126 PLANT-LIFE ON LAND [CH. 



of the formation of these wind-created Dunes. The 

 prevalent view is that the sand hurried along by the 

 gale is heaped up over that already present till a 

 slight ridge appears, which is then constantly increased 

 by more and more being carried over it from the 

 windward side. The steeper angle of the leeward 

 face is then due to gravity acting on the grains which 

 lose pace on the sheltered side. This accounts for 

 the steeper slope, which advances constantly but 

 slowly down the prevailing wind. The plain fact is, 

 however, that, putting such wind-formed Dunes on 

 one side since they do not form a leading feature 

 here at home, the existence of definitely shaped 

 Sand-Dunes on our shores and the genesis and 

 maintenance of Sandy Links are essentially due to 

 vegetable life. It may accordingly be a matter of 

 interest to consider carefully how they originate. 



The sand itself consists of the comminuted frag- 

 ments of rock or of sea shells, and is cast up by the 

 waves upon the beach. Thence it is liable to be carried 

 by wind upward to the land. Once deposited in any 

 given position each grain, being unattached, is free 

 to be moved on again to another spot by any gust of 

 wind. But the probability of this happening in the 

 case of any individual grain is less if it should have 

 lodged in some place protected from the wind, while 

 it is more likely that the wind-borne particles will in 

 the first instance settle wherever there is a relatively 



