36 W. Ferrel— Cyclones, Tornadoes and Waterspouts. 
acts and reverses the flow toward the center arising from the 
primary and initial cause of disturbance, while the part pressed 
out on the interior side toward the center, combines with this 
flow toward the center and increases it. For the same reason 
in the general motions of the atmosphere the flow of air below 
from the polar to the equatorial regions is reversed very near 
the surface, arek the gentle southwest winds of the middle lati- 
tudes are pro 
The Sequel condition, found in the unequal distribution 
of Eiupoeseare must be regarded simply as a primary cause 
of disturbance, giving rise merely to the initial cyclonic dis- 
turbances ; for without other conditions, depending upon the 
ygrometric state of the atmosphere, and u upon the rate of de- 
crease of temperature with increase of altitude in the atmo- 
sphere generally in which the cyclone exists, we could have no 
cyclone of long continuance or of much v iolence. With a dry 
atmosphere the air in the ascending savbarit of the interior 
would cool about one —, centigrade for each 100 meters of 
ascent, so that the air at a very moderate elevation would be- 
come colder and more dense than that of the strata of the sur- 
rounding atmosphere at the same altitude. The pressure 
then of the air at the surface in the interior would become 
never is except in some rare cases and very near the earth’s 
surface only. When this would take place the initial cyclonic 
disturbances — from this primary cause of disturbance 
wou 
I 
the rate of pesmi of temperature sic de increase of aiiteds 
in the surrounding atmosphere generally is less than that in an 
ascending current of saturated air, then the temperature of the 
air in the ascending current, at all altitudes, must be less than 
that of the air generally, and hence the column of ascending 
air is lighter than the surrounding air, and the ascending cur- . 
rent is kept up as long as it is supplied with air nearly satu- 
rated. If, however, after a time, this current comes to be 
supplied with dryer air, then it has to ascend to a much greater 
elevation before condensation of the vapor takes place, and as 
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