102 ME. T. I.EIGHTON ON THE LOWEE [May 1 895, 



respects, so far as it goes. Of course many new sections have been 

 opened since 1860, whilst at that date the significance of the cherty 

 veins in the sandstone was not understood. Where Drew refers 

 to chert he appears, always so far as I have observed, to mean the 

 compact, massive chert mentioned by Dr. Hinde (p. 405 of his paper) 

 as forming the central layers of the sponge-beds. 



There is considerable difficulty usually in obtaining a correct 

 knowledge of isolated sections in this country, the dip is often un- 

 certain from the amount of false-bedding, very few of the beds make 

 regular features, and even where they do so, for no considerable 

 distance ; hardness, except in a few cases, such as that of the thick 

 cherts of Leith Hill, appears to be due chiefly to local causes. 



I have endeavoured somewhat to make way for the present dis- 

 cussion by two papers recently contributed to the ' Proceedings of 

 the Geologists' Association,' in both of which papers, for the sake 

 of clearness, the accepted names of the different beds were used. 

 The first paper, read in December 1892, by Mr. G. S. Boulger and 

 myself on ' The Lower Greensand Area between Wotton and 

 Dorking,' x corrected a slight error in the map of the Geological 

 Survey in that district, and protested against the correlation of the 

 cherty sandstones of Wotton with the ironsands to the east. The 

 main point of that paper has remained unchallenged. The second 

 paper, published in November of last year, was a report on an. 

 'Excursion to Abinger,' 2 conducted by myself, and described the 

 wide spread of the Bargate Beds over the cherty sandstones on the 

 northern slope of Leith Hill. 



The object of the present paper is to show : — 



(1) That the chert-beds of Leith Hill and the area to the 

 west have been denuded from the country south of the present 

 Lower Greensand escarpment south of Dorking, and that therefore, 

 instead of a lithological change from east to west, as claimed by 

 Frederic Drew, 3 we have a lithological change from south to north, 

 from deep-water beds to shallow.* 



(2) That at the base of the Folkestone Sands an area of pebbles 



1 Proc. Geol. Assoc, vol. xiii. (1892) p. 4. 2 Ibid. (1893) p. 163. 



3 Mem. Geol. Surv. ' Geology of the Weald,' p. 121. 



4 [I do not use the expression ' deep-water beds ' in any sense as 'pelagic,' 

 and, in deference to the discussion on this point, would gladly substitute 

 any other formula which would convey the idea that between the southern 

 end of Leith Hill and Dorking there is on the upper part of the horizon 

 described by the Geological Survey asHythe Beds (i. e. the entire Local Groups 

 Nos. 2 and 3 of this paper) a change from ' a series of sponge-beds with some 

 sand ' through ' a series of sands with sponge-beds ' (the latter decreasing 

 northward in number and thickness) to ' a series of false-bedded clayey sands 

 and sands ' — the two series first mentioned being almost invariably without 

 false -bedding. Drew noticed the rarity of false-bedding in his Hythe Beds 

 of this country (Weald Memoir, p. 121), and in looking up this reference I 

 have but now discovered that the place (near Collickmoor Farm) where he calls 

 attention to the fact is close to the section at Boar Hill, to which I have here 

 pointed, on other evidence, as showing intermediate conditions. In contra- 

 distinction to this series are the overlying highly false-bedded grits or pebble- 

 beds of the acknowledged Bargate Series, showing conditions still more littoral. 

 — January, 1895.] 



