564 MOVEMEIS'T OF DUNES. 



is opened into them to a considerable depth, thereby giving the 

 wind access to the interior, where the sand is thus first dried, and 

 then scooped out and scattered far over the neighboring soil. The 

 dune is now a magazine of sand, no longer a rampart against it, 

 and mischief from this source seems more difficult to resist than 

 from almost any other drift, because the supply of material at the 

 command of the wind is more abundant and more concentrated 

 than in its original thin and widespread deposits on the beach. 

 The burrowing of conies in the dunes is, in this way, not unfre- 

 quently a cause of their destruction and of great injury to the 

 fields behind them. Drifts, and even inland sand-hills, some- 

 times result from breaking the surface of more level sand de- 

 posits, far within the range of the coast-dunes. Thus we learn 

 from Staring, that one of the highest inland dunes in Friesland 

 owes its origin to the opening of the drift sand by the uprooting 

 of a large oak.* 



Great as are the ravages produced by the encroachment of the sea 

 upon the western shores of continental Europe, they have been in 

 some degree compensated by spontaneous marine deposits at other 

 points of the coast, and we have seen in a former chapter that the 

 industry of man has reclaimed a large territory from the bosom 

 of the ocean. These latter triumphs are not of recent origin, and 

 the incipient victories which paved the way for them date back 

 perhaps as far as ten centuries. In the meantime, the dunes had 

 been left to the operation of the laws of nature, or rather freed 

 by human imprudence from the fetters with which nature had 

 bound them, and it is scarcely three generations since man first 

 attempted to check their destructive movements. As they ad- 

 vanced, he unresistingly yielded and retreated before them, and 

 they have buried under their sandy billows many hundreds of 

 square miles of luxuriant corn-fields and vineyards and forests. 



On the west coast of France a belt of dunes, varying in width 

 from a quarter of a mile to five miles, extends from the Adour 

 to the estuary of the Gironde, and covers an area of nine hun- 

 dred and seventy square kilometres, or two hundi'ed and forty 

 thousand acres. When not fixed by vegetable growths, these 

 dunes advance eastwards at a mean rate of about one rod, or six- 



* De Bodem van Nederland, i., p. 425. 



