The Lee County journal. (Leesburg, Ga.) 1904-19??, 1907-08-09

proper average-for most of the coun-
tries i'll the world Progress in this
class OF work is slow, and the princi-
pies on which it is baseu are not fully
understood. Moreover it is now be-
ginning to be evident that to perform
1t scientifically a man must be able
to obtain information from other parts
of the globe than his immediate sur
roundings. BY mail or by cable or
wireless telegraphy this will eventual
ly be feasible, for there are trained
weather observers well distributed
over the continents and islands OF the
whole world.
The first great step is to notice how
far, II at all, the temperature and pre-
cipitation in different regions vary
from the average OF past years TO
learn this, Of course, there must be
accurate records going back over
twenty or thirty years. For that mat
ter fifty or hundred would not be
too much. The fact is, the weather Is
seldom exactly what it ought to be-
1t Is generally toe hot or too cold, too
rainy or too dry. In a quarter or half
century many eccentricities occur.
Nothing is SO regular about the wealth.
er as its irregularity 1t will not do
to make comparisons with any one
recent year. a safe average can be
found only by using figures for long
term.
Something besides temperature and
precipitation must also be watched
and registered, too-the pressure Of
the air, as indicated by the barometer.
Now, at most places on the surface OF
the globe two sets of changes occur.
One is very apparent rise or fall of
the barometer in short periods, like
two or three days This is the only
change which is usually noted. The
other is very slight and not easily de-
tected, but it is important-not SO
much for the place where it occurs
as elsewhere. If a person possesses
the patience to do so and has the
daily records to use for the purpose,
he can figure out whether the average
| pressure for a given month or an in
/
ence may be and usually is small, but
If 1t is perceptible it has meaning
and is sure to exert an influence
somewhere or other.
The starting point in daily weather
forecasting for the United States is a
map showing the distribution Of air
/ over the country. On such a chart
are seen various highs" and lows, .
whose position changes from day to
day. These areas control several
phenomena In the first place, the
wind, which is air in motion, flows
from an area of high pressure to one
of low pressure. Hence it is possible
to foretell the force and direction Of
the breezes which will visit any 10
cality from the expected movement Of
these highs and lows during the ensu-
ing day With the wind are associ-
ated other things. If it is to come
from the south it ought to bring
northeast, north or northwest, it
promises cold. 1t may affect precipi-
tation in one of several ways. If, for
instance, it comes from the dry in
terror of the continent it cannot car
ry much vapor. If it blows in from
the sea it will have burden of mois-
ture which can be condensed on slight
provocation. It will be seen, there
fore, that air pressure and changes
in it lie back of almost all the other
features of weather which concern
the public.
1t is gradually coming to be real
lied that even slight excesses or de-
fciencies in pressure for a month or
two operate in the same way as more
rapid and extreme alterations. Some
where or other they promote unusual
warmth or cold and excuses or de-
fciencies in rainfall. 1t is easy to
understand, too, that when there Is a
drought in one part OF the globe there
may be an unusually wet season in
another, all as a result of only trifine
differences between the actual distri
button of air and the computed aver
age for quarter or half a century
Indeed. a large number Of such coin
cidences have been observed, and the
explanation here given is now accept
ed by weather experts A great deal
of comparison of records for differeni
Dlaces is necessary to show this rela
tionship. and as the facts cannot east
" be obtained for several months they
are of interest to only a few profes
sional meteorologists.
The knowledge that certain condi
tions may be expected in one country
At the same time as similar Cor oppo
sitel ones in another is important, bu
4 might not be very helpful in lon;
range forecasting- least in the ear
" stages Of the art. What is mos
needed for immediate use is the as
-,,rorca that something or other il