Theory of the Winds. 17 



the velocities are proportional to their distances from the 

 earth's axis. Indeed the atmosphere, when there is no wind, 

 is everywhere travelling towards the east at the same angular 

 velocity. If, however, the atmosphere be set in motion at 



any point, the air will not continue to move in the direction 

 in which it is urged, for it no longer has the same angular 

 velocity as the surface of the earth below it. It does not 

 matter in which direction the impulse acts. The air will be 

 deflected, and will not, in the absence of other forces, follow 



a straight course on the earth's surface. 



Fiff. 3. 



Fig. 3 shows an 



area in the Northern Hemisphere. If a mass of air at a be 

 forced in a northerly direction by some force, such as might 

 result from a temperature gradient, as it moves north it 

 reaches regions where the earth's surface is travelling less 

 rapidly than itself, and the air is deflected towards the 

 east, a . I£ the air at a is forced in a southerly direction, 

 Phil. Mag. S. G. Vol. 30. No. 175. July 1915. C 



