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. Boue'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 e 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. 
Ch.ti.Ik. 
a 
tf 
e 
rl. d 
a, Red clay and sand. 
b, Limestone like calcaire grossier, sometimes alternating with green marl 
and containing Eocene shells, 
e, Fresh-water formation, same as that of the department of Lot and Garonne. 
d, 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. Geol. de France, tome ii. p. 440. 
Vol. III. P 
