Ch. XV.] INLAND CLIFF NEAR DAX. 209 



groups. But on farther inquiry, the fact, on the contrary, has 

 furnished additional grounds of confidence in these characters. 



M. Ch. Desmoulins replied, in answer to M. Bout's objec- 

 tions, that the assemblage of Eocene shells are never intermixed 

 with those found in the ' moellon,' as he calls the sandy calca- 

 reous rock of the environs of Bordeaux and Dax; and M. 

 Dufrenoy farther stated, that the hills of limestone which bor- 

 der the right bank of the Gironde, from Marmande as far as 

 Blaye, present several sections wherein the Parisian (or Eocene) 

 limestone is seen to be separated from the shelly strata called 

 ' faluns/ or ' moellon,' by a fresh-water formation of consider- 

 able thickness. It appears, therefore, that as the marine faluns 

 of Touraine rest on a fresh-water formation, which overlies the 

 marine calcaire grossier of Paris, so the marine Miocene strata 

 of Bordeaux are separated from those of Blaye by a fresh- 

 water deposit *. 



The following diagram, therefore, will express the order of 

 position of the groups above alluded to. 



No. 52. 



A 



a, Red clay and sand, 



b, Limestone like calcaire grossier, sometimes alternating with green marl 



and containing Eocene shells. 



c, Fresh-water formation, same as that of the department of Lot and Garonne. 

 rf, Tertiary strata of the Landes, with Miocene fossils. 



Inland cliff near Dax, A few miles west from Dax, and at 

 the distance of about twelve miles from the sea, a steep bank 

 is seen running in a direction nearly north-east and south-west, 

 or parallel to the contiguous coast. This steep declivity, or 

 brae, which is about 50 feet in height, conducts us from the 

 higher platform of the Landes to a lower plain which extends 

 to the sea. The outline of the ground might suggest to every 

 geologist the opinion, that the bank in question was once 



* Bulletin de la Soc. G6ol, de France, tome ii. p. 440, 

 VOL. III. P 



