1885.] SAND-PLAINS OF BELGIUM. 435 



On a general average they may be said to be from 30 to 40 feet 

 above the level of the sea, but in some localities 100 feet and 

 upwards, and in others not above 30 ; and in some localities in 

 whicli the strand is composed mainly of shingle, as, for example, at 

 Kolberg, in Prussia, they are scarcely a few feet high. 



" The height of the sand-hills on the strand-dunes is dependent 

 both on the force of the wind and the size of the grains of sand, so 

 that the height of the sand-hills, taking into account the material 

 <if which tliey are composed, may be considered the measure of the 

 force of the wind and the magnitude of the sand combined. 



" The material of which the wind builds up dunes is usually the 

 strand-sand procured adjacent to the sea-bed. In streaks this sand 

 is often commingled witli particles of white mica ; in other places it 

 contains many grains of ironstone and granite. The size of the 

 transported grains, which depends on the strength of the wind, is 

 most apparent where they attain the greatest height. The fresh 

 strand-sand, thanks to the broken shells which it brings with it out 

 of the deep, contains lime ; but it loses this in the old washed-out 

 dunes, where it is greedily taken up by the strand grasses. 



" The form of a newly-formed dune is different from that whicli 

 has been broken down. Newly-formed dunes have the side 

 elevated towards the prevailing winds, and towards the west, north- 

 west, and south-west, a gentle acclivity of from 5° to 10°; only, when 

 a new dune arises on the remains of one that is broken down, is 

 the acclivity much more steep. The side exposed to the wind has 

 an acclivity never less than one of 30°; and where it is of little 

 breadth, it rises to 40°. 



" When, however, a dune is being broken down, other forms present 

 themselves, which vary with the destroying waves or wind. Then, 

 when the sea is ever washing on the coast, tlie dash of the waves of 

 the high tide undermine the base of the dunes, and the upper part 

 rises from this like a perpendicular wall, which the long roots of 

 the strand-grasses may maintain for a long time in that position. 

 A dune, on the contrary, scattered by the wind, presents only the 

 usual slope. 



" Indescribably waste appears the interior of such a stretch of 

 dunes. Everywhere we are surrounded by sands, which the slightest 

 wind puts in movement ; and only rarely does the sight of a living 

 creature break the loneliness — at most it is an oyster-eater turning 

 his prey hither and thither over sand-hills, or a lean hare speeds 

 through the valley, or a rabbit burrows in his hole. The wearisome 

 regular roar of the waves on the shore is the only sound that breaks 

 in upon the fearful stillness. For miles may one wander between 

 the dunes without any change of scene, or coming in sight of any 



