PLIOCEN-E PEEIOD JH EIJGLAND. 461 



where they surround islands of the Chillesford Clay, and form, as 

 described in Stage II., the chief part at least of the sands of Dun- 

 wich Cliff. 



The limits of the Crag estuary in Sheet 66 can be traced with 

 much approximation to truth. In fig. IX., drawn through the 

 fluvio-marine Crag and Chillesford Clay at Thorpe by Norwich, these 

 beds occupy a higher level, and have a greater thickness of chalk 

 intervening between them and the datum-line than is the case at 

 Bramerton, two miles to the south-east. The Crag also is thinner 

 and all of it is fluvio-marine, the division into a fluvio-marine bed 

 below and a marine one above (which exists at Bramerton) not ob- 

 taining here for the reasons already explained ; and this part of the 

 Crag is therefore more nearly synchronous with the marine than 

 with the fluvio-marine part of the Bramerton section. To the north- 

 west and west of fig. IX. large excavations occur in which both 

 the Crag and the Chillesford Clay are absent, and the chalk, rising 

 to a proportionately higher level, is overlain direct by the sands bl. 

 From this it results that the slight depression which extended the 

 estuary in the way already described did not suffice to submerge 

 the site of Norwich or the area to the north-west of that city, no 

 trace of either al or a 2 occurring in that direction, and the chalk 

 also rising westwards. One head of the estuary having been carried 

 by this depression northwards up to Aylsham, a branch was in 

 the same way carried past Norwich southwards for several miles, 

 coinciding apparently with a valley which, in the condition re- 

 sulting from the manifold changes treated of in this memoir, is 

 now represented by that of the Tese, the northern branch being 

 similarly represented by that of the Bure. This branch was pro- 

 bably divided by land from the head of an arm of the earlier part 

 of the main estuary which stretched up past Bungay from the south ; 

 and in it both the Crag and Chillesford Clay are but thinly repre- 

 sented, the former passing sometimes, near the head of the valley 

 about Saxlingham, into shingle, and the clay which overlies it 

 presenting but a small admixture of mica. The Crag-shingle at 

 Dichingham House near Bungay is full of the Crag- shells ; but at 

 Saxlingham I was informed that mammalian remains only occurred 

 in it. 



The river which fed this estuary with the mud from which the 

 Chillesford Clay resulted must have flowed from some region of 

 mica-schist or of granitic rock, and most probably, therefore, from 

 North Britain. At the base of this clay in Easton Bavent cliff 

 (north-east of Sheet 49) I observed rolled chalk, similar to that 

 which is so abundant in the Cromer Till (b£), to be imbedded, and 

 the clay in this part to be occasionally contorted slightly. This 

 shows that glaciers had at this time begun to grind down the chalk- 

 country, and to discharge their moraine into some arm of this river ; 

 and as North Britain, by reason of its latitude, would be propor- 

 tionately more glaciated, it seems most probable that the profusion of 

 mica which characterizes the clay was produced from the grinding 

 of these rocks in North Britain by the ice, which by this time had 



