the scale of
chroma. Colored balls on the branches tell their Hue. In order to show
the MAXIMA of color, each branch is attached to the trunk (or neutral
axis) at a level demanded by its value,--the yellow nearest white at the
top, then the green, red, blue, and purple branches, approaching black
in the order of their lower values. It will be remembered that the
chroma of the sphere ceased with 5 at the equator. The color tree
prolongs this through 6, 7, 8, and 9. The branch ends carry colored
balls, representing the most powerful red, yellow, green, blue, and
purple pigments which we now possess, and could be lengthened, should
stronger chromas be discovered.[12]

[Footnote 12: See Plate I.]

(35) Such models set up a permanent image of color relations. Every
point is self-described by its place in the united scales of hue, value,
and chroma. These scales fix each new perception of color in the child's
mind by its situation in the color solid. The importance of such a
definite image can hardly be overestimated, for without it one color
sensation tends to efface another. When the child looks at a color, and
has no basis of comparison, it soon leaves a vague memory that cannot be
described. These models, on the contrary, lead to an intelligent
estimate of each color in terms of its hue, its value, and its chroma;
while the permanent enamels correct any personal bias by a definite
standard.

(36) Thus defined, a color falls into logical relation with all other
colors in the system, and is easily memorized, so that its image may be
recalled at any distance of time or place by the notation.

(37) These solid models help to memorize and assemble colors and the
memory is further strengthened by a simple NOTATION, which records each
color so that it cannot be mistaken for any other. By these written
scales a child gains an instinctive estimate of relations, so that, when
he is delighted with a new color combination, its proportions are noted
and understood.

(38) Musical art has long enjoyed the advantages of a definite scale and
notation. Should not the art of coloring gain by similar definition? The
musical scale is not left to personal whim, nor does it change from day
to day; and something as clear and stable would be an advantage in
training the color sense.

(39) Perception of color is crude at first. The child sees only the most
obvious distinctions, and prefers the strongest stimulation. But
perception soo