MOVEMENT OF DUNES. 565- 



teen and a half feet, a year. "We do not know historically when 

 they began to drift, but if we suppose their motion to have been 

 always the same as at present, they would have passed over the 

 space between the sea-coast and their present eastern border, and 

 covered the large area above mentioned, in fourteen hundred 

 years. We know, from written records, that they have buried 

 extensive fields and forests and thriving villages, and changed the 

 courses of rivers, and that the lighter particles carried from them 

 by the winds, even where not transported in sufficient quantities 

 to form sand-hills, have rendered sterile much land formerly fer- 

 tile.* They have also injuriously obstructed the natural drainage 

 of the maritime districts by choking up the beds of the streams, 

 and forming lakes and pestilential swamps of no inconsiderable 

 extent. In fact, so completely do they embank the coast, that 

 between the Gironde and the village of Mimizan, a distance of 

 one hundred miles, there are but two outlets for the discharge of 

 all the waters which flow from the land to the sea ; and the east- 

 em front of the dunes is bordered by a succession of stagnant 

 pools, some of which are more than six miles in length and 

 breadth.f 



* The movement of the dunes has been hardly less destructive on the north 

 side of the Gironde. See the valuable articles of ^lisbe Reclxts in the Re- 

 vue dea Deux Mbndes for December, 1862, and several later numbers, entitled 

 " Le Littoral de la France." 



f Laval, Memoire aur les Dunes du Golfe de Oascogne, Annalea des Ponia. 

 et Ghaussees, 1847, p. 223. The author adds, as a curious and unexplained 

 fact, that some of these pools, though evidently not original formations, but 

 mere accumulations of water dammed up by the dunes, have, along their 

 western shore, near the base of the sand-hills, a depth of more than one hun 

 dred and thirty feet, and hence their bottoms are not less than eighty feet 

 below the level of the lowest tides. Their western banks descend steeply, 

 conforming nearly to the slope of the dunes, while on the northeast and 

 south the inclination of their beds is very gradual. The greatest depth of 

 these pools corresponds to that of the sea ten miles from the shore. Is it 

 possible that the weight of the sands has pressed together the soil on which 

 they rest, and thus occasioned a subsidence of the surface extending beyond 

 their base ? 



A more probable explanation of the fact stated in the note is suggested by 

 ^filisee Rec.us, in an article entitled Le Littoral de la France, in the Benue des, 

 Deux Mondes for September 1, 1864, pp. 193, 194. This able writer believes 

 such pools to be the remains of ancient maritime bays, which have been cut 

 off from the ocean by gradually accumulated sand-banks raised by the waves ^ 

 and winds to the character of dunes. 



