The Somerset herald. [volume] (Somerset, Pa.) 1870-1936, 1878-08-14
weather Probabilities

Every one who reads he.daily pa
pers is familiar with the weather
record issued from the War De-
partment, Office Of the Chief Signal
Cficer.o at Washington. These re-
ports give, FIRST, general statement
of what the weather has been for the
pasttwenty four hours all over the
country, from Main to California, and
from the lakes to the south Atlantic
States; and then the probabilities"
or indication" for the next twnty
four hours over this same territory
The annual reports Of the chief signal
officer show that in only compar-
lively few instances do these predic-
tons fail Of fulfllmeat. The reason
these prophesies are SO true is a sim
pie 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 Washing
ton.
We shall see presently how the
weather in.erprets itself to "Old
Probabilities Although it has prov
ed 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 exmaine its different
elements. The atmosphere has weight,
inst as water or any other fluid, al
though it seems to be perfectly bodl-
less. We must comprehend that the
transparent, invisible air is pressing
inward toward the centre 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. Some
times the rise is followed by cold winds
fros, and ice. What these changes
really indicate can be determined on
ly By comparing the barometric chang
es at certain hours sin number of
places very far apart. This is done
by the signal service Observations
made q. about l40 stations, in di fer
ent parts Of the country, at given
hours, and the results are at once tel
egraphed to Washington. where our
faithful weather clerk receives
them, reasoning out Of 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 great amount Of
moisture, and it shows "a 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 ;lvented called the "wet-bulb'
therm ometer. 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 yane
ard the thermometer. The /
vane shows the direction, and the
anemome;er indicates the velocity Of
the wind. 1t is by right understan-
ding Of all the instruments that the /
signal service officer is enabled to tell /
what the weather SAYS of itself; for
they are pens with which the weather
writes out the facts from which the 1
officer makes up the benefit Of ali /
concerned. Thus however wildly the I
storm NAV seem 70 come, il sends |
messengers telling just were it arose, |
what course it will take and how far
it viii extend. But il tells its secrets |
to those only who pay strict atten-
tion.