360 W. Ferrel—Relation between the Barometric Gradient 
tude which affect these oscillations. The rapidity of the gyra- 
tions in a cyclone, and consequently the amount of barometric 
depression in the center, depends very much upon the amount 
of aqueous vapor with which it is fed, and this diminishes from 
the equator to the pole. The great cyclones also, which move 
from lower to higher latitudes, continually increase in diameter, — 
and hence the amount of depression in the center, and the 
amount of barometric oscillation at any place caused by the 
passage of these cyclones over it, must increase toward the 
les. These two effects, however, tend in some measure to 
counteract each other. The monthly range of 0-1 of an inch 
expression of (10), upon which these results are based, is ob- 
tained directly from the former. ; 
24. Wherever the atmosphere over any large area of the 
earth’s surface receives a gyratory motion from any cause, this 
motion gives a value to u and v in (1), and, hence, likewise to 
The term, however, depending upon u, in any such case, 
i deve eng upon * sin /, 
nD 
= Sf 
