he same
proportion. If they be not--and a little reflection will make it
clear that they are not--the production of colour 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 portion
scattered to the total wave A pebble, placed in the way of the
ring-ripples produced by heavy raindrops on a tranquil pond, will
scatter a large fraction of each ripple, while the fractional part of
a larger wave thrown back by the same pebble might be infinitesimal.
Now we have already made it clear to our minds that to preserve the
solar light white, its constituent proportions must not be altered;
but in the act of division performed by these very small particles 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 colour. The other colours 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 proportions, from the violet to the red.

We have here presented a case to the imagination, pad, 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 sizes of the aether waves, sown in our atmosphere, the light
scattered by those particles would be exactly such as we observe in
our azure skies. When this light is analysed, all the colours of the
spectrum are found, and they are found in the proportions indicated by
our conclusion. Blue is not the sole, but it is the predominant
colour.

Let us now turn our attention to the light which passes unscattered
among the particles. How must it be finally affected? By its
successive collisions with the particles the white light is more and
more robbed of its shorter waves; it therefore loses more and more of
its due proportion of blue. The result may be anticipated. The
transmitted light, where short distances are involved, will appear
yellowish. But as the sun sinks towards the horizon the atmospheric
distances increase, and consequently the number of the scattering
particles. They abstract in succession the violet, the indigo, the
blue, and even disturb the proportions of green. The transmitted
light unde