CUEYES OF GEEATEST STABILITY. 165 



always the same dunes, the same shells scattered on the sand, the 

 same birds assembled by thousands on the edge of the lagunes, the 

 same lines of waves which pursue one another, and break with great 

 noise in a sheet of foam. In the whole field of view the only remark- 

 able objects are the spars of shipwrecked vessels that can be seen, 

 from afar on the white sand. However, the shores which present 

 the most regular series of convex and concave curves, which one 

 might call the outline of the greatest stability, are exposed also to 

 rapid erosions when the bulwark of defence which flanks them at 

 either of their extremities yields to the pressure of the waves. Thus 

 the shores of Medoc, which are the continuations of the uniform coast 

 of Saintonge, to the south of the bay of the Grironde, have incessantly 

 retreated before the sea ever since the rocky promontory (of which 

 the ledge of Cordouan is the sole remains) disappeared under the 

 united ravages of the river and the ocean. 



But if the sea demolishes on one side, it builds up on the other, and 

 the destruction of the ancient shores is compensated for by the 

 creation of new coasts. The clays and limestones torn from the 

 promontories, the shingle of every kind which is alternately thrown 

 up on the shore and swept back in the waves, the heaps of shells, the 

 silicious and calcareous sands formed by the disintegration of all these 

 fragments, are the materials employed by the sea for the construction 

 of its embankment, and the silting up of its gulfs. 



It is on each side of the cliffs or low points worn away by the 

 waves, that the work of reparation commences. Each wave accom- 

 plishes a double work, for in sapping the base of the promontory it 

 loads itself with fragments which it deposits immediately on the 

 neighbouring strand ; by the same action it causes the point to re- 

 treat, and the shore of the bay to gain. Thus, owing to two series 

 of apparently contrary results, the razing of the points and the filling 

 up of the bays, coasts more or less deeply indented, gradually ac- 

 quire the normal form with gracefully rounded curves. Whatever 

 be the outline of the primitive coast, each inflection of the new shore 

 rounds itself like the arc of a circle from promontory to promontory. 

 In those places where tlie ancient coast was itself semi-circular, the 

 sand or gravel cast up by the billows is deposited on the beach ; but 

 when the coasts are irregular and indented by deep creeks, the sea 

 simply leaves them and constructs sand or shingle banks in front of 

 them, which end by becoming the true shore. 



The formation of such a breakwater may be explained in a very 

 simple manner. The waves of the open sea, driven against the shore, 



