NATUEAL BEEAKWATERS. 157 



tion. Daring the period of the ebb, on the contrary, the water 

 which breaks on the shore is retained by the current of low water, 

 and is as though attracted towards the open sea : neither does it 

 attack the cliff with as much energy as the rising tide. The dif- 

 ference which exists between the force of the waves of the flow and 

 those of the ebb, can be measured by the respective extent of the in- 

 termediary platforms. 



If the waves march constantly to the assault of the shore to 

 transform into cliffs the heights of the coast, the latter, on their side, 

 are not satisfied with merely resisting by their mass, and by the 

 greater or less hardness of their strata, but many of them besides 

 take care, one might say, to protect their threatened base against the 

 waves. A thick vegetation of seaweed, like floating hair, drapes 

 the cornices, breaks the force of the surf, and changes into torrents of 

 eddying foam the enormous rollers which rush to attack the rocks 

 with great speed. Besides, all that portion of the rocks comprised 

 between the levels of high and low water is covered with balani and 

 other shells, numerous enough to give the stone the appearance at 

 certain hours of a swarming mass, and to form it afterwards into an 

 immense immovable carapace.* 



The coasts thus protected are precisely those which, by the solidity 

 of their rocks, would best , resist the attacks of the sea. As to the 

 cliffs composed throughout their thickness, or only at their base, of 

 less resisting materials, they give way too often for the molluscs and 

 seaweed to venture in great numbers on that part of the rock which 

 the waves have just assailed. Great blocks detach themselves from 

 the upper strata, and fall on the beach. Afterwards, under the action 

 of the waves, they break into smaller pieces, then into pebbles which 

 the surge rolls and chafes incessantly. Under these fragments, con- 

 stantly moved by the wave, no germ of animal or plant can develop 

 itself, no living organism brought from the open sea can exist there. 

 A desert is made even in the waters which dash against the roaring 

 mass. 



When this is the case, it is the crumbling masses and the pebbles 

 of the strand which themselves serve as bulwarks of defence to pro- 

 tect the wall of the cliffs from fresh damage. Supported in a slope 

 on the lower part of the rock, or else scattered in the waves and trans- 

 formed into shelves, the fallen blocks break the force of the waves, and 

 retard the progress of erosion. It is thus that on the coasts of the 

 Mediterranean, near Yintimillia, the lower strata of the cliffs are 

 * See below, the sections entitled, The Earth and its Flora, and the Earth and its Fauna, 



