I consider this paper as in many respects an exceedingly valuable contribution to our knowledge of the curious subject ot colour-blindness—1st, because it is the only clear and consecutive account of that affection which has yet been given by a party affected, in possession of a knowledge of what has yet been said and written on it by others, and of the theories advanced to account for it, and who, from general education and habits of mind, is in a position to discuss his own case scientifically; and 2ndly, for the reasons the author himself alleges why such a person is really more favourably situated for describing the phenomena of colour-blindness, than any normaleyed person can possibly be. It is obvious that on the very same principle that the latter considers himself entitled to refer all his perceptions of colour to three primary or elementary sensations—whether these three be red, blue, and yellow, as Mayer (followed in this respect by the generality of those who have written on colours) has done, or red, green, and violet, as suggested by Dr. Young, reasoning on Wollaston’s account of the appearance of the spectrum to his eyes—on the very same principle is a person in Mr. Pole’s condition, or one of any other description of abnormal colour-vision, quite equally entitled to be heard, when he declares that he refers his sensations of colour to two primary elements, whose combination in various proportions he recognizes, or thinks he recognizes, in all hues presented to him, and which, if he pleases to call yellow and blue, no one can gainsay him; though, whether these terms express to him the same sensations they suggest to us, or whether his sensation of light with absence of colour corresponds to our white, is a question which must for ever remain open (although I think it probable that such is really the case). All we are entitled to require on receiving such testimony is, that the party giving it should have undergone that sort of
education of the sight and judgement
, especially with reference to the prismatic
decomposition
of natural and artificial colours, for want of which the generality of persons whose vision is unimpeachably normal, appear to entertain very confused notions, and are quite incapable of discussing the subject of colour in a manner satisfactory to the photologist.
XI. Remarks on colour-blindness