Evening star., 1921-04-01

Though the United States has re-
versed its trade balance in material
products since the beginning of the
world war. and now" sends out more
articles and productk than other
countries send in," says a bulletin
issued from the headquarters Of the
National Geographic Society. there
is one commodity for the main sup
borders, and probably always will.
1t is our weather. necessity In our
daily life, but one that perhaps we
do not always appreciate.
"A certain part of our weather, to
be sure, might bear the brand. Made
in the U. S. A. but it is only a
minor portion. For the most part,
our supply of rains. SHOWS. billiards.,
cold waves and hot waves, tornadoes
and tempests come tumbling in from
the northwest and the west. A
smaller percentage come from the
north and the southwest. and a few
storms from the Gulf of Mexico and
the south Atlantic. But it is worth
noting that none of our weather en-
ters the country through the stretch
of the Atlantic coast north OF cape pc
Hatteras, the section into which
pours the vast bulk of our material
imports.
Alaska In Our Weather.
Though the United States proper
does not brew its own weather. there
is some consolation to enthusiasts for
the 'made-in- America movement in
the fact that the great majority OF
the disturbances that enter the states
originate in Alaska or in the great
warm cauldron of the north Pacific
between the Aleutian Islands and Ha-
wall, which is almost a United States
sea-
weather disturbances which enter
the United States accompany lows
and 'highs'-separated areas of low
and high atmospheric pressure as reg
istered by the barometer-which drift
in general from west to east. Atmos-
pheric pressure is the result of the
weight of the great sea of air COM
pressing the lower portion. Natur-
ally, in regions where the air is rari-
fed and is rising, the weight, and
therefore the pressure. is relatively
low; where the air is contracted and
is sinking the weight is greater and
the pressure is relatively high.
Heat is the chief factor in start
the start is made the movement is
contributed to by various causes, mo-
tably condensation into cloud and
rain that gives out to the air the
original heat of evaporation. Thus a
sort of chimney for rising air is es-
sure is reduced.
Most Rains Near ~Lows.'
'The areas of disturbance-'rows'
and 'highs'-made familiar to large
numbers Of people by the rough cir
cles and ellipses that indicate them
on the daily weather maps of the
United States weather bureau, cross
the continent normally in three or
Saor ,eo;v 20 .,
in the low areas or slightly in ad-
vance Of them. The rains that occur
in the arid parts of the west, how
ever. usually follow the passage of
lows
'In winter the great factory for
lows is the extensive body of warm
water south of the Aleutian Islands
and in the Gulf of Alaska. This re-
gion is kept warm by the Japan cur
rent. The air over the water is
warmed and tends to rise. This re-
permanent area Of low pressure prac-
tically throughout the winter.
From time to time such large
area of low pressure is developed that
fragments of the area, so to speak,
break Off and drift with the prevail
ing winds to the east. 1t is some
what like a bubble Of air under thin
ice breaking OFF from a larger bubble
and finding it's way with the flow of
the water to another location. Nor
mally a new low is thrown off every
few days.
Battle ON "Highs" and CLOVIS"
'"The most common course of these
lows is across the southern pan
handle Of Alaska and over British
Columbia, to cross the Canadian bor-
der into the United States in Al
called Alberta storms. A somewhat
fewer number of disturbances. called
north Pacific storms originating in
the same general region. enter be-
tween Puget sound and northern