le was fired from the pole, where there is practically no
motion, in the same direction along the longitudinal lines as before,
the observer would have to be in a position on the equator 1000 miles
west of this longitudinal line in order to see the projectile when it
arrived; therefore the apparent movement of the projectile would not be
along the line at the instant that it was fired, but along a line that
would cross the equator at a point 1000 miles west. When a southward
impulse is given to the air it follows, to some extent, the same law, so
that to one standing on the equator the northern trade wind will blow
from the northeast and the southern trade wind from the southeast.

Owing to the fact that the air rises in the heated zone there is always
a region of calms at this point where there is no wind and no rain.
There are two other regions of calms in the ocean, one at the north at
the tropic of Cancer and another at the south near the tropic of
Capricorn. As has been stated, there are currents flowing back in the
upper regions at the equator north and south, and these are called the
upper trades--the lower currents being called the lower trades. These
upper trades gradually fall till they reach the tropic of Cancer on the
north, where the lower part of the current stops and bends back toward
the equator, now becoming a part of the lower trade wind. This causes a
calm at that point where it turns. The upper parts of this current
continue on, in a northerly and southerly direction, on the surface
until they meet with the cold air of the north and south polar regions,
where there is a conflict of the elements--as there always is when cold
and warm currents meet.

The only point where the trade wind has free play is in the South Indian
Ocean, and this is called the "heart of the trades."

If the whole globe were covered with water there would be a more
constant condition of temperature; but owing to the great difference
between the land and water, both as to altitude and the ability to
absorb and radiate heat, we have all of these varied and complicated
conditions of wind and weather. The trade winds shift from north to
south and vice versa with the advancing and receding seasons, due to the
fact that the earth has a compound motion. It not only revolves on its
axis once in twenty-four hours, but it rocks back and forth once a year,
which is gradually changing the direction of its axis; and in addition
to these mo