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'''HURRICANE''' (Span, ''huracan''), a word of un-
determined origin, signifying a violent storm
of wind and rain, generally accompanied with
intense displays of lightning and thunder. Al-
though this term was originally special in its
application, it is now frequently used to desig-
nate not a peculiar class of storms, but in gen-
eral the strength of the most violent winds
known to mariners ; thus we may have storms
in any part of the world whose severest winds
may attain to the force either of a gale, a
storm, or a hurricane, according to the circum-
stances that attend their development. The
hurricanes of the Pacific ocean, the China sea,
and the northern portions of the Indian ocean
are called typhoons, and are from a scientific
as well as a practical point of view to be
classed in the same category with the hurri-
canes proper; but in what follows we shall
give only such facts and theoretical views as
belong specially to the hurricanes of the Atlan-
tic and southern Indian oceans. The gen-
eral subject of storms in their various aspects
wall be' treated under that title. To a per-
son occupying a stationary position toward
which a hurricane is approaching, it is said
that the storm is frequently heralded a day
beforehand by a peculiar haziness of the at-
mosphere, a cessation of the regular trade
winds, a lassitude perhaps induced by the hy-
grometric condition of the air, and an ominous
stillness. Then follow a steady slow fall of
the barometer, light breezes increasing to high
winds from some new quarter of the compass,
generally in the West Indies between S. E. and
N. E., and the obscuration of the entire heavens
by a uniform sheet of cloud of increasing den-
sity. When the storm has, in the course of
from 4 to 24 hours, finally arrived at ita great-
est severity, the fury of the wind and the con-
fusion of the scene become indescribable ; in
the midst of a drenching rain and a steady wind
that fills the air with a deafening roar, there
occur prolonged gusts whose violence equals
or excels the force of the strongest waves ; in
such gusts the largest trees are uprooted, or
have their trunks snapped in two, and few if
any of the most massive buildings stand unin-
jured. In the midst of the confusion incident
to the general destruction of property and life,
there occurs a mysterious calm, while a break
in the clouds and the diminished rainfall seem
to denote the end of the storm. But in the
course of from five minutes to five hours the
wind bursts with additional force from a direc-
tion opposite to that which had before pre-
vailed ; whatever had escaped the destructive
force of the first half of the hurricane is likely
to yield to its subsequent fury, and the ship-
ping which before perhaps had been blown out
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to sea, is now driven back upon the shore. If
now, instead of watching the storm from a
fixed standpoint, we take a general survey of
the ocean over which it rages, we shall observe
that the interval of calm in the midst of the
storm, as observed at the fixed station, corre-
sponds to a central spot in a large region of
violent winds and heavy rain ; these winds are
found to blow in spiral lines toward and around
the central region of calms, increasing in force
as they approach that centre. It will also be
seen that the whole system of winds moves
bodily over the surface of the earth. It is thus
easily understood why the stations over which
the centre of the hurricane passes should ex-
perience, after the central lull, a wind from
the opposite quarter to that which prevailed
immediately before. In the " Philosophical
Transactions" for 1698 Langford represents
the hurricanes of the West Indies as whirlwinds
advancing in a direction opposite to that of the
trade wind. Dampier (1701) says the West
Indian hurricanes and the Chinese typhoons
are of the same nature. In 1801 Capper pub-
lished a work on winds and monsoons, in which
he advanced the opinion that the hurricanes
at Pondicherry (1760) and Madras (1773) were
of the nature of whirlwinds whose diameter
would not exceed 120 miles. In 1820 and 1826
Brande broached the theory that the currents
of air in great storms flow from all directions
toward a central point. Dove (1828), in con-
troverting the views of Brande, explained the
observed directions of the winds on the as-
sumption of general rotary currents or whirl-
winds. In 1831 Mitchell expressed the opinion
that the phenomena of storms are the result
of a vortex or gyratory motion. The scanty
observations accessible to the authors previous-
ly mentioned were supplemented in 1831 by
Mr. Redfield of New York, who then published
the first of a series of remarkable papers on
the phenomena of storms, in all which he main-
tained that hurricanes were progressive vorti-
cose whirlwinds. His views were for a long
time controverted in America by Espy and
Hare. Sir William Reid published his first
papers on hurricanes in 1838, and subsequently
other works, in which he developed views simi-
lar to those of Mr. Redfield. Of the authors
previously mentioned, some laid a special stress
on the tangential, and others on the centripetal
movements of the winds ; at present, however,
following the studies of Redfield (18S9-'56),
Espy (1840-'57), Thorn (1845), Piddington
(1839-'54), Reid (1888-'50), Ferrel (1858), Mel-
drum (1851-'73), Mohn (1870), Reye (1872),
