e follow the Earth's
motion. It lags behind, and thus induces an easterly tendency to the
winds, so that a north wind becomes a north-east, and a south wind a
south-east. Here we have another constant cause of variation from the
northerly and southerly flow. We thus account for an easterly tendency
to the winds, but whence their westerly flow? It is simply explained
thus:

The motion of the Earth is greatest at the equator. It diminishes
gradually towards the poles, where there is no motion at all. The
atmosphere partakes of the Earth's motion when in contact with it; and
when thrown upwards by heat, as at the equator, it keeps up the motion
for some time, as it meets with no resistance there. Bearing this in
mind, let us now follow a gush of warm atmosphere from the equator. It
rushes up, and, turning north and south, seeks the poles. We follow the
northern division. When it left the Earth it had acquired a very strong
motion _towards_ the east,--not so great as that of the Earth itself,
but great enough to be equivalent to a furious gale from west to east.
If we suppose this air to redescend whence it rose, it would, on
reaching the equator, find the Earth going too fast for it. It would
lag a little, and become a gentle easterly breeze. But now, throw aside
this supposition;--our breeze rushes north; at latitude 30 degrees it
has got cooled, and swoops down upon the Earth; but the Earth at this
latitude is moving much slower than at the equator; the wind, however,
has lost little or none of its easterly velocity. On reaching the Earth
it rushes east much faster than the Earth itself, and thus becomes a
westerly gale.

There are, however, many other agents at work, which modify and disturb
what we may call the legitimate flow of the wind; and these agents are
diverse in different places, so that the atmosphere is turned out of a
straight course, and is caused to deflect, to halt, and to turn round:
sometimes sweeping low as if in haste; at other times pausing, as if in
uncertainty; and often whirling round, as if in mad confusion. To the
observer, who sees only the partial effects around his own person, all
this commotion seems but the disorderly action of blind chance; but to
the eye of Him who sees the end from the beginning, we may certainly
conclude that naught is seen but order and perfect harmony. And to the
eye of Science there now begins to appear, in what was formerly an
atmospheric chaos, an