South-west and North of France , and South of Germany. 135 
of lignites , and of fuci (Isle d’Aix), with siliceous infiltrations, 
and a particular fossil resin, like amber , and nests of hydrate of 
iron , under the form of brown iron-ore, and haematite, &c. 
This is the formation which affords nearly all the iron so active- 
ly employed in the Perigord of Poitou. Upon this deposit, 
which is more or less intermixed with green particles like chlo- 
rite, rests the coarse chalk , which presents, in Saintonge and 
elsewhere, some characters different from that part of the chalk 
of other countries. It is a kind of very white, compact, and 
porous limestone, which soils the hand very little, and is 
an aggregate of minutely triturated marine organic beings. 
Yet some larger bodies are found here and there ; for instance 
Serpulites, Caprinites, Ichthyosarcolites, some Pectens and Tri- 
gonia, &c. Upon this chalk, without chlorite, repose, on the 
north side of the basin, the chalk, with flints and siliceous petri- 
factions, containing Aleyons, Cyclolites, Nummulites, and many 
Echinites, Flustrse, Gorgoniae, Madreporse, &c. Near the Pyre- 
nees the chloride chalk, with crabs, is more abundant, and the 
chalk is very much destroyed and buried under the tertiary de- 
posites. 
The tertiary basin of the south-west of France contains four 
formations ; the molasse ; the coarse marine limestone ; the 
fresh water deposit ; and a great marine marly , and especially 
arenaceous deposit. The molasse taking the place of the plas- 
tic clay of other countries, presents, as in Switzerland, alterna- 
tions of marls, clay-marls of different colours, with calcareous and 
micaceous sandstones, and sometimes very coarse conglomerate , 
(nagelfluh). Very few traces of lignite are seen in it, and only 
in the uppermost part ; and in a few instances some remains of 
marine shells are seen in it (Libourne) ; but fragments of bones, 
probably of quadrupeds, exist here and there. 
Upon the undulating surface of this formation rests the coarse 
marine limestone , ( calcaire grossiere ), as it is distinctly seen all 
along the Dordogne from Libourne to Blaye. This calcareous 
deposit is divided into two parts ; the lower compact , the upper 
sandy , arid full of the most beaut fully preserved shells. The com- 
pact marine limestone contains no chjorite, but sometimes quartz- 
pebbles, and traces of bituminous beds, and even of lignites : it is 
a white or yellowish stone, more or less porous and indurated. 
