40 W. Ferrel—Cyclones, Tornadoes and Waterspouts. 
circumstances connected with the earth’s surface. The primary 
temperature disturbance is not sufficiently great and permanent 
enough to hold the cyclone to the spot where it originates, and 
it is carried forward by the prevailing general movements 
of the atmosphere, and the central area of warmer air is main- 
tained by the heat arising from the condensation of the vapor 
in the interior ascending currents supplied with moist air from 
the earth’s surface by means of the horizontal currents flowing 
e 
them in that direction, with an inclination still toward the pole. 
This seems to be the general tendency of cyclones originating 
everywhere near the equator, but they seem to make their way 
through toward the pole with greatest facility on the west sides 
of the Atlantic and Pacific oceans, because there the genera 
motions of the air are deflected around somewhat toward the — 
con 
mostly, the progressive motions of the cyclones depend rather — 
u 
n the general motions of the atmosphere at considerable _ 
_ It must not be supposed, however, that the progressive MO- 
_ tion of cyclones depends entirely upon that of the air in which 
