of air; so
that in either case no part of it is allowed to cool down sufficiently
to precipitate moisture.

It is a curious fact that often there will be a heavier dew under the
blaze of a full moon on a clear night than at any other time. The moon
has no screens about it of any kind to obstruct the free radiation of
heat. It is supposed to be a dead cinder floating in space and not
surrounded by an atmosphere, so that the sun's rays have full effect
upon it during the time it is exposed to them, and at that time it
becomes heated to a temperature of something like 750 degrees
Fahrenheit. For half the month, say, the sun is shining continuously
upon all or a part of it. In other words, the days and nights of the
moon are about two weeks long. The moon does not revolve upon its own
axis like the earth, therefore the same side or a portion of it is
exposed to the sun for 14 days. During the time that the moon is in the
earth's shadow it is supposed to fall to 187 degrees below zero, which
is 219 degrees below the freezing point. When the moon is full and is
heated up to over 700 degrees there is sufficient heat radiating from it
to be felt sensibly upon the face of the earth, and it would be felt if
it were not for the great envelope of atmosphere and its attendant cloud
formations that surround the earth. There are but few days in summer
when there is not a haze in the atmosphere, although we call the sky
clear, which intensifies the light and gives everything a warmer tone.
The heat coming from a full moon on a clear night is absorbed in causing
the aqueous vapors that are partly condensed in the higher regions of
the atmosphere, to be reabsorbed into transparent vapor. This clears
away the heat screen in the atmosphere and allows radiation to go on
more rapidly at the earth's surface, and thus cools it to a greater
extent when the moon is shining brightly than when it is dark and in the
shadow of the earth.

As we have already mentioned, the cold that is produced by radiation
through the blades of grass and other radiating substances may be
indicated by placing one thermometer on the ground and fixing another at
some point in the air. Sometimes the difference is very marked,
amounting to as much as 20 or 30 degrees. If under these conditions a
cloud floats overhead, forming a heat screen, its presence will be
readily noticed by a rise in the thermometer. Radiation into the upper
regions of the atmosphere is checked,