274 RAMBLES OF A NATURALIST. 



the south. Several rivers, amongst others the Cha- 

 rente, the Sevre, and the Saint Benoit, empty them- 

 selves into this basin, and their currents, which are 

 opposed to each other owing to the situation of their 

 mouths and the disposition of the coast, mutually 

 neutralise one another. Thus the detritus, which 

 has been carried away from the marshy districts 

 through which they have flowed, is prevented from 

 being discharged into the open sea. 



The ocean on the other hand contributes in two 

 different ways in maintaining and augmenting this 

 accumulation of mud. For a considerable distance 

 from the coast the sea is of very little depth, and its 

 bottom, which is composed of strata very similar to 

 those of the neighbouring districts, is readily in- 

 fluenced even by ordinary tides. The water flowing 

 within the space inclosed by the islands and the 

 coast penetrates into it by three straits *, and meets 

 on its passage with submarine beds, from which it 

 always takes up a certain amount of matter, while 

 the currents, impinging upon one another, serve only 

 to carry new detritus towards the shore. This cause 

 acts with a very much greater force, when the wind, 

 coming from the open sea, drives the high waves 

 of the Atlantic against the coast. At this time, the 

 bottom of the sea seems to be convulsed by the agi- 

 tation of these liquid masses, whilst the cliffs, which 

 are formed of yielding rock, giving way to the re- 



* These straits are the strait of Breton, between the island of Re 

 and the coast ; the strait of Antioche, between the islands of Re and 

 Oleron ; and the strait of Maumusson between the islands of Oleron 

 and the continent- 



