The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1875-09-23
bic. When telegrapbic reports can be easil,

bic. When telegrapbic reports can he easily
received from the Mississippi w .Iey 1t is posi-
BILE TO predict the approach Of. storm tweu-
ty four hours ahead of its r;oming. Along
the Atlantic coast OF the U nled> States rain
occurs most frequently with the wind
~ Ahe northeast. 1t has been noted at
II Haven that storm' begin with an east
wind and end WV westerly one, go
he same storm Is attended by both
but, as the rain or snow with the
I'll I'd generallrJ continues longest, the
eas Wind Ia rf corded as accompanying
RAIN gseafe r number Of the regular
houiA rtvs ton. Throughout most Of
the intS ne United States the princi'
pal WioG' part ruin comes with a westerly y!
now THE BAROMETER WORKS.
The instr uments used by the Signal Office
are affecter. before the wind actually begins
10 blow, or the rain to fall. The length of
time VIII .ch passes between the first appear
ance of change of weather and its actual
setting, in is not the same. 1t is much greater
when southwest wind is going TO succeed
northeast than when the opposite change
is about to take place. The wind usually
shifts with the SUD, from left to right, in the
northern hemisphere. A change in this di-
rcction is called veering. Thus an east wind
shifts to west through southeast, south, and
southwest, ard west wind shifts to east
through northwest, north, and northeast.
II the wind shifts the opposite way-yiZ.,
from west to southwest, south. and SOUTH
east-the change is called backing, and it
seldom occurs unless when the weather Is
unsettled. If the barometer be high (aboye
30.5) and remain steady for some days it is
because there is, so to speak,
SURPLUS OF AIR
at the place. The wind will be light and
the weather probably dry. a gale can ouly
set in when the air flows away, and it will
not at first he severe at the place. The wind
will be light also, but the weather will pro-.
baby be cloudy and wet. If the barometer
rises slowly from low level the weather
may become drier and the wind lighter, or
perhaps uie away. If the barometer falls
gradually from high level the weather may
become wetter anu more unpleasant. ln
general, whenever the mercury remains
steady we may expect settled weather, but
when it is unsteady we must look for
change, and perhaps 4 severe gale. In an
ordinary gale the wind often blows hardest
when the barometer just beginning to rise,
directly after being very low. Whenever
barometrical readings are lower over any
area than over those adj acent the air will
sweep around that area Us csnlre, and the
direction of the motion will be opposite to
that Of the hands of watch. Conversely,
the air will sweep round an area OF relatively
high barometrical readings in the direction
in which the hands OF watch move.
ATMOSPHERIC PRESSURE.
The existence of a deficiency Of atmosphere.
cal pressure, or W hat is termed barometr-
cal depression, over any district is accompa-
MED by the movement Of the air ip the
neighborine districts. The velocity OF the
ar depeudS at Least in great mea .ure,
though not abs ,utely-on the difference OF
barometIical readings over given distance.
or on what is termed the blrometrical
"grqdient." The gradients are expressed
| ia hundredths Of an inch of mercury per
fifty geographical miles. Among obscrva-
lions that have passed into proverbs in
the Meteorological Department are that
when the barometer falls suddenly in the
western part of New England it rises at
the same time in the Valley of the MissIs.
sipp, and also at ST. Johns, Newfoundland.
| In great storms the wind for several hun.
dred miles on both sides OF the line OF MINI
| mum pressure blows toward that line dl-
rect!y or obquely. The force Of the wind is
in proportion TO the SuddeneSs greatness
of the depression of the barometer. In
all great and sudden depressions OF the ba-
| romeler there is much rain Or snow.
Most storms commence in the far
west" but some commence in the United
States. The fluctuations of the barometer
are generally greater in the eastern than in
| the western parts Of the United States. Du-
ring The passage OF storms the wind gene
raily changes from the eastward TO the west
ward by the south. The northern part of
| the storm generally travels more rapidly TO-.
ward the east than the southern part. Du-
ring the high barometer on the day prece-
ding the storm it is generally clear and mild
| in temperature, especially if very cold wca-
| tbcr preceded. The temperature generally
| falls suddenly on the passage OF the centre
| OF great storms; so that sometimes, when q
storm is in the middle of the United States,
| the lowest temperature of the month will be
| in the west on the same day that tue highest
| temperature is in the cast.
POPULAR MISTAKE.
People imagine when we have north
easterly wind that we are TO have storm
| from the northeast, whereas the storm must
necessarily come from the southwest, or the
very opposite direction, bv reison of low
barometer being there. In the West lndes
| the cyclone season is from July to October.
| They originate near the equatorial limit OF
| the trade-Wind>, where these winds are lr-
regular and travel west. The air in cyclones
has not merely q movement of translation,
but also gyratory motion about the centre
of the storm. The motion of the air is spi-
rally inward, as has been shown in the
| storms of the United States but over the
OCEAN the whirling motion is usually more
decided than it is over the land.
NORTH OF THE EQUATOR
| this gyratory motion is from right TO left,
or in a direction contrary to that of the
| hands of watch; south OF the equator the
motion is from lett to right, or in the same
direction as that Of the hands of watch.
Near the centre OF the hurriciDe there is
generally a great fall Of rain. Storms are
caused by stroug and extensive upward
| motion OF the air, by which means its vapor
is condensed by the cold elevation.