212 GLACIA.L OEIGIN OP THE CLAT-WITH-IXII^TS. [June I912, 



the Pluvioglacial deposits and probably much older. The deposit 

 at Walter's Ash is not supposed to be of the uniform thickness 

 of 50 feet ; but the numerous pits which are scattered about the 

 district, 30 feet or more in depth, show that the deposit is thick. 

 AVith regard to Mr. Lamplugh's idea that the Bunter pebbles came 

 from the east instead of the west, it was not unlikely that, after the 

 Colne had been formed and the drainage re\ersed, Bunter pebbles 

 were introduced at a late stage from the Eastern Drift, and deposited 

 above those derived from the old Thames. The general fall in 

 the level of the gravels from Bourne End to Watford, and the 

 diminution in the size of the pebbles from west to east, would 

 indicate that the Bunter Pebbles came from the west. 



