xvii. SECTION NEAR LE WISH AM. 449 



Marlborough and Ashdown, but not so prominent or so regular. 

 They are often cavernous, like the ' Blowing-stone' near Uffington 

 Camp. One of the largest is 8 feet in the longest diameter. At 

 the Rectory, Rotherfield-Grays, several of these stones have been 

 collected, one 6 feet long ; and it is interesting to find them filled 

 with flints, which are, except in their greater size, comparable with 

 the pudding-stone of Hertfordshire. The basis is closely- cemented 

 sandstone. Mr. Hopkins, M. A., of Magdalen College, made me 

 aware of these localities. After examining these facts I was much 

 impressed by the probability that all the deposits of this kind 

 of stone in Wilts, Oxon, and Herts might be of the same or 

 nearly the same geological date; very pebbly on the eastern side, 

 partially so in the middle, rarely so, but occasionally shelly, in 

 the western district. 



Thus a tripartite pebbly series of sands, clays, and conglomerates 

 represents the lowest eocene formation in the Thames valley; 

 viz. 



Blackheath pebble-bed above. 



Woolwich clays and sands -| 



Thanet sands below j with P ebbleS occasiona %- 



One of the best sections yet published of the Woolwich and 

 Thanet beds is that of Loampit Hill, near Lewisham, in Kent %. 



Pebble-bed of Blackheath above. 



Woolwich beds, ft. 



Fine sand, yellow, and iron-shot 10 



Loam and plastic clay, with pyrites and leaves ; . . . 10 



Sands, yellow 3 



Clay, lead-coloured, with leaves 2 



Clay, brownish, with Cyrenae 6 



Clay, in three beds ; the upper and lower contain Cyrense, the 



middle oysters ......... 3 



Loam and sand; upper part cream-coloured with nodules of 



friable marl, lower part sandy and iron- shot ... 4 



Thanet beds. 



Ferruginous sand, with flint pebbles 12 



Greensand, coarse and pebbly 5 



Sand, ash-coloured, slightly micaceous 35 



Greensand, with green-coated flints I 



Chalk with beds and nodules of black flint. 



Next above is a great deposit of blue sediments, the upper part 



8 Geol. Trans, vol. iv. p. 287. 

 Gg 



