USE OF DUNES AS A BARRIER AGAINST THE SEA. 581 
of the winds in both directions,* and to have spontaneously 
clothed themselves 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 human trespassers are excluded, and graz- 
ing 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 suflices to bind the whole surface to- 
gether 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 Dunes 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 all points of 
the shallow North Sea where the agitation of the waves extends 
to the bottom, banks are forming and rolling eastwards. Hence 
* Bergsde (Reventlovs Virksomhed, ii., 3) states that the dunes on the west 
coast of Jutland were stationary before the destruction of the forests to the 
east of them. The felling of the tall trees removed the resistance to the lower 
currents of the westerly winds, and the sands have since buried a great extent 
of fertile soil, See also same work, ii., p. 124. 
