New Ulm weekly review. [volume] (New Ulm, Minn.) 1878-1892, 1881-07-27
NATURE OF CYCLONES.
Disturbing CAUSES.

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NATURE OF CYCLONES.
DISTURBING CAUSES.
St. Paul Dispatch, il !
The terrible disaster at New Ulm
has awakened considerable inquiry as
to the nature and cause Of tho winds
that can work such terrible havoc.
Through the courtesy of o. S. M. Cone
signal service observer at st. Paul, the
Dispatch is enabled to present 70 its
readers considerable information re-
garding cyclones. Loonis' Treatise
on Meteorology says of these, winds
that the Irregularities of the earth's
surface, especially in hilly countries,
greatly modify the direction Of the
wind, SO that in great storms the
movements of the atmosphere seem
very complex. and anomalous. Over
the ocean these disturbing causes do
not exist, hence it is found that in
violent storms the movements of the
air are much moro regular and uniform
This motion of the wind has generally
been found to be in great circuits, spi.
rally inward toward the centre of the
storm. These storms prevail in the
neighborhoOd of: the West India Is-
lands, where they have not long been
known by the name of hurricanes. In
the West Indies, cyclones are most ex.
clusively confined to the months from
July. to October, being most common
in the month of August; also in the
China Sea and Bay of Bengal they are
most prevalent at about the same peri
cd Of the year. In the northern lati.
tudes they are most common from Jan
uary to March. There is no instance
on record of hurricane having been
encountered on the equator, nor of any
having crossed that line, although two
have been known to range at the same
time on the same meridian, but on op.
posite sides of the equator and ten or
twelve degrees apart. They originate
near the equatorial limit of Trade
winds, where these winds are irregu-
lar. In the Northern Hemisphere dur
ing the early part of their course with
in the region of Trade winds, cyclones
travel toward the west inclining some
what toward the north. Near latitude
20 degrees the motion from the equa.
tor is more decided, and in latitude Is
degrees their motion is about north
west. Near the parallel Of 30 degrees
their course is almost exactly north,
and soon they begin to veer to the
east, after which their motion is near
ly parallel with the coast OF the United
States. Several storms have been
traced from latitude 10 degrees, up to
latitude As or so degrees, and the path
| Of greatest violence bears some resem-
blance to a parabola, of which the
most westerly point lies near the paral-
lei Of 30 degrees. In the Southern
Hemisphere cyclones pursue similar
course. The air in cyclones has not
merely movement of translation, but
also a gyratory motion about the CEN
tire OF the storm. The motion of the
air is spirally inward as has been al.
ready shown in the storms of the Unit
ed States, but over the ocean the
Whlrlintf motion is usually more
decided than it is over land.
North of the equator this gyratory
motion is from left to right, OF in di
rection contrary to that of the hands
of watch. South of the equator the
motion is from left to right, or in the
same direction as that of the hands of
4 watch. Near the centre of the hur-
ricane there is generally greet fall of
rain, which is usually accompanied by
the most magnificent display of thun-
der and ii htning. The rate at which
cyclones travel is very variable. In
the West India cyclones the highest
rate which has been observed is forty
three miles an hour, and the least ten
miles per hour; the mean being twenty
six miles. In the Bay of Bengal the
| observed rate varies from two to
thirty-nine miles per hour, and in the
China Sea sea from seven to twenty.
four miles per hour. In the South In
dian Ocean the observed rate Varies
from one to ten miles per hour Some
cyclones travel so very slowly that
they may almost be considered station
airy. The direction and velocity of
winds are, however, entirely distinct
from those of the storms progress.
While the storm sometimes advances
at the rate of ten miles an hour the
velocity Of the wind may exceed 100
miles per. hour. Previous to the COM
mencement of a cyclone, the air is OBJ.
served to be close, sultry and oppres-
sive, and the wind is moderate or calm.
A fresh breeze sets in from the east,
and rises and falls with y moaning
sOund-after few hours it is succeed
ed by a lull, which may last for an
hour or more, after which the wind
changes to the west often with great
suddenness, and blows with increased
violence. During the passage of a
cyclone, the barometer oscillates in a
remarkable manner, rising and falling
rapidly, so that great barometric os.
cillation almost always announces the
approach of tempest. The most ra-
pid fall begins from three to six hours
before the passage of the centre. The
barometer is lowest hear the middle of
the storm area, and begins to rise be.
fore the strength of the cyclone is ov-
er. The fall of the barometer during
the passage of the cyclone varies ac-
cording to the intensity of the storm.
1t frequently amounts to one inch, and
has been known to exceed two inches.
The rise of the barometer after
the storm is usually as rapid as
was it's fall the approach of the
storm. The duration of the
storm at any place depends upon the
extent of the storm, and the velocity
with which it advances. If the storm
be 100 miles in diameter, and advances
but twenty miles per hour, it duration
1T any place cannot exceed five hours.