The National tribune. [volume] (Washington, D.C.) 1877-1917, 1891-02-12
THE WEATHER.
Certain Laws as to Wind Direction.
BY LIEUT.. ]. P. FINLEY. U. 9. SIGNAL SERVICE.

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and Information cheerfully furnished. Every ef-
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10 the readers OF THE SArIoSAL TRIBUNE. All
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TEE NATIONAL TRIBUNE Office. Washington ID. 4. \
In the cyclone the circulation Of the air is
from left TO right around the seat Of the great
est depression OF the barometer while drawing
in towards it. On the other hand, in an anti
cyclone, or region thigh barometric pressure,
the winds blow spiraily outwards, not in a
direct course from the place of high to one Of low
pressure, but, on the contrary, very OblqueIy.
In cyclone in the Northern Hemisphere
the direction of the circular motion is left
handed, or in the direction opposite to that Of
the clock hands; while in an anti-cyclOne the
circulation is right handed, or coiucident with
that of the clock hands.
In tho Southern Hemisphere the direction
OF the circulation is reversed cyclones being
all right-handed spirals, while anti-cyclones
are left handed
This deviation Of the winds from the radial
direction Is as Ferrel has shown, q consequences
OF the earth's rotation. Ia general terms, any
mass OF matter whatever, moving in q recti-
linear path toward any point Of the compass
on the earths surface, tends TO deviate % the
right IN the Northern Hemisphere and % the
lett IN ths Southern Hemisphere. When the
velocity of the movement is expressed in miles
per hour, the detecting force varies as the
sine Of the latitude, being zero at the equator,
fact which explains why cyclones are un-
known within a few degrees Of the equator
and also the comparative slOwuess OF their
formation in tropical seas
In obedience to the above law, any set Of
Wlnd currents radiating from a center, curve
to the right and tend TO revOlve in the direc-
ton OF the clock hands in the Northern Hem
ispheTe; while any set of currents c1nverging
70 common center also diverge % the right
and tend to become centrifugal, but this ten
dency being resisted by the influence Of the
pressure gradient, they rcvove with a left
handed Curvature. Fcrrels law is perfectly
general. IL applies 10 any mass Of matter
whatever, whether solid, liquid or gaseous,
moving in any azimuth, on the surface OF a re-
Volving sphere or sphcriOd. Railway trains
and steamers rivers and marine currents, and
winds Of all kinds, equally obey the tendency
to deviate 10 the right in the Northern Hem
isphere, and to the left in the Southern. This
tendency increases in the same ratio as the We
locity Of their motion, and as the sine Of the
latitude Of the place
The law Of the winds rotation, which was
recorded as a fact Of observation by Lord Ba-
con. received its first partial explanation at the
hands OF Dove, the veteran meteOrOlOgist Of
Berlin. The law Of Buys Ballot expresses the
probable direction Of the wind as consequence
OF the observed relations Of pressure. IL states
that il line be drawn between the seats Of
highest and lowest pressure, the direction Of
the wind approaching this line will form an
angle OF CO. or So with IT, the Obtuse angle
being on the side Of the lowest pressure. In
other words, stand with your back 70 the wind,
and the storm center will be 10 your left and
the region Of fair weather 20 your right in the
Northern Hemisphere, and vice versa in the
Southern Hemisphere.