678 INLAl^D SAISTD-PLAES^S. 



decKvity is almost entirely free of sand, as it is driven to the plain 

 below by the southeast wind, which constantly alternates with the 

 wind from the south." * 



It is difficult to reconcile this description with that of Meyer, 

 but if confidence is to be reposed in the accuracy of either ob- 

 server, the formation of the sand-hills in question must be gov- 

 erned by very different laws from those which determine the 

 structure of coast-dunes. Captain Gilliss, of the American navy, 

 found the sand-hills of the Peruvian desert to be in general cres- 

 cent-shaped, as described by Meyer, and a similar structure is said 

 to characterize the inland dunes of the Llano Estacado and other 

 plateaus of the North American desert, though these latter are of 

 greater height and other dimensions than those described by 

 Meyer. There is no very obvious explanation of this difference 

 in form between maritime and inland sand-hills, and the subject 

 merits investigation. It is, however, probable that the great mo- 

 bihty of the flying dunes of the Peruvian desert is an effect of 

 their dryness, no rain faUing in that desert, and of the want of 

 salt or other binding material to hold their particles together. 



Inl(Wid ScmdrPlains. 



The inland sand-plains of Europe are either derived from the 

 drifting of dunes or other beach sands, or consists of diluvial de- 

 posits, or are ancient searbeds uplifted by geological upheaval. As 

 we have seen, when once the interior of a dune is laid open to the 

 wind, its contents are soon scattered far and wide over the adja- 

 cent country, and the beach sands, no longer checked by the ram- 

 part which nature had constrained them to build against their own 

 encroachments, are also carried to considerable distances from the 

 coast. Few regions have suffered so much from this cause, in 

 proportion to their extent, as the peninsula of Jutland. So long 

 as the woods, with which nature had planted the Danish dunes, 

 were spared, they seem to have been stationary, and we have no 

 historical evidence of an earlier date than the sixteenth century, 

 that they had become in any way injurious. From that period 

 there are frequent notices of the invasions of cultivated grounds 



* Travels in Peru, New York, 1848, chap. ix. 



