The Daily state journal. [volume] (Alexandria, Va.) 1868-1874, 1872-10-17
The Barometer on the Farm.

In taking an estimate of farmers rank
and proficiency, we generally turn to his
implements, the state of which is one OF
the many criterions of good farming. We
seldom see a good farmer with bad imple-
ments. Now there are implements other than
plows, harrows, reapers, etc. The work.
shop should be full of implements, the gar
den full of tools, and in the house there
should always hang good barometer.
How often do we hear from farmers
old men, too--who will protest that ba-
rQmeter is not good, and that they never
saw one upon which reliance could be
placed. These men mistake the principles
which regulate the rise and fall of col
umn of mercury. These expansions and
contractions are governed by natural laws,
which, under the Creator, are in their very
nature immutable.
Doubtless there are many of our readers
who understand the effects of changes of
the temperature and density of the atmos-
phere upon the mercury in the barometer
and thermometer but, without a doubt,
there are many who have never given the
least attention to the subject. For the
and concisely as possible explain the prin-
ClpleS WHICH Ildho ttlC udI OlIttSE d ttol VI
weather that is to come.
The atmosphere is a gaseous envelope
encirclng the earth, and it forms the ocean
of air, ut the bottom Of which we live.
When gas IS subject to an increase of
pressure, its volume becomes less, and
when the pressure is withdrawn the gas
Immediately expands again and becomes of
the same volume as before the pressure
was increased.
We have not space to enter here upon
the chemical causes, but we need only state
that the pressure upon this our atmosphere
is capable Of being saturated with and re-
tanning a maximum amount Of aqueous
vapor. When this air, saturated with aque-
Gus vapor, comes in contact with air of a
cooler temperature, it becomes incapable Of
holding it any longer and this vapor con-
gealing, falls in the shape Of rain, snow or
hail, according to the GOODNESS of the air
through which it passes before reaching the
surface of the earth.
IL has thus been established as fact
that before falling weather the pressure up
on the lower atmosphere becomes less, and
before fine weather the pressure becomes
greater. Now barometer in its simplest
form is only tube of a certain standard
proportion, height and size, filled with
mercury, closed at the top, open at the
bottom, and placed in an open vessel filled
with the same metal. Wher this is done,
the mercury in the tube, at certain STAN
dard state and temperature of the air, sinks
to certain point. 1t is sustained at this
point by certain pressure of the atmos-
phere upon the mercury in the vessel.
When the pressure becomes greater, or
before fine weather, the mercury in the
column is pressed upward in tho vacuum
above, and is said to rise when the press.
ure becomes less, or before falling weather,
the mercury in the tube falls.
Now, in noticing the action of the ba-
rometer, the rapidity with which it rises or
falls should be observed. If it falls rapid
ly in fine weather, the rainfall is near, and
il slowly it is probably far off; and yice
rersa if, during falling weather, it rises rap
idly or slowly, will the clearing weather be
nearer at hand or not.
Before thunder storm the barometer
gives us no indication, because the pressure
of the atmosphere having been SO great
the barometer has risen high, and that
the storm is actually upon us. But FREE
quently storms are indicated by sudden
or rapid fall of the mercury.
To make use of barometer, let slate
be hung near it, and let some member of
the family who is frequently in the house
note its height at different times, and record
the height and hour upon the slate we can
then Judge of the time which is likely to
elapse before the predicted change Of wea-
Their will occur. BY careful observation
of well-tested barometer, we cannot per-
haps predict in time the advent Of thunder
storms in catchy" weather; but we may
generally SO far judge of a steady change
of weather as to regulate the amount Of
hay we should cut at a time, when we
should cock such hay, or whether to cap
our grain stacks. ZIG. E. H." IN Can
ada Farmer.