(127) Such a set of charts forms an atlas of the color solid, enabling one to see any color in its relation to all other colors, and name it by its degree of hue, value, and chroma. Fig. 20 is a horizontal chart of all colors which present middle value (5), and describes by an uneven contour the chroma of every hue at this level. The dotted fifth circle is the equator of the color sphere, whose princ.i.p.al hues, R 5/5. Y 5/5, G 5/5, B 5/5, and P 5/5, form the chromatic tuning fork, paragraph 117.

[Ill.u.s.tration: Fig. 20.

Chart of Middle Value - 5 - Showing Unequal Chroma in circle of Hues. (See Fig. 2).]

(128) In this single chart the eye readily distinguishes some three hundred different colors, each of which may be written by its hue, value, and chroma. And even the slightest variation of one of them can be defined. Thus, if the princ.i.p.al red were to fade slightly, so that it was a trifle lighter and a trifle weaker than the enamel, it would be written R{5.1/4.9}, showing it had lightened by 1 per cent. and weakened by 1 per cent. The discrimination made possible by this decimal notation is much finer than our present visual limit. Its use will stimulate finer perception of color.

(129) Such a very elementary sketch of the Color Solid and Color Atlas, which is all that can be given in the confines of this small book, will be elsewhere presented on a larger and more complete scale. It should be contrasted with the ideal form composed of prismatic colors, suggested in the last chapter, paragraphs 98, 99, which was shown to be impracticable, but whose ideal conditions it follows as far as the limitations of pigments permit.

(130) Besides its value in education as setting all our color notions in order, and supplying a simple method for their clear expression, it promises to do away with much of the misunderstanding that accompanies the every-day use of color.

(131) Popular color names are incongruous, irrational, and often ludicrous. One must smile in reading the list of 25 steps in a scale of blue, made by Schiffer-Muller in 1772:--

A. _a._ White pure.

_b._ White silvery or pearly.

_c._ White milky.

B. _a._ Bluish white.

_b._ Pearly white.

_c._ Watery white.

C. Blue being born.

D. Blue dying or pale.

E. Mignon blue.

F. Celestial blue, or sky-color.

G. _a._ Azure, or ultramarine.

_b._ Complete or perfect blue.

_c._ Fine or queen blue.

H. Covert blue or turquoise.

I. King blue (deep).

J. Light brown blue or indigo.

K. _a._ Persian blue or woad flower.

_b._ Forge or steel blue.

_c._ Livid blue.

L. _a._ Blackish blue.

_b._ h.e.l.lish blue.

_c._ Black-blue.

M. _a._ Blue-black or charcoal.

_b._ Velvet black.

_c._ Jet black.

The advantage of s.p.a.cing these 25 colors in 13 groups, some with three and others with but one example, is not apparent; nor why ultramarine should be several steps above turquoise, for the reverse is generally true. Besides which the hue of turquoise is greenish, while that of ultramarine is purplish, but the list cannot show this; and the remarkable statement that one kind of blue is "h.e.l.lish," while another is "celestial," should rest upon an experience that few can claim.

Failing to define color-value and color-hue, the list gives no hint of color-strength, except at C and D, where one kind of blue is "dying"

when the next is "being born," which not inaptly describes the color memory of many a person. Finally, it a.s.sures us that Queen blue is "fine" and King blue is "deep."

This year the fashionable shades are "burnt onion" and "fresh spinach."

The florists talk of a "pink violet" and a "green pink." A maker of inks describes the red as a "true crimson scarlet," which is a contradiction in terms. These and a host of other names borrowed from the most heterogeneous sources, become outlawed as soon as the simple color terms and measures of this system are adopted.

Color anarchy is replaced by systematic color description.

APPENDIX TO CHAPTER V.

+Color schemes based on Brewster's mistaken theory.+

[Ill.u.s.tration]

Runge, of Hamburg (1810), suggested that red, yellow, and blue be placed equidistant around the equator of a sphere, with white and black at opposite poles. As the yellow was very light and the blue very dark, any coherency in the value scales of red, yellow, and blue was impossible.

