Page:Popular Science Monthly Volume 29.djvu/834

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LTHOUGH there is no general agreement as to whether black and white are or are not colors, it is very commonly held both by scientists and artists that they are not colors. Encyclopædias, dictionaries, and text-books usually class black and white separately from colors, defining the former as the absence of all color and the latter as the sum of all colors. Von Bezold ("Theory of Color," p. 41) says, "An object appears black if, in the light falling upon it, those species of rays are wanting which alone it is capable of reflecting"; and, again, "White and black . . . which, indeed, are not colors at all in the true sense of the word." But, on page 90 of the same work, the heading of paragraph 48 is "White is a mixed color"; and, again, on page 113 it is stated that "white and all the very pale colors which are closely allied to it must be counted among the cold colors." It is not meant to attach much importance to such little inconsistencies in this very excellent work, but simply to indicate an indecision regarding the limitation of the word color. For another instance may be quoted Field, an English artist, who says of black that the artist is bound to regard it as a color; that "it is colorless, but extinguished light"; that "to be perfect it must be neutral with respect to color and destitute of sheen or reflective power in regard to light," and that "there is no perfectly pure and transparent black pigment." And the same author regards white light as colorless. These latter quotations are not made to emphasize their obvious inaccuracies, but to further illustrate the absence of anything like a unanimity of opinion regarding the classification of black and white in the chromatic scale. Many other opinions might be quoted, showing not only an indecision on the particular point herein discussed, but also widely different ideas concerning the nature of black and white.

In endeavoring to answer the question propounded we can do little more than test the propriety of restricting the application of the word color to less than the entire range of visual impressions. It will be necessary first to inquire just what relation black and white have to other retinal impressions.

At the outset it should be noted that we have no retinal standard. An object may convey a color impression which varies in the same individual with the conditions of rest or fatigue of the eye, with the character of the prevailing illumination, and also according to the influence of neighboring bodies which may produce effects of contrast. There is often a temporary or permanent difference in the color-perception of the two eyes of the same person; and among persons there are of course still wider differences, even excluding abnormal