On the Geology of East Anglia. 547 



1. The unfossiliferous sands of the Red Crag. 



2. The unconformity between the Lower and Middle Glacial 

 deposits. 



3. The mode in which the Upper and Middle Glacial were 

 accumulated. 



The views of the authors under the first head were similar to and 

 confirmatory of those advanced in the previous paper by Mr. Whit- 

 aker ; but they pointed out that the Hed Crag, which these sands, 

 in an altered form, represent, could not belong to the Chillesford 

 division of that formation, by reason of the casts of shells which 

 had been preserved not comprising any of the more characteristic 

 Chillesford species, and of their including among them forms con- 

 fined to the older portions of the Red Crag. They also pointed out 

 that the Chillesford Clay had been removed over all the area occupied 

 by these sands by denudation prior to the deposition of the Middle 

 Glacial, which rests upon these sands wherever they occur. The 

 removal of the Chillesford Clay, the authors consider, was due in 

 part, if not entirely, to the great denudation between the Lower and 

 Middle Glacial, which gave rise to the unconformity discussed under 

 the second head. 



This unconformity they illustrate by lines of section traversing 

 most of the river-valleys of Central and East Norfolk and Suffolk. 

 These show that such valleys were excavated after the deposit of 

 the Contorted Drift, and out of that formation and the beds under- 

 lying it. They also show that the Middle and Upper Glacial have 

 been bedded into these valleys, as well as spread (the middle only 

 partially, but the upper more uniformly) over the high grounds 

 formed of Contorted Drift out of which they were excavated, and 

 thus generally conceal that deposit, which manifests itself only in 

 the form of occasional protrusions through these later formations, 

 but which they consider constitutes, though thus concealed, the main 

 mass of the two counties. 



The authors also describe a glacial bed as occurring at various 

 localities in the bottom of some of these valleys, and which in one 

 case they have traced under the Middle Glacial. This they regard 

 as having been formed in the interval between the denudation of 

 the valleys and their subsequent submergence beneath the Middle 

 Glacial sea ; and inasmuch as such valley-bed invariably rests on the 

 Chalk in a highly glaciated condition, they attribute its formation 

 more probably than otherwise to the action of glaciers occupying 

 the valleys during an interglacial interval of dry land. They also 

 suggest that, if this was so, it is probable that the forest and mam- 

 malif erous bed of Kessingland, instead of being coeval with the pre- 

 glacial one of the Cromer coast, may belong to this interglacial 

 interval — that is to say, to the earliest part of it, before the glaciers 

 accumulated in the valleys, and when the climate was more tem- 

 perate, any similar deposits in these interglacial valleys having 

 been for the most part subsequently ploughed out by the action of 

 the glaciers. 

 In discussing the subject under the third head, the authors point out 



