70 On the Rotary Action of Storms. 
The deflecting power thus applied is not small. The rotary 
motion of the earth varies as the cosine of latitude, and the dif- 
ferences of velocity for any differences of latitude are easily com- 
puted. The following are samples; being differences of velocity 
for 1° or 694 miles of latitude. 
Between lat. 2° and 3° diff. of velocity 0.79 miles per hour. 
6¢ 66 3° 66 4° 66 66 1.11 6¢ 66 
66 66 10° 66 11° 13 6¢ 3.31 6¢ 79 
66 66 939 66 QAC 66 66 7.25 6c 66 
73 66 42° 66 A3° 66 66 12.28 66 43 
The differences of velocity for one mile, or 51.84” of latitude, 
are as follows. 
Latitude. Difference of velocity for one mile north. 
10° A feet per minute. 
23° 9 a “ 
42° 15.4 * ef 
A3° Mids ee ce 
45° LB Fs Me 
The deflection of easterly and westerly breezes by reason of 
the spherical form of the earth, also, can be computed ; and it is 
obviously no less important than the deflection produced in me- 
ridional winds. ‘The angle between the courses north and east, 
at any point, is a right angle; and if two points in the same lati- 
tude are taken, it is evident that the obliquity of the north courses 
from the two points, equals the obliquity of the east courses from 
the same points. 
These results show that in the northern states a fire large 
enough to affect the atmosphere over a few acres may possess the 
essential force for generating a whirlwind, and may produce it in 
fact if the day be caim. A large storm, covering the whole 
country with its centripetal currents, must produce a vortex 
about the centre, which will combine the principal energies of 
the storm. The tornado and water spout must revolve with 
terrific violence. 
The necessary condition, centripetal motion, may arise when- 
ever a central spot subjected to intense heat is surrounded by a 
cool atmosphere. This state of things, on a small scale, may 
occur in a summer’s day, upon a ploughed field surrounded by 
