gether
with others which result, in their effect upon the eye, from
modifications by combination with each other. These colors appear in
the spectroscope to the eye, in horizontal bands of variable width
according to the media through which the light passes, as violet,
indigo, blue, green, yellow, orange and red. Now the different elements
of the various objects we see, when white light falls upon them, absorb
some of its constituent rays and return some to the eye separated from
the others, thereby producing the various sensations of color. There
are several reasons, however, why persons differ in their judgment of
them. Practically every stone has qualities which would produce a
definite degree of color to the eye under the same conditions. But
exactly the same conditions always are almost impossible, for the
variation of position when the stones are placed side by side is
sometimes sufficient to affect the light vibrations and therefore the
color appearance to the eye, in favor of one of them.
Again,
the eyes which see, vary. A ray of pure white light passed through a
prism divides, on the screen, into the spectroscopic bands, which merge
one into the other in a definite unvarying gradation, but no two
persons would draw the dividing lines between them in the same places.
One sees more yellow and less green and the others vice versa. Beyond
this, it is being found that many people are absolutely blind to some
colors. There is of course a normal average perception, but many are
not up to that average, and of those above it, few have trained the
faculty, under the distractions of a broken surface of sharply
reflective and refractive material, sufficiently to see clearly the
exact color of it. The sensa-
