PRESTWICH WOOLWICH AND READING SERIES. 89 



Sonning Hill (^Railway-cutting). PI. I. Diag. A, Loc. sect. 7. 



Feet. 



Subangular flint-gravel, ochreous, — varies in thickness, averages 12 



{Basement-bed of the London Clay, — ^fossiliferoiis brown clay with yeUow 



and green sand, pebbles, and septaria 5 



f /. Slightly mottled bluish and red, passing eastward into grey, clay ... 10 

 Ic. An irregular seam of sand, in some places yellow, in others of a 



light bluish colour 2 



/'. Mottled brown and blue "j 



/. Dark grey l^clays 23 



j. Mottled red and grey, the lower part lighter J 



- i. Irregular seam of white sand 2^ 



h. Red clay 1^ 



g. Light grey clay 0^ 



f. Very dark grey clay 6 



e. Red clay 2 



d. Light grey clay 1 



^c. Yellow sand with bands of brown clay* 2 



At Twyford the section consists almost entirely of compact mottled 

 green and red clay. Northward of this district we find several out- 

 liers of the lower tertiaries reposing upon the elevated chalk district 

 of Oxfordshire, Berkshire, and Buckinghamshire. A very striking 

 instance of this occurs at Nettlebed, nine miles due north of the main 

 mass of the tertiaries at Reading, and only two miles distant from 

 the edge of the chalk escarpment. The tertiary beds here attain a 

 height of 820 feet above the sea-level. No fossils are found in this 

 section, which is interesting, however, from its showing blocks of 

 sandstone in situ. 



Fig. 4. — Nettlebed Hill {section from several small pits in brick- 

 field). 



Feet. 

 1. Gravel, chiefly flint-pebbles — averages about... 5 



^^ c. "White and yellow sands with ironstone nodules : 



^j^ flint and a few quartz pebbles occur in the 



T^ lower part of this bed 12 



^-z J^ ^^=^=^^^7^ d. Light greenish clay, whitish sand and masses 

 -^:^^^^^^=-^^ qf sandstone, and red sands and clays 10 



'x. ^' "{ J^l^ck I- slightly mottled clays 7 



c { ^M^ [ Light green J 



-i^S- - ^^ b. White sand with some large and very compact 

 ■ifiiigiriiMiT— in — -mTnLigr^ concretionary sandstones in the upper part of 



" — ~ jT • ' 'V"'''"T^°'n^" it, also a few dark red ferruginous nodules ... 10 



nr~~r]~^^~p a. Green sand and flints 1 



45 

 4. Chalk 10 



The two high and conspicuous hills between Maidenhead and 

 Henley are formed by tertiary outliers. Another outlier forms the 



* Beneath this bed, which was the lowest exposed, were said to be 10 feet of 

 dark clay reposing upon 5 feet of ash-colouied sands, succeeded by the green- 

 coated flints 1 foot, and then chalk. 



