PLANTING OF SAND DUNES. 77 



Finally, by a decree dated April 29, 1862, the whole charge of the 

 works relating to the dunes was assigned to the ministry of finances, 

 and the immediate care to the forest administration, where they now 

 remain.^ 



The amount of sand brought up from the sea every year, and the rate 

 of progression of the dunes inland will depend upon the nature of the 

 coast, the geological formations exposed to attrition, and the direction 

 and force of the prevailing winds. It was the opinion of Br^montier, 

 who executed the first successful planting of dunes on the southwestern 

 coast of France about a century since, that these accumulations of sand 

 were formed less rapidly in earlier times than at present, or they would 

 have produced greater effects, and it is estimated that on this coast the 

 sea delivers about 25 cubic meters of sand annually to a linear meter of 

 shore.^ On the coast of Southwestern France, between the mouth of the 

 Loire and the Adour, the sea is bordered by dunes which were formerly 

 aggressive, occasioning great loss by actually burying fertile regions 

 and villages with sand, the country still further inland being sterilized 

 from want of shelter from ocean winds. 



No planting upon sand dunes can be attempted, nor can it be main- 

 tained when once begun, without the protection of a barrier along the 

 shore. This shelter is nothing else than an artificial dune, raised by 

 the wind itself, by placing obstructions in its way that compel the 

 moving sands to settle in the place and manner where they are needed. 



In forming a littoral dune, a continuous line of paling is first erected 

 parallel to the shore line,/ind about a hundred yards back from high- 

 water mark. This paling is made ot boards about l.GO meters (4 feet G 

 inches) long, from 12 to 15 centimeters (5 to 6 inches) wide, 1^ inches 

 thick, and sharpened at the lower end. A trench about 15 inches deep 

 is dug, and into this the boards are driven sevm or eight inches, so 

 that when the trench is filled up they will stand about a meter out of 

 the ground.^ 



A space an inch wide is left between the boards. The sand is not 

 raised like, dust, but generally glides along near the surface, piles up 

 in front of the paling, and, passing through, is deposited behind. The 

 process goes on till the boards are buried, when they are raised one at 



'■Les Codes dela Legislation Forestiere, Paris, 186(5, pp. 215-220. 



^Br^montier's estimate was 21^ cubic meters. Laval, from observations made in 

 1824-'32 (Anales des Pouts et Chaussees, 1847, p. 218), estimates it at 25 cubic meters. M. 

 Dutemps du Gris, conservator of forests at Bordeaux, fixes the rate of progression inland 

 at 4.3 meters (14 feet) a year, aud the amount brought up is 75 cubic meters to every 

 meter of coast line. {Supplement to Bagneri's Manual of Sylviculture, English transla- 

 tion, p. 72. 



^A primitive idea was to build a solid wall ; but this would sooner or later be buriep 

 entirely, A barrier made by a ditch and ridge of earth would serve while it lasted, 

 and hurdles, formed of stakes aud brush interwoven, would do service till buried or 

 pressed down by the weight of sand, aud might be carried up by repeated additions 

 at the top to a certain distauc i. A close board fence would cause eddies that would 

 scoop out a hollow in front, until the crest was level with the top of the obstruction, 

 when it would spt-edily be filled, and the obstruction buried. A paling secured to 

 string-piers, with spaces between, was next tried, .and did well till buried; but this 

 could not be raised. Such a fence in sectious required too much force to raise ; and 

 finally a plain series of separate boards, that might be drawn up singly from time to 

 time, was found best aud cheapest. Enough sand passes through to bank up equally 

 on both sides, and the force of the wind is somewhat relieved by the openings that 

 allow it to pass. It is only by oblique currents that a breach might be formed in ex- 

 posed places. 



A row of stakes driven into the sand, with brush woven in between a little way up, 

 and more added as they fill up (the stakes being raised from time to time), has been 

 tried, but found on the whole not so desirable as planks. These vary, according to 

 circumstances, from 1.5 to 2 meters in length. 



