88 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



tificial excavation, if other sections, such as fig. 19, did not exist 

 close by. The gravel (c) fills up the inequalities in the sand. 



Fig. 20. — Section in Erith Pit. 



If • '" 'j \ ' \ '^i%i '"'"'i' i" i T "i^^'IjLr^^ 1*^ 'I' I ^^ 







L-i 



JL 



Rearranged Thanet sand is frequently met with in these gravels, 

 which were formed out of materials derived from this bed during the 

 excavation or deepening of the Thames valley and its tributaries at 

 this period. The large buU's-head flints from the basement-bed are 

 carried down to lower levels (owing to their weight) and deposited 

 on the new surface of the chalk. 



The pebbles from the Woolwich bed are most abundant in the 

 middle part of the Thames Quaternary series, and have been carried 

 a great distance from and below the escarpment before they were 

 redeposited in the gravel. 



Pig. 21 is from a drawing on wood by Mr. S. Skertchly of a mass 



Fig. 21.— Erith Pit. 



M 



b. Thanet Sands. 



deb 

 c. Woolwich shell-bed. 



d. Purple clay. 



of Thanet sands (6) 38 feet in length by 7 feet 10 inches in width, 

 with a portion of the Woolwich pebble-bed attached to it, lying upon 

 and against one piece of the Woolwich shell-bed 12 feet by 6 feet 



