THEORY OF THE EARTH. 143 



already mentioned. Wherever human industry 

 has not succeeded to fix these downs, they advance 

 as surely and irresistibly upon the land, as the al- 

 luvial formations from the rivers encroach upon 

 the sea. In their progress inland, they push before 

 them great pools of water, formed by the rain which 

 falls on the neighbouring grounds, and which has 

 no means of running off in consequence of the ob- 

 structions interposed by the downs. In several 

 places these proceed with a frightful rapidity, 

 overwhelming forests, houses, and cultivated fields, 

 in their irresistible progress. Those upon the coast 

 of the Bay of Biscay* have overwhelmed a great 

 number of villages, which are mentioned in the re- 

 cords of the middle age ; and even at present, in 

 the single department of Landes, they threaten no 

 fewer than ten with almost inevitable destruction. 

 One of these, named Mimigan, has been in danger 

 for the last fifteen years from a sand-hill of more 

 than sixty feet in perpendicular height, which obvi- 

 ously continues to advance. 



In the year 1802, the pools overwhelmed five fine 

 farm-houses belonging to the village of St. Julian, f 

 They have long covered up an ancient Roman 

 road, leading from Bourdeaux to Bayonne, and 

 which could still be seen about thirty years ago, 

 when the waters were lower than they are now.f 



* See Report respecting the Downs of the Gulf of Gascony, or Bay 

 ef Biscay, by M. Tassin, Mont-de-Marsan, an. X. 

 f Memoir on the Means of fixing the Downs, by M. Bremontier. 

 \ Report of M. Tassin, formerly cited. 





