354 Qn the Geologtf of the Isle of Wight, S^c. [May, 



about the surface in the northern parts of the island, near Cowes 

 and Ride, we cannot speak with the same conlidence, though 

 they may, perhaps, generally be traced to the same formatioju 

 From all these facts we conclude, that the upper freshwater rock 

 doe« not occupy so large a superficial extent as has been 

 imagined. 



On a review of all the phenomena presented by the tertiary 

 deposits of the Isle of Wight, I see no good reason for altering 

 their present classification — a conclusion which every one must 

 arrive at with pleasure who properly estimates the scientific 

 researches of Mr. Webster. At the time he commenced his 

 examination of the Isle, little was known respecting our newer 

 strata, nor had any one successfully attempted to identify them 

 with the similar formations of the Continent. In proof of the 

 truth of this assertion, we have only to recollect that there 

 appeared in 1811, under the sanction of the Geological Society, 

 a paper by Dr. Berger, in which the strata over the chalk were 

 confounded with the strata under the chalk ; and in which the 

 Portland oohte was, by a magical power of misarrangement, made 

 to represent the calcaire grossier of the Paris basin ! 



VIII. Diluvium. 



This paper has already extended to so great a length that we 

 shall omit some of the observations we intended to offer on the 

 gravel beds of the district. It is true that in many parts of the 

 Isle the external form of the country has little connexion with 

 its physical structure. The accumulation of diluvium may, 

 however, be sometimes traced to specific denudations. Thus, 

 we find that the masses of gravel which are so much accumulated 

 to the north-west of Newport are connected with one of the 

 greatest denudations exhibited by the whole chalk range. The 

 denudation of Brading is, perhaps, still more remarkable. The 

 small rivulets which spring on the south side of the central 

 range do not descend into the sea by the way which nature 

 seems to point out to them ; but cut directly through the chalk 

 downs, and find an outlet in Brading harbour. This fact proves 

 that these rivulets have not excavated their present channels, 

 and that the greater inequalities presented by the surface of the 

 Isle have not arisen out of the long continued action of those 

 destructive causes which are now in operation. Many other 

 parts of our great chalk range present the same phenomenon. 



P. S. The fifty-ninth number of Sowerby's Mineral Conchologv 

 has appeared during the j)assage of the preceding paper through 

 the press. It is now attempted to arrange under the genus 

 potamides a great many shells which have been considered as 



