CAUSES OF UNUSUAL WEATHER PERIODS 269 



FIG. 194. Principal paths of lows of the world (Approximate). Lows of 

 South Temperate zone not charted. Lows in the tropics occur in late summer 

 and autumn; in temperate zones, at all seasons. 



FIG. 195. Paths of lows in an autumn month (10 years). Note the 

 scattered distribution. Half the total number are near the northern border 

 Compare with Fig. 196, paths for November, 1909. 



