The Columbia herald. [volume] (Columbia, Tenn.) 1850-1873, 1871-09-15
TORNADOES.

4
So In the family way.
| TORNADOES.
Tn cir Progress and Appearance fl
the Southern Stntes-Rcmarkabl
Phenomena.
(From the New York Evening Post.]
In the August number of the Amert
can Journal of Sciepce and Arts
Professor Hampton 8. Whitfield, o
the University Of Alabama, has very
Interesting article on tOrnadoes In tht
Southern States, from which we take
the following extracts:
"The tornado Is a storm which has
two distinct movements, the one pro-
gressive along the surface Of the earth,
the other gyratory, like that OF a toI
spinning on its axis. 1t whirls as II
goes, and Its force is 80 great that nc
| structure Of wood, brick or stone can
stand before 1t. Even the solid hills
quake and the ground trembles
beneath its march. Fortunately, its
track in this country Is very narrow.
/ have not yet found traces Of any one
exceeding two hundred yards in
breadth.
"The progress of Tornadoes is
always, in the Southern States, from
a point south of west to a point north
of east, and, although sometimes va
ried by prevailing winds, this direction
is characteristic, and due, as shall
show, to the rotation of the earth on
Its axis. The gyration Is always from
right to left, and this also, as Is known,
Is an effect of the earth's rotation.
"On the south side of the tornado,
then, the greatest power Is exhibited,
for here the gyratiOn is forward or
coincident with the translation, while
on the north side, the gyratory motion
being contrary to the progression, the
effect is least. At the front and rear,
where the gyration crosses the path,
the effect must be the same.
zone Of the most remarkable ac-
commandments Of the tornado is the
black column or spout, extending from
the cloud down to the surface. Itpre-
cisely resembles column Of black
smoke, such as pours from the pipes Of
q steamer burning pine wood; 1t is,
in fact, condensed vapor or cloud, in
tepsified In blackness by the dust and
rubbish carried up from the ground.
The tornado is she'll or hollow cyl
inder of air, and all its energy lies In
its rotating rim, which is powerfully
compressed by two antagonistic forces,
centrifugal and centripetal. The rapid
whirl draws the air from the center
toward the circumference, where it is
met and opposed by the inrushing
winds. There is, consequently rare
faction, q great reduction of tempera-
ture by expansion and condensation Of
vapor within the shell.
1.-THE spout does not hug the earth
continuously, but rebounds or rico
chefs along the uneven surface, often
skipping the valleys, but generally
desolating the hills. 1t is disposed,
however, 1T every recurrence to strike
at the same points. 1t is not an es-
tablished fact, but Is commonly be-
Iieyed, and with some reason, that
the tornado does, In the course of
wears, return along its beaten path,
and that IL is unsafe to build where
one has ever passed.
"Such an opportunity as fell to my
lot of witnessing the formation and
course of tornado Is rarely enjoyed
and the phenomena observed on that
occasion are of great value In illustra.
ting the origin of these whirlwinds.
On the 10th of April, 1867, at ten
o'clock A. NJ, was approaching Tus-
caloosa, on the Elyton road, the gen.
eral direction being east and west.
The weather was hot and oppressive,
while perfect came prevailed both at
the surface and In the upper regions,
for the leaves were not stirred upon
the trees, and the heavens were cover
ed with fragmentary clouds, perfect
ly at rest. Occasional large drops OF
rain fell, and there was now and then
lightning. The atmosphere was evil
IDENTIFY surcharged with vapor and In q
condition OF great electrical excite
ment At the distance Of three and
q half miles from town, an elevated
ridge, over which the road passed,
afforded an extended view, and 1 saw
a mass Of black cloud, detached and
hanging over the western horizon.
1t appeared nearly circular In shape,
with the exception of a slight angular
projection, like an inverted cone, at Its
lower edge.
"The most remarkable fact disclos-
ed by the phenomena of this storm is
the inherent power Of progression
which It unQuestionably possessed.
After the gyration was established 1t
began at once to travel eastward, not
driven by any wind, but plowing its
own way through the tranquil atmos-
phere with tremendous speed. Here
Is presented q problem, which, so far
as L know, has not heretofore been
propounded. Its solution Is important
to the science of meteorOlOgy. The
fact that tornadoes invariably move
from the southwest to the northeast
is we'll established, as also the fact
that, by an impulse acquired from the
earth's rotation on its axis, they gy.
rate from north by west to south.
This backward gyration is thus ex-
planned: All parallels OF latitude
decrease in diameter, and therefore in
| circumference, rs we go toward the
poles Of the earth. AS they all revolve
In twenty-four hours, it follows that
every one, approaching the pole on
either side of the equator, moves
around more slowly than the one
preceding it. Therefore, a current
moving southwark, to the vortex of a
tornado in the northern hemisphere,
finds that vortex rotating eastward
with superior velocity, and is left
behind, or projected to the west, while,
for the same reason, a current blowing
porthward to the vortex finds It's rota-
ton with inferior velocity, and pre-
serving its own easterly momentum,
Is hurled forward or projected to the
east. Thus the south half of the rim
being impelled eastward, and the
north half westward, the backward OF
left-handed gyration is fixed and
maintained. Just the reverse is true
in the southern hemisphere of the
earth, while on the equator the gyra'
ton would be free to take either di-
rection.
"The process of formation is easily
comprehended. In an atmosphere
supersaturated and unduly heated a
the surface, let calm prevail Ovel
many miles of territory. The equili
brium is powerfully disturbed. A
great volume of elevated air begins t.