Chevreul, of Paris (1861), seeking uniform color scales for his workmen at the Gobelins, devised a hollow cylinder built up of ten color circles. The upper circle had red, yellow, and blue s.p.a.ced equidistant, and, as in Runge's solid, yellow was very light and blue very dark. Each circle was then made "one-tenth" darker than the next above, until black was reached at the base. Although each circle was supposed to lie horizontally, only the black lowest circle presents a level of uniform values.

Yellow values increase their luminosity thrice as fast as purple values, so that each circle should tilt at an increasing angle, and the upper circle of strongest colors be inclined at 60 to the black base. Besides this fault shared with Runge's sphere, it falls into another by not diminishing the size of the lower circles where added black diminishes the chroma.

Desire to make colors fit a chosen contour, and the absence of measuring instruments, cause these schemes to ignore the facts of color relation.

Like ancient maps made to satisfy a conqueror, they amuse by their distortion.

Brewster's mistaken theory underlies these schemes, as is also the case with Froebel's gifts, whose color b.a.l.l.s continue to give wrong notions at the very threshold of color education. As pointed out in the Appendix to Chapter III., the "red-yellow-blue" theory inevitably spreads the warm field of yellow-red too far, and contracts the blue field, so that balance of color is rendered impossible, as ill.u.s.trated in the gaudy chromo and flaming bill-board.

These schemes are criticised by Rood as "not only in the main arbitrary, but also vague"; and, although Chevreul's charts were published by the government in most elaborate form, their usefulness is small. Interest in the growth of the present system, because of its measured character, led Professor Rood to give a.s.sistance in the tests, and at his request a color sphere was made for the Physical Cabinet at Columbia.

CHAPTER VI.

COLOR NOTATION.

+Suggestion of a chromatic score.+

[Ill.u.s.tration: Fig. 21.]

(132) The last chapter traced a series of steps leading to the construction of a practical color sphere. Each color was tested by appropriate instruments to a.s.sure its degree of hue, value, and chroma, before being placed in position. Then the total sphere was tested to detect any lack of balance.

(133) Each color was also _written_ by a letter and two numerals, showing its place in the three scales of hue, value, and chroma. This naturally suggests, not only a record of each separate color sensation, but also a union of these records in series and groups to form a _color score_, similar to the musical score by which the measured relations of sound are recorded.

(134) A very simple form of color score may be easily imagined as a transparent envelope wrapped around the equator of the sphere, and forming a vertical cylinder (Fig. 21). On the envelope the equator traces a horizontal centre line, which is at 5 of the _value scale_, with zones 6, 7, 8, and 9 as parallels above, and the zones 4, 3, 2, and 1 below. Vertical lines are drawn through ten equidistant points on this centre line, corresponding with the divisions of the _hue scale_, and marked R, YR, Y, GY, G, BG, B, PB, P, and RP.

(135) The transparent envelope is thus divided into one hundred compartments, which provide for ten steps of value in each of the ten middle colors. Now, if we cut open this envelope along one of the verticals,--as, for instance, red-purple (RP), it may be spread out, making a flat chart of the color sphere (Fig. 22).

+Why green is given the centre of the score.+

(136) A cylindrical envelope might be opened on any desired meridian, but it is an advantage to have green (G) at the centre of the chart, and it is therefore opened at the opposite point, red-purple (RP). To the right of the green centre are the meridians of green-yellow (GY), yellow (Y), yellow-red (YR), and red (R), all of which are known as _warm colors_, because they contain yellow and red. To the left are the meridians of blue-green (BG), blue (B), purple-blue (PB), and purple (P), all of which are called _cool colors_, because they contain blue.

Green, being neither warm nor cold of itself, and becoming so only by additions of yellow or of blue, thus serves as a balancing point or centre in the hue-scale.[31]

[Footnote 31: To put this in terms of the spectrum wave lengths, long waves at the red end of the spectrum give the sensation of warmth, while short waves at the violet end cause the sensation of coolness. Midway between these extremes is the wave length of green.]