part 1] THE SECTION AT WOBMS HEATH. 31 



Woking, this bed was well developed, and, as mentioned, contained 

 chert-pebbles not found at lower horizons. At St. George's Hill 

 it was practically absent. 



A measurement of the total thickness of the London Clay 

 might be made at the Crystal Palace, where, as well as at Shooter's 

 Hill, Clay gate Beds occurred, and were described by Mr. Whitaker 

 in ' The Geology of London.' [The thickness is estimated at 

 380 feet.] 



Mr. Gr. M. Daties, in reply, said that it was not suggested that 

 the pipes were once empty, and Avere subsequently filled with the 

 various deposits. The sand and pebbles were originally deposited on 

 a more or less level surface of Chalk, and were slowly let down pari 

 passu with the solution of the Chalk and the formation of the 

 Clay-with-Flints. He welcomed the facts elicited by the discussion 

 regarding the quartzite and other pebbles in the Blackheath Beds. 

 With regard to the white pittings on the flint-pebbles, he believed 

 that they were due to solution aided by pressure at the points of" 

 contact of the pebbles. 



