OF THE BAGSHOT BEDS OF THE LONDON BASIN. 169 



p. 386). To the evidence there adduced I now add the following 

 facts : — (1) A new clay-pit at Warfield shows (so far as any- 

 bedding can be traced in the London Clay) a dip in accordance with 

 that previously recorded. (2) The laminated clay- and-sand bed 

 (referred to horizons Nos. 9 & 10), which rests horizontally on the 

 London Clay in the brick-field, is found to do so also in two recent 

 weU-sections on the western side of the Bracknell Hills, and is 

 exposed in the cutting to the west of the Station. (3) Along the 

 east flank of the same hills the fine quartz-sand exposed at the 

 Eracknell cutting is proved (by wells and other sections) to be 

 intercalated between the clayey bed (which cannot, therefore, be a 

 " passage-bed ") and the London Clay, from Borough Green * to 

 Holly Spring. (4) Strong lithological evidence of lower horizons 

 of the London Clay (abounding in Septaria) in the brick-fields to 

 the west t. Post-Eocene movements of the ground have probably 

 given a slight tilt to the west of the Bagshot Beds in these hills. 

 This may account for the higher level of the pebble-bed recorded 

 in the eastern part of the Bracknell cutting, and so does away with 

 any necessity for referring that to the Upper Bagshot. All this 

 requires a slight alteration of the Bracknell portion of fig. 2, p. 388 

 of the Quart. Journ. Geol. Soc. vol. xliii. 



The beds of the Middle Group (the two clays J with the inter- 

 mediate green earthy sands and traces of a pebble-bed above) crop out 

 below the 300-foot contour north of Caesar's Camp, with at least 100' 

 of Upper Bagshot above them. London Clay is found in the valley 

 just south of Easthampstead Church, and has been proved lately in 

 a well 12 ft. deep at the village school, indicating a considerable 

 attenuation of the Lower Sands exposed in a sand-pit at the foot 

 of the Church Hill on the east side. A line drawn due south from 

 Caesar's Camp passes halfway between Wellington College and 

 Bagshot Orphan Asylum, at both of which places we know the 

 thickness of the green earthy sands (41' and 58' respectively). 

 Taking the mean of these (50'), and the intermediate distances, 

 we find by ordinary rules of stratigraphy that the green earthy 

 sands should have thinned away to by the time Easthampstead 

 Church is reached §. There seems therefore no longer any 

 difficulty in understanding how the Upper Sands of Bill Hill with 

 their subjacent pebble-bed come at once upon the beds of horizons 

 Nos. 9 & 10 at Old Bracknell. (Compare sections E to I of my 

 paper.) 



* A fine section in a sand-pit near the inn. 



t The fine yellow sands, " false-bedded," mentioned as occurring in this brick- 

 field (Quart. Journ. Geol. Soc. vol. xlii. p. 405) I have never been able to find ; 

 but I have seen rather extensive masses of sands answering to that description 

 included in an older (pre-glacial) gravelly drift, which rests on an eroded 

 surface of London Clay. 



I The lower clayey beds (Nos. 9 & 10) are very well exposed (5' or 6' vertical) 

 at the back of the pond by the Bracknell road ^ mile further west along the same 

 line of valley. A good deal of the fine oak and beech timber of Easthampstead 

 Park grows in the strong loamy soil furnished by these beds. 



§ Compare note on Section K of this paper, 

 a. J. G. S. No. 174. N 