and many others, it is generally acknowledged
that the combination of both these movements
with an upward one is an essential feature of
every hurricane, so that the movement of the
surface wind is more correctly described as an
ascending spiral. Concerning the direction of
this movement, Dove, and independently of
him Redfield, concluded that in the storms of
Europe and the American coast the winds move
<!-- p. 81 -->
in a circuit abont the storm centre, contrary
to the direction of the motion of the hands of
a watch when the latter is laid on the ground
with its face upward. Furthermore, Dove
made the important remark that in the hurri-
canes of the southern hemisphere the air re-
volves in an opposite direction ; this general-
ization, announced by him, apparently with
some limitations, was by the labors of Reid
(1838) converted into an accepted law. The
law of the rotation of winds around the storm
centre is considered to be of the highest im-
portance in its practical bearings on the in-
terests of navigation, and may be stated in
other words as follows : If in the northern (or
southern) hemisphere you stand with the cen-
tre of the hurricane on your left (or right)
hand, the wind will be on your back. The
determining cause of this law of rotation, and
of the distinction between the hurricanes of
the northern and southern hemispheres, was
imperfectly understood by early writers, as
Taylor and Herschel, but was rigidly demon-
strated in a remarkable mathematical memoir
by Ferrel in 1858, who showed that the rota-
tion of the earth on its axis affects the direc-
tion not merely of north and south winds, but
of every wind, in such a manner that in the
northern hemisphere winds tend as they move
forward to deflect to the right hand, but in the
southern hemisphere to the left hand. This ten-
dency, which is known either as Poisson's or
as Ferrers law, is in large storms sufficient
to determine the direction of rotation, while in
storms of comparatively small dimensions acci-
dental circumstances may conspire to annul or
even reverse the direction of rotation. Thus
we are provided with the means of harmoni-
zing, at least in great part, the views of Hare,
Espy, and others, with those of Redfleld and
Reid. There are unfortunately but few actual
measurements of the velocity of the stronger
winds that occur within the limits of a hurri-
cane. In general it appears that the velocity
increases as we proceed from the outer limits
toward the centre of the storm, but suddenly
diminishes to feeble irregular winds and calms
within the central space. From the observed
destructive force of some gusts it has also been
contended that a velocity of 10 m. per min-
ute must have been momentarily attained, but
such computations are not very satisfactory.
The highest hurricane winds that have ever
been actually observed have on the British
coast attained a velocity of 130 m. per hour;
in the comparatively small hurricane of August,
1871, the observers in Florida of the United
States army signal corps recorded a velocity
of 85 m. per hour ; all these winds of course
were interspersed with gusts of great violence.
The diameter of the region of calms varies
from 30 m. to a much smaller size, and prob-
ably even to nothing. It would seem that in
some hurricanes, as frequently in the smaller
tornadoes on land, the so-called axis of the
storm rises temporarily above the surface of
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the earth. The central space in general, -ac-
cording to Redfleld, increases in diameter as
the storm moves away from the equator north-
ward or southward. A heavy rainfall extend-
ing far beyond the region of most violent winds
attends all hurricanes. The quantity of water
that falls during the prevalence of these storms
forms a large percentage of the total annual
rainfall over the hurricane regions, and in this
respect they perform an important service to
mankind. At Mauritius in the Indian ocean a
single storm has been known to be attended by
a rainfall of more than 10 inches. The area of
cloud and rain is especially extended on the
N. and E. quadrant of the storms of the North
Atlantic ; it is sometimes much contracted,
though rarely wanting, on the west side of the
hurricanes of both the northern and southern
hemispheres. The movements of the clouds
have been carefully observed, especially by
Redfleld (1832-'42) and Ley (1866-'70), and
the result is well expressed by Reye (1872):
" While on the earth's surface the storm wind
in spiral curves gradually flows inward, it
forces the flying storm clouds in spiral curves
outward, and removes them away from the
axis of the cyclone." This generalization was
fully explained from a theoretical mechanical
point of view by Ferrel, and was shown by
him to be a consequence of the rising or np-
ward movement of the masses of air that are
drawn into the whirlwind. The clouds then
must move in spirals opposed to the move-
ments of the lower winds. Redfleld estimates
the angle between the winds below and the
clouds above to be about 22'5. The baro-
metric disturbance is one of the most remarka-
ble features of a hurricane. The nearer one
approaches the centre, the lower is the baro-
metric pressure, and at the centre the depres-
sion is frequently two or three inches. The
first notice of an approaching hurricane, when
it is yet 100 to 400 m. distant, is usually given
by the steady fall of the barometer; as we
approach the centre the fall is more rapid.
