PART IN.

THE ATMOSPHERE.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We live at the bottom of a vast ocean of air, which, like the ocean of: water, is subject to three
general movements—waves, tides, and currents. By means of waves, its upper surface is heaved in
huge mountain-like masses in one place, and hollowed out in deep valleys in another. By means of
currents, circulatory movements are set up, which effect a constant interchange between the air of the
equatorial and the polar regions. By means of tides, the depth of the atmosphere is increased in some
places and decreased in others.

Of these three movements of the atmosphere, currents are of the greatest importance. Aérial cur-
rents, or winds, are similar to oceanic currents, but are more extensive and rapid, owing to the greater
mobility of air.

By retaining and modifying the solar: heat, absorbing ri distributing moisture, supplying animals
with oxygen and plants with carbonic acid, the atmosphere plays an Important part in the economy
of the earth.

Meteorology is the science which treats of the atmosphere and its phenomena.

Oe ee

Seer rhoO NL:
THE ATMOSPHERE.

——n$¢00—_

CHAPTER I. proportion, by weight, of nearly 77 per cent. of
nitrogen to 23 per cent. of oxygen.. To these
must be added a nearly constant quantity of car-
bonie acid, about 5 or 6 parts in every 10,000

227. Composition.— The atmosphere is a me- parts of air, or about a cubic inch of carbonic acid
chanical mixture of nitrogen and oxygen, in the to every cubic foot of air, and a very variable pro-

85

General Properties of the Atmo-
sphere.