The daily gazette., 1878-07-16
+ ow the Weather Is Foretold

In former times the chief herald of the
weather was the almanac, which, ambit-
aously propbesied whole year of cold and
heat, wet and dry, dividing up the kinds
fweatherauite impartiaily, if not always
correctly.
But the almanac, good as it was now
and then, and the weather-wse farmers.
correct as sometimes they might have
been, We're not always able to impart ex-
act information to the country; and they
have been thrown quite into the shade Of
late, by one who is popularity known un-
der the somewhat disrespectful title of
sold Prob" or "Old Probabilities" He
has become the herald of the weather to
the sailor, near tine rocky, dangerous
coasts; to the farmer, watching his crops,
and waiting for good days to store them !;
totke traveller anxious to pursue his Jour
ney Under fair skies; and to the girls and
boys who want to know before they start
TO the woods fora picnic, what are the
probabilities" astO rain.
Every one who reads the daily paper is
familiar with the "Weather Record" is
sued from the "war department office of
the chief signal, officer" at Washington.
These reports give, first, general state
'ment of what the weather has been, for
the past twenty-four hours, all over the
country, from Maine to California, and
from the Lakes to the South Atlantic
states; and then the probabilities, or
''indicatiODs," for the next twenty-four
hours, over this same broad territory. The
annual reports of the chief signal officer
show that in only comparatively few in
stances do these daily predictions fail of
fulfillment.
The reason these prophecies are so true
is simple and yet wonderful one.-
The weather itself tells the observer what
it is going to do, some time in advance,
and the telegraph sends the news all over
the country, from the central signal office
at Washington
We shall see, presently how the weather
interprets itself to sold Prebabilities."-
Although it has proved such fruitful
subject of discourse in all ages, yet am
afraid many people who pass remarks
upon it do not really think what the
weather is made of. Let us examine its
different elements.
The atmosphere has Wight, Just as
WtfeSh Va sby otuCt III
seems to be perfectly bOdiless. We
must comprehend that the transparent
invisible air Is pressing inward toward
tho centre OF the earth. This pressure
varies according to the state of the
weather, aud the changes are indicated
by an instrument called n barometer
GENERALLY speaking, the falling of the
mercury in the tube of the barometer in
dicates rains, and its rise heralds clear
weather. Sometimes the rise is followed
by cold winds, frost and ice. What these
changes really Indicate, however, can be
determined emily by comparing the baro.
metric changes, at certain hours, IN a
number of places very far apart. This is
done by the signal service. Observa-
tons are made at about one hundred
and forty stations, in different portions
OF the country, at given hours, and the
results are telegraphed at ouce to Wash
ingion. where our faithful weather
clerk" receives them, reasoning out
from them probabilities" which he
publishes three times i'll every twenty
four hours.
But the atmosphere varies not only
in weight, sot also in temperature. The
thermometer tells AS of such changes.
Besides this, the air contains a great
amount of moisture, aud iU shows as
much variation in this characteristic as
in the others. For the purpose of max
ing known the changes in the moisture
of the atmosphere, an instrument has
been invented called q "wetbulb" ther-
mometer.
We are thus enabled to ascertain the
weight or pressure. the temperature, and
the wetness of the air, and now 1t only
remains for us to measure the force, and
point out the direction of the wind. This
Is done by the familiar weather-vana
and thermometer. The vane shows the
direction. and the thermometer is an IL
srument which indicates the velocity
of the wind.
1t is by right of all these understand
ing of all these instruments that the sig
nal service officer is enabled to tell what
the weather says of itself; for they are
the pens with which the weather writes
out the facts with which the officer
makes up his reports for the benefit of
all concerned. Thus, however wildly
and blindly the storm may seem to come
it sends messengers telling just where ir
arose, what course it will take, and how
far it will extend. But 1t tells its secrets
to those only whepay strict attention.
James II. Flint, 50. Nicholas for JutU