﻿42 SARSEN-STONES IN A CLATPIT. [Feb. I905, 



Mr. Whitaker said that, 40 years ago or so, 1 he had published 

 a brief description of pits like those now described by the Author, and 

 they were then, as now, worked for the greywethers which were 

 used as building-material for Windsor Castle. The source of such 

 greywethers was not confined to one horizon of the Lower Tertiary, 

 and he had actually seen Eocene sandstone of Eeading age in 

 place. He thought that no other explanation of the facts than 

 that given by the Author would hold good. 



Prof. Sole as said that he had visited the pits described, under the 

 guidance of the Author, and was glad to be able to concur with him 

 in his conclusions as to the history of the sarsens. He thought that 

 the more superficial deposits of the pits might require further ex- 

 planation, and would not be surprised to find that ice in some form 

 had played a part in their formation. 



Mr. W. P. D. Stebbing, in commenting on the paper and on 

 Mr. Barrow's remarks, mentioned that the irregular dissolution of 

 the Chalk of the North Downs (as seen in sections at Tadworth on 

 the Chipstead- Valley Railway) had caused the Lower Tertiary 

 formations above to sink into the hollows between the upstanding 

 pinnacles of Chalk, and so, in the long railway-cutting, to give the 

 effect of a wave-like contour to these beds. He also mentioned the 

 cutting-through by this railway of a small bowl-shaped mass of 

 pure white sand, which under certain past conditions might have 

 been cemented into a sarsen-stone, and then would have occurred in 

 the section just as those observed by the Author in the Chilterns. 



Dr. Salter referred to similar deposits at Hyde Heath, near 

 Chesham, in which big polished blocks of pebbly greywether are 

 found. At Ayot Brickyard (Hertfordshire), the Eocene deposits dip 

 down into huge pipes in the underlying Chalk. 



[ x ' Geology of Parts of Middlesex, Herts, Bucks, &c.' Mem. G"eol. Surv. 

 (1864) pp. 66, 71. 



Sir Joseph Prestwich regarded the greywethers of this region in Buckingham- 

 shire as belonging to the Reading Series. He mentioned that ' on the Chalk- 

 hills above Bradenham, 3 miles northward (of High Wycombe), sandstone- 

 blocks are very numerous, and, although enveloped in a ferruginous clay- 

 drift, they are, I believe, nevertheless, nearly in situ.' In a footnote he specifies 

 Walter's Ash and Napple Common Quart. Journ. Geol. Soc. vol. x (1854) 

 p. 127.— Ed.] 



