The Barre daily times. (Barre, Vt.) 1897-1959, 1907-06-08
Al Study Of the Circulation Of
the Worlds Atmosphere.
FORCES THAT MOVE THE AIR
Contrasts in Temperature High and
Low Pressure and a Law Of Nature
Called the DETECTING Force Of
the Earth's Rotation.

the room. Nearer the ceiling the
warmer air ~ forced out of the win.
dow, thus completing a general atnos.
pheric circulation on a miniature scale.
These currents OF air, which might
properly be called wind would not
occur II the air within doors was not
warmer aud consequently lighter than
the air without.
The range In temperature between
the equator and the north pole amounts
in winter to considerably more than
100 degrees r., and In summer the
contrast Is also great. Moreover, In
summer the continents are warmer
than the oceans, bnt III winter the re-
verse Is true. Three examples win
serve to illustrate how such contrasts
affect the winds OF tile world.
At the equator the temperature aver
ages about so degrees throughout the
year. Consequently the lower air flows
In from regions Of high pressure on
each side, forming what are known as
the trades. These winds cover nearly
one-hnlf Of the eagth's surface ana
blow with much steadiness the year
round.
The monsoons, or "seasona. Winds"
OF India and the Indian ocean are the
most interesting Of their Glars. In
summer the cooler ocean air pushes IN
toward the land, while the warmer air
over the continents rises to consid-
cradle height and then fiows out to
sea, forming a systematic circulation
between ocean and continent. In win
ter the ocean is warmer than the con-
tinent, and the winds reverse their
direction
The land and sea breezes" occur
with much regularity near large bodies
OF water ia some parts Of the world.
The ocean Is cooler than the land dur
ing the day and warmer at night, caus-
ing on small scale daily inter-
change or air similar 20 that caused
by the monsoons.
A clear knowledge Of the term "air
pressure" Is very helpful In studying
the causes OF wind. Air, like a stone,
presses against the ground-ln other
words. It has weight. amounting to no
less than 2,1iT pounds upon every
square foot Of the enrth's surface at
sea leyel--but. unlike a stone. the at
mosphere is elastic to high degree
and also presses IN all other directions.
On account Of this elasticity Of the
air, certain forces which arise from
differences In temperature and the
.nm tt,f. ..a4atfr, oa.sSn ~ IN haQofne
dense or heavy in some regions and
rare or light in other regions.
1t Il the effort OF the atmosphere to
overcome these pressure differences
and resume state Of equal density
that causes the winds 20 blow.
The column Of mercury in a barome-
ter tube is always just balancing a
column Of air of the same diameter.
reachlag from the barometer to the
top OF the atmosphere. If the afr IS
dense the mercury viii OF course stand
/ high In the tube, and 70 express this
condition we use the term high
pressure" but II the air IS rare the
mercury will stand low in the tube,
and pe then use the term 'low pres
sure
Over the United States. Canada md
other parts OF the world the pressure
{ IS ascertalned each day at numerous
stations. The barometer readings, ex-
p-esscd in inches of mercury, are tele-
gtaphed to q central point and there
I cEartei on map. The exact regions
where the pressure Is high or low
may then be seen at glance. 1t has
been learned from such observations
Tint these areas are constantly moving
eastward at ON average rate Of about
600 miles per day.
Technically the low pressure areas
arr called cyclones and the high
pressure areas "auticyclones." They
/ arc frequently 1000 or more niles In
/ diameter. Tho little storms OF great
j destructive force so often called cy.
/ clones are really tolnaaocs
! The higher the pressure IN any par-
tIcular region relative to soma other
region the greater will be the velocity
I ot the wind The winds blow much
faster in winter than ia SUMMER, be-
cause the greater contrasts Of tempera-
4 ture cause more decided differences IN
/ pressure.
Observations demonstrate, however,
I that the wind never blows IN atraight
lines, because all bodies OF air When
4 ia motion are acted upon by law Of
I nature called the 'doaecting force OF
7 the earth's rotation" This force turns
all wind to the right Of its course In
the northern hemisphere and to the
| left IN the southern.
Thus If a wind In our hemisphere
1 starts north 1t IS soon turned slowly
toward the northeast or If it starts
west It viii soon turn toward the
northwest. When 1t is remembered
I that at the equator the earth IS rotat-
ing at tho enormous velocity Of 1,035
miles an hour, one will not wonder that
such detecting force could exist All
areas Of high aud low pressure, from
whatever cause, therefore become
whiting masses Of air, and little
thought will show that they must turn
IN opposite directions In the north
ern hemisphere the low areas. OF
CLOVIS" rs they are designated on the
weather map. always rotate in al.
rectlon contrary to that Of the hands
ofa watch.--Iouth's Companion.