79 



of these places contain beds of very large flints more or less 

 rolled. These gravels of West Norfolk set in almost along the 

 same line as that about which the Middle Glacial ceases (from 

 Hingham on the S. to Wells on the N.). They are also com- 

 posed almost entirely of large flints, which are mostly so rolled 

 as to resemble cannon-shot. 



"These cannon-shot gravels sometimes contain masses of sand 

 formed of chalk grains, and as they are never overlain by the 

 chalky clay, but in a few instances have this clay under them, 

 it may be that, if not of post-glacial age, they are a local modi- 

 fication of such clay due to the action of some powerful current 

 over this part of Norfolk, which dissolved all the soluble part of 

 the moranic material forming that clay and rolled the flints 

 into the cannon-shot form. 



" The absence of these gravels over the southern part of East 

 Anglia is a peculiar feature, but some beds of gravel on the 

 AVolds about Speeton and Bacton seem to bear a similar 

 relation to the Purple Clay of those places." 



With respect to the last paragraph above quoted, it is now 

 found that the gravels are not absent over the more southerly 

 parts of East Anglia, but that they extend through West 

 Suffolk into Cambridgeshire, and that they form quite as 

 important a series of deposits as the Middle Glacial beds below. 

 In many parts of Suffolk and Cambridge these gravels closely 

 resemble those of the Middle Glacial, so closely that I think 

 they must have originated under similar citcumstances ; if 

 therefore the Middle Drift is a marine deposit, then these 

 gravels are probably marine, and they must be taken as forming 

 part of the Glacial Series of East Anglia. I am therefore led to 

 think that it may ultimately be found convenient to group this 

 series into an Upper and Lower Division in the way suggested 

 below, each division having an argillaceous member overlaid 

 by a set of loams, sands and gravels. 



1. Cromer Till and ] 



Contorted Drift > Lower Glacial. 



2. Middle Drift 



3. Chalky Boulder Clay ) tt r^i • i 



"^ ^ \ Upper Glacial. 



4. rlateaux Gravel 



i Upper 



