135. Having produced the scale of twelve colors in the values of
their greatest intensities, and as intense as possible, we get an
approximation to the Spectrum with this difference, that the color
Violet-Red (Purple) which we get in pigments and mixtures of pigments
does not occur in the Spectrum and, so far as we know, does not belong
in the Spectrum. We have in the Spectrum a sequence which begins
with Red and ends with Violet. It is a sequence, not a circuit. In
pigment-mixtures, however, we have a circuit, clearly enough, and
Violet-Red is a connecting link between Violet and Red.