'366 Dr. Fitton on the Strata [Nov, 



that relates to the beds between the chalk and the Purbeck lime- 

 stone, in the " Outlines " of Messrs. Conybeare and Phillips ; a 

 work so very remarkable for the judgment and success with which 

 its multifarious contents have been brought together and ren- 

 dered consistent. In the account of the wealds of Kent and Sus- 

 sex,* described for the first time by Mr. Conybeare in that pub- 

 lication, the tract between the chalk and the Hastings sands is said 

 to be occupied by a ridge composed of Green sand,' quite distinct 

 from the < Iron sands ' of Hastings, and separated from them by 

 a well-marked valley, containing the ' Weald ' clay. But in 

 the description of the Isle of Wight, f the very same denomina- 

 tions are applied to strata entirely different ; the author adopt- 

 ing the arrangement of Mr. Webster, and regarding the lower 

 part of that island as composed of one series only of ferruginous 

 sands, which he identifies with those of Hastings : so that the 

 reader of the descriptions afterwards given of other parts of 

 England, in which these sands and clays occur, must connect 

 with those terms a different meaning, according to the dis- 

 trict which he may happen to have first seen, or may adopt as 

 the type of his comparison. Mr. Conybeare indeed has himself 

 admitted the obscurity in which this part of the British series 

 of strata is involved ; and has ascribed it, not merely to the 

 imperfect state of our information, which seems tome to be the 

 true cause, but to a greater variation of structure and composi- 

 tion in these beds, when occurring in different quarters, than has 

 been observed in other members of the series, —or than will, I 

 believe, be found in reality to exist. 



The standard publication to which Mr. Conybeare and all 

 other geologists have referred, in treating of the Isle of Wight, 

 is the well known letters of Mr. Webster to Sir Henry Engle- 

 field,^ — a work which has given to that instructive district an 

 almost classical celebrity, and has contributed most essentially 

 to the recent progress of geology in this country. It seems to 

 me, however, from what I have recently seen, that Mr. Webster's 

 arrangement of the lower strata of the Isle of Wight has been 

 adopted without sufficient examination ; for though he has iden- 

 fied in a general manner the sands of Hastings and Tunbridge 

 Wells with his ferruginous sands, and stated that the weald clay 

 belongs to this formation, and has also mentioned grit stone as 

 occurring in it, he does not appear to me to have duly appre- 

 ciated the relations of the different members of this part of the 

 series ; having overlooked the important natural features re- 

 sulting from the presence and situation of the weald clay, and 

 mentioned the Purbeck beds as constituting the lowest strata of 

 the Island- From a paper recently presented to the Geological 

 Society by Mr. W~ebster, an abstract of which has been pub- 



* Outlines of the Geology of England and Wales, p. 144, &c. 

 + Page 135. % London. 4to. 1816. 