The law by which the pressure diminishes, as
well as the variations from it, may be illus-
trated by two examples, the first showing a
very regular depression, the second giving a
great and rapidly increasing rate of fall. The
first example is Redfield's Cuba hurricane of
Oct. 4-7, 1844, for which we have the follow-
ing pressures : at the centre, 27'7 in. ; at 100
m. distance, 28-0 in. ; at 200 m. 29-0 in. ; at
300 m., 29-5 in. ; at 400 m., 29-8 in. The
second example is from Buchan (1871), and re-
lates to the Bahama hurricane of October,
1866. On the evening of the 1st of October
we have the following pressures : at the cen-
tre, 27'7 in. ; at 15 m. distance, or the radius
of the central column, 27'8 in. ; at 300 m.,
29-7 in. ; at 500 m., 29-8 in. ; and at 800 m.,
30-0 in. The ratio at which at a fixed station
the barometer falls on the approach of a hurri-
cane differs from the preceding by reason of
the progressive motion of the storm toward or
<!-- p. 82 -->
from the station ; on board a vessel, the baro-
metric fall is further complicated by the move-
ment of the observer. The best idea of the
barometric disturbance is given by a chart of
synchronous observations on which isobaro-
metric lines are drawn, these isobars will
be found to be crowded together on one side
(generally the advancing half) of the storm
more than on the other, and to enclose a small
oval or circular region of lowest pressure, al-
most if not quite identical with that of the
area of calms, though sometimes apparently in
advance of it. In a general way it may be
stated that the velocity of the wind increases
with the crowding of the isobarometric lines.
The exact relation between the two is quite
complicated, and may be deduced from the
formulas of the above mentioned treatise by
Ferrel, combined with the considerations in-
troduced by Peslin in 1867 and Reye in 1872.
It is evident that the law above given for the
rotation of the wind may be converted into a
rule for finding the centre of calms, which will
also hold good for finding the centre of lowest
barometer ; this latter is generally spoken of
as the storm centre or axis. Buys-Ballot has
expressed this generalization in the form known
as Buys-Ballot's rule, viz. : in the northern
hemisphere stand with your back to the wind,
and the lowest pressure will be on your left
hand and somewhat in front thereof; a rule
that applies especially to, and was apparently
suggested by, the behavior of the winds of
hurricanes and similar storms. The dimen-
sions of hurricanes generally increase from day
to day until the dissipation of the entire storm,
while the intensity of the winds is believed on
the average to diminish somewhat ; this will
however depend upon the atmospheric condi-
tions favoring the development or the deca-
dence of the disturbance. Given a proper sup-
ply of warm moist air, and it can be shown that
the central depression with the attendant wind
and rain must steadily increase up to a certain
limit. These favorable circumstances are gen-
erally found combined in a remarkable degree
in the region of the Gulf stream, the Kuro Siwo,
and similar ocean currents; accordingly, on
reaching these the area of cloud and rain ex-
pands, as also do the diameters of the isobaric
curves. The dimensions of the central depres-
sions vary quite irregularly, hut appear on the
average to increase as the storm continues;
while the actual height of the barometer at
the centre changes much less, but is believed
to diminish gradually so long as the intensity
of the wind increases. If a curve, enclosing
a region in which the winds attain the force
ordinarily described as a moderate gale, be as-
sumed as the limit of the storm, it will be
found that in the earliest stages of the hurri-
cane it has a diameter of from 50 to 200 m.,
which increases in the course of 5 or 10 days
to from 400 to 1,200 m. ; thus a disturbance
that may have been originally designated as
small or local, increases so as to involve half
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the surface of the North Atlantic ocean. The
track of the centre of the hurricane is a fair
indication of the progress of the storm over
the earth, and much labor has been bestowed
upon such collations of logs of vessels as would
elucidate this important branch of the subject.
But notwithstanding the labor expended, there
have as yet been very few hurricanes traced
back to what appears to be very near their
origin, and in not a single instance has unmis-
takable evidence of their origin been adduced.
