108 ME. T. LEIGHTON ON THE LOWER [May 1895, 



surface over various parts of the Lower Greensand outcrop, and sug- 

 gests that they have been let down from beds otherwise denuded. 

 Without doubt that is a correct explanation in many places, but it 

 cannot be so here, since it has been shown by F. Drew, 1 as well as 

 myself, that the beds of this district are sandy throughout. 



It is true that, on p. 121 of the Weald Memoir, Drew notices 

 that ' in Betchworth and Deepdene Parks there is some sandstone ' 

 (by which I understand from his other references ' cherty sandstone '), 

 but I do not think that this could have been in situ, — ■ 



(1) Because the base of the Folkestones, as corrected by the 6-inch 

 map, places nearly the whole area of these parks within the upper 

 division of the Lower Greensand ; (2) because the chief exposure 

 of the chert-drift is in Deepdene Park over Folkestone Beds ; and 

 (3) because I should be glad to be able to state certainly that 

 cherts occurred in the lower beds here, but am unable to do so. 



The extreme difficulty of determining whether the cherts are in situ 

 or not, from small exposures near the surface, has been referred to 

 above (p. 105), and, having once been found in the wrong, 2 I have 

 need to be extremely careful now. In October, 1893, 1 noticed a bed 

 of sandy chert about 6 inches thick in the buff sands near the southern 

 end of the Lower Greensand outcrop in Punchbowl Lane, close to the 

 B.M. 312, which then appeared to be in situ. It seemed to give the 

 required evidence of the thinning-out of the cherts in this direction, 

 and since the position lies between Deepdene and Betch worth 

 Parks, if correct, it would have confirmed Drew's observation. 



I still incline to the opinion that the bed was in situ when the ob- 

 servation was made, but in the autumn of 1894 it had altogether the 

 appearance of having been let down in the way suggested by Dr. 

 Hinde, 3 or at least a portion of it had that appearance, for it was 

 associated with other loose drift. Of course, the appearance referred 

 to may have been brought about by the slipping of the bed down the 

 slope. The rapidity of such changes has been already noticed here 

 (p. 107), and but for the associated drift, which I did not notice before, 

 I should now be able to speak with certainty. Whatever may be 

 the history of the bed in question, it cannot controvert my argument, 

 because, — 



(1) If the bed is in situ and Drew's observation is correct, it 

 only proves my view of the northerly thinning of the chert; (2) if 

 it has simply been lowered by denudation, it provides me with the 

 same evidence ; and (3) if it is true drift, it becomes only another 

 link in the evidence afforded by other drifts at higher and lower 

 levels. 



The surface of the escarpment about Glory Wood is strewn with 

 pieces of chert ; and in Chart Lane, between the entrance to Deep- 

 dene Park and the top of the hill, from 8 to 10 feet of drift lies upon 

 an extremely uneven surface of the Folkestone Beds. The bottom 



1 ' Geology of the Weald,' 1875, p. 134. 



2 Proc. Geol. Assoc, vol. xiii. (18U3) p. 141. 



3 Phil. Trans. Roy. Soc. vol. clxxvi. (1885) p. 406. 



