THE DESERT CLIMATE 



13 



unless one minute fall rapidly succeeds another. 

 We need to distinguish between the actual rainfall 

 and that part of it which reaches the roots and so 

 becomes available to plants, and subsequently to 

 animals. 



In other desert climates the opposite condition 

 occurs, for the rain falls in large amounts on a very 

 few days in the year. This is characteristic of very 

 many deserts and may be so extreme that a single 

 day's downpour exceeds the total rainfall of an 

 unusually dry year. As examples one may quote 

 the following figures : 



Such excessive rainfall is comparatively un- 

 available to plants and animals because a great 

 proportion of it runs off the surface of the ground 

 into the river beds, and only a small part soaks into 

 the soil at the place where it fell. The torrent 

 which is produced in the stream bed is extremely 

 destructive to plant and animal life (page 50). I 

 conclude, then, that statistics of the average number 

 of rainy days per month, or year, or of variation 



