The New York herald., 1871-10-21

that the caut,onary signal shall be hosied whcneve
the winds are expected 20 be as high "a TWENTY-FIVE
miles AN hour and 20 continue ut that velocity FOL
several hours, within radius OF iVo niles VI ''
station.
add second signal, giving warning ol severe gaes
Each signal. as now used, Is expected TO holo
s which bol 'e spuee waS noisteu When no signal
displayed II indicates that the ONCE has no know
ledge OF any approaching danger suincient 10 JUSTLY
the issue OF storm warning. But as tiils Is no!
only the case when really no danger exists. but
also, In many cases, may be the consequence or the
failure OF the teegrspnic connection OF tho central
office o. Washington with outlying stations. Inc
absence OF the danger signal should not lead tle
mariner TO relax his watchiulness OF the weather
10 neglect TO obtain the latest and fullest lnlor
nation from the station observer and elsewhere:
To obtain the most exact information iet him GEL
lished by this once, and also the general "Synopses
and Probabties,n or the s0called Press Reports
furnished all newspapers free OF cost.
II the mariner finds that high winds are prevail
Ing within 200 miles OF the port a. when ne ~ ~
ne should ns: ascertain n9oancss w' tnese e ha
winds. According to meteorlc laws we!l known,
the cause OF this severe disturbance OF the atmos
phere Is usually an excess OF barometrc pressure
over some district and . deficiency over some
neighb0nng region. Tho atmospheric ocean, ike
cease 10 maintain an equilibrium, which ever
eludes IL
area OF violent winds will be correspondn9ly con-
tracted as In t0rnadoes land and especially SUCH
tornad0es as are seen In the mississippi valley.
IL IL o well established fact that all storms IN.
crease in severity as they contract. and on the con
trary, lose Their r0atory velocity ana tangentiai
violence o. their area becomes larger
High above the earth both regular ana abnormal air
currents frequently blow with immense force ana
velocity, and make themselves kn0wn by the furious
speed they give 10 scud cloud, cirrus clrro-stratus
and other clouds. Thus at Mount washington the
Signal Service observer frequently reports violent
sOntheriy wind on its summit, when oil arOtnd the
base OF the mountain there are Orsk nOrtnery
winds and pice versa. 1t Is evident that this upper
air current has an influence upon the aerial strata
beoW It, Even II no fall in the barometer be noticed
Drlsk winds may be experienced owing 10 tne Iact
tnaL the air In rapid motion overhead may urag
along with 1t that on the SURFACE OF the ground;
but IN general II may stated that ninety per cent
OF the Winds that are dangerous 10 nayigatOrS are
accompanied by areas OF notably hiRn ana iOw
barometer, Now when the barometer failS over any
region the inertia OF the surrounding AR causes
similarly large mass OF air moving with rapidly
preserves its motion after the exciting cause Is re-
moved. Thus 1t may happen that strong winus exist
In regions at whcn no barOmetrc dlsturDAnce eXlstS
at the moment but has existed short Time pre-
viously
Again the space enclosing the partial vacuum,
into which the wind tends TO rush, ftseif moves
slowly over the earth, and thus the WIND at any
point appears still longer to delay to follow the
barOmetric disturbance. This delay WILL OF course.
vary with the motion OF the central area OF low
pressure or that OF the negnD0rlng hign pressure.
The general consequence or the preceding cOnslc-
erations IL that the area covered by the weather
Chart presents 10 our view one, TWO or tnrec regions
OF low pressure and one or two or hign, and tnat
between these out much nearer TO the low than the
hgn barometer we find the strongest winds. AS
regards the direction OF the winds they may bo
described as not tending directly to the centre OF
aud in upon il in sinuous spiral In direction con-
trary TO the movements oil tho hands OF watch when