The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1878-10-12
How the Weather is Foratnld.

In former times the chief herald of the
weather was the almanac, which ambitious
ly prophesied whole year of cold aud
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 exact in
formation 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, y
or "Old Probabilities" He has become
the Herald of the Weather to the sailor.
near the rocky, dangerous coasts; to the
farmer, watching his crops, and waiting
for good days to store them; to the trav-
eler, 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 picnic, what are the "probabil-
tiles" as to 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 twenry-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 reports
of the Chief Signal Officer show that in
only comparatively few instances do these
daily predictions fail of fulfllment.
The reason these prophesies 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 cOun-
try from the central signal oifice at Wash
ington.
We shall see, presently, how the wealth
er interprets itself to sold Probabilities.
Although it has proved such a fruitful sub
ject Of discourse in all ages, yet am afraid
many of the people who pass remarks upon
1t do net really 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 press
ing inward toward the centre of the earth.
This pressure varies according to the state
of the weather, and the changes are indi-
Gated by an instrument called a barometer.
Generally speaking, the falling of the mer-
curry in the tube of the barometer indicates
rain, 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 determin-
ed only by comparing the barometric
changes at certain hours, in number of
places very far apart. This is done by the
Signal Service. Observations are made at
about one hundred and forty stations in
different portions of the country, at given
hours, and the results are telegranhed at
once to Washington where our faithful
weather clerk" receives them, reasoning
out from them the probabilities" which
he publishes three times in every twenty
four hours
But the atmosphere varies not only in
weight but also in temperature The
thermometer tells us of such changes.
Besides this, the air contains a great
amount of moisture, and it shows as much
variation in this characteristic as in the
others. For the purpose of making known
the changes in the moisture in the atmos-
phere, an instrument has been invented
called the ''wet-bulb" thermometer.
We are thus enabled to ascertain the
weight or 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 anemometer is an in
strument which indicates the velocity of
the wind.
Its by right understanding of these in
struments that the signal 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 from
which the officer makes up his reports for
the benefit of all concerned. Thus, how
ever wildly and blindly the storm may
seem to come, it sends messengers telling
just where it arose and what course it will
take, and how far it will extend. But
1t tells its secret 10 those only who pay
strict attention.+.S Nicholas.