The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1875-08-21

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tremity Of Nova Scotia, to the West Indies.
The West India stations are found to be par
ticularly valuable in winter, as q large proper
ton Of the most violent winter storms originate
there.
LOCATION OF STATIONS.
In the United States there are stations in
all the principal cities. On the Pacific coast
| there are three, viz, at Portland, Oregon,
and San Francisco and San Diego, California.
Besides these are stations at st. Pauls and
st. Mitchelrs Islands, Alaska. These, how
ever, are not in telegraphic communication
with the Central office. The Gulf and Atant.
lc coasts, and the northern boundary formed
by the st. Lawrence river and the Great
Lakes, have a continuous chain of stations
~ in number = where observations are made
and cautionary signals are displayed. eau
tionary signals are also displayed at the life
saving stations on the New Jersey and North
Carolina coasts, which are reached by tele
graph.
A government telegraph line commences
at Cape May and runs along the coast to
Peck's Beach, Atlantic city, Barnegat, Squan
Beach, Long Branch and Sandy Hook, thence
across the country to Philadelphia, Baltimore,
Washington, and south to Norfolk, Cape
Henry, Kittyhawk and Cape Hatteras, N L.
and an appropriation has been MADE to ex-
tend it further south along the coast. A sim
liar telegraph also exists along the Pacific
coast from San Diego TO Portland, and an
| appropriation has been made to extend it
| from San Diego, through Fort Yuma, Mari
copa Wells, Prescott and Tucson, Arizona,
to Apache. This is expected to be Of great
value in predicting storms originating in the
southwest.
Some accounts Of the life and work Of the
observers at the stations on the submits of
Mount Washington, 62s5 feet above the sea
level, and Pixies Peak, l4,2l6 feet above the
sea level, would be found interesting, but as
these stations are Of no value in predicting
| storms, but are merely used for observations
Of the upper currents of the atmosphere, they
have no proper place in this article.
Having thus given some idea Of the extent
Of the Service and the geographical area in =.
cluded in the working Of the departments, it
remains to give description d the instru.
.ments used and the method Of making obser
yations and the manner in which storms are
predicted frsm the results Of the observations
made.
THE INSTRUMENTS.
The instruments in use at the Philadelphia
station, in the Chamber of Commerce build.
ing, on Second street, above Walnut, are
identical with those used at all the other sta.
tions. They consist of the barometer, for
measuring the pressure Of the atmosphere ;
the common thermometer and self.registering
maximum and minimum thermometers the
hygrometer for determining the relative hu-
midity Of the atmosphere the thermometer
for measuring the force of the wind the wind
yane for determining the direction of the
wind the rain gauge for measuring the rain
fall, and clock.
The rain gauge is exposed on the roof Of
the building, the thermometers and hygro.
meter are placed in that unreasonably ugly
cupola on the top of the tower on Second
street, and which is called the instrument
shelter; the wind vane and thermometer are
fixed upon long rods projecting above the
roof Of the instrument shelter, and the clock
and barometer are in the Office in the second
story of the tower. A complete duplicate set
OF instruments is kept on hand, to provide
against accident or emergency.
With the common thermometer all are ia
miliar. 1t consists simply of bulb and tube,
| from which the air is exhausted and the bulb
filled with mercury at q given temperature.
The bulb is then Theoretically sealed, and the
expansion or contraction OF the mercury from
heat or cold causes it to rise or fall in the tube.
The barometer is the most important of
the instruments used and is also familiar TO
most intelligent persons. 1t consists of a
glass tube, about 80 inches in length, one end
of which is Theoretically sealed the air is then
entirely exhausted from the tube and the open
end plunged into reservoir containing mer.
curry. Now the mean height of the barometer
at the sea level is 29.82 inches, hence it fol-
lows that the whole weight of the atmosphere
is equal to that of a sphere Of mercury cover
inn tha uhsx1A trta.. a,f Nk.. .l.l..
tending TO the height of 29.S2 inches. This,
therefore, is the normal height of the mercury
in the tube Of the barometer at the sea level,
and any variation from this point can only be
local and indicates an atmospheric disturb.
ance at that point.
If the barometer falls below 1882 inches it
shows that the atmosphere from some cause
has become lighter than it should be normally
at that point The surrounding atmosphere,
being heavier, Of course presses toward the
point where it is rare, the winds yeer towards
that locality and it becomes at once, the cen.
tire Of an atmospherical disturbance called n
storm. Thus it will be seen that the height
of the barometer and the direction of the
wind are most important points to be ascer.
tainedin making an observation. Experience
having shown that storms travel from west to
east, and low barometer being found at a
given locality, il is safe to predict that within
certain time, the length OF which is also de.
termined by experience, similar condition
of things may be expected at localities east.
ward of the place where the observation is
made. The violence ofthe coming storm nav
also be Appropriated hv taking into consid.
Grafton the relative height of the barometer At
the storm centre and at localities surrounding.
If the barometer is very low at the centre
and very high at places Surrounding. then n
serious disturbance exists and violent and
dangerous winds NAV be expected. and IL sueb
winds prevail TODAY Mt 81 point saw three hun.
dred miles from the coast, il Is safe 10 expect
that tomorrow the storm centre. following
the natural law, will have travelled 10 or near
the coast. attracting to il The surrounding
winds. Hence cautionarv signals are m once
ordered to be dsplayed. and The mariner in
harbor may delay his departure TO sea. while
the sea captain who NAV be near dangerous
coast, where there Is no safe barbor, sees Inc
ominous red tlap. or lantern, and Al once
leaves the vicinity of the rocks and breakers
for The omen sea whore he nav mo roa,,,,ra IL
shin and outride the storm with more safety
The hyprometer consists merely oftwo orj.
nary mercury Thermometers, which CORES.
pond exactly in their reading. They are