The general position of hurricane tracks in the
earlier parts of their course therefore remains
obscure, although the immense accumulation
of material by the labors of the various na-
tional government weather bureaus is rapidly
dissolving our ignorance on this point. So far
as the known hurricane tracks are concerned,
it may be stated that in the North Atlantic
ocean each uniformly appears to be a segment
of a parabola having its axis coincident with
the parallels of 25 to 35 N. latitude, and the
longitudes of whose apices fall between the
meridians 40 and 100 west of Greenwich,
but mostly between 65 and 85. At the
southern extremity of the parabolic track, the
branch passes either to the north of or over the
Windward islands, while the northern branch
passes to the south of or over Newfoundland.
In a few cases the first portion of the track
has been traced southeastward nearly to the
coast of Senegambia, and the latter portion
of the track northeastward to the ocean be-
tween Iceland and Scotland ; some tracks that
curve northeastward before reaching Ion. 40
may even strike England or France. The hur-
ricanes of the southern hemisphere describe
similar parabolic tracks, which lie at a corre-
sponding distance south of the equatorial belt
of calms, and are symmetrically disposed with
reference thereto. Very few have been traced
in the South Atlantic ocean, but in the south-
ern Indian ocean the majority of the hurricanes
pass from Sumatra and Java sonthwestward
to within 500 m. of Madagascar, then south-
ward and southeastward. In general, Mohn
(1870) and Reye (1872) state that all cyclones
(of which hurricanes are the grandest examples)
move in the direction in which for the longest
time the warmest and moistest air has been
rising, and producing the heaviest cloud and
rainfall. If we combine with this law the
tendency of the whirlwind as a whole to move
away from the equator, as proved by Ferrel,
it seems to the writer that we have a very
close approximation to the full statement of
the reason for the parabolic form of their orbits.
The rate of progression of the West Indian
storm centres varies from 50 m. per hour in a
few cases to 10 or 15 as the other extreme ;
that of the storms of the southern Indian
ocean varies from 1 to 20 m. The rate in gen-
eral in the North Atlantic increases with the
growth and northward movement of the hurri-
cane, and, though sometimes quite variable, is
not so much so as in the case of the similar
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storms of the Indian ocean. The rate of
progress must be carefully distinguished from
the velocity of the wind, as the latter has no
known relation to and far exceeds the former.
The waves and swells produced by the hur-
ricane winds are a most important feature;
these waves are the largest and most formi-
dable known to the mariner. They form with
greatest regularity at points directly in advance
of the approaching storm centre ; at other
points they form a confused mass of crossed
sea ; in the neighborhood of the land the con-
fusion is increased by the waves reflected from
the shores. Such is the equality of the con-
test of opposing waves, that near the central
region these sometimes lose their progressive
movement and become stationary pyramidal
waves, simply rising and falling. The smaller
waves that are propagated in all directions
from the region of severest winds, degenerate
into long gentle swells that outrun the storm
in its progress, and announce its presence sev-
eral hours or a day in advance of its arrival.
Besides these waves, it is believed that the
extended region of low barometer allows the
formation of a peculiar " cyclone wave," which
is similar to the tidal wave of mid-ocean. The
cyclone wave is coextensive with the area of
low barometer; it is highest at the central
lowest pressure, where its elevation above the
ordinary sea level should be a foot or more for
each inch of barometric depression. From
the earliest times the months from July to Oc-
tober have been known in the West Indies as
the " hurricane season." A table published by
Poey in 1855 gives the distribution by months
of 355 hurricanes recorded on the Atlantic
between 1493 and 1855. According to this
work, there are recorded in this period in all
in January 5, February 7, March 11, April 6,
May 5, June 10, July 42, August 96, Septem-
ber 80, October 69, November 17, December
1 ; bnt the annual period is probably not very
correctly shown by this list, because of the
imperfections of the earlier records. More
recently Poey has revised his list and added
many later hurricanes, and has published in
the Paris Comptet Rendv* for Nov. 24, 1873,
and Jan. 5, 1874, the results of a comparison
between hurricanes and the frequency of solar
spots. His results seem to remarkably confirm
those of Meldrum, who had previously stud-
ied the hurricanes of the Indian ocean from
the same point of view. Poey states that in
the majority of cases the years of the great-
est number of hurricanes are also the years
of the greatest sun-spot frequency. The ex-
tensive researches of Koppen (1873) have
shown that the amount of heat received from
the sun varies annually with the sun spots,
whence we infer that the variations in solar
heat produce a similar variation in the terres-
trial evaporation, and an increased tendency
to the formation of hurricanes. The actual
number of hurricanes visiting any limited re-
gion is of course very small. Since the year
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1700 the centres of about 25 have been known
to pass quite near the coast of Georgia and
South Carolina, which is by far the most fre-
quently visited portion of the United States.
