To the rarefaction of the air at the equator, and the daily revolution
of the earth, is attributed the origin of the Trade-Winds, which blow
from the east or a little to the north of east, north of the equator,
and east or south of east after we are south of the equator. The hot
current of ascending air is replaced by cold winds from the poles.

But why are we not constantly subject to the action of north winds,
which we rarely are? Because of the diurnal motion of the earth, which
at the equator equals one thousand miles an hour, the polar winds in
coming down to the equator do not have any such velocity, because
there is a less comparative diurnal speed in the higher latitudes. The
air at the poles revolves upon itself without moving forward;--at the
equator, the velocity, as we have mentioned, is enormous. If, then,
says Professor Schleiden, we imagine the air from the pole to be
carried to the equator, some time must elapse before it will acquire
the same velocity of motion from west to east which is always found
there. Therefore it would remain behind, the earth gliding, as it
were, from beneath it; or, in other words, it would have the
appearance of an east wind. Lieutenant Maury adopts the same
explanation. It is, indeed, that of Halley, slightly modified.

The warm air, ascending from the equatorial regions, rushes to the
poles to be cooled in turn, sliding over the heavy strata of cold air
below.

The northern trade-wind prevails in the Pacific between 2° and 25° of
N. Latitude; the southern trade, between 10° and 21° of S. Latitude.
In the Atlantic the trades are generally limited by the 8th and 28th
degrees of N. Latitude. The region of calms lies between these trades,