2          Color Standards and Nomenclature.

number of colors they all fail to supply a ready or
convenient means of identifying and designating the
colors—the principal utility of a work of this kind. It is
in the latter respect that the present work is believed to
meet, more nearly than any other at least, this essential
requirement, and in this consists whatever originality
may be claimed for it.

The "key" to the classification or arrangement here¬
with presented is, of course, the solar spectrum, with its
six fundamental colors and intermediate hues, augmented
by the series of hues connecting violet with red, which
the spectrum fails to show. If, with the red-violets and
violet-reds thus added to the spectrum hues, the band
forming this scale be joined end to end a circle is formed
in which there is continuously a gradual change of hue,
step by step, from red through orange-red and red-orange
to orange ; orange through yellow-orange and orange-
jellowto yellow; yellow through green-yellow and yellow-
green to green; green through blue-green and green-blue
to blue; blue through violet-blue and blue-violet to violet;
and violet through red-violet and violet-red to red—the
starting-point—with intermediate connecting hues. In
the solar spectrum, both prismatic and grating, but
especially the former, the spaces between the adjoining
distinct colors are very unequal; therefore for the present
purpose an ideal scale must be constructed, so that an
approximately equal number of equally distinct connect¬
ing hues shall be shown. Distinctions of hue appreciable
to the normal eye are so ^ww^ numerous* that the
criterion of convenience or practicaiM|^y must determine
the number of segments into which the ideal chromatic
scale or circle may be divided in order to best serve the
purpose  in view.    Careful  experiment   seems to have

*.\r(.'i>rdiug to Aubert more than 1000 hues are distinguishable in the spectrum,
though among them all the hues hetweeen violet and red arc wanting.