180 
CHAP. X. 
THE WEALDEN FORMATION. 
The very appropriate term of Wealden^ was sug- 
gested by Mr. Martin, to designate the strata which 
in the South-east of England, are interposed between 
the lower arenaceous beds of the chalk formation 
and the Portland oolite ; the Purbeck limestones 
and shales being considered as the lojvest members 
of the group. The fluviatile origin of these va- 
rious deposits is now universally admitted : and we 
may be permitted to express our gratification, that 
our humble labours have, in some measure, assisted 
in the establishment of a fact, of so much interest 
and importance to British Geology. 
Taken in a general view, this formation may he 
described as a series of clays and sands, with subor- 
dinate beds of limestone, grit, and shale, contain- 
ing freshwater shells, terrestrial plants, and the 
teeth and bones of reptiles and fishes ; univalve 
shells prevailing in the upper, bivalves in the 
lower, and saurian remains in the intermediate 
beds ; the state in which the organic remains 
occur manifesting that they have been subject to 
the action of river currents, but not to attrition 
from the waves of the ocean. 
The entire area comprised between the escarp- 
