302 RAMBLES OP A NATURALIST. 



composed of the alluvial deposits that have been left 

 by the sea. 



To comprehend the whole extent of these accumu- 

 lations of soil, one ought to proceed about six miles 

 north of La Rochelle to the bay of Aiguillon. In 

 our own time this bay forms a nearly regular 

 crescent, whose entrance is scarcely more than 7000 

 yards across, while its depth is 9000 yards. For- 

 merly the sea entered the land from Longueville to 

 the Point Saint Clement by an opening of more than 

 34,000 yards. The gulf then widened, and gave off 

 deep and indented secondary bays in all directions, to 

 the north as far as Luon and Maillezais, to the east 

 as far as Niort and Grip, and to the south as far as 

 Benon and Aigrefeuille. From the entrance of the 

 gulf to Niort, the distance was not more than fifty 

 kilometres *, while it was forty-two kilometres from 

 to Aigrefeuille. To go in a straight line from 

 to Aigrefeuille it was necessary to cross the 

 gulf from north to south, passing over about forty- 

 two kilometres of water, while at the present day 

 this journey may be made entirely by land. Longue- 

 ville is now about twenty-five kilometres from the 

 shore, Luon more than twelve, Maillezais about 

 twenty-nine, Niort forty-eight, Grip forty-nine, 

 Benon twenty-one, and Aigrefeuille about twenty- 

 two. Between the southern extremity of the bay 

 of Aigrefeuille, and the ancient basin of Fouras, the 



quality of the salt. The blue clay is the only one which yields a 

 very white salt, whilst the product of the yellow clay, is always 

 coloured with the same hue. 



* [The kilometre is 1093 yards.] 



