S8 8. V. WOOP, JUN., AND F. W. HARMEK ON THE 



but over the country traversed by this valley the Upper Glacial is 

 usually underlain by the Middle Glacial, which is often in great 

 thickness, some of the wells, as we learnt, going through upwards 

 of 70 feet of it. As elsewhere in East Anglia, however, the 

 Contorted Drift occasionally protrudes through the Middle Glacial 

 and shows itself on the highest ground overlain by the Upper Glacial. 

 At Guist also is a fine section of the Contorted Drift over the pebbly 

 sands ; but mostly in this part of Norfolk the pebbly sands have 

 thinned out and the Contorted Drift rests on the Chalk direct. 



That portion of the Wensum valley which extends on either side 

 of the line of section VII., affords several instances of what we re- 

 gard as the same bed as that marked a in sections V. and VI. 

 The character of the bed in this district differs somewhat from that 

 which it presents nearer Norwich, where traversed by the lines of 

 the last-mentioned sections ; for instead of being, as there, a tough 

 elay full of chalk debris, it here generally consists of a greenish 

 gritty deposit more sand than clay ; but in one exposure this is 

 overlain by clay exactly like that at Cringleford, Trowse, and 

 Thorpe already described, with a sheet of glaciated chalk (torn 

 from the glaciated chalk of the valley-floor) interposed between the 

 two *. The bed in every exposure that we have met with rests on 

 Chalk in this glaciated condition ; and, indeed, the Chalk in all the 

 Norfolk valleys, where not protected by the Lower Glacial sands, or 

 the Crag, presents this feature, indicative, as it seems to us, of the 

 action of the interglacial ice upon it. So completely is the condi- 

 tion of the Chalk changed by this action in some places that, 

 instead of affording a porous surface of light land, it has become 

 retentive and water-sodden, of which striking examples may be found 

 in the bottoms on Bridgham, Eoudham, and Croxton Heaths between 

 East Harling and Thetford, where, the Contorted Drift having been 

 interglacially denuded, the Middle Glacial sand has been deposited on 

 this glaciated chalk, which has been again laid bare by Postglacial 

 denudation. Where this has taken place the chalk surface holds 

 water as well as the most tenacious clay. The explanation of the 

 different character presented by this bed a about Lyng and Elsing 

 (that is to say, in the portion of the Wensum valley illustrated by 

 section VII.) seems to us to be found in the different condition of the 

 beds out of which the valley is here excavated having furnished a 

 different pabulum for the valley ice to degrade. Thus nearer 

 Norwich the Chalk rises high up the valley-sides (see section V.), the 

 Contorted Drift there has a good deal of clay in it (forming of itself 

 a true brick-earth), and patches of the Chillesford Clay (though these 



* This is to be seen at an excavation 6 furlongs S.W. by S. of Lenwade 

 bridge, and 13 furlongs E. by S. of Lyng church. Other sections of the same 

 bed (but without the clay capping) will be found in the same neighbourhood, 

 as follows, viz. 3 furlongs S. of Lenwade bridge, 5 furlongs S.E. of Lyng 

 cburch, 5 furlongs W. by N. of Lyng church, and 9 furlongs W. of Lyng church. 



Tbe first two of these are shown in the map accompanying our '' Introduc- 

 tion " by dots of the same shading as the Upper Glacial Clay, to which forma- 

 tion we then supposed them to belong. The others lie beyond the limits of 

 that map. 



