



On. XVIIL] 



DELTA OF THE EHONE. 



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Mediterranean, driven by winds from the south, sand-bars 

 are often formed across the mouths of the river : by these 

 means considerable spaces become parted off from the sea, 

 and subsequently from the river also, when it shifts its chan- 

 nels of efflux. As some of these lagoons are subject to the 

 occasional ingress of the river when flooded, and of the sea 

 during storms, they are alternately salt and fresh. Others, 

 after being filled with salt water, are often lowered by evapo- 

 ration till they become more salt than the sea ; and it has 

 happened, occasionally, that a considerable precipitate of 

 muriate of soda has taken place in these natural salterns. 



the latter part of Napoleon's career, when the excise 

 laws were enforced with extreme rigour, the police was em- 

 ployed to prevent such salt from being used. The fluviatile 

 and marine shells enclosed in these small lakes often live 

 together in brackish water ; but the uncongenial nature of 

 the fluid usually produces a dwarfish size, and sometimes 

 gives rise to strange varieties in form and colour. 



Captain Smyth, in his survey of the coast of the Medi- 

 terranean, found the sea, opposite the mouth of the Rhone, to 

 deepen gradually from four to forty fathoms, within a distance 

 of six or seven miles, over which the discoloured fresh water 

 extends ; so that the inclination of the new deposits must be 

 too slight to be appreciable in such an extent of section as a 

 geologist usually obtains in examining ancient formations. 

 When the wind blew from the south-west, the ships employed 

 in the survey were obliged to quit their moorings ; and when 

 they returned, the new sand-banks in the delta were found 

 covered over with a great abundance of marine shells. By 

 this means we learn how occasional beds of drifted marine 

 shells may become interstratified with freshwater strata at a 

 river's mouth. 



Stony nature of its deposits. — That a great proportion, at 

 least, of the new deposit in the delta of the Ehone consists of 



tained. 



matter 



Montpelie 



from the sea near the mouth of the river, imbedded in a crys- 

 talline calcareous rock. Large masses, also, are continually 

 taken up of an arenaceous rock, cemented by calcareous 



