1850.] AUSTEN— SANDS AND GRAVELS OF FARRINGDON. 467 



cretaceous escarpment. We were unable to confirm the representa- 

 tion of Dr. Fitton, that the lower greensand occurs at the top of 

 Swindon Hill (p. 265). Day-house Farm is also described as afford- 

 ing the Purbeck, Hastings, and Wealden beds in superposition on the 

 Portland, but we have shown that it is the lower portion of the 

 Portland only which occurs at that place : the sands which Dr. Fit- 

 ton has represented as lower greensand at this place* (the minera- 

 logical resemblance having probably induced the view), belong to 

 the middle portion of the Portland series, as indicated by Trigonia 

 gibbosa. Sow. 



The principal point of interest presented by the section along the 

 east side of the great quarry at Swindon, and which, if observed here 

 or elsewhere, has been useless so far as any inference from it is con- 

 cerned, is the fact that the period which is marked by considerable 

 disturbance, by irregular deposits, carbonaceous materials, and fresh- 

 water forms, is overlaid by tranquilly deposited beds of marine sand 

 and sandstone of the Portland series. Dr. Fitton appears to have 

 overlooked the fluvio-marine conditions indicated at the Swindon 

 pits, but it is this higher portion of the Portland series which I 

 imagine he notices at p. 265, and describes as white calciferous sands, 

 with concretions in which are Portland fossils, and occurring at the 

 top of Swindon Hill, and occupying the position of the beds at 

 Dinton, full of Ostrece and Mytili, which surmount the alternating 

 series of clays, limestones, and fossil sandstones containing Cyclas 

 and Cypris. 



I do not propose to enter now on any speculation as to the physical 

 features of the Wealden, particularly as I propose to make the whole 

 body of the evidence we possess as to the nature and extent of its 

 area the subject of a distinct communication. The conditions indi- 

 cated by the series of beds at Swindon, containing freshwater forms, 

 were at no time those of a closed or land-locked area of fresh water, 

 but rather the conditions of a sea contiguous to a body of fresh 

 water, and into which masses of fresh water were discharged. Neither 

 is it necessary here to ascertain the portion of the Wealden group 

 with which the Swindon beds are synchronous ; that they are the 

 geological equivalents of some portion is sufficiently clear, and the 

 point which the Swindon section clearly establishes is, that the 

 Wealden is not, as has hitherto been represented, a freshwater accu- 

 mulation of an area of dry land subsequent to the oolitic period, 

 but was contemporaneous with the Portland, and perhaps even luith 

 older portions of the oolitic series. 



The other points which suggest themselves as deserving of notice 

 arise out of a comparison of the two masses of Portland strata at 

 Bourton and Swindon, — the distance which separates them is from 

 six to seven miles. In the lower portions of both occur beds of sub- 

 angular pebbles, which mineralogically are identical, and in all proba- 

 bility derived from the same source. That the dispersion of these 

 pebbles was not due to some momentary disturbance is clear from 

 the thickness of the beds through which the pebbles range at 

 * Loc. cit. Section No. 17, pi. 10 a. 



