234 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 18, 



Materials filling the Pipes. — Pipes and furrows, of various dimen- 

 sions, occur more or less on all the following strata, and are filled 

 with the following deposits. I arrange them in the order of relative 

 antiquity, commencing with the oldest : — 



1 . In the chalk some are filled, in the tertiary districts of London 

 and Hampshire, with the lower eocene sands. Others are filled with 

 more recent deposits. The former infilling is distinguishable by 

 means of the green-coated flints which it contains. 



2. In Norfolk they are filled with the Crag. See fig. 3. p. 236. 



3. There also some are filled with reconstructed gravel, formed 

 from the materials of the Upper and Lower Erratic Tertiaries*, 

 brought to lower levels during the period of re-elevation and denuda- 

 tion f. 



4. On the northern flanks of the North Downs they are filled with 

 the Dartford gravel J, which I refer to the same period of re-elevation. 



5. Near the chalk-escarpments overhanging the Wealden area, and 

 on the highest tabular summits of the chalk hills, the pipes are filled 

 with " cledge §," a mixture of clay, sand, and unabraded and unfrac- 

 tured flints. This I refer to part of the same period of re-elevation, 

 considering it to have been laid dry somewhat sooner than the Dart- 

 ford gravel. 



6. When any member of the erratic tertiaries, or the chalk on 

 which they rested, has been so exposed by denuding action as to be 

 the bed nearest the surface, it is worn into furrows and pipes of small 

 dimensions, and these are filled with the loamy deposit which I call 

 the " warp-drift ||," and which contains, and occasionally passes into, 

 masses of sharply-fractured flints and heaps of chalk-rubble. This is 

 part of the angular flint-drift of Sir Roderick Murchison** . I refer the 



Fig. 1. — Section near Portobello Inn between Farningham and 

 Wrotham, Kent. 



Scale 12 feet to 1 inch. S. 



Talus. 



T.-iIus. 



a. Dark ferruginous clay with flints. c. Seams of rounded eocene pebbles. 



6, b'. Liglit-colourcd saiidy loam. d. Red and yellow ochraceous sand. 



e. Clay, sandy loam, and eocene pebbles, in irregular alternations, horizontally stratified ; 

 becoming obscure towards the south part of the section. /. Chalk. 



* The Lower Erratic Tertiaries comprise the Boulder-clay ; the superincum- 

 bent gravels, &c. with erratic blocks being the Upper Erratics. See Quart. 

 Journ. Geol. Soc. vol. vii. p. 21 ; and ibid. vol. ix. p. 295. 



t See Table, Quart, Journ. Geol. Soc. vol. L\. p. 295. 



:[: See Quart. Journ. Geol. Soc. vol. L\. pp. 287, 295. 



§ Quart. Journ. Geol. Soc. vol. viii. p. 275. 



II Quart. Journ. Geol. Soc. vol. ix. Table, p. 295. 



** Quart. Journ. Geol. Soc. vol. vii. p. 349. 



