142 rRELTMINARY WORKS. 



fence is placed at a convenient distance behind it, to prevent 

 the sand which has passed through the pahng from being 

 carried inland ; when the first wattle fence has been entirely 

 covered, a fresh one is made to replace it. In this way the 

 dune is forced to adopt a moderate slope on both sides, which 

 is essential to its permanent maintenance. The latter is 

 effected by growing on it certain plants which are capable of 

 living under such conditions. Amongst these the marram 

 grass, Psamma {Ammoph'da) arcnaria, takes the first place ; 

 it has the property that, as the sand rises around it, its stalk 

 grows higher and develops numerous adventitious roots at 

 the joints. Other plants used for the same purpose are 

 Eli/nnts arcnarius and Care.v arouivia. 



The second measure, or the temporary fixation of the area 

 covered with sand behind the littoral dune, consists in 

 covering the area with various materials, such as the 

 branches of coniferous trees, heather, broom, furze, seaweed, 

 turf, etc. ; the last, when obtainable, is best. These materials 

 (except the turf) are kept in their place either by fastening 

 them down with pegs, or by placing shovelfuls of sand 

 upon them. 



The third measure consists in stocking the temporarily 

 fixed area with trees, shrubs, and grasses. Of trees the 

 Scotch pine and the cluster pine (Pin us Pinaster) are specially 

 adapted ; seed of these may be sown or transplants put in. 

 Of other plants Psamma arcnaria, Eh/miis arcnarius, Carcx 

 arenaria, broom {Sarothamnus scoparius), and furze {Ule.v 

 nana), may be mentioned. It is essential to maintain the 

 temporary cover until it is replaced by the permanent growth. 

 On the west coast of France the second and third measures 

 are done simultaneously. There, a mixture consisting of 

 9 pounds of cluster pine seed, 8 pounds of broom, and 3^ 

 pounds of I'samiiia arcnaria per acre are sown, and im- 

 mediately after it the ground is covered with brushwood, 

 which is kept in its place by occasional shovelfuls of sand. 

 The })ineK, the broom, and the marram grass come up 



