But then the wind at the high-pressure area 

 is lighter than it is at the low, and circles out- 

 wardly until it finally moves off in the direc- 

 tion of a low-pressure area, gradually bending 

 in the other direction until finally it moves 

 the reverse of the hands of a clock although 

 now it is in a smaller circle, and with a more 

 rapid motion. It moves spirally and up- 

 wardly about the low-pressure area until it 

 reaches a point in the upper air, where it goes 

 through the same gyrations in an opposite di- 



asf / "~^\ 



Wzsf 



rection. Now imagine the whole combination 

 moving from west to east at an average rate of 

 thirty miles per hour, and imagine further 

 that this system is linked to other systems 

 that are following along, and you have some 

 idea of the weather changes as they occur in 

 the middle United States. 



