38 W. Ferrel—Cyclones, Tornadoes and Waterspouts 
around its axis there cannot be any gyratory motion, but the 
interchanging motion between the central and external part 
is entirely radial. Cyclones are therefore never observed on or 
very near the equator. 
If there were no friction between the air and the. earth’s sur- 
face, all the conditions of a cyclone could be satisfied by 
case the linear velocity of the gyrations would be very great 
near the center. The greater the amount of friction between 
the air and the earth’s surface the less is the velocity of these 
gyrations, and the greater the inclination of the direction 
of motion at the earth’s surface from the direction of the 
the same, the nearer the equator the greater the inclination, so 
that at the equator it becomes 90°, and the motion, as already 
stated, is radial. In the exterior, or anticyclonal part, where 
the gyrations are reversed, this inclination at the earth’s surface 
is outward from the tangent. At all altitudes some distance 
above the earth’s surface the friction is small and the gyrations 
are more nearly circular, but a little inclined toward the center 
in the lower part where the interchanging motion is towa 
the center, but outward from the center above, where this 
motion is from the center. 
e : 
atmosphere on each hemisphere of the globe, with the cold 
les as their centers, are simply two examples of cyclones 
of this sort. The gyrations here, in the northern hemisphere, 
are around the pole from right to left, as in an ordinary 
eyclone, and the contrary in the southern hemisphere, while at 
a certain distance from the center, or pole, these gyrations 
