298 CONCLUDING OBSERVATIONS. 



corresponding with the termination of the Sussex Downs, at Beachyhead; 

 and the northern point at Calais, with that of the Kentish hills, at Dover. 

 The included area contains beds of Green and Iron sand, but the greater 

 part of the coast is composed of a calcareo-argiHaceous formation, which 

 underhes the sand last mentioned, and is considered by Professor Buckland 

 as identical with the Oxford clay*. 



This occurrence of the more ancient deposits, within a zone of chalk 

 hills, is a problem exceedingly difficult of solution. From the appearance 

 of the strata, as shewn in the plan and section, one might be almost led to 

 suppose that the chalk, at some remote period, was continuous over the 

 whole extent of country that now forms the counties alluded to, and that 

 by some unknown catastrophe the central mass of chalk had been swept 

 away, and the underlying deposits forced into their present situation, I 

 do not, however, mean to insinuate, that such has actually been the case, 

 but that the mode in which the strata are disposed presents such an 

 appearance ; for although (as an eminent geologist f has remarked), the 

 truncated form of the escarpment of the chalk, evidently shews it to have 

 once extended much farther than at present, stiU it would be highly rash 

 to assume, that at any period it actually covered the whole space in which 

 the inferior strata are denuded. 



We shall now proceed to take a rapid sketch of the geological features 

 of the several formations previously described, that their most important 

 characters may be placed in a conspicuous point of view. 



1. The Iron sand (p. 24), requires but a brief notice. It has been 

 shewn to consist of various strata of sand and sandstone, including beds 

 of ironstone (p. 28), shelly limestone (p. SO), and coal (p. 34). The Hme- 

 stone bears a considerable resemblance to the upper beds of the Purbeck, 

 and is supposed to form the base, upon which the iron sand rests ; yet 

 there is reason to conclude that in some instances (p. 33), these deposits 

 alternate. The shells enclosed in the hmestone are wholly bivalve ; some 



* Vide Phillip^ Geological Outlines, p. 155. f Rev. W. D. Conybeare, Phillips' Outlines, p. 144, 



