The star. (Reynoldsville, Pa.) 1892-1946, 1903-08-05
cLoupBuRsTs.
Result Of Hills interfering With an
OnrushInu Storm,

| Onrusnino Storm.
| Cloudbursts Of the gigantic type
which caused the cataclysm at Hepp-
ner, Ore, are almost invariably the re-
suit OF an interference of hills or
mountains with the onrushing wnirl-
wind enfolding an electric storm.
To obtain a clear ideo of this terrific
| phenomenon one must first remember
that the thunderstorm Is a strong hori-
zontal gyration of the air; in fact.
small cyclone. which has progressive
as well as a rotatory motion.
| AS the air begins its whirling motion
the centrifugal force of the outer ring
causes rarefaction In the central area
of the whlrl Inrushes or air from all
sides of the storm then take place, es-
pecially at its base, and these masses
OF air quickly form a powerful and
rapid ascending current in the heart
of the nascent tornado.
The genesis OF the whirlwind is now
complete, but its gyratory motion Is
usually soon intensified by the existing
| hygrometric conditions.
II the atmosphere Of any region,
| whether II be level or mountainous,
contains a large amount OF water vapor
the ascending current in the centre of
the thunderstorm will have its volume
and velocity largely augmented. This
is easily understood since the moist up
rising air in the centre is constantly
reaching cooler and cooler strata of the
atmosphere where its vapor is conden-
sed into rain or hail. Moreover, the
condensation of the vapor contained in
the ascending current is further and
intensely chilled by expansion as II en-
ters higher and higher levels, where
the barometc pressure is greatly re-
duced, until. at 1000 or 1000 feet above
the earth the rising column Of air, cap
ped with magnificent cumulus clouds,
has much of its moisture wrung out
of II in the shape of heavy rain drops,
often intermingled with hail.
In this second and incomplete stage
Of the storms development the rain
power of human comprehension. The
precipitation in a short time amounts
to hundreds of thousands Of tons OF
water to the square mile.
During the passage OF a series of
thunderstorms over Syracuse, N. Y,
on June 8, 1876, eight inches OF rain
fell, and 1t would not be difficult to cite
many like records Of torrential down.
pours occurring in comparatively
level country.
| When 1t is borne in mind that a sin
gle inch Of rainfall over one square
mile weighs in round numbers, sixty
thousand tons. 1t can readily be inferred
that fall half Of that registered at Sy-
racuse within a day, II descending up
on a plain or valley carved by several
converging streams. is fully competent
to create a gigantic flood, and where
| the ground In which the converging
streams meet is slightly depressed the
flood can become a rushing, irresistible
wall of water.
| But when the storm which advanced
upon the mountains, the drainage of
whose slopes converges near Heppner,
the case was very different from that
Just cited as occurring in level coun-
try.
In advancing upon hills or noun
tains Of moderate elevation the torna-
die whirl or even severe thunder
storm is capable of producing the gen.
uine cloudburst In the immediate CEN
tire of the storm on its approach to
a mountain where we might expect the
heaviest rain the rain drops, falling
from the cumulus cloud, are arrested
and massed up aloft by the action Of
the powerful ascending current, and
this process of amassing the rain in the
folds of the storm cloud goes on as
long as the cyclonic or rotatory motion
of the storm is fully maintained
Standing Immediately unuer the CEN
tire of the whirlwind, one might then
notice but little and possibly no rain,
because there the uprising current pre-
vents the downward rush of the water.
But when the cyclone in its swift
fight strikes range of hills or noun
tains the rotatory motion of the storm
Is mechanically stopped, its gyration
ceases, the ascending current in its CEN
trail area can no longer support the
masses Of rain collected in the high
storm clouds, and as the body Of
the travelling whirl scales the noun
tain top the accumulation of rain in
the upper regions falls with terrific
force upon the leeward side of the
mountain sometimes excavating deep
holes six feet deep and thirty feet in
diameter.
The result is precisely the same as IL
a lake could be suspended in mid air
for time and then allowed to drop
en- masse upon the soil.-New York
Herald.
Modern Cliff DwelIers Of France.