558 USE OF DUNES AS A BARRIER AGAINST THE SEA. 



with a dense growth of the various plants, grasses, shrubs and 

 trees which nature has assigned to such soils. It is observed in 

 Europe that dunes, though now without the shelter of a forest 

 country behind them, begin to protect themselves as soon as hu- 

 man trespassers are excluded, and grazing animals denied access 

 to them. Herbaceous and arborescent plants spring up almost at 

 once, first in the depressions, and then upon the surface of the 

 sand-hills. Every seed that sprouts, binds together a certain 

 amount of sand by its roots, shades a little ground with its leaves, 

 and furnishes food and shelter for still younger or smaller growths. 

 A succession of a very few favorable seasons suffices to bind the 

 whole surface together with a vegetable network, and the power 

 of resistance possessed by the dunes themselves, and the protection 

 they afford to the fields behind them, are just in proportion to 

 the abundance and density of the plants they support. 



The growth of the vegetable covering can, of course, be much 

 accelerated by judicious planting and watchful care, and this 

 species of improvement is now carried on upon a vast scale on 

 the sandy coasts of "Western Europe, wherever the value of land 

 is considerable and the population dense. 



Use of Dimes as a Barrier against the Sea. 



Although the sea throws up large quantities of sand on flat lee- 

 shores, there are many cases where it continually encroaches on 

 those same shores and washes them away. At aU points of the 

 shallow ISTorth Sea where the agitation of the waves extends to 

 the bottom, banks are forming and rolling eastwards. Hence the 

 sea-sand tends to accumulate upon the coast of Schleswig-Holstein 

 and Jutland, and were there no conflicting influences, the shore 

 would rapidly extend itself westwards. But the same waves which 

 wash the sand to the coast undermine the beach they cover, and 

 still more rapidly degrade the shore at points where it is too high 

 to receive partial protection by the formation of dunes upon it. 

 The earth of the coast is generally composed of particles finer, 

 hghter and more transportable by water than the sea-sand. "While, 

 therefore, the billows raised by a heavy west wind may roU up 

 and deposit along the beach thousands of tons of sand, the sama 

 waves may swallow up even a larger quantity of fine shore-earth. 



