The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1881-05-28
TOrnadoes, HailgtOrms and WaterspOuts.

to occur, we are equally apt to suffer from
outbreaks of newspaper meteorology which
are sometimes almost as appalling as the
phenomena they attempt to explain. We
may be excused, therefore, for assuming
that the subject is enc of popular interest,
and for compiling some of the moro signi-
ficant and certain results of observation
and scientific deduction with regard to the
origin, conditions and behaviour of this
class of storms.
\ favorable opportunity for doing this
is furnished by the recent publication of
the 10th appendix to the report of the
Superintendent of the United States Coast
and Geodetic Survey, for 1878, contain
ing the second part of Mr. William Fer
rel's researches on cyclones, tornadoes and
waterspouts, in which the theory of cy-
clones is mathematically discussed at great
length, with comparison of the results
thus obtained with the facts of observa-
tiOn. We may safely draw from this
treatise such Information as may seem of
interest at this time, with reasonable con-
fdence that we shall not be misled with
respect either to fsets or inferenees. Al
though largely similar TO cyclones, and
governed by the same general principles,
tornadoes form distinct class of meteoric
phenomena. The initial temperature con-
ditions which give rise TO cyclones gener-
ally extend over large areas. The condi-
tioDs Of tornadoes depend rather upon YER
teal relations of temperature, under which
the unstable equilibrium Of the atmos-
phere is liable to be violently disturbed by
slight local changes of temperature eaus-
ing the under stata oe air to burst up
through the oyerlying strata. 4 cyclone
IS usually broad, fat, gyrating disk Of
atmosphere, very many times greater in
width than in altitude; a tornado may be
regarded as a column Of gyrating air in
which the altitude is several times greater
than its diameter. The enormous velOci-
ties Of the ascending currents in tornado
appear to be caused BY differences between
the gyra,ory veloeities above and those
very near the earth's surface. The form
er largely prevent the air from pressing
in to Gil up the partial vacuum near the
centre, while the smaller gyratory velOci-
ties near the earth allow it to rush in
there to supply the draugbi, The tenden-
ey Of friction is constantly to use up the
energy Of gyratiou so that the tornado can
not eOntinue very long. The ascending
currents carry up an enormous amount OF
aqueous vapOr into the upper regions Of
the air, where il is condensed aud pro-
duces the heavy rains observed in conuec-
tion with tornadoes. An ascending cur
rent Of 60 meters a second, which eaunot
Be unusual 10 tornadoes, would furnish,
under extreme conditions Of air saturation,
four inches Of rain minute, il it were to
fall directly back. With such an ascend
ing velocity, however, no rain could so fall.
I, would be thrown outside the vortex,
giving AZ immense though lighter fall Of
rain over a larger area, especially if the
tornado in its irregular progressive mo
iious should remain stationary or nearly
SO for several minutes. If the velocity Of
ascending current IS not so great that the
water is all carried up to where the cur
rents are outward from the vortex, and yet
great enough to prevent its falling back,
there may be in the lower part Of the
cloud ! vast accumulation Of rain, prevent
ed from falling by the ascending currents
and from being dispersed by the ioaowing
currents from all sides toward the vortex.
When the sustaining energy Of the lorna
do Is exhausted BY friction or by the
weight Of water accumulated in the cloud,
the water is liable to fall in mass, causing
what is called a cloud burst. This is es-
pecially liable to occur in mountainous re.
gions, for contact with mountain must
greatly interfere with the gyratOry motion
of the tornado aud the infOWing currents
below, aud tend to break up the system at
once and let the whole load of water drop
suddenly.
The water in clcad bursts is generally
poured down. Long before the ascending
currents are reduced so as to allow the
water to fall in drops it seems to collect at
certain places and force its way in solid
stream down through the ascending air.
Having once made an outlet for itself the
water is necessarily accelerated in velocity
so that before reaching the earth the stream
may be pouring with irresistible force, cut
ting, when it strikes, the sharply marked
aud often deep chasms LET; by cloud bursts
especially on hillsides.
When the ascending current carries the
yapor into the region Of frOst-which is at
lower altitude within the gyrating fun
mel than outside Of 1.-THE condensed va.
Dor is converted into hail The small
hailstones may then be kept suspended
near the base of the snow cloud and en-,
larged by additions of freezing rain. In
this way compact homogeneous hailstones
of ordinary size are formed At the
height of 1000 yards the air has lost more
than half its density, yet an ascending We
locity of twenty yards a second, which
must be DO unusual one in tornadOes
would sustain even at that altitude hail
stones of considerable size. 1t is not ne
cessary that the hailstones should remain
in the freezing region long time, or re-
main stationary. They may be carried
from this vortex out where the ascending
current is small, and dropping down som'
distance may be carried into the vortex b!
infowiig currents and again thrown up t.
the region of frost. The nucleus of larg'
hailstones is usually compaeted snow.