Theory, of Colour Vision. 411 



must be no minus signs. This condition admits of an 

 infinite number of triangles, and there is no unanimity 

 among the adherents o£ the Young-Helmholtz theory, as to 

 where they place the corners ; Konig and Dieterici, Helm- 

 holtz, and Abney all obtain widely differing results. The 

 corner must be fixed from other considerations than the 

 facts of colour-mixing as recorded by Newton's diagram. 



Exception may quite properly be taken to the fact that 

 the results in the Table are given in terms of luminosity. It 

 would be better in future work to state them in terms of 

 energy — to say, for example, that a yellow was matched by 

 a mixture of standard red and standard green, the energy 

 of red radiation received per second by the eye being so 

 many times the energy of green radiation, and to add at the 

 foot of the table the luminous equivalents of the standard 

 radiations for the observer in question. If we state the 

 results in terms of each individual observer's luminosity, 

 they are not directly comparable, and it seems unnatural to 

 state a colour-blind individual's results in terms of another 

 man's luminosity. As the table stands at present, the 

 results are stated in Sir William Abney's luminosity values. 

 I thought it better to leave them in this form, as I was not 

 certain what multipliers to use to reduce them to terms of 

 energy. If, however, we use the luminous equivalents given 

 by RE. Ives*, namely R = 278, G = 889, and B = 44, and 

 reduce Dieterici's results, we obtain : — 



Table II. 



X. E. G. B. 



6559 ., 103 -3 



6302 • 100 



6063 90 10 



5842 69 31 



5638 41 59 



5451 17 83 



5281 100 



5128 -50 111 39 



4991 -42 69 73 



4869 -31 33 98 



4759 -15 11 104 



4659 - 5 4 101 



4569 100 



4488 4 -2 98 



4413 6 -3 97 



4342 8 -4 96 



* Phil. Mas?. Dec. 1912. 



