COLOR-VISION AND COLOR-BLINDNESS. 695 



named Harris, a shoemaker at Mary port, CiunberlaiHl, who had also a 

 color-blind brother, a mariner. Soon afterwards, the ease of Dalton, 

 the chemist, was fully described, and led to the discovery of other ex- 

 amides of a similar kind. The condition was still however looked npon 

 as a very exceptional one; insomuch that the uame of "Daltonism" 

 was proposed for it, and is still generally used in France as a synonym 

 for color-blindness. Such use is objectionable, not only because it is 

 undesirable thus to perpetuate the memory of the physical intirniity of 

 an eminent philosopher, but also because Dalton was red-bliiul, so 

 that the name could only be correctly applied to his particular form of 

 defect. 



Color-blindness often escapes detection on account of the use of color 

 names by the color-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 difference 

 may appear to them so slight that their interpretation of either color- 

 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 color names incorrectly ; and a common result is that they 

 rather avoid such names, and shrink from committing themselves to 

 statements about color. Dr. Joy Jetteries gives an interesting descrip- 

 tion of the almost unconscious devices practiced by the color-blind in 

 this way. He says : 



" The color-blind, who 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 color, are equally quick-witted 

 in avoiding so doing. They have found that there are names of certain 

 attributes they can not comprehend, and hence must let alone. They 

 learn also what we forget, that so many objects of ever^^-day life 

 always have the same color, as red tiles or bricks, and the color names 

 of these they use with freedom ; whilst they often, even unconsciously, 

 are cautious not to name the color 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. T have often recalled to the color-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 

 almost unaware, so much had it become matter of habit. Another im- 

 portant point is, that as violet blindness is very rare, the vast majority 

 of defective eyes are red or green blind. These persons see violet and 

 yellow as the normal eyed, and they naturally apply these color names 

 correctly. When therefore they fail in red or green, a casual observer 

 attributes it to simple carelessness, — hence a very ready avoidance of 

 detection. It does not seem possible that any one who sees so nnich 

 correctly, and whose ideas of color so correspond with our own, can 

 not be equally correct throughout, if they will but take the pains to 

 notice and learn." 



