44 W. Ferrel on motions of Fluids and Solids 
the pole is greater than on the other side toward the equator, and 
hence the cyclone moves in the direction of the greatest pressure. 
It is not to be supposed, however, that there is an actual transfer 
of all the atmosphere of a cyclone from the equator to the polar 
regions. For the motions and pressure of the cyclone being 
greater on the polar side, where the deflecting forces which cause 
it are greatest, its action upon the atmosphere in advance of it i3 
greater than on the equatorial side, where these forces are much 
3. 
less, and hence new portions of the atmosphere are being contin- 
ually brought into action on the one side, while the resistance of 
the earth’s surface, and the adjacent portions of atmosphere on 
the other side, are continually overcoming the comparatively 
weak forces there, and destroying the gyratory motion of the 
cyclone; so that the centre of the cyclone is being continually 
formed in advanced portions of the atmosphere. Since many 
cyclones are more than one thousand miles in diameter, the 
difference in the violence of its action on the two sides is very 
considerable. Hence the interior and most violent portion of @ 
cyclone, always gyrating from right to left in the northern hem- 
isphere, and the contrary in the southern, must always gradually 
move towards the pole of the hemisphere in which it is. While 
between the equator and the tropical calm belt, it is carried 
westward by the general westward motion of the atmosphere 
there, but after passing the tropical calm belt, the general motion 
of the atmosphere carries it eastward, and hence the parabolic 
form of its route is the resultant of the general motions of the 
atmosphere, and of its gradual motion toward the pole. 
