gives the color-tone and saturation of the
mixture. For example, mix red and yellow: then the resulting color
is a saturated reddish yellow. Mix red (760) and green (505): the
resulting yellow is non-saturated, since the straight line between
these two points lies inside the figure. If the straight line
joining two points passes through W, the colors located at the two
points are complementary.

Spectral colors are themselves not completely saturated. The way to
get color sensations of maximum saturation is first to stare at one
color, so as to fatigue or adapt the eye for that color, and then to
turn the eye upon the complementary color, which, under these
conditions, appears fuller and richer than anything otherwise
obtainable. The corners, R, G, and B, denote colors of maximum
saturation, and the whole of the triangle outside of the heavy line
is reserved for super-saturated color sensations.

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{218}

Physics tells us of the stimulus, but we are concerned with the
response. The facts of color-blindness and color mixing show very
clearly that the response does not tally in all respects with the
stimulus. Physics, then, is apt to confuse the student at this point
and lead him astray. Much impressed with the physical discovery that
_white_ light is a mixture of all wave-lengths, he is ready to believe
the sensation of white a mixed sensation. He says, "White is the sum
of all the colors", meaning that the sensation of white is compounded
of the sensations of red, orange, yellow, green, blue and
violet--which is simply not true. No one can pretend to get the
sensations of red or blue in the sensation of white, and the fact of
complementary colors shows that you cannot tell, from the sensation of
white, whether the stimulus consists of yellow and blue, or red and
bluish green, or red, green and blue, or all the wave-lengths, the
response being the same to all these various combinations. Total
color-blindness showed us, when we were discussing this matter before,
that white was an elementary sensation, and nothing that has been said
since changes that conclusion.

Consider _black_, too. Physics says, black is the absence of light;
but this must not be twisted to mean that black is the absence of all
visual sensation. Absence of visual sensation is simply nothing, and
black is far from that. It is a sensation, as positive as any, and
undoubtedly elementar