n are of no value. When a season is once established,
either as a rainy season or a dry season, it is likely to persist in
this character until a change comes that is produced by the movement of
the sun in its course northerly and southerly, and the change produced
from this cause requires several weeks of time.

If accurate weather predictions could be made for a long time in
advance, or for even a week, they would be of incalculable value. But it
is doubtful if ever this will be brought about, as there are too many
necessarily hidden factors which enter into the calculations. If
stations could be established all over the oceans with sufficient
frequency, and an equal number at a sufficient altitude in the air, I
have no doubt that much that is now mysterious might be made plain.

CHAPTER XIV.

HOW DEW IS FORMED.

Reader, did you ever live in the country? Were you ever awakened early
on a summer's morning to "go for the cows"? Did you ever wade through a
wheat field in June--or the long grass of a meadow--when the pearly
dewdrops hung in clusters on the bearded grain, shining like brilliants
in the morning sun? Have you not seen the blades of grass studded with
diamonds more beautiful than any that ever flashed in the dazzling light
of a ballroom? If not, you have missed a picture that otherwise would
have been hung on the walls of your memory, that no one could rob you
of.

Everyone has noticed that at certain times in the year the grass becomes
wet in the evening and grows more so till the sun rises the next day and
dispels the moisture, and this when no cloud is seen. Dew is as old as
the fields in which grass grows. It was as familiar to the ancients as
it is to us, and yet it is only about three-quarters of a century since
the cause of it has been understood. We even yet speak of the dew
"falling" like rain. In former times some scientists supposed that it
was a fine rain that fell from the higher regions of the atmosphere.
Others supposed it to be an emanation from the earth, while still others
supposed it was an exudation from the stars.

"By his knowledge the depths are broken up and the clouds
drop down dew" (Prov. iii. 20).

The first experiments carried on in a scientific way were by Dr. Wells,
a physician of London, between the years 1811 and 1814.

Everyone has noticed in warm weather the familiar phenomenon of water
condensed into drops on the outside of a pitcher or tumbler con