ACCIDENTS BY EAIL AND SEA. 135 



many partisans. But when will it be in a condition to meet the exigen- 

 cies of the physiological doctrine of colors in a more satisfactory manner 

 than the Young-Helmholtz theory 1 This is yet unknown. With regard 

 to the defect now occupying our attention, it seems very doubtful, to 

 judge by the trials that have been made, whether this theory would better 

 meet practical necessities than that of the three cardinal colors. And 

 it is precisely these practical requirements that have led us to mention 

 the theory here. 



Up to the present time, the theoretical problem of color-blindness 

 has undoubtedly been the object of more serious attention, and has been 

 richer in results than the practical. Now, as the latter is nevertheless 

 of singular importance, and the difficulties to be encountered to solve it 

 in a satisfactory manner seem, in many respects, of only secondary 

 importance, it is not easy, in reality, at the first approach, to find a suit- 

 able explanation. It will not, therefore, be uninteresting, we believe, to 

 cast a rapid glance over this side of the question from a historical 

 point of view, which will, in the first place, bring out the fact of which 

 we speak, and perhaps also contribute to bring to light the point at 

 which it is necessary to look for the cause of this state of things. The 

 first writer who seriously occupied himself with the investigation of 

 color-blindness in the various departments of practical life, and especially 

 drew attention to the possible accidents occasioned by the employment 

 of color-blind individuals on railways and at sea, and generally in all 

 operations where colored signals are used, was George Wilson, professor 

 of technology at the University of Edinburgh. * Wilson's researches 

 were purely practical in aim and end. The mistakes made by the 

 students of his laboratory in judging the colors of chemical precipitates 

 led him to reflect upon this subject, after reading the memoir in 

 which Dalton describes his own anomaly. For a long time, he tells 

 us he scarcely dared suspect any of his pupils of having so rare anin- 

 tirmity, but, like many after him, he took courage, proceeded to make 

 an examination, and found that not only were his suspicions perfectly 

 correct, but that color-blindness was far from being so uncommon 

 as usually supposed. 



He dilates at length, in his memoir, on the peculiar characteristics of 

 seventeen color-blind individuals; eight were examined by himself, and 

 the others described by difl'erent observers, or the color-blind them- 

 selves. These cases were distributed as follows: fourteen men and 

 three women ; sixteen cases were congenital, and one proceeded from 

 a cerebral affection caused by a fall from a horse. It must be re- 

 membered that this last case had not been examined before the acci- 

 dent; a circumstance rendering the verification of the pathological 

 origin of color-blindness difiScult, but the description seems to authorize 



• Researches on color-blindness, with a 8npj)lement on the danger attending the 

 present system of railway and marine colored signals. By George Wilson. Edin- 

 burgh, 1855. 



