both sides
blows in toward the equator under the warm air, where the heat of the
sun warms it again, and, in turn, it rises. This is going on all the
time and is one of the chief things that starts the winds blowing."

"But winds don't always blow the same way," said the farmer; "you talk
as if they did."

"Some of them do," Anton replied. "There are lots of places where the
winds hardly change, at all, but always blow in the same direction. You
read of sailing ships taking the 'trade winds' when coming from Europe
to America. Those are all easterly winds and blow towards the American
coasts all the year round."

"I don't see how they can," the other objected.

"They do, Mr. Tighe," the Forecaster interrupted, endorsing Anton's
statements; "the trade winds are the downflowing currents of cold air
that Anton spoke of, which come down at either side of the equatorial
belt to replace the warm air which is rising. The trade winds, however,
form only a narrow belt and blow only near the surface of the earth.
Above them, you can see the lighter clouds blowing eastward with a
westerly wind, so that, quite often, in the trade winds, you can look
overhead and see two layers of clouds driving in opposite directions."

"You mean to say that there are different layers of wind?" queried the
farmer.

"Sure," put in Ralph, the cloud expert, "I've got photographs that show
that up clearly. You've seen clouds going at different rates, haven't
you, Mr. Tighe, some fast and some slowly?"

The other nodded and turned to the Forecaster, who continued.

"There are always several layers of wind, and, except above the
equatorial belt," he said, "the direction of the upper air winds is
generally towards the east."

"How can you tell that?"

"By the clouds, or by kites and balloons. But we don't even need to do
this, because there are a few places that rise above the lower layers of
the trade winds. Thus, the Peak of Teneriffe, which is in the trade-wind
belt, has a continuous easterly wind on its lower slopes and a
continuous westerly wind right at the summit.

"This gives three belts of weather in the tropical and sub-tropical
zones. The first of these is a light up-flowing east wind on or near the
equator--it shifts a little to the north or south with the change of the
seasons; a belt of heavy rains and calm, the rains being due to the
warm, moist, uprising air cooling by expansion so that the moisture is
condensed--this region