The morning call., 1891-01-29
CYCLONES.
cold Probabilities" Issues a
Circular.

Lieutenant Finley of the United States
Signal Service has issued the following cir
cular on cyclones, believing that it will tend
to make the daily forecast Of weather of
more practical Value:
About fifty years ago Plddington OF Calcutta,
East India first applied the term cyclone TO all
circular storms of whatever area. The earliest
published account OF storms where the curying
OF The winds Is recognized was by Captain Lang
ford III 1893 In paper on the West IBdIa hurri-
canes, which lie called "whirlwinds" The term
cyclone comes from The Greek cycles, which sig
niles, among other things, the coil of "a snake.
Its application to the most important OF all
meteorological disturbances is not intended to
affirm that she area described by the storm is
true circle, but rather expressing sufficiently
The tendency OF the air 10 a circular motion. The
word IS now accepted by the leading meteorolo-
gists OF the world as properly distinguishing a
certain class of storms. The cyclone is a broad
disturbance, having diameter OF from 300 TO
500 miles, and sometimes 1000 miles. IL Is
vast eddy in The atmosphere aud moves along IN
that medium very much as the eddies In
stream of water. The air does not have an &C
tual circular motion AT any place within the
storm area, but only tendency TO spiral move
ment.
But even this tendency Is not revealed by re-
ports from single station. Ii Is necessary to
obtain observations from the entire area OF dis
turbance, which. when plated on a chart, dis
closes tile general movement of the air gradually
inward toward the center, where it rises 10 the
upper cloud region and flows outward on all
sides. This motion of The air gives rise TO west
cry winds south of The cyclonic center SOUTH
north aud nOrtheTly winds on the west. AT the
center of the area there is a calm space ten
fifteen miles In diameter known as the "eye of
the Storm his Is very ngerous part OF the
cyclone for vessels to encounter as they become
motionless ana are then suddenly caught at
disadvantage by the rear OF the storm. The
barometer Is lowest al the center and increases
outward to the circumference.
The form OF the cyclonc area Is either circular
or elliptical generally tbe latter. The direction
of progressive movement Is from west 10 east,
under the influence of The rotation OF the earth;
aud while not directly visible, Is apparent in the
passing changes OF tue weather The rate OF
movement Is on the average about thirty miles
per hour, being most rapid IN winter, with a
MAXIMUM of fifty miles, and least rapid In sum-
meI, with a minimum OF about ten miles. The
tour quadrants OF a cyclone have distinct and IN.
variable characteristics, as follows:
In the northeast quadrant, great humidity,
high winds, precipitation and heavy Clouds es.
pecially IN the southern portion. III the south
east quadrant, the maximum of heat and moist
ure, the region Of all classes of local storms es-
peclaily the tornado. In The southwest quad
raut, clearing weather. with dasnes OF ram in
the eastern portion, falling temperature and
diminishing humidity. In The northwest quad
rant Is the minimum OF heat and moisture,
genaral absence OF clouds, and brisk, cold winds
Some cyclones may preserve their Identity in
passing entirely around the earth, but the gener-
ality only make about one-Inird OF that distance,
and then disappear i'll The general circulation Of
the atmosuhprp