Southern planter - The W&M Digital Archive

1859.] THE SOUTHERN PLANTER. 391
during the growing season, receives much
more heat than the corresponding waters
of the same latitude ; and, though the radiation
at night is less from the water than
the land, yet the accumulating increase of
temperature of the latter will he much
greater than that of the former. The reverse
takes place in the winter. While,
therefore, the mean temperature of the
ocean and of the land, in the same latitude,
may remain the same, the tendency of the
land is to receive the greater portion of the
heat of the whole year during the months
of summer, and thus, by a harmonious arrangement
with respect to the production
of organic life, to increase the effect of the
solar radiation, and to widen the limits
within which plants of a peculiar character
may be cultivated. Proximity to the sea,
however, has another effect on the climate,
which depends upon the currents of the
former, by which the temperature of the
earth, due to the latitude, is materially
altered. Heated water is constantly carried,
from the equatorial regions towards
the poles, and streams of cold water returned,
by means of which the temperature
of the earth is modified, and the extremes
reduced in intensity. * * *
The effect of the prevailing currents of
air, on the climate of different portions of
the earth, is no less marked than proximity
to the sea. * * * * *
Professor Coffin, in his admirable paper
on the winds of the northern hemisphere,
has shown that, from the equator to the pole,
the whole space is occupied by three great
belts, or zones, of prevailing wind; the first
extends from the equator to an average latitude
of 35° north, in which the current is
from the northeast, constantly growing less
intense as we approach the northern limit;
the second is that from 35° to about
T)0°, the current from the west being more
intense in the middle of the belt, and gradually
diminishing, almost into a calm, on
either side ; third, from 60° to the pole, or
rather, to a point of greatest cold in the
Arctic regions, the -wind is in a north-
easterly direction.
The first of these belts would constitute
what is called the trade winds, produced by
the combined effects of the heat of the sun,
and the rotation of the earth ; the second,
is the return trade, and the third, the cur-
rent which would be produced by an oppo-
site effect to that of the rarefaction of the
:;<
air by the sun at the equator, namely,
the condensation of the air by the cold
portion of the earth. The air should flow
out, in every direction, from the coldest
point, and, combining its motion towards
the south with the rotation of the earth, it
should take a direction from the cast to the
west, or become a northeasterly wind.
The effects which these currents must have
upon the climate of the United States will be
made clear by a little reflection. The trade
winds within the tropics, charged with vapor,
impinging upon the mountainous parts of
South America, in their course towards the
west, will deposit their moisture on the
eastern slope, and produce a rainless district
on the western side. Again, a lower portion
of the Atlantic and Gulf trade wind
will be deflected from these mountains along
the eastern coast of the United States, and
through the valley of the Mississippi, as a
surface w r ind, and thus give rise to the moist
and warm breezes from the south, of our
summers, while the principal or upper por-
tion of the trade wind, or the return wester-
ly current, sweeping over the Pacific ocean,
and consequently charged with moisture,
will impinge on the coast range of moun-
tains of Oregon and California, and, in ascending
its sloped, deposit moisture on the
western declivity, giving fertility and a
healthful climate to a narrow strip of coun-
try bordering on the ocean, and sterility to
the eastern slope. All the moisture, however,
will not be deposited in the passage
over the first range, but a portion will be
precipitated on the western side of the next,
until it reaches the eastern elevated ridge
of the Rocky mountain system, where, we
think, it will be nearly, if not quite, ex-
hausted. East of this ridge, and, as it were,
in its shadow, there will exist a sterile belt,
extending in a northerly and southerly direction
many hundred miles. The whole
country, also, included between the eastern
ridge of the Rocky mountains and the Pa-
cific Ocean, with the exception of the narrow
strip before mentioned, will be deficient
in moisture, and on account of the heat,
evolved, as before shown, by the condensation
of moisture on the ridges, will be at a
much higher temperature than that due to
latitude. This mountain region, and the
sterile belt east of it, occupy an area about
equal to one third of the whole surface of
the United States, which, with our present
knowledge of the laws of nature, and their