NOTES ON THE FIXING OF THE DUNES. 249 



lines ; at other times they run zigzag. This de- 

 pends on the form of the coast line. Thus between 

 the Adour and the Gironde the first case presents 

 itself; while near the promontory of la Couhre, 

 where the wind blows from several points, the 

 elevations and depressions are entirely irregular. 



It is to these moving sand-hills that the name of 

 dnnes has been given. According to information 

 furnished by M. Dutemps du Gric, Conservator of 

 Forests at Bordeaux, it has been ascertained that 

 the average rate of their progression towards the 

 interior is fourteen feet a year, and that the quantity 

 of sand thus brought up is in the proportion of 109 

 cubic yards for every yard of coast-line. The hollow 

 between two consecutive dunes, called lette by the 

 inhabitants of the district, is very variable. It is 

 flat at the bottom and generally marshy when the 

 dunes are devoid of all vegetation. 



One can easily conceive the great importance of 

 fixing and utilising these dunes, whose onward 

 march has swallowed up everything before it, and 

 has been a perpetual source of danger to human 

 dwellings, which more than once have had to retire 

 before them. 



The first attempt to fix these sand-hills was made 

 with hurdles and certain plants having well-deve- 

 loped roots, such as the Psamma arenaria, a 

 Euphorbia, Festuca, &c. But these succeeded only 

 temporarily. At length the Cluster Pine was tried 

 with all the desired result. This pine is admirably 

 adapted to the locality. It is indigenous in the 

 parts of France possesing a mild climate ; its tap- 



