1890.] on Colour-Vision and Colour-Blindness. 127 



The attempts hitherto made in this country to exclude the colour- 

 blind from railway and marine employment have not been by any 

 means successful. As far as the merchant navy is concerned, so- 

 called examinations have been conducted by the Board of Trade, with 

 results which can only be described as ludicrous. Candidates have 

 been " plucked " in colour at one examination, and permitted to pass 

 at a subsequent one ; as if correct colour-vision were something 

 which could be acquired. Such candidates were either improperly 

 rejected on the first occasion, or improperly accepted on the second. 

 On English railways there has been no uniformity in the methods of 

 testing, except, in so far as I am acquainted with them, that they 

 have been almost uniformly misleading, calculated to lead to the 

 imputation of colour-blindness where it did not exist, and to leave it 

 undiscovered where it did. In these circumstances, it is not surprising 

 that great discontent should have arisen among railway men in rela- 

 tion to the subject ; and this discontent has led, indirectly, to the 

 appointment of a committee by the Royal Society, with the sanction 

 of the Board of Trade, for the purpose of investigating the whole 

 question as completely as may be possible. 



It is perhaps worth while, before proceeding to describe the 

 manner in which the colour-sense of large bodies of men should be 

 tested for industrial j)urposes, to say something as to the amount of 

 danger which colour-blindness produces. A locomotive, as we all 

 know, is under the charge of two men — the driver and the fireman. 

 In a staff of one thousand, of each, allotted to one thousand loco- 

 motives, we should expect, in the absence of any efficient method of 

 examination, to find forty colour-blind drivers and forty colour-blind 

 firemen. The chances would be one in twenty-five that either the 

 driver or the fireman on any particular engine would be colour-blind ; 

 they would be one in 625 that both would be colour-blind. These 

 figures appear to show a greater risk of accident tban we find realised 

 in actual working, and it is manifest that there are compensations to 

 be taken into account. In the first place, the term " colour-blind " is 

 itself in some degree misleading ; for it must be remembered that the 

 signals to which the colour-blind person is said to be "blind" are 

 not invisible to him. To the red-blind, the red light is a less 

 luminous green ; to the green-blind, the green light is a less luminous 

 red. The danger arises because the apparent differences are not 

 sufficiently characteristic to lead to certain and prompt identification 

 in all states of illumination and of atmosphere. It must be admitted, 

 therefore, that a colour-blind driver may be at work for a long time 

 without mistakes ; and it is probable, knowing as he must that the 

 differences between different signal lights appear to him to be only 

 trivial, that he will exercise extreme caution Then it must be 

 remembered that lights never appear to an engine-driver in unex- 

 pected places. Before being intrusted with a train, he is taken over 

 the line, and is shown the precise position of every light. If a light 

 did not appear where it was due, he would naturally ask his fireman 



