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Waves of all sizes impinge upon the particles, and you see
at every collision a portion of the impinging wave struck
off. All the waves of the spectrum, from the extreme red
to the extreme violet, are thus acted upon. But in what
proportions will the waves be scattered ? A clear picture
will enable us to anticipate the experimental answer. Re-
membering that the red waves are to the blue much in the
relation of billows to ripples, let us consider whether those
extremely small particles are competent to scatter all the
waves in the same proportion. If they be not—and a little
reflection will make it clear to you that they are not—the
production of color must be an incident of the scattering.
Largeness is a thing of relation ; and the smaller the wave,
the greater is the relative size of any particle on which the
wave impinges, and the greater also the ratio of the scat-
tered portion to the total wave. A pebble placed in the
way of the ring-ripples produced by our heavy rain-drops
on a tranquil pond will throw back a large fraction of the
ripple incident upon it, while the fractional part of a larger
wave thrown back by the same pebble might be infinitesi-
mal. Now we have already made it clear to our minds
that to preserve the solar light white, its constituent pro-
portions must not be altered; but in the act of division
performed by these very small particles we see that the
proportions are altered; an undue fraction of the smaller
waves is scattered by the particles, and, as a consequence,
in the scattered light, blue will be the predominant color.
The other colors of the spectrum must, to some extent, be
associated with the blue. They are not absent but deficient.
We ought, in fact, to have them all, but in diminishing pro-
portions, from the violet to the red.

We have here presented a case to the imagination, and,
assuming the undulatory theory to be a reality, we have, I
think, fairly reasoned our way to the conclusion that, were
particles, small in comparison to the size of the ether-waves,

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