446 EOCENE PERIOD. CHAP. 



ft. in. 



Sand, white, irregular ... 2 6 



Red clay ' .16 



Light grey clay . . . . . . . . T' o 6 



Very dark grey clay . . . ' ' 6 



Kedclay . .20 



Light grey clay .10 



Sand, yellow, with bands of brown clay . . . . . a o 



Dark clay - r . . 10 o 



Sand, ash coloured L not exposed in the cutting < ..50 



Green-coated flints J L * 

 Under this the chalk. 



Mr. Prestwich gives also an excellent section at Clayhill, New- 

 bury, which in general range matches that at Sonning Hill : 



ft. 



JBasement bed of the London clay, consisting of brown clay 



and traces of shells . . . . . . . 10 



Mottled, red, and bluish clay . . . . . . . 15 



White sand i 



Mottled clay . . ....... . . .10 



Sands and loam . . . . . . . . .10? 



Light-coloured and ochreous sand, laminated .... 3 



Clay dark grey, laminated, sand grey and green, and a few pebbles 8 

 The same, with Ostrea bellovacina . . . . . . i 



Clay dark grey, with greensand ; no oysters .... 2 



The same, with oysters, teeth, &c., pebbly i 



The game, with pebbles and a few unrolled flints i 



Chalk, with tubular perforations filled with greensand . . 20 



In these sections no mention is made of the well-known ' Druid' 

 sandstone of Wiltshire, or of the flinty pudding-stone of Hert- 

 fordshire. Sands of greater thickness occur in other excavations, 

 usually under the mottled clays, and it is very conceivable that 

 they may elsewhere be represented by hard sandstones, as some 

 of the pebbly sands may have become converted into siliceous 

 pudding-stone. In this way perhaps we may account for the 

 'Druid' sandstones, or 'Grey Weathers,' or 'Sarsen' stones, which 

 lie in such abundance about Ashdown in the Berkshire valleys, and 

 between Marlborough and Avebury in those of Wiltshire. They 

 lie at present for the most part in much confusion; but it is not 

 difficult to perceive that they are parts of a more extensive stratum, 

 once deposited unconformably in the previously excavated valley 

 of chalk. The loose sands in which these masses were concretionary, 



