ACCIDENTS BY RAIL AND SEA. 137 



quite positively coDcluded that this method is not altogether safe. 

 Wilson acknowledges as possible that some of the color-blind might pass 

 unperceived, especially when, to save time, the examination is made more 

 hastily than the method allows. 



The classification is not better regulated ; in fact, it distributes the 

 color-bliud into three classes: 1st, those who confound red with green; 

 2d, those who confound brown with green ; and, 3d, those who confound 

 blue with green. This distribution is not founded upon any theory, nor 

 is it either the exact expression of well-defined kinds. Wilson himself 

 agrees that those who make the mistakes characterizing the first class do 

 not fail to make those of the second also. The second group might there- 

 fore be correctly regarded as the same kind as the first, of an inferior 

 degree. With regard to the third class, it is more than doubtful whether 

 the greater number of the cases which it includes can be classed under 

 the head of color-blindness. It also seems that Wilson hesitated with 

 regard to this, since he has excluded this group from one of his tables. 

 This class contributes the most also in rendering the proportion of color- 

 blindness as great as Wilson found it. From these statements, the 

 statistics given by this author cannot be regarded as very useful. 

 Besides, the number of cases examined is too limited, especially as the 

 particular figures forming the sum-total differ considerably among them- 

 selves. There is, however, another reason rendering Wilson's work of 

 great importance, and worthy of being especially mentioned here. Wil- 

 son's constant aim, in fact, was to direct attention to colorblindness in 

 its connection with practical life, and that in a very extended sense. He 

 shows that an individual whose anomaly from infancy has been estab- 

 lished should avoid selecting a profession in which his defective sense of 

 color might occasion difficulties and annoyances to himself as well as to 

 others. According to Wilson, the color-blind should never become paint- 

 ers, dyers, weavers, tailors, chemists, botanists, geologists, physicians, etc. 

 Amongst the occupations in which the color-blind risk being the cause of 

 embarrassments and annoyances to themselves as well as to others, and of 

 real and serious accidents, Wilson especially mentions those of the 

 sailor and railway employ^, because the color-blind, who have a peculiar 

 tendency to confound the very colors employed as signals at sea and 

 on railways, may in this way occasion even death itself. 



Wilson does not confine himself to pointing out these dangers to their 

 full extent, but proposes preventive measures. For this purpose, he 

 suggests very sensibly the only two measures that could be taken: to 

 preserve the colored signals in actual use, — red (= danger), green (= 

 attention), and white (the ordinary light of lanterns, that is yellow = 

 clear track), and in this case eliminate all the color-blind ; or else 

 retain all, and change the signals. Wilson decides in favor of the latter 

 alternative, which he considers preferable. He says that the managers 

 of railways have been very unfortunate in their choice of colors, select- 

 ing precisely those, red and green, the color-blind confound the most. 



