40 Mr. Webster's RepI^ to Dr. Fitton. [Jan. 



have described them, beginning with that next to the chalk, as 

 green sand, blue clay or marl, and a red or ferruginous sand. 

 Of the first, we have a remarkably fine example in the vale 

 of Pewsey, celebrated for its fossils ; and tbe latter (the ferru- 

 ginous) is well seen at Woburn and Leighton Beau.desert. 

 These I consider as undoubted tjfpes of the formations in ques- 

 tion, being described vmder these names by all geologists to the 

 present day, in the tables and maps which have been published. 

 It will, therefore, simplify this discussion if we attend to two 

 points. 



1 . Whether the bed which I have called green srrnd, viz. the 

 Underclift', Isle of Wight, and the Reigate stone, be the same 

 bed with that so called by Smith and Townsend on the west of 

 the chalk, and particularly in the vale of Pewsey ? 



2. Do the Woburn and Leighton Beaudesert sands agree 

 with that bed in the wealds of Surrey, Kent, and Sussex, which 

 is between the Folkstone bUie marl and the weald clay, and 

 which is seen at Cox Heath, Nutfield, Wolmer Forest, &c. ; or 

 with the Hastings beds in Sussex, which are below the wealil 

 clay ? 



With respect to the first, I might observe, that the UnderclifF 

 has been actually called green sand not only by me, but by Mr. 

 Conybeare in his " Outlines ;" by Prof. Buckland in his Table of 

 the English Strata printed for distribution ; by Prof. Sedgwick ; 

 in short by all English geologists who have attached the same 

 name to the bed in the vale of Pewsey ; and I might show that 

 Dr. Fitton in his paper admits what 1 have before endeavoured 

 to prove, that the Underclifi" is identical with the Reigate stone. 

 The thing, therefore, seems to be done. Pewsey = L'^nderclifl' 

 by Mr. Conybeare ; Reigate = Underchff by Dr. Fitton ; 

 and hence, since things equal to the same are equal to each 

 other, Pewsey = Reigate. Q.E. D. But I will not take this 

 advantage ; since Dr. Fitton has done me the honour to hint 

 that these gentlemen followed me vvith respect to UnderclifF 

 being = Pewsev, a circumstance which I never heard of before 

 itAvas rumoured that I was wrong.* 



I find that Mr. W. Smith, in the memoir which accompanies 

 his geological map of England, applies the term green sand to 

 the bed inimeciiateli/ beioic the chalk, and above the blue marl, 

 or oak tree clay. This blue marl he identifies in his map witii 

 the Tetsvvorth clay, and with the gault, the latter being admitted 

 by ail to be the same as the Folkstone clay. It appears to me 

 to be clear, therefore, that the ovec^z .w//f/ of Smith could not be 



* Mr. Conybeare states, (" Outlines," p. ISO,) that "in 1SI3 he made a touv in tbd 

 Isle of AVig-ht and in Purbeck, and fnnned detailed lists of tlie several strata constitut- 

 ing the series as exhibited in tiie various poinls wl.ere their sections are exposed in that 

 interesting district," 



