COLOR-BLINDNESS; ITS DANGERS AND ITS DETECTION - Softcover

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879 edition. Excerpt: ...green-blind, on the other hand, find that the green light is weaker (that is, darker) than the red. With the next opportunity these color-blind find the same. Kailroad employes are therefore rather more sure; yet much is dependent on the special lanterns used. One familiar with the nature of color-blindness will do better to use lanterns with different glass from that commonly employed, when desirous of exhibiting the precise character of this defect. Let him take one with a thin pale-red glass, and another with thick dark-green glass. The color-blind will then readily take the green light for red, and red for green or colorless. If the glass of the green light is smoked, he will take it for red. Cover the colorless light with steam or dew, and it appears to him green. Or let one do as I,--namely, have lanterns, the glasses of which are prepared for this purpose, and differ from each other, some having colorless or so-called smoked glass of varying absorptive power,--and they will quickly be convinced that the color-blind is guided in his decision solely by the intensity of the light " Another circumstance assists the color-blind in telling the lantern's light at a distance, which is also dependent on the intensity of the light, though this connection is not at once seen. It is the varying way in which the light radiates outwards. This radiation is most intense with the ordinary lantern, since this is the brightest (strongest in light); whilst, when the lantern-light is weak (red or green), the radiation is very little or nothing. A color-blind railroad employe told me he thus distinguished the signals. It need be hardly said how unsafe this is." " We see, therefore, that practice is of no avail for the color-blind. Otherwise an employe, who has...