THEORY OF THE EARTH. 133 



Progress of the Downs. 



THE downs or hillocks of sand which the sea 

 throws up on low coasts, when its bottom is 

 sandy, have already been mentioned. Wherever 

 human industry has not succeeded in fixing these 

 downs, they advance as irresistibly upon the land 

 as the alluvial depositions of the rivers advance 

 into the sea. In their progress inland, they push 

 before them the large pools formed by the rain 

 which falls upon the neighbouring grounds, and 

 whose communication with the sea is intercepted 

 by them. In many places they proceed with a 

 frightful rapidity, overwhelming forests, buildings, 

 and cultivated fields. Those upon the coast of the 

 Bay of Biscay * have already overwhelmed a great 

 number of villages mentioned in the records of the 



the Araxis, from which the Tanais, which is a branch of it, 

 takes its origin, into the Palus Maeotis." Who does not see 

 that this nonsense, which is neither founded upon peripli nor 

 periods, is nothing else than the strange idea of Alexander's 

 soldiers, who took the Jaxartes or Tanais of the Transoxian for 

 the Don or Tanais of Scythia ? Arrian and Pliny distinguish 

 these two rivers from each other, but the distinction does not 

 appear to have been made in the time of Aristotle. How, 

 then, could such geographers as these furnish us with geolo- 

 gical documents ? 



* See the Report upon the Downs of the Gulf of Gascony 

 (or Bay of Biscay) by M. Tassin Mont de-Marsan, an x. 



