Fig. 62 1. Thev are useful for fore- 

 telling the results of fatiguing the eye for different colours. They are 

 constructed on the basis that equal stimulations of all three components 

 give rise to the sensation of white. If the eye is fatigued with white 

 light the effect will be to tire each equally, and therefore the same 

 white seen by such an eye will appear darker. H the eye is fatigued 

 for SSN 48-6, RS and GS are equally fatigued. Suppose they are 

 fatigued so that the ordinates of the curves are reduced to one-half, and 

 then a colour, about SSN 42, of which the normal composition is IRS 

 to 2GS, is observed. The effect will be to make the new relationship 

 ^RS to IGS. Since the proportion remains the same no change in hue 



\I00 



90 



60 ^ 

 ;d 



70 e 



•> 



60 _> 





 SO 3 



ao S 



50 I 



20 "^ 



10 



20 22 24 26 26 30 32 34 36 36 40 4! 44 46 *8 SO 52 S4 S6 Se 60 



Scale of Spectrum SSN. 



Fig. 65. Percentage of the R, G, and B sensations in the spectrum colours when e(|ual 

 stimulations of the three sensations give rise to the sensation of white. (Abney.) 



will be observed. Suppose, however, a colour about SSN 60, where 

 there is no GS is observed. The only effective fatigue will be for RS, 

 and the red will merely appear darker. 



One more example. Suppose the fatiguing colour is about 42, 

 where the ordinate of GS is twice that of RS, and suppose the fatigue 

 reduces the ordinates to one half. They are then RS = \ and GS = |. 

 The eye then observes SSN 50, where RS is 54-5 and GS 42-5. As 



observed RS will be ^ = 13-6, and GS will be -^ = 21-25, i.e., as 



1 : 0-64. This is about the ratio found at SSN 44. Therefore the 

 yellow at SSN 50 will appear to the fatigued eye as a green of SSN 44, 



1 Abney, p. 240. 



