50 Mr. Warburton on the Bas^shot Sand 



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For the boundary -line which we have traced round the sand, from its eastern 

 extremity at Esher, is also the boundary line which marks the appearance of 

 the London clay, a zone of which completely encircles the sand, exhibiting 

 itself at a lower level than the sand, and emerging from beneath it. 



The London clay may be traced round the sand from Kingston Common at 

 the foot of Esher Hill to Claygate Common and Jessop's Well ; thence to 

 Leatherhead Common, Bookham Common, and Ripley, where septaria are 

 found in making ditches. A well 180 feet deep was dug in clay at Horsley, 

 in the refuse of which I observed septaria and some of the commoner shells 

 of the London clay. From Ripley the clay may be traced to Worplesdon. 

 The next place along the boundary-line where I have observed the clay is in 

 some pits in Crondall parish, north-west of Farnham ; the stiff land at Hartley 

 Row is probably occasioned by its presence. 



Clay with septaria and pyrites is found in pits below the level of the sand in 

 the parish of Finchhampstead near to Broms Hill. At Sheep Bridge, between 

 Stratfield-le-saye and Reading, the clay appears with its septaria in the brook 

 which crosses the road at that bridge ; and the clay and septaria are well 

 known to the well-diggers in that neighbourhood. Still further to the west, 

 at Mortimer near to Silchester, I found septaria in a bank of blue clay; and it 

 is highly probable that the clay extends still further to the west at the foot of 

 the high ground which lies to the south of the vale of the river Kennet. 



From Binfield a bed af clay may be traced without interruption along the 

 northern acclivity of Windsor Forest to St. Leonard's Hill, Cooper's Hill, and 

 thence to Egham, where (as we have already seen) the nature of the clay is 

 fully exhibited. 



It appears then that the sand uniformly rests upon the London clay : it 

 remains to be ascertained whether it is to be considered as diluvian debris, or 

 as belonging to a regular stratum. Since the sand has not hitherto been found 

 extending beyond the limits of the London clay, or immediately incumbent on 

 the chalk or any other bed beneath the London clay, it would seem probable, 

 for this reason alone, that it belongs to a regular stratum ; and this opinion 

 has been confirmed by an attentive examination of the beds of the sand itself. 

 Those parts of the sand which are nearest the surface are generally more 

 or less mixed with angular chalk flints and other diluvian debris, such as is 

 found upon the surface in almost every part of the London Basin. But below 

 this diluvian matter I have not observed any angular flints, nor any beds but 

 such as in the aggregate materially differ from those which are of diluvian 

 origin. The highest of the undisturbed beds consist of a meagre sand, 

 somewhat ochreous, and not distinguishable from the diluvian sand by any 



