The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1885-08-15
CYCLONES AND TORNADOES.
sysant They Are and How They Differ-The
Conclusions of Science.

storms OF THIS character, 1t may De of interest to
present to the readers of the Ledger some of the
latest conclusions of science Concerning such
storms The words cyclone and tornado, for
instance. are frequently used INTERCHANGEABLE,
though they refer to quite different wind
phenomena. Yet meteorologists are coming to
tAs conclusion that all powerful wind storms
eeiong to either the cyclone or the tornado class,
ara 1t may be well to point out their dis
tinetions.
livery wind indicates that in some place the
atmosphere has become thin or the heav-
lsf air surrounding at once flows from all sides
toward this space so as to restore the equb-
TlHm of density. Why the air becomes rare at
special points is a question too large to be here
considered. 1t is mainly due to the effects OF
solar heat and radiation. Such rarifed spaces
fnsy occur in long lines. as along seacoast
where there is difference IN rapldIty OF heating
and cooling between land and water. These
produce land and sea breeZes which have none of
the cyclone conditions. But such breezes are
xnsld in character, and most If not all powerful
storms cyclOnic
In q cyclone the rarefaction OF the air occurs
in limited space, not in a long lire, and the
movement of the surrounding air is inward from
eTery side toward the center Were the earth
Standing still there would he strai GIT lines Of
xlDd blowing in from every direction to each
Tarcfied center. and their length and vigor would
depend the degree of rarefaction OF the air in
this center. But the rotation of the earth On its
2xS affects the movement Of the winds and de-
fleets thom from their straight lines of motion.
They still approach the center but in long
curves instead of in n direct line. The final re-
salt is q great circling wh;rl in the air, a huge
atmospheric spiral, each line of which gradually
curves in toward the partial vacuum in the cen
tfr Of the whirl, and as the winds approach the
cEnter their Speed increases until where the
Farefaction is extreme they become destructive
storms. But in the center of the whirl calm
prevails. The opposing air currents cheek each
others movements or force each other into an
upward flow. This up draft of air from the
Center Of the whirl has its effect in a violent
rain storm. The warm and moist air. drawn
upwards as through a great chimney into the
upper atmosphere. and its moisture there rap
idly condensed by sudden chilling gives rise TO
q rainfall Of unusual violence.
1t may further be remarked that the center of
cyclone is never fixed and sometimes travels
with considerable rapidity. The causes which
produce the rarefaction apparently travel
ing causes. In consequence in all places
which the central line of a cyclone passes there
Is first wind in direction, which steadily
increases IN violence. But as the center of the
cyclone approaches, the wind lullS and a calm
succeeds, attended by a violent downpour Of
rain. Then there springs up wind III the oppo-
site direction, rapidly increasing in violence
while the rain ceases. Finally, the wind slowly
iGLls, as the cyclone moves onward to new local
tiles.
This change in the direction of the wind is
necessary. from the fact that the winds all curve
inward toward the rarefied center, and must
sides Of this center These discoveries in cycion-
lie phenomena have been of the utmost import
aisee 20 navigation, since an experienced captain
knows from the direction OF the wind in a severe
storm just how to steer his ship esca Do its eX-
tremest violence, lie makes all speed from the
locality Of the center Of the cyclone.
A tornado ia also cyc'onc or spiral wind, but
differs in cause and character from the regular
cyclone. The latter covers hundreds or perhaps
thousands of miles between jts extreme limits.
The limits of the tornado few hundred
yards. 1t is. in fact 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 cur
rents The opposing currents check each others
onward flow and cause a spiral down setting
w0irl, with water vacuum empty space in
Its center into which the air must be strongly
sucked The other cause of water eddieS is an
under water vacuum The writer observed
marked instance of this on the day after the
great storm at one Of the water gates leading to
the turbines at Fairmount. The water was be-
ing rapidly sucked from beneath into the turbine
shoot, producing partial vacuum, which exert
oil q powerful down draugLt on the surface
waters. In consequence, eddies formed the
outer edge of the disturbance, moved inward
with increasing width and vigor, yielding a roar
ing sound escmbling that of the tornado in min
iature, and finally disappearing at the gate to
be succeeded by ever new ones
The aerial eddies known as tcrnadoes seem to
be counterparts OF these water eddies, or rather
pools tornado is nlalstrom 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 desciibed-the meeting Of opposing 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 minute repre-
Sentation of the aerial eddy in the wind whr!s in
StreotS which ard
less rupdlty, sucking up dust and sticks in their
course precisely as the tornado sucks up trees.
roofs aud other yielding objects. There seems
some reason to believe that the recent tornado
was due to the same cause which produces these
small whiris, namely the meeting Of two oppos-
ing winds. Three tornadoes are reported from
this storm. one III Bucks county and one in Della
ware and Maryland, in addition to the Phila-
dephia one. If wind opposition was their cause
there must have been extended line of power,
full opposed currents.
Another explanation offered for torradoes is
that OF partla! vacuum in the upper air, caus-
ing vigorous vertical wind. which moves No
ward with spiral whir Whether either of
these theories is trustworthy remains to be
proved. The analogy with water eddies would
lead to the idea that the two causes Of these
eddes might be similarly operative in aerial
whi-!s But an analogy is not proof. and much
further observation is needed ere the question
can be settled.
The clouds which accompany the tornado are
due to the rapid condensation of atmospheric
vapor II the line Of the whrlwind In this con-
necton it may be said that a photograph of a
Western tornado has recently been taken, which
differs radically in form from our recent tor
nado, as described by several observers The
photograph represents a huge bank of cumulus
clouds, with snake like column extending
from its lower surface to the earth, the
column gradually decreasing in size downward
In tins 1t resembles in form the waterspout
which is phenomenon of the same character
The Philadelphia tornado, on the contrary, is
described as an isolated cloud at first lying in a
horizontal direction, and finally assuming the
appearance Of vertical cone with its base
resting on the EARTH its apex upward In this
respect its form was opposite TO that of the tor
0ado, whirlwnd, or waterspout as usually de
scribed, though it resembed our ordinary dust
whiris There seems some reason to believe
then that tornadoes may arise from two causes
lone, revolving upward push of the air, due