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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



exquisitely beautiful such pictures are, and how 

 completely they give us all requisite information 

 as to form, surface-texture, solidity, and distance, 

 and even to some extent as to color — for almost 

 all colors are distinguishable in a photograph by 

 some differences of tint, and it is quite conceiv- 

 able that visual organs might exist which would 

 differentiate what we term color by delicate gra- 

 dations of some one characteristic neutral tint. 

 Now, such a capacity of vision would be simple 

 as compared with that which we actually possess 

 — which, besides distinguishing infinite grada- 

 tions of the quantity of light, distinguishes also, 

 by a totally distinct set of sensations, gradations 

 of quality, as determined by differences of wave- 

 lengths or rate of vibration. At what grade in 

 animal development this new and more complex 

 sense first began to appear we have no means of 

 determining. The fact that the higher verte- 

 brates, and even some insects, distinguish what 

 are to us diversities of color, by no means proves 

 that their sensations of color bear any resem- 

 blance to ours. An insect's capacity to distin- 

 guish red from blue or yellow may be (and prob- 

 ably is) due to perceptions of a totally distinct 

 nature, and quite unaccompanied by any of that 

 sense of enjoyment or even of radical distinctness 

 which pure colors excite in us. Mammalia and 

 birds, whose structure and emotions are so simi- 

 lar to our own, do probably receive somewhat 

 similar impressions of color ; but we have no evi- 

 dence to show that they experience pleasurable 

 emotions from color itself when not associated 

 with the satisfaction of their wants or the gratifi- 

 cation of their passions. 



The primary necessity which led to the devel- 

 opment of the sense of color was probably the 

 need of distinguishing objects much alike in form 

 and size, but differing in important properties — 

 such as ripe and unripe, or eatable and poisonous 

 fruits ; flowers with honey or without ; the sexes 

 of the same or of closely-allied species. In most 

 cases the strongest contrast would be the most 

 useful, especially as the colors of the objects to 

 be distinguished would form but minute spots or 

 points when compared with the broad masses of 

 tint of sky, earth, or foliage, against which they 

 would be set. Throughout the long epochs in 

 which the sense of sight was being gradually de- 

 veloped in the higher animals, their visual organs 

 would be mainly subjected to two groups of rays 

 — the green from vegetation and the blue from 

 the sky. The immense preponderance of these 

 over all other groups of rays would naturally 

 lead the eye to become specially adapted for their 



perception; and it is quite possible that at first 

 these were the only kinds of light- vibrations 

 which could be perceived at all. When the need 

 for differentiation of color arose, rays of greater 

 and of smaller wave-lengths would necessarily be 

 made use of to excite the new sensations re- 

 quired ; and we can thus understand why green 

 and blue form the central portion of the visible 

 spectrum, and are the colors which are most 

 agreeable to us in large surfaces ; while, at its 

 two extremities, we find yellow, red, and violet 

 colors, which we best appreciate in smaller 

 masses, and when contrasted with the other 

 two or with light neutral tints. We have 

 here probably the foundations of a natural 

 theory of harmonious coloring, derived from 

 the order in which our color-sensations have 

 arisen, and the nature of the emotions with which 

 the several tints have been always associated. 1 

 The agreeable and soothing influence of green 

 light may be in part due to the green rays hav- 



1 There is reason to believe that our capacity of dis- 

 tinguishing colors has increased even in historical times. 

 The subject has attracted the attention of German philol- 

 ogists, and I have been furnished by a friend with some 

 notes from a work of the late Lazarus Geiger, entitled 

 "Zur Entwickelungsgeschichte der Mensehheit" (Stutt- 

 gart, 1S71). According to this writer it appears that tho 

 color of grass and foliage is never alluded to as a beauty 

 in the Vedas or the Zenda-vesta, though these produc- 

 tions are continually extolled for other properties. Blue • 

 is described by terms denoting sometimes green, some- 

 times black, showing that it was hardly recognized as a 

 distinct color. The color of the sky is never mentioned 

 in the Bible, the Vedas, the Homeric poems, or even in 

 the Koran. The first distinct allusion to it known to 

 Geiger is in an Arabic work of the ninth century. " Hya- 

 cinthine locks'" are black locks, and Homer calls iron 

 "violet-colored." Yellow was often confounded with 

 green, but, along with red, it was one of the earliest colors 

 to receive a distinct name. Aristotle names three colors 

 in the rainbow— red, yellow, and green. Two centuries 

 earlier Xenophanes had described the rainbow as purple, 

 reddish, and yellow. The Pythagoreans admitted four 

 primary colors— white, black, red, and yellow ; the Chi- 

 nese the same, with the addition of green. If these state- 

 ments fairly represent the early condition of color-sensa- 

 tion, they well accord with the view here maintained, that 

 green and blue were first alone perceived, and that the 

 other colors were successively separated from them. 

 These latter would be the first to receive names ; hence 

 we find purple, reddish, and yellow, first noticed in tho 

 rainbow as the tints to be separated from the wide-spread 

 blue and green of the visible world which required no dis- 

 tinctive color-appellation. If the capacity of distinguish- 

 ing colors has increased in historic times, we may, per- 

 haps, look upon color-blindness as a survival of a condi- 

 tion once almost universal; while the fact that it is still so 

 prevalent is in harmony with the view that our present 

 liii r h perception and appreciation of color is a comparative- 

 ly recent acquisition, and may be correlated with a gen- 

 eral advance inmental activity. 



