NATURAL CHANGE OF COAST LINE. 
331 
strncting within its borders wharves, piers, lighthouses, break¬ 
waters, fortresses, and other facilities for his commercial and 
military operations; and in some countries he has permanently 
rescued from tidal overflow, and even from the very bed of 
the deep, tracts of ground extensive enough to constitute val¬ 
uable additions to his agricultural domain. The quantity of 
soil gained from the sea by these different modes of acquisition 
is, indeed, too inconsiderable to form an appreciable element 
in the comparison of the general proportion between the two 
great forms of terrestrial surface, land and water; but the 
results of such operations, considered in their physical and 
their moral bearings, are sufficiently important to entitle them 
to special notice in every comprehensive view of the relations 
between man and nature. 
There are cases, as on the western shores of the Baltic, 
where, in consequence of the secular elevation of the coast, the 
sea appears to be retiring ; others, where, from the slow sink¬ 
ing of the land, it seems to be advancing. These movements 
depend upon geological causes wholly out of our reach, and 
man can neither advance nor retard them. There are also 
cases where similar apparent effects are produced by local 
oceanic currents, by river deposit or erosion, by tidal action, or 
by the influence of the wind upon the waves and the sands of 
the sea beach. A regular current may drift suspended earth 
and seaweed along a coast until they are caught by an eddy 
and finally deposited out of the reach of farther disturbance, 
or it may scoop out the bed of the sea and undermine promon¬ 
tories and headlands; a powerful river, as the wind changes 
the direction of its flow at its outlet, may wash away shores 
and sandbanks at one point to deposit their material at an¬ 
other ; the tide or waves, stirred to unusual depths by the 
wind, may gradually wear down the line of coast, or they 
may form shoals and coast dunes by depositing the sand they 
have rolled up from the bottom of the ocean. These latter 
modes of action are slow in producing effects sufficiently im¬ 
portant to be noticed in general geography, or even to be 
visible in the representations of coast line laid down in ordi- 
