150 History of the Sanens* 



rock is covered with Drift. Around the village of Wickharn there 

 are a great number of Sarsen Stones, all of which have been moved 

 from their original position. Some of the blocks contain flint 

 pebbles. I ascertained that they were all got from the neighbouring 

 fields, and were in no case brought up from a lower level; so that 

 they must have originally rested on some of the highest parts of 

 the Reading Beds, if not on the top of them, the Wickharn outlier 

 being very thick. This does not accord with Mr. Prestwich's 

 suggestion that they belonged to the white sand at the lower part 

 of this outlier (Q. J. G. S., vol. x., p. 126). I think, moreover, 

 that, had these stones been formed from the white sand, some of 

 them would be still left in place, and, being so hard, would make 

 some feature and be seen on the sides of the ridge. A large flat 

 stone near Wormstall Farm must be nearly two tons in weight." 

 Mr. Whitaker notes : — " Mr. Prestwieh has come to the conclusion 

 that the Greywethers once formed a part of the Reading Beds, for 

 the following reasons : — 1 . That their distribution is in accordance 

 with the range of the Lower-Eocene Tertiaries [see the table at 

 page 131] rather than with that of the Bagshot Sands, to which 

 they have been referred ; and having thus limited their age to the 

 Lower-Eocene Period, 2, that there is no good evidence of their 

 belonging either to the Basement-bed of the London Clay or to the 

 Thanet Sand, and therefore that they must belong to the intermediate 

 Reading Beds. This conclusion is supported by the facts— that the 

 occurrence of the Greywethers is proportioned to the development 

 of the sand-beds in that formation ; c that the lithological structure 

 of each variety is respectively in accordance with the mineral com- 

 ponents forming the strata [of the Reading Beds] in the immediate 

 vicinity of the place where these rock-blocks are found ' ; and that 

 sandstone has been noticed in place in the Reading Beds. Admitting 

 the force of these arguments, I cannot but think, however, that it 

 is very probable that some, perhaps very many, of the Greywethers 

 have once formed a part of the Bagshot Sands (which formation is 

 known to contain beds of sandstone in places), more especially at 

 the western end of the London Basin, where the Lower Tertiaries 

 are thinner than elsewhere, and where, consequently, the Bagshot 



