84 S. V. WOOD, JTJN., AND F. W. IIAEMEE ON THE 



is merely part of the interglacially denuded valley, which was 

 deeper than the present, and extends down the river beneath the 

 marshes, and the Postglacial gravel which underlies them ; for Mr. 

 Samuel Woodward, in his ' Geology of Norfolk ' (1833), mentions that 

 what he calls a subsided mass of the same blue clay as that of 

 Strumpshaw Hill (the ordinary Upper Glacial clay of the district) 

 was found beneath the marshes of the Yare in digging the canal 

 which joins the Yare and Waveney. 



The Yare below Norwich is formed by the confluence of the 

 Wensum (the principal stream) with it ; and in describing the 

 geological features of the two valleys we take a line of section (V.) 

 across them near to the confluence of their streams. 



The removal of the Lower Glacial sands and Contorted Drift along 

 the slope of the interglacial valley portrayed in the cut has taken 

 place very extensively in places along both these valleys — a circum- 

 stance which, until we came to perceive the fact of this interglacial 

 denudation, was a source of infinite perplexity to us in mapping the 

 beds and working out their succession in this part of Norfolk, as 

 was also the occurrence of sections of clay with chalk debris in the 

 bottoms of these valleys and resting on the Chalk, which resembled 

 in their physical composition the wide-spread Upper Glacial ; and it 

 was not until one of us had the opportunity of making excavations 

 which proved that this valley-clay in one instance at least (Cringle- 

 ford, in section Y.) passed under the Middle Glacial, that we could 

 get any satisfactory evidence as to its geological position. 



Thus in a paper published in the Journal of the Society for 1867 

 (vol. xxiii. p. 88), one of us described two exposures of a bed of clay 

 made up chiefly of chalk debris and resting upon the Chalk in a 

 glaciated condition in the Yare valley near Norwich (at Trowse 

 Junction and at Thorpe Asylum) ; and we then interpreted this bed 

 as being of valley-origin and posterior to the Upper Glacial ; but 

 having subsequently met with so many instances of the Upper 

 Glacial sweeping over the sides of the interglacially denuded valleys, 

 wo were compelled to think that our original view of the valley- 

 origin of the bed in question was erroneous, and that it could only 

 be the Upper Glacial clay out of its usual place; and accordingly we 

 so represented it in the map which accompanies the " Introduction" 

 to the ' Crag Mollusca Supplement.' The crucial test applied, how- 

 ever, by excavations at Cringleford, and continued reflection upon 

 the observations which we have made during more than ten years 

 on the geological features of East Anglia, have led us to the belief 

 that our original view of this bed being of valley-origin and un- 

 connected with the Upper Glacial was so far correct — but that, 

 instead of its being posterior to the Upper Glacial, it is really of 

 interglacial age, intermediate between the Contorted Drift and 

 Middle Glacial, and a formation belonging to the interval which is 

 indicated by the general unconformity between those deposits, and 

 which has become exposed by the removal from it of the Middle and 

 Upper Glacial during the Postglacial re-excavation of the valley. 

 We have not reproduced here the woodcuts used in the paper in the 



