St. Tammany farmer. [volume] (Covington, La.) 1874-current, 1891-04-18

FoREcAs1,No THE WEATHER.

, foREcAsTINo THE WEATHER.
Something About tho Operations and Par.
apherpalla Of the signal Once.
Making weather is a somewhat diff
cult and expensive business. Nine hun.
drcd thousand dollars, in round num-
bers, is the Signal Services estimate OF
the cost for this year. Last year Con-
grcss appropriated ssl6.s5o. and for
twenty years the appropriations have
approximatcd the latter sum.
Only the most delicate and perfect in
struments are used. Take. for instance,
that self-rcgistering aneroid barometer.
The entire apparatus Ia inclosed in q
little case q foot long by Eve inches
wide and high. Behind the glass front
there is coil made Of aluminium disks,
in size and form very like the familiar
poker-chip, but black In color. These
aluminium chips are eight in number,
and are about an eighth of an inch
apart, but connected with each other.
Each disk is hollow, and all but the top
one are perfect Vacuums- To the top
disk is fixed little post which operates
ION simple-lever principle) the long
arm reaching to the brass drum at the
other end of the box. This drum re-
wolves by clock-work. Upon it. is
wound strip Of paper, ruled horizon
tally and perpeadicularly. The space
between two perpendicular lines
represents two hours The horizontal
lines mark one-twentieth OF an inch
variation in atmosphere.
The aluminium disks respond directly
to the atmospheric weight As heavier
air presses them down the front end OF
the little lever on top goes down. the
back end goes up, tie back end Of the
long lever goes down, and the front
end, which holds the fine-pointed PEN
Gil resting against tho revolving paper,
goes down, and the record Il made.
The whole machine is in this little box,
and the glass door is kept closed. The
barometer operates perfectly in any
place where the air can get to it at all
as well in vault as upon the roof,
except that the readings are reduced to
the freezing point, and allowance 10
made for the difference In tempera-
ture. Rather simple, isn't il? Yet the
little box came all the way from; Paris,
where it Is made.
The thermometer is more difficult.
There is a curved bulb made of alumni
ium and filed with alcohol. A rise
or fall of onehsIf of degree in tenn
pcrature affects the alcohol sufficiently
to change slightly the curvature of this
delicate bulb. A needle rests against
this bulb. The change in curvature
rises or lowers the needle, which in
turn opens and closes an electric cir.
cuit communicating with the register
ing apparatus in the Office below. The
record lKsmade, as in the barometer,
npop q sheet of ruled paper wound
about q brass drum. which revolves by
clock-work. This instrument. also, is
made in Paris.
A very simple modification of the an
cient weather-cock indicates the direc-
ton of the wind, and IT'S velocity is
measured by the thermometer. There
is . shaft about two feet and u half
high. On top of that two shafts are
fastened at right angles. At the end of
each horizontal arm there is a hollow,
semi-glObular metal-cup. The wind
blows into the cups, and the arms turn
around.
The rain gauge is simply q cylinder
for rain to fall in. with q float which
the rain raises up. The snow gauge
has no float, and only an ornamental
adaptation of the topless tin pint can in
which any one can measure the fall Of
snow.
However, the wind vane, anemomc-
ter and rain gauge are all supplied with
electrical appliance which register au-
tomatically in the ofice-all upon one
sheet fastened 60 . revolving drum.
Those are the tools of the trade. Sim
liar ones are in use in all the signal sta
tons Every morning at seven o'clock
the observations are telegraphed to the
Chicago Office from all the stations, ex-
cepting a few east of Washington. Upon
the data thus received the local Office
bases its forecast.
They take q map Of the United States
and Canada, aboat two and half feet
by one and half, upon which the great
superficial features, the boundaries of
the States and the location of the sig
nal stations are indicated by faint
black lines. On this isothermal lines
are made with blue pencil, and bar
ometical conditions are indicated in red.
In Q general way, in making mp the
forecasts, regard is first paid to tho
point Of lowest barometer and the point
of highest barometer. The lowest point
is, of course, at the storm center. The
wind flows naturally from the high
point toward the low. The conforma-
ton of the earth's surface has much to
do with the atmosphere's movement,
and is taken largely into account In
predicting.
The science is as yet in an expert.
mental state, and the operator, guided
BY experience. uses his judgment in
making deductions. Some general laws
and . larger number Of general facts
have been discovered. For example,
that in the southeast quadrant of .
region influenced by point Of low ba-
rometer there is usually precipitation
rain or snow-depending upon the tenn
perature; that in the southwest quad
rant there is most wind; that . de-
cidedly high barometer in Monitoba is
usually followed by q cold wave here.
A decidedly high barometer closely fol-
lowing decided low also brings severe
cold weather in winter, but Il is usually
Of short duration, etc.
The information gathered BY the Sig
-, C>vv;~> ;e Constantly sfu6ied bv