KNOWLEDGE AND OPINION IN REGARD TO COLOUR-BLINDNESS. 469 



Konig opposed the ancient trichromic explanation of colour-blindness, preferring the 

 newer hypothesis of Leber ; but he joined Dr Dieterici in an endeavour to test the 

 applicability of the older system to various modifications of colour-vision, including 

 the dichromic. They analysed the various spectra, and drew the corresponding sensation- 

 curves. They then endeavoured, by laborious and complicated calculations, to discover 

 the fundamental colour-sensations applicable to them, and they decided on three, viz. : — 



A red, inclining more to purple than the extreme end of the spectrum ; 



A green, of w. 1. about 505 ; and 



A blue, of w. 1. about 470. 



All these corresponded nearly with three of Hering's fundamental colours, his fourth 

 one being the yellow complementary to the blue. 



There were, however, some difficulties in this choice of the fundamentals, and a few 

 years later Helmholtz himself took the question in hand by elaborate calculations, and 

 showed that the problem, as they had put it, was insoluble. 



Gotter, 1888. 



In later years, investigators have turned attention to the argument of Krenchel, 

 that there is no indication of any natural peculiarity which gives any preference to 

 one or more colours over others, so as to point to them as specially distinguished. There 

 is certainly the extreme predominant brightness and luminosity of yellow, and the fact 

 that, under increasing heat, other warm colours tend towards it ; but this does not seem 

 to be considered important by the advocates of Young's theory, who have so long ignored 

 it altogether, except as a subsidiary compound of red and green. 



Professor Goller, admitting without hesitation the yellow and blue dichromic 

 colours, has remarked that a certain degree of what he calls Ursprilnglichheit, i.e., a 

 character of originality, seems to attach to them, as their sensations seem more permanent 

 and more delicately constituted for the appreciation of their finer nuances. He finds, 

 for example, the sensitiveness of the eye for them, as expressed by the smallness of the 

 fraction of appreciation of differences of hue, quite remarkable. The eye can, he says, 

 distinguish in yellow a difference of " Helligkeit" of yif^, and for blue y^y ; whereas for 

 red the fraction is TT -g, for green 3-^, and for violet y^. He thinks he finds evidence 

 in favour of Donders's idea that yellow and blue were the original colours of the 

 spectrum, and have been extended by later evolution in both directions. The element 

 of distinctness of nuance has since been used with great ability by Helmholtz in another 

 way. 



Hillebrand, 1889. 



An elaborate essay by this author on the difficult subject of the connexion between 

 colour and luminosity, is also briefly noticed in "Data," AD. 



