LfTTORAL DEPOSITS. 97 



the action of the sea, owing to their hardness or the 

 unalterable nature of their composition. 



The most common of all minerals in the littoral 

 deposit of France, at the level of low-tide, is trans- 

 parent quartz. It is distributed in such profusion 

 that the deposit is sometimes almost entirely com- 

 posed of it. This is to be accounted for by its 

 extreme hardness and its abundance in the cliffs. 



The clays are found in the deposit at the bottom 

 of gulfs and retired creeks ; tliey are carried away 

 in the form of mud, and settle down when the seif is 

 calm and deep. In some cases where beds of clay 

 or schist abound on a coast (as at Honfieur), the pro- 

 portion of clay contained in the littoral deposit is 

 very great. 



Carbonate of lime or chalk is found in very 

 variable proportions, and is derived from calcareous 

 rocks and the remains of molluscs. In the Meditei- 

 ranean it is most abundant when the cliffs are com- 

 posed of calcareous rock, as at Nice and Marseilles. 

 Its fragments are always well-rounded. On the shores 

 of the Ocean, the Littoral deposit of lime is small, 

 because the movement caused by the tides dissolve3 

 and disposes of it very rapidly even when it is strong 

 or compact. An instance of this may be observed 

 between Havre and Dunkirk, or, better still, at 

 the foot of the Lower Pyrenees. It may even happen 



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