ravity (the moisture
constantly falling to the lower part of the film) it will continually
grow thinner, and horizontal bands of color will appear upon it,--first
red, then followed by the other colors of the solar spectrum, ending
with violet.

It is also stated that every color of light has a definite wave length.
Where a band of blue color appears upon the film we know that its
thickness is right for the wave length of that particular color which is
reflected from the back of the film to the eye. If we could conceive the
blue vault of the heavens to be half a sphere of a soap bubble, the
color that the sky would appear to us (if the light could be thrown upon
it from beneath) would be determined by the thickness of this film. If
the film was 1-156,000 of an inch the sky would be red instead of blue.
To reflect the other colors the film would have to grow thinner for each
color, in the progression from red to violet. The color of the sky is
determined by a light-reflection from minute globules of moisture
floating in the air. If the sky is blue, then the globules must be of
the right diameter to reflect that color. The various tints and
colorings of the sky are determined by what is found in the atmosphere,
and this is the reason why skies differ in coloring and tone in
different sections of the globe. The finest skies are probably found in
semi-tropical regions like southern Italy, Greece, and California.

In 1892 I visited Greece in the early part of June. In crossing the
Adriatic, from Brindisi to Patras in Greece, the route was through the
Ionian Islands that are grouped along the southwestern shore of Albania.
The sky was without a cloud, and its beautiful blue color was reflected
in the waters of the Adriatic, and I never shall forget the impression
made upon my senses when we first came in sight of the mountains on the
west coast of Albania. At this point they rise abruptly from the water
and are colored with that peculiar azure haze, mixed with a shading of
warmth, which is an effect that distance gives in the classic atmosphere
of old Greece. The effect upon the beholder is to intoxicate the senses
and to fill him with that deliciously poetic feeling that always comes
when standing in the presence of the sublime in nature. It was not the
mountains themselves that produced the effect, for I had seen grander
than these; but it was the sky on the mountains. When we look at a
distant mountain it seems to be part