CHAPTER XXV. 

 MOVEMENTS OF THE ATMOSPHERE. 



714. Primary Cause of Winds. Winds usually begin, in 

 one of two ways, represented in Fig. 261. In the lower 



f ** ^^* 



/ -.. =fc,. 



Fia. 261. Diagram showing the origin of wind movements. 



part of the figure the white portion represents a region 

 where the air is expanding. When this occurs the lower 

 and heavier air is carried upward and brought alongside 



