9 



throughout the remains of freshwater shells, are visible on the sum- 

 mit of the cliffs between Gris-nez and Equihen : where a thin bed oc- 

 curs of somewhat bituminous clay, abounding in silicified wood, the 

 cavities of which are coated with minute crystals of quartz. This 

 bed corresponds precisely to that which exists on the top of the Isle 

 of Portland, bearing there the name of' Dirt,' and abounding in si- 

 milar wood ; and on the French coast it is associated with beds of 

 limestone, different from the stone beneath, and containing shells 

 in great numbers, apparently of the genera Cyclas and Ampullaria. 

 The next stratum of the Boulonnois is the same with that which 

 occurs at Garsington and Shotover-Hill in Oxfordshire, and at Brill 

 and other places in the vicinity of Aylesbury in Buckinghamshire, — 

 and which has hitherto been regarded as the representative of the 

 Portland limestone. — Respecting its geological relations, however, 

 some doubts still remain to be cleared up ; since, although several 

 of the fossils are the same with those of the Isle of Portland, the 

 aspect of some of the beds, differs a good deal from that of the 

 Portland stone; and the characters agree in many respects with 

 those of the lowest beds of the Shanklin-sands in the vicinity of 

 Hythe. The formation in the Boulonnois consists, as in Oxford- 

 shire, of calcareous concretions of great size, abounding in petrifac- 

 tions, and imbedded in yellowish somewhat ferruginous sand : and 

 the appearance of the stratum, especially between Gris-nez and Au- 

 dreselles, where the shore is covered with these enormous masses 

 fallen from the sands above, is exceedingly striking and remarkable. 

 To this formation a series of beds succeeds, the equivalent of the 

 strata between the Portland limestone and the coral rag : — corres- 

 ponding precisely to those of the shore near Weymouth, and con- 

 sisting of alternations of sand, limestone and clay ,in some instances 

 bituminous and abounding in fossils. — These occupy the whole of 

 the lower part of the cliffs from Gris-nez to Equihen, and are visible 

 in several places in the interior. The pisolite and coral rag are not 

 seen upon the coast, but come up at a short distance within it ; and 

 their outcrop is conspicuous at Basinghen, and along a line extend- 

 ing from that place, by Wierre and Hautenbert, to Alinctun. On 

 the north of that line this formation is succeeded by a valley con- 

 stituting a very remarkable feature of the country, and occupied by 

 beds of clay containing fossils identical with those of the Oxford 

 clay, and including, especially at the lower part, subordinate beds of 

 sand and calcareous grit. These are followed on the north, near 

 Marquise, by the equivalent of the Bath-oolite, (the Cornbrash and 

 Forest-marble, which precede the oolitic beds near Bath, being in- 

 distinct or wanting) : — and this formation seems to come in without 

 any intervention, immediately after the gault or subjacent sand, on 

 the north of the denudation ; where it occupies the surface, in nearlv 

 horizontal strata placed unconformably over beds of the coal forma- 

 tion, or of mountain-limestone. — The former of these is disclosed in 

 a small space only, in the vicinity of Hardinghen : and the author 

 refers for an account of it to a Memoir now preparing for publication 

 by M. Gamier of Arras. — The mountain limestone, which is the 

 lowest formation of the Boulonnois, in some places comes in imme- 



