124 Mr. B. Brudenell Carter [May 9, 



individual could not remain concealed, either from himself or from 

 those around him ; but such a conjecture would be directly at variance 

 with the truth. Just as it was reserved for Mariotte, in the reign of 

 Charles II., to discover that there is, in the field of vision of every 

 eye, a lacuna, or blind spot, corresponding with the entrance of the 

 optic nerve, so it was reserved for a still later generation to discover 

 the existence of so common a defect as colour-blindness. The first 

 recorded case was described to Dr. Priestley by Mr. Huddart, in 1777, 

 and was that of a man named Harris, a shoemaker at Maryport, in 

 Cumberland, who had also a colour-blind brother, a mariner. Soon 

 afterwards, the case of Dalton, the chemist, was fully described, and 

 led to the discovery of other examples of a similar kind. The condi- 

 tion was still, however, looked upon as a very exceptional one ; 

 insomuch that the name of " Daltonism " was proposed for it, and is 

 still generally used in France as a synonym for colour-blindness. 

 Such use is objectionable, not only because it is undesirable thus to 

 perpetuate the memory of the pl)ysical infirmity of an eminent 

 philosopher, but also because Dalton was a red-blind, so that the 

 name could only be correctly applied to his particular form of 

 defect. 



Colour-blindness often escapes detection on account of the use of 

 colour-names by the colour-blind in the same manner as that in which 

 they hear them used by other people. Children learn from the talk 

 of those around them that it is proper to describe grass as green, and 

 bricks or cherries as red ; and they follow this usage, although the 

 difi'erence may appear to them so slight that their interpretation of 

 either colour-name may be simply as a lighter or darker shade of the 

 other. When they make mistakes, they are laughed at, and thought 

 careless, or to be merely using colour-names incorrectly ; and a 

 common result is that they rather avoid such names, and shrink from 

 committing themselves to statements about colour. Dr. Joy Jefferies 

 gives an interesting description of the almost unconscious devices 

 practised by the colour-blind in this way. He says : — 



" The colour-blind, w'ho are quick-witted enough to discover 

 early that something is wrong with their vision by the smiles of their 

 listeners when they mention this or that object by colour, are equally 

 quick-witted in avoiding so doing. They have found that there are 

 names of certain attributes they cannot comprehend, and hence must 

 let alone. They learn, also, what we forget, that so many objects of 

 every-day life always have the same colour, as red tiles or bricks, and 

 the colour-names of these they use with freedom ; whilst they often, 

 even unconsciously, are cautious not to name the colour of a new object 

 till they have heard it applied, after which it is a mere matter of 

 memory stimulated by a consciousness of defect. I have often 

 recalled to the colour-blind their own acts and words, and surprised 

 them by an exposure of the mental jugglery they employed to escape 

 detection, and of which they were ^.Imost unaware, so much had it 

 become matter of habit. Another important point is, that as violet- 



