HEIGHT OF SAND-HILLS. 207 



CHAPTER XXIY. 



HEIGHT OP THE HILLOCKS. — ADVANCE OF THE DUNES.— ^-DISPLACEMENT OF 

 "ETANGS." — DISAPPEARANCE OF VILLAGES. 



In Europe tlie highest hillocks of sand are found on the coast-line of 

 the Netherlands, on the Atlantic coasts of France, and in Scotland 

 on the shores of the Firth of Tay. As to the dunes of the Medi- 

 terranean, they are generally lower than those on the coast of the 

 ocean. The gulfs of the south of Europe having a hardly percept- 

 ible tide, their sandy shores are not incessantly displaced, like 

 those on the strands of the ocean, and consequenctly they are less 

 exposed to the winds which drive before them the finest par- 

 ticles. It is to the north of Africa, round the gulfs of the 

 Syrtes_, where the ebb and flow have the greatest development, and 

 where sandy beaches occupy vast tracts, that the Mediterranean 

 dunes attain the most considerable height. In France, those that 

 are seen from Port Vendres to the mouths of the Phone, hardly rise 

 to more than 18 or 21 feet in height, because the banks on which 

 these hillocks are formed have not a sufficient breadth, and above 

 all, because the prevailing wind, the mistral, blows from the north- 

 west, and carries the sand from the etangs into the Mediterranean. 



On the coast of the Landes of Gascony, where the waves of the 

 sea bring six millions of cubic yards of sand each year,* a great 

 many dunes exceed the elevation of 225 feet. There is even one, 

 that of Lascours, whose long ridge, parallel to the sea-shore, attains 

 261 feet in several places, and raises its culminating dome to a 

 height of 291 feet. It is true that this height seems to mark in 

 France the extreme limit of the ascent of the sand, for the ranges of 

 dunes situated to the east of the dune of Lascours, are far less 

 elevated. One would be tempted to admit that, after having arrived 

 at this great height, the lower strata of wind from the west, com- 

 pressed by the more elevated masses of air, have not the necessary 

 power to cause the particles of sand to mount again, and are 

 * Laval, Annates des Fonts-et-Chausees, 1842. 



