The native American., 1839-03-16

tends to height short OF nifty miles above tht
sea level. II revolyes with the globe, and with i
all atmospheric phenomena, as rain, hail, snow
whirlwinds and storms Of every description.
state Of rest or equilibrium among It's particles
produces a calm; when disturbing cause enters
the balance is destroyed, and wind OF greater OF
less force ensues. Wind is therefore air in mo-
ton, the result Of propagation Of aerial cur,
rents from various causes.
| Alteration in temperature is perhaps the most
usual, as the most important cause of Winds
There ara two opposite modes in which they may
| be propagated. In the first, the air over any
given locality may be condensed by cold, as by q
shower of rain its elasticity is weakened when
deprived Of portion Of its heat, and currents,
towards all surrounding quarters, flow from over
the cooled surface. In the second mode, the
blast takes place in one direction, and the pro-
gressye march Of the wind is in a contrary drec-
ton. As, for instance, Wargentnc. speaking oil
the winds in the north of Europe, says, "when
the winds proceed from the west. they are felt al
Moscow earlier than at Abo, in Finland, though
| the latter city is 400 leagues farther west than
Moscow; and this wind does not reach Finland
until after il has blown over Sweden" DIR.
Franklin was the first to make the observation,
that winds are felt TO blow sooner st the spot
where the great disturbance in the air occurs than
| at points more remote. He had observed a solar
eclipse at Boston, and in few hours afterwards a
northeast storm passed over that city: news
reached him sometime afterwards that the eclipse
had been rendered invisible at Charleston, S, c.,
| in consequence of the prevalence Of a noriheas,
storm at that place. He drew the inference that
| it was an extension of the same storm, and that,
along the Atlantic coast of America, northeast
storms begin at the southwest and proceed TO
I, A. n IL
hour. The law here deduced was Of more gene
raj application than the American philosopher
suspected, and the generalization has been lately
made by MIR. Rcdfeld, Of New York.
), As an illustration Of the propagation Of air
currents by the first mode, we will quote Captain
Horsburgh, Of the British navy: " have several
times, in calm weather, seen cloud generate and
difuse breeze on the surface of the sea, which
spread in different directions from the place Of de-
scent. A remarkable instance Of this occurred in
Malacca Strait, during calm day, when fee
was in company. Abreeze commenced suddenly
| from dense cloud; its centre of action seemed
| to be in the middle Of the feet, which was much
scattered. The breeze spread in every direction
from centre, and produced singular appear
ance in the fleet, for every ship hauled close to
wind as the breeze reached her, and when it be-
came general, exhibited to view the singular spec
tacle of each ship sailing completely round cir
! Gle, all Of them at the same time being close
hauled" 1t is thus that an impulse given to any
point of the atmosphere is SUCCESSFULLY propa-
gated i'll all directions in waves diverging from
the ceSlre of sphere to greater and greater dis
tances, but with decreasing intensity, like the
waves formed in still water by the falling Of a
stone.
In the second mode for the production Of winds,
vacuum or dlminntion Of pressure being at any
he air = soe nS sads Il TO iii I'D the Va,
Gated spaces, commences its motion, Of course,
nearest the point Of deficient equilibrium, from
which the currents gradually retire, as Dr. Frank
lin so happily conjectured.
The trade winds are usually ascribed to the
heat of the sun, occasoning aerial currents, by
the rarefaction of the air at the equator, which
causes the cooler and denser part of the atmos-
phere to rush in lateray from the surrounding re-
gions, and flow along the surface Of the earth to-
wards the equator; the heated air at the same
time rises 10 The higher strata, and passes towards
the poles. Thus are formed two opposed cur
rents in the direction Of the meridian. But the
air in rotation with the earth diminishes its We
locity as we approach either pole. In approach
ing the equator, it revolves slower than the cor
portions of the earth over which it
rests and the hand held up strikes against it with
the excess velocity Of any body revolving with
the earth. This reaction deveiopes resistance
opposed 10 the direction Of rotation. Thus, TO a
person snpposing himself to be at rest, the wind
will appear to blow in contrary direction TO the
earth's rotation. or from east to west, which is The
direction Of the trade winds.
The sea and land breezes are produced by the
same general causes as in ordinary winds, acting
with some regularity, however, SO as TO induce a
periodical flow of currents of air, during one por-
ton of the day, from the sea, and for the remain
der from the land. In the Indian Archipelago,
a singular phenomenon is frequently noticed at a
certain hour in the day, and near the period when
the breeze will change its direction. 1t has been
ascertained by intelligent navigators in those
seas, that there is, short distance off shore, a
space entirely calm, lying between the land and
sea breeze. 1t is sometimes five or six fathoms
wide, and is bounded on the sea and land side by
a line, up to which either wind blows; but there
it is reflected upwards, and loses its former dircc-
ton. In Kotzebue's Voyage round the World,
occurs curious passage describing singular phc-
nomenon. When on his voyage from New Arch
angel TO California, being in latitude 40 deg, he
met with two violent contpndjn6 winds blowinU