Mr. Webster o« //6^ Strata lying over the Chalk. 209 



the same quality, which appears to be owing to calcareous spar 

 cementing the parts together. In our blue clay there is a con- 

 siderable quantity of carbonat of lime in a sparry state, as is evi- 

 dent from the septaria. 



The middle and upper beds of the French calcaire grossier 

 frequently contain a sandstone, with marine shells which agree, 

 though not entirely, with those of the calcaire. This sandstone is 

 sometimes white and friable, and sometimes shining and almost 

 translucent. The shells are frequently white, calcareous, and well 

 preserved, though sometimes broken and mixed with pebbles. 



The sandstone which forms the uppermost beds of the rocks of 

 Bognor, already described, do not differ much from this description. 

 It contains some fossil shells of the same species, though not in 

 such numbers as the lower beds; and some of those in the lower 

 beds, as the pinnse, are not met with in the upper beds j the shells 

 also are frequently whitened. 



By connecting all the above circumstances it would appear, 

 that if we could suppose a blending or mixture between the French 

 plastic clay, which is blackish and contains organic bodies, and the 

 lower beds of the calcaire grossier with its green earth and fossils, 

 we should have a compound agreeing sufficiently near with our 

 London clay under all its varieties ; with this difference, that that 

 of the French basin would have a greater proportion of calcareous, 

 and ours of argillaceous matter. We may therefore fairly infer 

 that they belong to the same epoch. But with respect to the 

 upper beds of the calcaire grossier of France, no strata have yet 

 been discovered in this country that correspond to them. Whether 

 any such ever existed, and whether any traces yet remain, may 

 perhaps prove a fit subject for future enquiry. 



Vol. II. 2d 



