. Refraction and motility of the eye, with chapters on color blindness and the field of vision . of two colors isnot so intense as that in which all the colors are combined. The results of experiments made by the mixture ofvarious pigments do not correspond to those made withdecomposed white light. The reason for this is that nopigments are absolutely pure, but possess color, becausewhen light falls upon them they absorb some rays whilethey reflect others. Thus gamboge reflects the yellow rayschiefly, but also many of the green, at the same time absorb-ing the blue and some of the red. Thus it
. Refraction and motility of the eye, with chapters on color blindness and the field of vision . of two colors isnot so intense as that in which all the colors are combined. The results of experiments made by the mixture ofvarious pigments do not correspond to those made withdecomposed white light. The reason for this is that nopigments are absolutely pure, but possess color, becausewhen light falls upon them they absorb some rays whilethey reflect others. Thus gamboge reflects the yellow rayschiefly, but also many of the green, at the same time absorb-ing the blue and some of the red. Thus it is yellow, butnot the pure yellow of the spectrum. Indigo, on the otherhand, absorbs the red and yellow and reflects the blue and COLOR-BLINDNESS. 321 some green rays. When gamboge and indigo are mixed,the result is green, because the first absorbs the blue, whilethe last absorbs the yellow and red, while both reflect thegreen. If, however, we take a pure spectral color whichexcites in us the same sensation as gamboge and mix it withanother which corresponds to indigo, the resulting impres-. Fig. 102. sion is that of white instead of green, which goes to showthat mixtures of pigment may produce very different effectsfrom mixtures of the sensations produced by those pig-ments separately. Tn dealing objectively with pigments, we find that bycombinations of the three so-called primary colors red, blueand yellow and their derivatives, we can produce all theother colors. On the other hand, in dealing with the sub-jective sensations produced by decomposed light or com- 21 322 REFRACTION AND MOTILITY OF THE EYE. paratively pure pigments, we find that by combining invarious proportions the sensations produced by red, blueand green (instead of yellow) we can not only producewhite, but by varying the proportion and intensity of thethree, produce the sensation of any other color of the spec-trum. These results show that our recognized color sensa-tions may be reduced to three, that is to
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