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. 
: weg “ “ Phw cs 
Oo « fo 
3 “ype « 4yo 73 331 ts 66 
6 “« 930 « QAO & “ 7.25% ts 
“ s 4Qo s 430 & “« 4298 és 
“The differences of velocity for one mile, or 51.84” of latitude, 
are as follows. 
2 ge Latitude. Difference of velocity for one mile north. 
oS nce, 10° 7 4 feet per minute. 
“es 23° 9 “ & 
sud 42° 15.4 “ 
43° 16.75%, te 
45° 16.3 ee 
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. F 
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 calm. 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. t 
The necessary condition, centripetal motion, may arise when- 
ever acentral spot subjected to intense heat is surrounded by # 
cool atmosphere. This state of things, on a small scale, may 
oceur in a summer’s day, upon a ploughed field surrounded by 
