Savannah morning news. [volume] (Savannah) 1868-1887, 1885-08-11
CYCLONES AND ToRNADoEs.
An Interesting Account of What They
Are and How They Differ.

which our city has just been visited, and
the somewhat misty ideas generally en-
tertained concerning storms of this char
acter, it may be OF interest to present to
the readers OF the Ledger some OF the
latest conclusions of science concerning
such storms. The words cyclone and tor
nado, for instance, are frequently used
INTERCHANGEABLE, though they refer to
quite different wind phenomena. Yet
meteorologists are coming TO the conclu-
sion that all powerful wind storms belong
to either the cyclone or the tornado class,
and 1t may be well to point out their dis
I tinctions.
Every wind indicates that In some place
the atmosphere has become thin OF. rare.
The heavier air surrounding at once
flows from all sides toward this place, so
as TO restore the equilibrium of density.
why the air becomes rare at special
points Is question too large to be here
considered. 1t is mainly due 10 the
effects of solar heat and radiation. Such
rarlned spaces may occur in long lines,
as along seacOast where there is a
difference in rapGity of heating and cool
| ing between land and water. These pro-
duce land and sea breezes which have
none OF the cyclonic conditions. But
such breeZes are mili in character, and
most if not all powerful storms are cy-
clOnic.
In cyclone the rarefaction Of air oc-
ours IN limited space, not in a long line,
and the movement of the surrounding air
Is inward from every side towards this
centre. Were the earth standing still
there would be straight lines of wind
| blowing in from every direction TO each
rarehed centre, and their length and vigOr
would depend on the degree Of raretactiOn
of astt~ FN,Esr
ton of the earth on its axis affects the
movement of the winds and defects them
from their straight lines Of motion. They
| still approach the centre, but in long
curves instead ofin direct line. The final
result is a great clrcling whirl in the air,
a huge atmospheric spiral, each
line OF which gradually curves in toward
the partial vacuum in the centre of the
Whlrl, and as the winds approach the
centre their speed increases until, whore
the rarefaction is extreme, they become
| destructive storms. But in the centre Of
the whirl a calm prevails. The opposing
air currents check each others move
ments or force each other into an upward
flow. This up draught of air from the
centre of the whir has its effect in a vi0-
| lent rainstorm. The warm and moist air
drawn upward as through great chin
ney into the upper atmosphere, and its
| moisture there rapidly condensed by q
sudden chilling, gives rise to a rainfall Of
unusual violence.
1t may further be remarked that the
centre of a cyclone is never fixed, and
sometimes travels with considerable
| rapidity. The causes which produce the
rarefaction are apparently travelling
/ causes. In consequence, in all places
| over which the central line of cyclone
! passes there is first a wind in one direc-
| ton, which steadily increases in violence.
! But as the centre Of the cyclone APP
/ proaches the wind lulls and a calm sue
/ ceeds, attended by violent dOwnpOur OF
| rain. Then there springs up wind in
the opposite direction, rapidly increasing
in violence, while the rain ceases. Finally
the wind slowly lulls as the cyclone moves
| onward to new localities.
This change in the direction of the wind
/ is necessary from the fact that the winds
all curve inward toward the rarified cen
| ire, and must therefore move in opposite
| directions on opposite sides of this centre
These discoveries in cyclonic phenomena
have been of the utmost Importance to
| navigation, since an experienced captain
knows from the direction of the wind in a
severe storm just how TO steer his ship to
| escape its EXTREMIST violence, he makes
all speed from the locality Of the centre
of the cyclone.
A tornado is also a cyclonic or spiral
from The regular cyclone. The latter COW
ers hundreds or perhaps thousands OF
miles between its extreme limits. The
limits of the tornado are few hundred
yards. 1t is, in fact, a local eddy in the
air, and has marked points of similarity
TO eddies in the water. Water eddies are
due to two causes. One of these is a
meeting of two opposite currents. The
opposing currents check each others on
ward flow. and cause spiral, down-set
ting whirl, with q water vacuum or
empty space in its centre, into which
the air must be strongly sucked
The other cause of water eddes is an
under water vacuum. The writer OBJ
served a marked instance of this on the
day after the great storm at one of the
water gates leading TO the turbines at
Paramount. The water was being rapidly
sucked from beneath into the turbine
shoot, producing partial vacuum, which
eXerted powerful down draught on the
surface waters. In consequence. eddies
formed on the outer edge of the dis
turhance, moved inward with increasing
width and vigor, yielding a roaring sound
Tesem bling that OF the tornado in minia-
ture, and finally disappearing at the gate,
TO be succeeded by ever new ones.
The aerial eddies known as tornadOes |
seem to be cnunterparts of these water
eddies, or rather Of the more extensive
e0QleS kbOWu as WulTlpOOis. a tornado |
is maelstrOm in the air, an atmospheric |
whirlpool directed upward as a water |
whirlpool is directed downward. 1t has, |
perhaps, two separate causes, similar TO |
those Just described-the meeting of op- |
posing currents and the up draught |
caused by partial vacuum in the upper |
air.
This. however, is by no means certain, |
since the real causes of tornadoes are by |
no means known. Yet we frequently see |
a minute representation Of the arial eddy |
in the streets, which travel onward with |
more or less rapidlty, sucking up dust |
and sticks in their course, precisely as
the tornado sucks up trees, roofs and |
other yielding objects. There seems some !
reason TO believe that the recent tornado
was due to the same cause which pro-
duces these small whhls-namely. the
meeting of two opposing winds. Three
tornadOes are reported from this storm
one in Bucks county, and one in Della
ware and Maryland, in addition TO the
Philadelphia one. lfwind opposition was
their cause, there must have been an eX-
tended line OF powerful opposed currents.
Another explanation offered for lorna
does is that OF partial vacuum in the
upper air, causing q vigorous vertical
wind, which moves upward with a spiral
whfrl Whether either of these theories
i. H..