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Color-Blindness.This defect of vision is often called " Daltonism," because a noted chemist of the name Dalton was a sufferer from this defect, and described very graphically the way in which different colors appeared to him. To Dalton blood appeared of a color similar to that called bottle-green; grass had a color almost identical with red objects. Green cloth-such as is used to cover tables - appeared of a dull red color. " When this kind of cloth loses iib color, as other people say, and turns yellow, then it appears to me a pleasant green. Very light green paper, silk, etc., are white to me. Colors appear to me much the same by moonlight as they do by candlelight. By lightning and electric light they appear as by daylight. A light drab woolen cloth seems to resemble a light green by day. " Dalton's defect of vision led him into the commission of some ludicrous mistakes. " Firstly, he was a Quaker, and would not wear the sword, which is an indispensable appendage of ordinary court dress. Secondly, the robe of a doctor of civil laws was known to be objectionable on account of its color-scarlet-one forbidden to Quakers. Luckily, it was recollected that Dalton was afflicted with the peculiar color-blindness which bears his name, and that, as the cherries and the leaves of the cherry-tree were to him of the same color, the scarlet gown would present to him no extraordinary appearance. So perfect, indeed, was the color-blindness, that this most modest and simple of men, after having received the doctor's gown at Oxford, actually wore it for several days in happy unconsciousness of the effect he produced on the street. " When asked what color this gown appeared to him, Dalton pointed to some of the evergreens outside of the window and said that, to his eye, the colors were alike. The lining of the gown, which was pink silk, he could not distinguish from sky blue. A boy eleven years old, who was color-blind, saw a woman passing by with a basket on her arm. He told his mother that the woman had chickens in the basket, because he saw the red feathers hanging out. These proved to be green leaves, with which the woman had covered the butter which she carried in the basket. A relative of this boy, who was in the navy, bought a blue uniform coat and vest, and trousers to match them ; the latter garment proved, however, to be red. " Six men - uncles, nephews and cousins - in one family, all belong to the Society of Friends ; and their mistakes in selecting articles of dress have been rendered especially conspicuous by the preference which members of that religious body give to the least brilliant and most unconspicuous colors. One of their number provided himself with a bottle-green coat, intending to purchase a brown one ; and selected for his wife, who desired a dark gown, a scarlet merino. Another, who is an upholsterer, purchased scarlet for drab, and had to rely upon his wife and daughters to select for him the fabrics needed in the course of his profession. A third, who is a farmer, could not tell red apples from the surrounding green leaves, except by their shape. All of them confounded red with green, olive with brown, and pink with blue. One of the younger men, whose profession requires him to deal much in colored tissues, has found that the 'only way of telling the difference between scarlet and green, or blue and crimson, is to take them into a room lighted with gas or candles,' when the distinction which was invisible by daylight becomes apparent." " A post-office clerk in Prussia was found to be constantly in trouble with the stamps. The accounts would come wrong. Sometimes there was not enough money in return for stamps sold, and on other occasions there was too much. This made dishonesty on his part less likely; but it was incomprehensible how he would make the accounts so entangled. At length it was discovered that he was color-blind, and could not distinguish red from green stamps. " -Boston Medical and Surgical Journal, December 27, 1877. No doubt letters in the United States find their way to the dead letter office as unpaid, from the color-blind senders putting on red two-cent instead of green three-cent stamps, since we all, from habit, regard the color rather than the number on a postage stamp, especially when in haste. Color-blindness is a congenital defect - that is to say, it is born with the individual - in the majority of cases. In 1845, Dr. Earle reported color blindness in five generations of his own family. Instances are also known in which this defect has resulted from dis ease and from injury. It is interesting to observe that all physicians who have investigated the subject, find that color blindness is more frequent in males than in females. Within the last ten or fifteen years the attention of railway and steamship authorities has been directed to this subject ; for it is evident that since trains and ships are largely dependent for their safety upon the accurate recognition of the colored lights employed as signals, a failure on the part of engineers, switchmen, pilots, etc., to distinguish between red and green might be followed by the most serious accidents. In fact, several catastrophes have been traced to color-blindness on the part of such employes. Many railway and steamship lines subject their men to examination as to their ability to detect colors ; and in Sweden such examination is required by law. In order to detect the color-blindness of an individual, it does not suffice to simply ask him to name the colors of different objects presented to him, for he may have a perfectly accurate perception of the color, and yet from lack of familiarity with the names, he may designate this color by an improper name. Hence, the only reliable method is to give him an opportunity for matching colors. This is done by presenting to him a pile of worsted skeins of a great variety of shades ; one of these, say a dark green, is put aside, and the person is requested to select from the pile the other skeins which seem to him to have the same color. If he have the usual form of color-blindness, he will select red and scarlet among other dark colors as similar to the green. Dr. Jeffries presents the following recapitulation of the subject: One male in twenty-five is color-blind in a greater or less degree. Of this defect they may even themselves be wholly unconscious. The defect is congenital. It exists in varying degrees. It is largely hereditary. It may be also temporarily or permanently caused by disease or injury. It may exist in one eye only. It is incurable when congenital. Exercising the eyes with colors and the ears with their names, helps the color-blind to supplement their eyes, but does not change or increase their color perception. Experiment and experience show that we are forced to use red and green marine signal lights to designate a vessel's direction of motion and movements, and at least red lights on railways to designate danger. Form, instead of color, cannot be used for these purposes. There are many peculiar conditions under which railway employes and mariners perform their duty, which render colored signals, and especially colored lights, difficult to be correctly seen. These signals can never be correctly seen by the color-blind. There are such among railroad employes, officers, pilots and sailors. There is, therefore, great danger from color-blindness. Railway and marine accidents have occurred from it. There is no protection but the elimination from the employes of railways and vessels of all persons whose position requires perfect color perception, and who fail to possess this. But first, if you want to come back to this web site again, just add it to your bookmarks or favorites now! Then you'll find it easy! Also, please consider sharing our helpful website with your online friends.
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