Cleveland morning leader. [volume] (Cleveland [Ohio]) 1854-1865, 1860-07-25
The Grenf Tornndoes.

a professor in the Miami University writes
as follows in the Cincinnati Gazette of the
great tornadoes;
A few facts in reference to that class OF tor
nadoes which have been so prevalent this
season, may prove interesting to your numer-
rous readers. They are the results of care
full observations for the past fifteen years.
The heavy storms in the Mississippi valley,
and indeed, of the Atlantic coast, are found
in the great atmospheric current from the
southwest. This current is doubtless the at
mosphere from the tropics on its way to the
north pole, in exchange for the cold air Of
that region, which, in our north and north
west winds, passes back to the equator.
4 knowledge of this great system of at
mospheric interchange Is necessary for an IN
derstanding- of these violent disturbances
which prevail in this and in lower latitudes
pass over, as not pertinent to the purpose
in hand, all the notifications to which these
currents are subjected at certain ATTITUDES, by
the action Of causes not yet understood.
Of the existence of these currents there can
be no doubt Their interruptions, their con-
hicts, the sliding, now of this, now of that,
over the other, all these are questions which,
however important, need not be introduced
here.
The great fact is this: OUr heagy rams gen.
erally are found IN the track Of this southwest
current; and olT toraadoss, 1gitk scarcely an
exception, are found imJedded in IL, and moriag
along lgith it, The reason of this is obvious.
It is a warm and moist current, and, when
cooled sufficiently, will give out that mois-
ture.
One more fact in reference to this current:
As it sweeps towards the northeast, it curves
gradually more and more to the east. On a
large scale this IS due to the motion of the
Garth on its axis, but in our local storms TO
the pressure on their northern borders made
by the northwest current. This accounts for
another fact: that our tOrnadocs, when
traced a considerable distance, move in a
curve line bending towards the south; and
sometimes near the end of their course the
direction is south of east. The great lorna
do Of January, 1854, so destructive at Bran
/ don, Ohio, had a direction at that place N.
! "a degrees E. In western Pennsylvania
/ where it spent its force, the direction was a
little south of east. The southwest current
in which it was embedded, was traced by the
writer from Arkansas, through Southern IL
lAubAs9 4AuLttL1 eiLA N'lllb AlllU W est
ern Pennsylvania All along this track it
/ was so warm, though in January as TO re-
/ quire no fires; while at the same time in
/ Iowa, Northern Illinois and Indiana the
1 thermometer was either below or but little
/ above zero. This leads me to notice another
{ fact, very significant in explaining these vio-
/ lent disturbances. These storms are 6ordcred
/ on the north by cold lcind from the north
1oest. This cold wind presses upon the warm
/ current from the southwest, gradually defects
/ it eastward, mingles with it, and being the
/ heavier, finally slides under it. All these
storms, as every observer knows, are followed
| by cool northwest winds. Such was the case
after the Cincinnati Tornado of May 81:
and for eight days subsequent to the almost
unparalleled violence exhibited at Camanchc.
/ northwest winds, ,uncomfortaJly cold prevailed
! throughout this region.
The tempest does not make the northwest
wind which so generally ly succeeds it, nor has it
much influence in cooling it. The evapora-
/ ton after a shower does, of course, cool the
/ air somewhat at the surface of the earth; but
/ ths condensation which made the shower also
/ gave outheat. The northwest wind and the
moist and warm southwest, maintain in this
/ valley, owing to the topography of the coun-
/ try, peculiar and very close relations. They
come very sharply into contact-the one very
cool, from its frozen home-the other very
warm and moist, from the Gulf or the Pa
cifc. All the conditions necessary to pro-
duce violent commOtions in the atmosphere
are present. and the result is what every me-
teOrologist, knowing these conditions, would
expect
The writer does not mean to attribute these
/ tornadoes, some of which are almost as vio-
lent rs a blast from q huge cannon, to the
meeting, merely, of the two currents referred
to. l mention them as facts, and very i'm
portant ones; but the full explanation of
these strange phenomena meteorological sci
ence cannot yet give.
The writer does not intend to enter into
any labored description of the various and
combined motions Of the wind in a tornado.
The motion is substantially made up of
three elements: 1st the acensional velocity;
I'd, the velocity of rotation, and Sd, the pro-
gression.
The velocity of rotation is usually the
greatest, and to it the destructive effects seem
mainly due. From thirty to fifty miles per
hour is the usual rate Of progress, while the
rotation may vastly exceed it.
From the same calculations upon the force
of the wind in the Brandon storm, the rota-
ton could not have been less than I72 miles
per hour. At the rate of l72 miles an hour
the velocity is one-ffth that of a cannon
ball
The Cincinnati storm was distinguished for
its breadth, and especially for a high pro-
gressive velocity. In this latter respect it
stands pre-eminent. The progress was so
rapid as to obscure the rotation, and to render
it difficult in some parts TO detect it at ALL
From the cursory examination which the
writer has not yet been able to give, it seems
probable that if there was a general whirl
reaching across the track, it was, at the sur
face of the earth, broken up into several sub
ordinate whirls, at one time acting separately,
again commingling either in conflict or to
unite their forces in more deadly energy
This irregularity is just what any one, ac.
quainted with the nature of elastic fluids
would expect under the circumstances.
No tornado of considerable breadth could
maintain a regular rotation along a surface SC
! broken as the valley of the Ohio. The case
if rs supposed, is not entirely singular CleaI
. evidence was obtained at one place in the
Brandon tornado, that two whirls co-existed
side by side. This was supposed at the time
= to have been due to the fact that about one.
third Of the breadth of the storm was labor.
ing at that point in dense forest, while the
rest was sweeping over cleared ground.
Along the centre Of tie path of a tornado
the barometer stands lower than the average