The Republican. [volume] (Oakland, Md.) 1877-current, 1878-09-21
How the Weather is ForetoId.

III lOlLlef lllneS, Gne cnlef herald of
the weather was the almanac, which
ambitiously prophesied whole year of
cold and heat, wet and dry, dividing up
the kinds of weather quite impartially,
if not always correctly.
But the almanac, good as it was now
and then, and the weather-wise farmers.
correct as sometimes they might have
been, were 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
under the somewhat disrespectful title
of "Old Prob" or "Old Probabili-
ties" He has become the herald of the
weather to the sailor, near the rocky,
dangerous coasts; to the farmer watch
ing his crops, and waiting for good
days to store them; to the traveller,
anxious to pursue his journey under
fair skies; and to the girls and BOYS
who want to know, before they start to
the woods for a picnic, what are the
probabilities" as 10 rain.
Every one who reads the daily paper
is familiar with the Weather Record
issued from the "War Department.
office of the Chief Signal Officer" at
Washington. These reports give, first,
a general statement of what the wealth
er 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 " Indications" for
the next twenty-four hours, over this
same broad territory The annual re-
ports of the Chief Signal Officer show
that in only comparatively few instan-
ces do these daily predictions fail of full
fillment.
The reason these prophesies are so
true is simple yet a wonderful one.
The weather itself tells the observer
what it is going to do some time in adj
vance, and the telegraph sends the
news all over the country, from the cen
trail office at Washington.
We shall see, presently, how the
weather interprets itself to "Old Prob
abilities" Although it has proved
such fruitful subject of discourse in
all ages, yet | am afraid many people
who pass remarks upon it, do not real
ly think what the weather is made of.
Let us examine its different elements.
The atmosphere has weight, Just as
water or any other fluid, although it
seems to be perfectly bodiless. We
must comprehend that the transparent,
invisible air is pressing inward toward
the center of the earth. This pressure
varies according to the state of the
weather, and the changes are indicated
by an instrument called barometer.
Generally speaking, the falling of the
mercury in the tube of the barometer
indicates rain, and its rise heralds clear
weather. Sometimes the rise is fol-
lowed by cold winds, frost and ice.
What these changes really indicate,
however, can be determined only by COM
pairing the barometric changes, at GER
tain hours, in number of places very
far apart. This is done by the Signal
Service. Observations are made at
about 40 stations, in different portions
OF the country, at given hours, and the
results are photographed at once to Wash
ington, where our faithful weather
clerk receives them, reasoning out
from them the probabilities" which
he publishes three times in every twen-
ty-four hours.
ouO VIC atmosphere varies not only
in weight but also in temperature.
The thermometer tells us of such
changes.
Besides this, the air contains great
amount of moisture, and it 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 "wet bulb''
thermometer.
We are thus enabled to ascertain the
weight of pressure, the temperature,
and the wetnesS of the air, and now it
only remains for us to measure the
force, and point out the direction of the
wind. This is done by the familiar
weather-vane and the thermometer.
The vane shows the direction, and the
thermometer is an instrument which in
dictates the velocity of the wind.
1t is by right understanding of all
these instruments that the signal serv-
ice officer is enabled to tell what the
weather says of itself; for they are the
pens with which the weather writes out
the facts from which the officer makes
up his reports for the benefit of all con-
cerned. Thus, however wildly and
blindly the storm may seem to come,
it sends messages telling just where it
arose, what course it will take, and how
far it will extend. But it tells its secret
only to those who pay strict attention.
st. Nicholas.