The National tribune., 1890-06-26
THE WEATHER.
Gyrntory Hollon Of Cyclones.
BY LIEUT.. }. p. FrSLEY. U. s. SIGNAL sERvrc

by LIEUT.. J. p. FINLEY, q. s. SIGNAL SERVICE.
Correspondence invited. suggestions desired.
ard Information chcrrfuily furnished. Every e.
foTt employed 10 make this bureau 81 practical nsa
20 the readers Of TnE NATIONAL TRIRUSg All
communication. should be- addressed- Weather.
JHE SA1IoSAL TRIBUNE Office. Washington. -. c.
While the atmosphere is clear and somewhat
quiet. the tendency IS for the upper strata to
cool down 10 so iow temperature IN comparison
with that OF the eafih's surface aud the lower
strata, that the unstable state IS induced, IL not
for dry air. AZ least in the ease OF saturated air.
This occurs although the air without ascending
currents is rarely. and only near the earth's
surface completely saturated, yet If there is
only a slight local temperature disturbance Ia
little excess OF temperature over some central
area above that oil tie surrounding air. D YER
teal circulation is started which continues
until there is such an interchange aud Inversion
OF the air Of the upper and lower strata that
the unstable state Is destroyed and the stable
state aud comparative calmness aud cearness
arc again restored for while until broken up
again in perhaps short time IN similar
manner as before.
II the earth had no rotation on It's axis the
air IN its vertical circulation, in all cases of
local aud temporary disturbances, would move
in the lower strata directly toward the central
part Of the area Of higher temperature aud less
pressure and out from Il above, and there
would be no gyratory motion around the center
OF the ascending column OF air. But in conse-
qucnce Of the cartA's rotation where a body
moves in any direction on the earths surface
there Is 4 force which defects it 10 the right in
the northern hemisphere, and the contrary in
the southern. Ia the case Of q central force
acting upon the body, as where air il forced ia
from al sides toward center by pressure
gradient. this DETECTING force is strengthened
By the relative RyTatOry motion OF the body
itself. The air in the lower strata, ia being
forced ia from all sides toward the center runs
into a gyratiOn around this center, and this
In the Northern Hemisphere is from right "a
/ left. or contrary 10 the motion OF the hands
/ Of watch. This may be illustrated by means
Of the behavior Of water in a shallow basin
/ where il is allowed TO run ont through hole in
| the center. IL the basin Is al rest, aud the
/ water in the basin has no motion Of any kind
1 before the hole is opened, the water flows di
/ rectly from all sides toward tho center with
out any PyratoTy motion. But If the basin
/ although the water with reference 10 tho basin
! is perfectly at rest, has the least gyration
! around it's center, the water in approach ng
! toward the center runs into "A gyration around
that center, aud the gyralOry velocity becomes
very great near the center
/ II IS somewhat the same where the air oyel
considerable area Of the earth's surface il
forced from all sides toward the center Tn,
AIR 0f this area gyra.es, in consequence of til,
earth's rotation around its center with an an
gUlar velocity proportional TO the sine of Tia,
i latitude; aud 80 the air, In running in from al
sides toward the center, runs into gyratioI
around the center just as the water ia TIN
basin. The principal difference in the tW,