664 Geological Society : — 



Beds. Some of the pebbles of pnddingstone and of the large 

 waterworn flints show distinct evidences of noding. No rocks 

 foreign to the district have been found. 



As a general rule, the gravel becomes coarser in depth, the 

 lower sections containing a high percentage of large waterworn 

 flints. In no case are the pebbles crushed as in the Glacial beds, 

 and they usually lie quite horizontally. The spaces between the 

 pebbles are completely filled with loose sand and small stones. 

 The small stones are mostly Reading pebbles and white quartz, 

 with a few pebbles of lydite. The gravel is quite homogeneous. 



Recent researches appear to indicate that the quartz and lydite 

 pebbles in this district have been derived from the Lower Green - 

 sand (which crops out north and north-west of the Chilterns) 

 after the final breach of the Chiltern scarp, in the gaps of which 

 the quartz-pebbles are found in such abundance. If this be 

 correct, it would indicate not only that the materials of which the 

 gravels are composed came from the north, but also that the vast 

 quantities of quartz-pebbles which are found everywhere in the 

 upper plateau-gravels nearest to Little Heath are derived from the 

 same source. 



Reasons are adduced in support of the contention that the 

 loamy sands and gravels are marine deposits laid down in a shallow 

 sea ; and that they cannot be of Glacial origin. 



The area over which the gravels have been found extends for 

 over a mile and a half south-east and north-west, by about half a 

 mile north-east and south-west. The} r thin out towards the north- 

 west, where the} r are only found in occasional outliers around which 

 the Glacial beds rest directly upon the Chalk. It is clear that 

 there must have been a considerable erosion of the pebble-beds 

 before the Glacial beds were deposited. 



As to the age of the loamy sands and gravels, the presence of 

 the pebbles of puddingstone proves that they cannot be Reading 

 Beds, and as they rest directly upon the Chalk, the London Clay 

 and Reading Beds must have been denuded before their deposition. 

 They must be later than the Miocene movements, and are obviously 

 pre-Glacial. They are apparently of marine origin, and their 

 similarity to the high-plateau gravels farther south and to the 

 beds at Headley Heath, Netley Heath, etc. suggests their 

 contemporaneous deposition with these gravels. They are pro- 

 bably, therefore, of Pliocene age. 



2. ' Notes on the Correlation of the Deposits described in Mr. C. 

 J. Gilbert's paper with the High-Level Gravels of the South of 

 England (or the London Basin).' By George Barrow, F.G.S., 

 M.LM.M. 



The gravels described in the jDreceding paper belong to a series 

 of widespread deposits of which the harder constituents have 

 usually been derived from two areas only : one within the Chalk- 

 escarpment (or local), the other beyond this escarpment, but 



