226 WEATHER AND CLIMATE 



of ascending and cooling air they are storm areas. The 

 extent of the precipitation varies in different parts of a 

 cyclone according to the direction from which the ascending 

 air has come. Note the direction of the wind and the rain- 

 fall area as shown on the map (page 225) . Air which comes 

 from continental interiors is dry, while that from great water 

 areas contains much moisture, much of which it deposits 

 when it cools by ascending (page 125). To these cyclones 



is due the larger part of 

 the rain which falls in 

 middle latitudes. 



The anti-cyclone is just 

 the opposite of, a cyclone. 

 The center of an anti- 

 cyclone is a place of clear 



FIGURE 90. DIRECTIONS OF WINDS IN , , , . , 



AN ANTICYCLONE AND IN A CYCLONE sky and high pressure. 



The air movement is 



slowly downward and outward from the center. (Figure 

 90.) These winds are dry, cool, and gentle. 



Paths of Cyclonic Storms across the United States. If 

 you will watch the weather maps for several days in succes- 

 sion, you will find that cyclones or " Lows " move in a general 

 eastward direction. The accompanying map shows the 

 paths of a large number of cyclonic storms across the United 

 States. It will be seen from this that although these paths 

 vary considerably, yet the general direction is a little north 

 of east. The movement of cyclones is in the general direc- 

 tion of the prevailing winds of the middle latitudes. 



In winter time the average rate of motion of the cyclone 

 across the continent is about 800 miles a day, while in summer 

 it is only about 500. The velocity of the wind in the cyclone 



