Year: 1877

In a recent essay Prof Elias Loomis
has traced the genesis of oUr great
storms. They generally, he finds, begin
in the neighborh0od of the Rocky noun
tains. A few can be traced to the Pacific
ocean, near the northern boundary of the
United States, but no example Is found
of any considerable storm arising on the
Pacific coast 0uth of Oregon. 4 large
proportion OF our great storms originate
and are developed wholly within our
territory. The following is the usual
process in the birth of a storm To begin
with. there is generally an area of several
hundred miles diameter, through which
the barometer stands at the mean. On
opposite sides of this area-generally
east and west-at a distance of perhaps
600 miles apart, are areas of high
barometer. The rise of the mercury in
these side areas is usually One-quarter of
an inch or more above the mean, some
times it is a full inch above. The
atmosphere in these two side areas begin
10 move toward the central area. The
currents thus established are detected
towards the right by the earth s rotation,
and a diminished pressure at the center
the inflow increases and comes from all
sides The area Of low pressure assumes
an oval form, but if the winds are very
violent, it may be mole nearly circular.
{ With rotation, a centrifugal force Il
develOped which increases the depression.
An upward movement of the atmosphere
within the depression area is contin nous
otherwise the inflow would restore the
equilibrium. This upward movement
carries large amounts of aqueous vapOr,
! which, when cooled at a higher level,
condenses as rain. The heat, liberated
by condensation, increases the rarefaction
OF the area and thus rain increases the
force of storm, though never originating
it. The latter conclusion may also be
'rdeduced from the fact that the inflow
begins before there is any precipitation OF
rain.


As to the forward progress of the
storm, the following general observations
NAV be made The west wind, which is
characteristic of this part of the world,
carries along the storm area. 1t may,
however, meet Interruptions, such as
local storm. In that case the low area,
thus arrested in its forward progress, will
be the seat of increasing force during the
interruption, and the storm tor n few
davs afterwsrd is likely TO show greater
violence. The disturbance which consti-
tutes the storm is plainly within the
lower currents of the atmosphere, the
upper currents being comparatively un-
affected. The pressure of the general
wind from the west tends to fill up the
rarefied area on that side, both above and
below. On the east side only the lower
or surface wind constitutes an inflow,
while the upper portion of the storm is
rnnvfnu fOWqrd the ur11or
of the west wind 1t follows that the
upward motion within the storm area
takes place Caiefiy on the east side of the
area, the molten being 50 rapid that the
inflow is insufficient to restore equili-
brium. A further result of this process
IS that the depression at the center is
constantly transferred toward the east.


But If there should be great preciFi-
tation of vapor on the west side of the
storm area. the center may be prevented
from going eastward; may be held sta
tionary, or may even be quite diverted
toward the west. Several remarkable
instances of this exceptional kind were
cited. In one of the most striking of
these ca ases-December 3Oth, 1874, to
January 18th. 1S75-the storm center
oscillated within a range of about 1000
miles from west to east. During the most
of that time the winds on the west ofthe
area blew with the force of hurricanes,
accompanied by snow, set and low
temperature. The explanation offered
in that instance by Prot. Loomis is that
the extensive precipitation on the west
side of the low center was probably a
cause of the slow progress, and was itself
due TO a eold wind from over the contI-
nent, underAowing a warm current aris-
iug from near the gulf stream.