W. Ferrel— Cyclones, Tornadoes and Waterspouts. 35 
latitudes, and there must be a great many local irregularities in 
the distribution of temperature independent of the great genera 
disturbance of the equality of temperature between the equato- 
rial and polar regions. These must give rise to corresponding 
motions of the atmosphere which are superadded to those of the 
general motions. If in the unequal distribution of temperature 
it should happen, as it must frequently, that there is a some- 
what circular area with higher temperature in the interior and 
with temperature gradients increasing somewhat regularly on 
all sides from the center outward, we should have, at least 
approximately, the initial condition of acyclone. There would 
and this by virtue of the earth’s rotation, has a gyratory motion 
around its center, equal to that of the earth’s rotation multiplied 
into the sine of the latitude of this center. Hence, as in the 
case of the general motions of the earth, this interchanging 
motion between the central and exterior part of the warmer 
and more rarified air, must give rise to gyrations around the 
center from right to left in the northern hemisphere, with gyra- 
tions the contrary way in the exterior part, and these gyrations 
in contrary directions must give rise to gradients of pressure 
increasing in the central part from the center outward, but in 
theexternal part to a gradient of pressure increasing from the 
outward limit of the gyrations toward the center, so that there 
must be a belt of high pressure with its maximum where the 
interior gyrations in proceeding from the center, vanish and 
change signs. These exterior gyrations and the gradients aris- 
ing from them are generally small in comparison with those of 
the interior, and they are generally so interfered with b 
humerous irregularities, that they are not readily shown by 
observation, but to deny that they exist, would be to deny the 
truth of a fundamental and well established principle in 
mechanics. 
. The increased pressure under the belt of high barometer 
surrounding the central part of the cyclone causes a modifica- 
tion of the flow of air toward the center very near the surface, 
for the air: is forced out from beneath in both directions, the 
flow toward the outward border very near the surface counter- 
