PRESTWICH WOOLWICH AND READING SERIES. 95 



In the collection of the Geological Society is a series of specimens 

 and a section of a well at Twyford near Acton, particulars of which 

 are annexed. A bed of black bituminous clay with appearance of 

 decomposed shelly matter occurs about 20 feet down in the mottled 

 clays. 



Well-section, Twyford. PI. I, Diag. A, Loc. sect. 17. 



Feet. 



T J r<t \i- Yellow clay 38 



London Clay. |^_ gj^^ ^j^^ _ ^.^^ 



I. Basement-bed fc. Rock 1 



of the London < b. Sand and clay with pebbles 1 



Clay. [a. Pebbles 1 



T,7 , . , , I y. Mottled clays 36 



II. Woolwich and I c i o 



T, J- o ■ i ^- sand 3 



Reading Senes.-^^ Clay, not traversed 2 



252 



Stratum b.i. here contains, as at White Cliff Bay, small fragments 

 or pebbles of the underlying mottled red clays, as well as flint- 

 pebbles. 



At Watford we have seen that the shingle beds of the Woolwich 

 series repose immediately upon the chalk. The Thanet Sands are 

 absent also at Pinner. 



Section of a shaft at Pinner near Harrow. 



(Mr. J. Morris.) 



Feet. 



London Clay ... Marly clay 12 



I. Basement-bed 1 i c i vi, u n i i ■ i 



J... r J \ 0. Sand with shells and septana 1 



l;%^™ J- Veia of pebbles 1 1 



fd. Soapy marl 5 



n. Woolwich and \ c. Mottled clay — red, blue, green, &c 26 



Reading Series, < b. Pure white sand, sometimes ferrughious, and contain- 



idjeet. ing masses of sandstone, very irregular 4 



\^a. Green marly sand with flints 4 



To the Chalk 53 



At Willesden there are several deep wells, but I have not been able 

 to obtain an exact section of any of them. From a good supply of 

 water, however, being obtained before reaching the chalk, it is probable 

 that the Thanet Sands have here commenced. At Netting Dale this 

 deposit evidently exists ; but in the following section it is probably 

 confounded with the shingle beds of the Woolwich series ; the 

 " Pebbles and Sand " including, I believe, two distinct beds. 



tration of which subject that gentleman has collected an amount of evidence of 

 this description, as will, I expect, throw much light on the local changes which 

 these beds undergo. 



