138 COLOR-BLINDNESS IN ITS RELATION TO 



This opinion does not extend to the signals used during the day. But 

 Wilson fails, and very naturally, when he proposes other colors prefer- 

 able, according to his judgment, for night-signals ; for example, a blue 

 light, excellent in all other respects, cannot fail to be useless in conse- 

 quence of the small amount of power it is capable of acquiring in an 

 ordinary lantern. Wilson reaches the conclusion that colors should be 

 discarded as .principal signals; they should be employed, he says, only 

 as auxiliary, and founds his system of signals on form, motion, and num- 

 ber. He enlarges to some extent upon this subject in a supplement to 

 his memoir, into the details of which we cannot now enter. 



The dangers which threaten travel by rail and sea, and the disasters 

 resulting from mistakes of the color-blind with regard to colored signals, 

 were clearly understood and distinctly expressed, and the measures to be 

 taken to avoid them plainly proposed more than twenty years since. If, 

 therefore, it is now asked, as would be natural, to what practical results 

 all this has led, we might reasonably expect, especially when we recall the 

 attention that Wilson awakened on the subject amongst his contempora- 

 ries, that an important reformation for assuring public safety would long- 

 since have been accomplished not only in England, but in every civilized 

 country. A mere glance over the existing condition of things, however, 

 reveals the fact that the answer is not satisfactory. The only practical 

 result mentioned by Wilson in his work as a result of his writings, is 

 the resolution of the Great Northern Eailway Company that the entire 

 personnel must in future prove themselves free from this defect of the 

 chromatic sense before entering the service ; and, as Wilson says, the 

 public is indebted for this wise measure to one of the directors of the 

 company, Mr. Graham Hutchison, whose attention was called to Wil- 

 son's works by Dr. Mackenzie, of Glasgow. We see by this that the 

 numerous articles written by Wilson before publishing his views and 

 experience in full had aroused public attention to an interesting phe- 

 nomenon in the scientific world, but had not led to any practical appli- 

 cation, except in the one case in which a physician had succeeded in per- 

 sonally interesting one of the directors of a railway company in the ques- 

 tion. We know not how far other administrations have followed this 

 example. It is very probable that this measure has not been adopted by 

 a single company in Dalton's country, where color-blindness was dis- 

 covered in the first place, and where it was studied with so much care 

 that England was long regarded as the veritable land of this anomaly. 



It would appear then that no considerable change has taken place in 

 the matter since Wilson's time. With regard to the English navy, we 

 still lack positive information. 



With regard to France we are more fortunate. For a long term of 

 years. Dr. A. Favre, of Lyons, was occupied with the practical side of 

 this question, and made different investigations into the perception of 

 colors, especially amongst the employes of the ParisLyon-Mediterraueau 

 Company, of which he was for a long time one of the consulting physi- 



