ARTIFICIAL DUNES. 567 



Ccmi/rol of Dimes h/ Mem, 



There are three principal modes in which the industry of man 

 is brought to bear upon the dunes. First, the creation of them 

 at points where, from changes in the currents or otlier causes, 

 new encroachments of the sea are threatened ; second, the main- 

 tenance and protection of them where they have been naturally 

 formed; and tliird, the removal of the inner rows where the 

 belt is so broad that no danger is to be apprehended from the 

 loss of them. 



In describing the natural formation of dunes, it was said that 

 they began with an accumulation of sand around some vegetable 

 or other accidental obstruction to the drifting of the particles. 

 A high, perpendicular cliff, which deadens the wind altogether, 

 prevents all accumulation of sand ; but, up to a certain point, the 

 higher and broader the obstruction, the more sand wiU heap up 

 in front of it, and the more will that which falls behind it be 

 protected from drifting farther. This famihar observation has 

 taught the inhabitants of the coast that an ai-tificial wall or dike 

 will, in many situations, give rise to a broad belt of dunes. 

 Thus a sand-dike or wall, of three or four miles in length, thrown 

 in 1610 across the Koegras, a tide-washed flat between the Zuider- 

 zee and the ]^orth Sea, has occasioned the formation of rows of 

 dunes a mile in breadth, and thus excluded the sea altogether from 

 the Koegras. A similar dike, called the Zijperzeedijk, has produced 

 another scarcely less extensive belt in the course of two centuries. 



A few years since, the sea was threatening to cut through the 

 island of Ameland, and, by encroachment on the southern side 

 and the blowing off of the sand from a low flat which connected 

 the two higher parts of the island, it had made such progress, 

 that in heavy storms the waves sometimes rolled quite across the 

 isthmus. The construction of a breakwater and a sand-dike have 

 already checked the advance of the sea, and a large number of sand- 

 hills has been formed, the rapid growth of which promises com- 

 plete future security against both wind and wave. Similar effects 

 have been produced by the erection of plank fences, and even of 

 simple screens of wattling and reeds.* 



* STAHiNa, De Bodem van Nederland, i., pp. 329-831. Id., Voormaals en 

 TTiana, p. 168. Akdresen, Om Elitfarmationen, pp. 280, 295. 

 The creation of new dunes, by the processes mentioned in the text, seema 



