part 1] LITTLE HEATH SANDS AND GRAVELS. 47 



.and Hertfordshire, including Mr. Gilbert's district. Owing mainly 

 to the war, that work has not been published, except the very 

 brief abstracts which appear in the Summaries of Progress. There 

 exists in manuscript, however, a complete new survey of the 

 Beaconsfield and Aylesbury sheets, with descriptive memoirs. If 

 those memoirs had been published. Mr. Gilbert would have had the 

 -opportunity of criticizing the speaker's account of the deposits at 

 Little Heath. 



Mr. Gilbert claims for these deposits an extension of a mile and 

 a half : it is an underestimate, for thej' are scattered over some 

 hundreds of square miles of the Chiltern plateau. In 1911 the 

 speaker read to the Societj^ a joint paper, by Capt. Noble and 

 himself, on the Glacial origin of the superficial deposits covering 

 that plateau; a paper which caused a warm discussion. Mr. Barrow, 

 among others, opposed the ideas expressed, and it was therefore 

 gratifying to find that he now spoke of the ' Glacial ' deposits, as 

 if their age were a matter of common knowledge. 



The re-survey was for three years under the superintendence of 

 ■Clement Reid, and among the occurrences especially looked for were 

 Pliocene deposits. Reid had an unrivalled knowledge of Pliocene 

 beds, and came direct from Cornwall hoping to find a representative 

 ■of the Pliocene 400-foot platform that he had mapped there. He 

 came to the conclusion that there was no evidence for its existence. 

 Mr. Barrow had seen newer sections, but the speaker would like 

 him to remember that the idea of a 400-foot Pliocene platform 

 had occurred to his predecessors. 



The chief point in the papers seemed to be the age of the 

 •deposits called Pliocene. No fossils have ever been found. 

 Mr. Barrow seemed to rely mainly on the presence of pebbles of 

 vein-quartz, which (he says) are never found in the Reading Beds 

 of the London Basin. The speaker was not convinced that these 

 cjuartz-pebbles never occur in Reading Beds, and saw no reason 

 why they should not do so : for, as one proceeds from the Thames 

 Yalley towards the Chilterns, there are changes in the character 

 •of the Reading Beds : for instance, there appear the Hertfordshire 

 Puddingstone and beds which produce sarsens, and also flint-pebbles 

 that are but partly rounded and sometimes large, instead of the 

 perfectly-formed ones so numerous in, say, the Croydon area. 

 These features indicate that the margin of the deposits is being 

 approached. Good sections may be said to be non-existent; such as 

 occur show signs of disturbance, and so it is open to anyone to «:ay 

 that the pebbles have been introduced later. Quartz-pebbles have 

 been recorded by Mr. Osborne White as extremely abundant in 

 Reading Beds in the Lane End outlier, west of High Wycombe, 

 where he says London Clay caps the deposit, proving it to be in 

 place. He also records lydite-pebbles and subangular flints, which 

 characterize the deposits that Mr. Barrow regards as Pliocene. 



It is established that the Reading Beds rest on a plane cut across 

 the gently-folded Chalk. Thus at Taplow, near Maidenhead, 

 Reading Beds rest on the Marsupites Zone ; farther north, at High 



