32 LONDON DISTRICT. 



On the maps of the London District only the two divisions, 

 Bagshot and Bracklesham Beds, are shown. We have now to 

 add an outlier of Barton Beds at St. George's Hill, Weybridge, 

 and possibly another at St. Ann's Hill, Chertsey. 



In dealing with our present area it will be convenient first to 

 describe the general characters of each division, and then in 

 referring to their distribution to treat them as one series, which 

 may be conveniently termed the Bagshot Series. This is the 

 more desirable, as doubt has been expressed about the corre- 

 lation of the strata in some localities, and about their method 

 of formation. Thus, clay marked on the map as Bracklesham 

 Beds, between Weybridge and Chertsey, was grouped with the 

 Bagshot Beds by W. H. Hudleston ; and portions of the Bagshot 

 Beds near Brentwood and Warley are considered by Mr. H. W. 

 Monckton to be more nearly allied to the Bracklesham Beds, 

 and in this view he received support from Irving. 1 



BAGSHOT BEDS. 



This formation is composed for the most part of fine white, 

 buff-coloured and sometimes crimson sands, with occasional 

 seams of white or grey pipe-clay and local beds of flint pebble - 

 gravel : lignite is also met with. 



It occupies some of the higher grounds, including the 

 prominent hills of Harrow, Hampstead and Highgate ; it extends 

 over the picturesque heaths and wooded tracts south of Chertsey, 

 Weybridge and Esher; and in the north-eastern part of our 

 area it caps the hills at High Beech, Cabin Hill, south of 

 Lambourne End, Havering-atte-Bower, Great Warley Street 

 and Brentwood (on the eastern margin), and the hilly ground 

 at South Weald and Kelvedon Hatch. The full thickness in 

 the district probably does not exceed 120 ft., where overlain by 

 Bracklesham Beds. 



Prestwich regarded the beds as of marine origin, and referred 

 to * the shoaling of the sea after the deposition of the London 

 Clay and the shiftirg and somewhat eroding currents of the 

 shallower sea of the Lower Bagshot.' 2 That some parts of the 

 area of deposition in the London Basin may have been estuarine 

 or even fluviatile was maintained by Irving, 3 but evidence of this 

 mode of origin has not been obtained within our district. Unfor- 

 tunately little assistance in settling the question is afforded by 

 palaeontology : unrecognizable plant remains are the only fossils, 

 though casts referable to three genera of marine gasteropods 

 have been found in Essex beyond our Eastern margin. 4 



In the Bagshot Sand of Hampstead Heath Mr. A. B. Dick 

 found about 94 per cent, of grains of quartz and felspar, one or 

 two per cent, of flint fragments, and less than one per cent, of 



1 Nature, vol. xlii, 1890, June 26, p. 198, and July 3, p. 222. 



2 Quart. Journ. OeoL Soc., vol. xlii, 1886, p. 171. 

 s OeoL Mag., 1891, pp. 357-364. 



' Geology of London ' (Mem. Oeol. Surv.), vol. i, 1889, pp. 266-276. 



