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 is that of the Colorist, such as Titian, whose work shows great fulness of hues without the violent extremes of white and black.

(122) Not only does the mount of the color sphere permit its rotation on the vertical axis (white-black), but it is so hung that it may be spun on the ends of any desired axis, as, for instance, that joining our first color pair, red and blue-green. With this pair as poles of rotation, a new equator is traced through all the values of purple on one side and of green-yellowon the other, which the rotation test melts in a perfect balance of middle gray, proving the correctness of these values. In the same way it may be hung and tested on successive axes, until the total balance of the entire spherical series is proved.

(123) But this color system does not cease with the colors spread on the surface of a globe. The first illustration of an orange filled with color was chosen for the purpose of stimulating the imagination to follow a surface color inward to the neutral axis by regular decrease of chroma. A slice at any level of the solid, as at value 8 (Fig. 19), shows each hue of that level passing by even steps of increasing grayness to the neutral gray N$8$ of the axis. In the case of red at this level, it is easily described by the notation $R 8⁄3$, $R 8⁄2$, $R 8⁄1$, of which the initial and upper numerals do not change, but the lower numeral traces loss of chroma by 3, 2, and 1 to the neutral axis.

(124) And there are stronger chromas of red outside the surface, which can be written $R 8⁄4$, $R 8⁄5$, $R 8⁄6$, etc. Indeed, our color measurements discover such differences of chroma in the various pigments used, that the color tree referred to in paragraphs 34, 35, is necessary