108 Proceedings of Boy al Society of Edinhurgh. [sess. 
a perfectly clear conception of normal-eyed people’s different 
colours, and can tell his conception, by the aid of his other eye, for 
others normal sighted. His definitions are thus, in opposition 
to persons colour-blind in both eyes, perfectly reliable. I have in 
every instance let the person in question point out an objective 
colour with his normal eye for every one of his conceptions with 
his abnormal one. Indirectly we find in this way which qualities 
of perception are wanting in the abnormal eye, in comparison with 
the normal one. 
The two principal colours in the spectrum for the red-blind are, 
as to their fundamental tone, yelloio and blue. The yellow 
commences a little later, reckoned from the end, than the red of the 
normal-eyed (about Fraunhofer’s line C), and stretches over the rest 
of the red, orange, yellow, yellowish-green, and ends in the blue- 
green (between Fraunhofer’s lines h and F, nearer to the latter), 
where a narrow neutral colourless belt forms the limit against the 
other principal colour, hlue^ which stretches through the remaining 
part of the spectrum corresponding with our cyan-blue, indigo, and 
violet. 
The tone of the red-blind person’s first fundamental colour is not 
perfectly golden-yellow, but seems, for the normal eye, to have a 
shade of greenish-yellow, perhaps best defined as citron-yellow in 
the lighter, and as olive-green in the darker shades. His other 
fundamental colour does not seem to be purely cyan-blue or indigo, 
but is rather a blue with a perceptible shade of violet. It might 
be called indigo-violet. 
H. 
Bemarks by Von Kries on HippeVs One-Eyed Case. 
We find that the spectrum is shortened at the red end, and that 
consequently a relative want of sensitiveness for red light exists. 
We may also assume that the matches will be such as are 
attributed to the typical red-blind, i.e.^ that a very luminous 
red will be matched with a faint blue-green. If we draw from this 
fact the conclusion that the red component has fallen out, and in 
consequence only the green and the blue (or violet) components are 
excited by white light, then the Young-Helmholtz theory leads to 
the conclusion that the white of the abnormal eye will be the 
