Page:Popular Science Monthly Volume 78.djvu/449

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439
WEATHER PROVERBS

as often happens when the clouds are low, it appears to be unusually large; and, conversely, when the clouds are very high a halo in them, because the distance to it commonly is underestimated, impresses one as being correspondingly small.

Now the higher the clouds the swifter the winds that carry them along and the farther removed they become from the storm center. Hence, a halo that appears small is due to clouds far removed from the storm that produced them, while one that seems large, since it is caused by relatively low and, therefore, slow-moving clouds usually indicates that the storm is comparatively near.

Moon

"But chiefly look to Cynthia's varying face;
There surest signs of coming weather trace."
Aratus.

Many people have supposed, and some still hold, that the moon appreciably controls the weather, and there are numerous proverbs based on this assumed relation. But careful study of the records shows that the moon's influence on the weather, beyond a very small tidal effect on the atmosphere, as indicated by the barometer, is negligible, if indeed it has any influence at all. As has been well said:

"The moon and the weather
May change together;
But change of the moon
Does not change the weather.
If we'd no moon at all,
And that may seem strange.
We still should have weather
That's subject to change."

However, the appearance of the moon depends upon the conditions of the atmosphere, and, therefore, proverbs based upon phenomena of this nature are more or less sound and have much value. Thus:

"Clear moon
Frost soon,"

"Moonlit nights have the heaviest frosts,"

and others of this class are true enough, because on the clearest nights the cooling of the earth's surface by radiation is greatest and hence most likely to cause, through the low temperature reached, precipitation in the form of dew or frost.

The meaning of haloes and coronas about the moon has already been explained, and the proverbs connected with them, foretelling bad weather, fully justified.

The following is a somewhat interesting moon proverb:

"Sharp horns do threaten windy weather."