THE ATMOSPHERE 



129 



wind in these regions is almost wholly a matter of the direc- 

 tion of an inrush of surface air into areas of low pressure, or 

 of an outrush from areas of high pressure. In other words 



FIG. 49. The direction of winds into a low. The solid lines are isobars, 

 and the shaded areas in the east and southeast quadrants show where pre- 

 cipitation commonly occurs. The whole storm area may be thought of as 

 an inverted funnel with its centre of least pressure the place for escape of. air 

 upward. 



this is a region of variable winds controlled almost wholly 

 by the successive passages across country of areas of high 

 and low pressure. 



The conditions that have been discussed above cause the 



