The Winds Bes 131 
sure point. This spiral motion is counterclockwise in the 
Northern Hemisphere, clockwise in the Southemn Hemi- 
sphere. Winds exhibiting such spiral motion are called cy- 
clones, may extend in a large vortex several thousand miles in 
diameter. Naturally at different points in the cyclone the 
winds will be met in different directions. By observing the 
direction of the wind it is possible to determine the direction 
of the storm center, the so-called eye of the storm. For ex- 
ample, in the Northern Hemisphere the storm center will 
DETERMINATION OF 
DIRECTION OF STORM 
CENTER IN NORTH- 
1 ERN HEMISPHERE 
TO STORM CENTER 
bear about ten points (measured clockwise) from the direc- 
tion from which the wind is blowing. In the Southern Hemi- 
sphere, measure the ten points counterclockwise. Having ob- 
tained the bearing of the storm center one may then estimate 
its distance by the barometer’s rate of falling. Combining 
bearing and distance gives a fair approximation of the posi- 
tion of the storm center. Successive determinations may be 
made and the path of the storm plotted. The usual speed of 
a storm center will be found to be about 15-20 knots. 
In the tropics, analogous, smaller, but much more violent 
