292 Report of the Committee on Colour- Vision. 



The neutral colour on the Young-Helmholtz theory in the case 

 of the red-blind, would be a peacock-green, and in that of the 

 green-blind a purple. 



The table shows that a signal exhibiting certain hues of green 

 might be mistaken for a red one, since they both might appear to 

 the one class green and to the other red ; and that with one hue of 

 green (differing slightly in the two cases, however) it would give 

 the same sensation as white. In only one case, viz., that in which 

 the dominant spectrum colour to the normal-eyed is well on the 

 blue side of the neutral points, would the signals be distinctly 

 different in colour. 



Colours of The following table gives the wave-length in the spectrum of the 

 railway dominant colours of the signals which have been adopted by some 

 signal glasses. Q ^ principal railway companies when illuminated by (1st) a 

 light of the whiteness of the arc electric light, which does not 

 differ much from that of day-light, and (2nd) by gas-light. The 

 percentage of white light mixed with the spectrum colour is also 

 shown, together with the luminosity of the light transmitted. 

 How closely the green signals approach to the neutral points of 

 the completely colour-blind, when the mental standard of white- 

 ness is that of daylight, can be well judged if it be remembered 

 that these points lie between 5,200 and 4,900 for both types (see 

 Note c, page 304). 



Glass. 



Electric light. 



Gas light. 



Domi- 

 nant 

 •wave- 

 length 

 in ten 

 millionths 

 of million 

 (?) 



Per- 

 centage 

 of white 

 light in 

 colour. 



Lumi- 

 nosity, 

 naked 

 light 

 = 100. 



Domi- 

 nant 

 wave- 

 length. 



Per- 

 centage 

 of white 

 light in 

 colour. 



Lumi- 

 nosity, 

 naked 

 light 

 = 100. 



f" G-reat "Western ruby 



6250 

 6200 

 6250 

 4925 

 4925 

 5100 

 5000 



1 



^ 4925 

 1 



J 



|5500 



7 

 

 

 46 

 38 

 61 

 54 



24 

 32 



10-4 

 10-4 

 9-0 

 21 -8 

 16 "2 

 19 -2 

 15 -0 



7-6 

 9-1 



6275 

 6200 

 6275 

 5070 

 5050 

 5170 

 5120 



5050 

 5320 



12 

 

 

 50 

 34 

 62 

 40 



22 

 50 



13 -1 

 130 

 10 -o 



18- 1 



125 



19- 4 

 15-0 



6-9 

 10-6 



p§ 1 L.B.S.C 



[_ G-reat Northern .... 

 f G-reat Western .... 



L.B.S.C 



G-reat Northern .... 

 Great Eastern .... 

 2 Saxby and Farmer's, 

 © <J as ordinarily sup- 

 ^5 plied where no 

 special glass is or- 

 dered 



j Bottle green glass 

 l_ (District Railway) 



In a testing-room, when signal lights are used as tests, colour- 

 blind persons may possibly be able, with practice, to name the 

 different coloured signals correctly, recognizing them by their 



