﻿26 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 20, 



covered by others, in which a careful search, continued for many years 

 by my relation the late Mr. William Trimmer, in the numerous brick- 

 fields and gravel-pits opened in them, detected no fossils. The upper 

 or non-fossiliferous deposits of the low grounds extend over the higher 

 districts, ranging south of the Uxbridge Road, by Ealing, Hounslow, 

 Heston, Norwood, Southall, Drayton, Harnondswirth, and Cowley. 

 The lower deposits, and consequently the upper, appear, by the evi- 

 dence of the granitic and other foreign detritus, recently collected at 

 Brentford by Mr. Morris, to have been formed subsequently to the 

 denudation of the erratic tertiaries. I should refer the upper or 

 non-fossiliferous deposits to the period of the Warp in Norfolk ; and, 

 if my views on this subject be correct, it becomes an interesting ques- 

 tion for future investigation, whether the agencies which produced 

 these upper deposits had any connection with the disappearance of 

 the great mammals. 



23. At the same time that I think we have evidence of nearly the 

 whole of England being submerged during the erratic period, it is by 

 no means improbable that both subsidence and re-elevation commenced 

 from the north ; so that the district south of the Thames, connected, 

 perhaps, at that time with the Continent, may have remained above 

 water when Norfolk was submerged ; and portions of Norfolk and of 

 the still higher regions north and west of it may have emerged while 

 Dorsetshire, Hampshire, and Sussex remained beneath the sea. Por- 

 tions of the desiccated bed of the glacial sea may have connected the 

 emerging northern districts with portions of the Continent which 

 escaped the glacial submergence, and may thus have afforded facilities 

 for immigrations of colonies of plants and animals which had been 

 driven southwards during the period of subsidence. 



Deposits of Gaytonthorpe. 



The valley of the Nar opens to the estuary of the Wash. Its 

 marine clay, described by Mr. Rose *, containing shells exclusively of 

 existing species, associated with bones of extinct elephantine mam- 

 mals, follows the windings of the valley for three miles to the north- 

 east, and for about the same distance to the south-east. Its range, 

 laid down by Mr. Rose on the Ordnance sheets exhibited to the So- 

 ciety, shows that the width of this ancient estuary formation is, on 

 the average, about half a mile. Two miles north of its eastern half, 

 and at a somewhat greater elevation, is the smaller valley of Gayton- 

 thorpe, opening also to the Wash, and ranging north-east for about 

 two miles from the village of Gaytonthorpe. It is filled with depo- 

 sits, the variable character of which is shown in the several marl and 

 clay pits opened along its course. Their width, which is somewhat 

 more than a quarter of a mile at the western end, contracts to less 

 than one-eighth of a mile at the eastern end. They are traversed 

 nearly in their centre by the road from Gaytonthorpe to Massingham 

 Heath. 



The following is a description of the sections exhibited at the dif- 

 ferent pits, commencing at the most western. 



* Loc. cii. 



