Morning journal and courier., 1880-08-10
Hartford, June 25,
WHAT THE CoLoR-BL1ND SEE.

Mir. William Pole, an English writer on scientific subjects, who is himself color blind, has lately written an interesting paper on color-blindness, in which he covers all that is now known about this defect of vision. It is little singular that only within hun dred years has it been definitely known and described. An English shoemaker named Harris was the first to notice in himself and suspect in others an inability to discriminate all colors. Dr. Priestley's attention at tracted to the case, and it was the.subject of letter read before the Royal society in 1787. It was reserved, however, for John Dalton, the discoverer of the ''atomic the ory,' to elaborate and generalize, a number of years later, the facts of color blindness. Dalton was nearly 30 years of age before noticing his own visual defect. Comparing one day his impression of the color of ger anium flower with that of his friends, he be- came convinced of the singularity of his vision and was led into its investigation. The result was the first distinct setting forth of the difference between the color-blind and people of normal sight. On account of Dal- tons investigation of the matter, color blind ness is frequently called Daltonism.
 So much for the historical part of the subject. Mir. Pole proceeds to consider what the color-blind see Strictly speaking, he says, the ''Dalto- nian' has only two color impressions, yellow and blue; yet his sensations of vision give him. 1, pure white; ?, pure black; 3, inf nite varieties of gray f, yellow in great fu of iTte binafinnS of these with the varieties of gray; 6, blue in 8 great variety of -intensities; 7, combinations of these with the varieties of gray. Such ,olor sensations as red, green, orange, violet and all their combinations are unknown to the color-blind. Still, these colors make up- on him distinct visual impressions. Red, for instance, appears dark yellow or yellow brown pink or crimson seems simply gray or dark blue. Green is more perplexing- yellow greens, such as predominate in nature, appear as combination of gray and yellow :; neutral greens, varieties of gray; and blue greens, combinations of blue and gray vio- let appears dark or shaded blue, and brown 8 mingling of yellow and gray.
 We call especial attention to what this stu dent and victim of color blindness has to say of it's connection with the running of rail- roads. One of the most common symptoms of color blindness is the confounding, under certain circumstances, of red with green, and it has been taken for granted that color blind engine-driver or helmsman must be unable to distinguish between the contradic- tory signals. and frightful pictures are drawn of the danger the public are constantly in- curing But what asks Mir. Pole, says the memorable logic of facts and he answers the question as follows:
 In this country we have not only had tolerable experience of the working of rail roads for half a century, but have gath cred mass of information about railroad ac- cidents which is unknown elsewhere. Every casualty that occurs in the three kingdoms is carefully inquired into by government board and a report is published as to it's causes; and yet, so far as I know, never, in a single instance, since railroads have been in use, has accident been traced to the mistaking of red for a green night sig nal. And when we consider that, accord ing to the statistics, about one in every twenty five engine drivers must have been color blind, it follows that, if the notions of the alarmists had been true, numbers of col isions would have occurred every day-in fact, that the traffic of the country could not have gone on. The truth is, the agitation has arisen from the difficulty the normal eyed investigators have in understanding ex- actly what we the color blind, really see. We could tell them that although the red and green lights do not give the true red and green sensations,y yet still they strongly con- trasted to us, and we are in no danger of mistaking one for the other. The only acci- dent ever heard of in regard to the color of a signal was a curious one @ driver, when approaching signa1-post, had been looking into very bright fire, which so affected his vision that for the moment he lost the per ception of red, he mistook the red light, not for green, but for white, and going at full speed through the wrong points dashed into a train in a siding. On the whole, then, I think the alarm on this subject is unnecessa- rily magnifed but at the same time do not deny possibility of danger under certain circumstances, and would by no means dis courage reasonable precautions in the selec- tion of men. The agitation has at least had some good result, for not only has it induced Q wide discussion of the phenomena of the defect, but 1t has given rise to many inge- nious and systematic means of discovering it's existence, which previously was a difficult matter.
 It is worthy of note that though Mr. Pole, who writes so intelligently and sensibly con- corning color blindness, is himself color blind, he has succeeded as draughtsman and colorist of drawings. Dalton, too, made himself famous in chemistry, science in which color is an important clement