9' 



might be possible to employ the piping as a measure of the 

 time since glaciation [PL i. fig- lo). 



Attention was called to such caverns at the British 

 Association meeting at Norwich in 1868, by Dr. John 

 Evans, and by Air. T. V. Holmes of some at Caterham, in 

 the Proc. Geol. Association, IX. Vol. 



The masses of ice and snow enclosed blocks of stone 

 which were undoubtedly the means of tearing up under- 

 lying rocks when the resistance was sufficient. By this 

 means rocks would be denuded when not plastic. Large 

 pieces of hard Greensand and Wealden rocks were dis- 

 lodged and moved away without much effort, thus far in 

 no instances have I yet found any scratched or crushed. 



Flint pebbles of the Eocene beds are often found 

 scratched or crushed, however, as are pebbles and flakes 

 of river gravels ; (the pitting of Eocene pebbles from reci- 

 procal pressure aided by the penetrating effect of sharp 

 quartz grains on the altered surface of the pebble has 

 assisted this). Masses of the Oldhaven pebble beds are 

 often found to have been moved en bloc, perhaps solidified 

 by ice at the time ; where the edges of the blocks grated 

 against each other, the pebbles are splintered in lines more 

 or less vertical. 



I saw an instance at Swanscombe of the passage of a 

 mass of stones over a large flint block in the chalk, too large 

 to move, from which two passing stones had separated 

 flakes, each stone carrying away a flake with it to distances 

 of 18 and 6 inches respectively before the movement was 

 arrested. 



There is, therefore, no reason why rocks should not be 

 found having glacial striae of this glaciation. 



The product of the glacial destruction in the distiict 

 South of the chalk, differs slightly from that in the 

 North. The trail is found filling up the smaller val- 

 leys to a greater extent with a confused mass of rubbish, 

 much resembling "spoil," except that it is still more 

 confused, this is from subsequent shifting often, streams 



