side ; because the wind in its course, not conforming to 

 the inequality, or course of the bank, or other obstruct- 

 ing medium, forms, on the leeward side, a kind of eddy, 

 into which the sand, being much heavier than air, is 

 immediately deposited. 



If the winds change in an opposite direction, the 

 same operation is continued, until the sand is at last 

 heaped up in a ridge of a pyramidal shape, on the top 

 and sides of which, vegetation at length springs up, 

 and serves to increase the obstruction, and detain the 

 sand. Subsequently, other successive strata of allu- 

 vion are annually deposited, at the base of the bank. 

 This is, in the same manner, afterwards hurried by 

 the winds towards the summit, where it is, in part, 

 detained by the growth of vegetables. Thus it con- 

 tinues to be elevated, while the neighbouring low 

 grounds experience the trifling augmentation of an an- 

 nual deposite of alluvion, from the waters that over- 

 flow them. 



At length the violence of the current of the river, 

 or the beating of the waves against the bank, breaks 

 down a portion, and forms a somewhat inclined or per- 

 pendicular front, against which the winds are more 

 directly apposed. Should they prevail with more than 

 ordinary force or strength, or should they blow either 

 obliquely, or at right angles across the river loaded 

 with dust, or should they even, by their force against 

 this upright bank, raise a torrent of dust, it is elevat- 

 ed into the air, and deposited more immediately on the 

 margin of the bank next the river. 



