crepancies of red, yellow, and blue, which have been falsely taught
as primary colors, can no more be tuned by a child than the musical
novice can tune his instrument. Each of these hues has three variable
factors (see page 14, paragraph 14), and scientific tests are necessary
to measure and relate their uneven degrees of Hue, Value, and Chroma.

Visual estimates of color, without the help of any standard for
comparison, are continually distorted by doubt, guess-work, and the
fatigue of the eye. Hardly two persons can agree in the intelligible
description of color. Not only do individuals differ, but the same eye
will vary in its estimates from day to day. A frequent assumption that
all strong pigments are equal in chroma, is far from the truth, and
involves beginners in many mishaps. Thus the strongest blue-green,
chromium sesquioxide, is but half the chroma of its red complement, the
sulphuret of mercury. Yet ignorance is constantly leading to their
unbalanced use. Indeed, some are still unaware that they are the
complements of each other.[25]

[Footnote 25: See Appendix to Chapter III.]

It is evident that the fundamental scales of Hue, Value, and Chroma must
be established by scientific measures, not by personal bias. This system
is unique in the possession of such scales, made possible by the
devising of special instruments for the measurement of color, and can
therefore be trusted as a permanent basis for training the color sense.

The examples in Plates II. and III. show how successfully the tuned
crayons, cards, and water colors of this system lead a child to fine
appreciations of color harmony.

PLATE II.

COLOR STUDIES WITH TUNED CRAYONS IN THE LOWER GRADES.

Children have made every example on this plate, with no other material
than the five crayons of middle hue, tempered with gray and black.
A Color Sphere is always kept in the room for reference, and five color
balls to match the five middle hues are placed in the hands of the
youngest pupils. Starting with these middle points in the scales of
Value and Chroma, they learn to estimate rightly all lighter and darker
values, all weaker and stronger chromas, and gradually build up a
disciplined judgment of color.

Each study can be made the basis of many variations by a simple change
of one color element, as suggested in the text.

1. Butterfly. Yellow and black crayon. Vary by using any single
crayon with black.

2. Dish. Red crayon, b