Nearly all those of the Indian ocean pass near
to the islands of Mauritius, Rodriguez, &c.
Concerning the origin and cause of the hurri-
canes of the Atlantic ocean comparatively
little is positively known, but it seems by
analogy that they may originate wherever
the lower stratum of warm moist air is rapidly
elevated above the sea level, whether (1) by
being pushed up over an elevated plateau or
mountain chain, or (2) by the under-running
of a layer of cold dry air, or (3) by the conflict
of two opposed and nearly balanced currents
of warm moist air. In numerous instances one
or the other of these cases seems to have oc-
curred ; and as these, combined with (4) the
radiation of heat into space, are the prevailing
causes that determine the origin and growth
of storms in general, there seerns no reason
in the case of hurricanes to appeal to more
forced theories. The immense mechanical
power stored up in the heat and vapor of
moist air has been abundantly demonstrated
by Espy, Peslin, and Reye. Whenever, by the
action of either of the four causes just men-
tioned, the process of condensation of vapor
into cloud, rain, or snow begins, there at once
occurs an influx of air from all sides, and from
below as well as from above, to fill up the par-
tial vacuum thus created; this influx toward
a central region is immediately followed, as
shown by Ferrel, by the formation of a whirl
whose subsequent development is entirely de-
pendent on the supply of moist air. The hur-
ricanes of the southern Indian ocean are thus
generated in the region of calms between the
N. W. monsoons and the S. E. trade winds of
that ocean. Similarly hurricanes have been
known to originate in the neighborhood of
Florida when a cold north wind has swept
under the warm moist air of the gulf and
ocean. Another class originates in a similar
manner in the western portion of the gulf of
Mexico after a Texas norther has prevailed for
a few days. A few begin in the interior qf
Texas when a high barometric pressure on the
gulf, or a low pressure in the western territo-
ries, forces or draws the air of the gulf up over
the plains of Texas. But by far the larger class
of the Atlantic hurricanes, including those of
greatest extent and violence, appear to origi-
nate between the Windward islands and the
African coast, and generally quite near to the
latter; apparently these begin with heavy rains
in the region of calms, such as are accompa-
nied on the African mainland by the peculiar
harmattan and tornadoes of that coast, which
may be, so far as we know, either the conse-
quence or the determining cause of the heavy
rains. The storms that originate here may
either move as far west as the American coast
before recurving toward Iceland and Norway,
or may describe a much shorter route, and
<!-- p. 84 -->
finally arrive at Great Britain, or possibly at
Portugal. Rules for the Avoidance of Hurri-
canes at Sea. The researches of Bedfield first
led to the suggestion of certain rules for the
direction of navigators. The erroneous theo-
ries of the purely circular and of the radial
movement of the hurricane winds early led
their respective advocates to the suggestion of
rules for avoiding the dangers of these storms,
which later and more correct views as to the
spiral or vorticose movement have somewhat
modified. It may in general be said that a
vessel's safety can only be assured by the pos-
session of a reliable barometer, either aneroid
or mercurial ; and having this, the navigator
should proceed thus : First, as soon as the
ocean swell, the falling barometer, the clouds,
and the rain announce that a hurricane exists,
though it may be 500 m. from him, he should
at once lay to long enough to ascertain how
rapidly the barometer is falling and the wind
increasing, and in which direction the course
of the wind is changing. If the wind increases
without materially changing its direction, the
storm centre is advancing directly toward him ;
if, however, the wind veers or backs, the di-
rection in which the centre is at any moment
may be approximately determined by the rule
above given, viz. : " in the northern or south-
ern hemisphere, stand with your back to the
wind, and the centre will be on your left or
right hand, and in front." The mariner may
then by due consideration of his own desired
course, and the customary track of hurricanes
in that part of the ocean, so alter his course as
to avoid the storm centre on the one hand and
a lee shore on the other, and may indeed, if
there be plenty of sea room, take advantage
of the strong wind to hasten his own course.
Further details on this subject are given in all
works on navigation. It is very rare that a
navigator cannot by cautious manoeuvring thus
avoid the dangerous portions of a hurricane;
on the other hand, it is said that many ocean
steamers, relying upon the power of their en-
gines, the strength of their build, and their
great speed, deliberately plough through the
heart of the severest storms rather than incur
a possible delay of a few hours in order to
avoid them. The hurricane of August, 1873,
which destroyed over 1,000 vessels on our At-
lantic coast, and those of October, 1873, and
February, 1874, afforded numerous instances
of such bravado.