It must be recollected that a volume of air, when once put in motion, will move on, like any other body, by the mere force of its own momentum, till that motion is destroyed by its friction against the substances along or through which it is impelled.

Any one who has observed the ring of smoke sometimes projected from the mouth of a cannon will be sensible that this is true.
It may likewise be of use, before going further, to consider, that, if the globe, instead of being unequally heated; were equally heated at all parts, from pole to pole, and being surrounded by an atmosphere, were then made to revolve on its axis, it would carry the atmosphere round with it exactly at the rate at which it was itself going.

That portion of the air in contact with the equator would move about 1000 miles in one hour, while that in latitude 90 deg.

would be as motionless as the poles themselves.
From this it will be seen, that, while the equator moves at the rate of 1000 miles an hour, the district about the latitude 30 deg.

moves only 860, or 140 miles slower.