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 scale with measured intervals and definite terms. Likewise, coloristic art must establish a scale, measure its intervals, and name its qualities in unmistakable fashion.

(8) It may sound strange to say that color has three dimensions, but it is easily proved by the fact that each of them can be measured. Thus in the case of the boy’s faded cap its redness or is determined by one instrument; the amount of light in the red, which is its, is found by another instrument; while still a third instrument determines the purity or  of the red.

The omission of any one of these three qualities leaves us in doubt as to the character of a color, just as truly as the character of this studio would remain undefined if the length were omitted and we described it as 22 feet wide by 14 feet high. The imagination would be free to ascribe any length it chose, from 25 to 100 feet. This length might be differently conceived by every individual who tried to supply the missing factor.

(9) To illustrate the tri-dimensional nature of colors. Suppose we peel an orange and divide it in five parts, leaving the sections slightly connected below (Fig. 4). Then let us say that all the reds we have ever seen are gathered in one of the sections, all yellows in another, all greens in the third, blues in the fourth, and purples in the fifth. Next we will assort these in each section so that the lightest are near the top, and grade regularly to the darkest near the bottom. A white wafer connects all the sections at the top, and a black wafer may be added beneath.