&2 8. V. WOOD, JUN., AND F. W. TIARMER ON THE 



[n the Quarterly Journal of the Society for 1800 (vol. xxv. 

 p. 446), we gave a section of the valley of the Yare at Norwich, 

 disclosed by the sewer-works of that city then in progress. 



This section, which crosses the Yare valley about 4 miles west of 

 the point where the chalk floor rises into viow above the water-line 

 of the rivers, was very perplexing to us at the time ; and we were at 

 first drivon to suppose that the deep hole in the Chalk in which 

 the Middle Glacial sand was found in association with the chalky 

 clay beneath the river-level (so out of their usual place) was due 

 to some exceptional erosion by glacier or iceberg agency. A study 

 of the way in which the East- Anglian valley-system has arisen, how- 

 ever, has satisfied us that, whatever may have been the eroding 

 agency, there is nothing exceptional in this occurrence, and that it 

 harmonizes with the general structure indicated by the uncon- 

 formable relation of the Lower to the Middle and Upper Glacial 

 deposits. 



Indeed, in a foot-note to the paper just quoted, we pointed out 

 that the erosion under consideration was connected with the con- 

 version of the Lower Glacial formation into land, and the occupation 

 of the valleys in it by ice prior to its depression beneath the sea 

 which deposited the Middle Glacial. 



We have here reproduced that section (fig. 4), because it is essen- 

 tial to the proper description of the subject-matter of this paper. 

 The dotted lines indicate what we considered at the time, and still 

 consider, 10 have been the excavation of the Yare Valley subse- 

 quently to the deposition of the Contorted Drift, and prior to that 

 of the Middle Glacial sand. 



Whether the chalky clay (a) associated with the Middle Glacial 

 sand in the hole beneath the level of the river be the Upper Glacial 

 clay, or a bed of clay precisely resembling it, which occasionally 

 occurs beneath the Middle Glacial sand in some valleys (and amongst 

 them the upper valley of the Yare, as shown in section V., p. 85) is 

 immaterial to the subject, because it leaves the excavation of the val- 

 ley subsequently to the deposition of the Contorted Drift unaffected, 

 the clay in question, whatever it be, being an entirely different 

 material from this drift, which everywhere in the neighbourhood 

 around is a red semistratified brick-earth. The sand and clay (a and 

 6) were so bedded against each other in the sewer-excavation, and 

 so flooded with water, that we could not satisfactorily learn which 

 overlay the other ; but, from such information as we could obtain, 

 we understood that their relative position was as represented in the 

 above section : we have, however, since been told by one of the work- 

 men that the clay was over the sand, in which case it would be 

 merely the ordinary Upper Glacial clay (6) of the high ground. 



No doubt, what thus appears to be a hole below the river-level * 



* The left side of the hole is drawn perpendicular, as the Chalk was very 

 close to the sewer-shafts. The excess of the vertical over the horizontal scale 

 of the section greatly exaggerates the slopes ; but in the case of the sewer-exca- 

 vation the perpendicularity may be owing to the Chalk, where the line of 

 section traverses the interglacial valley, having formed on one side of it a cliff. 



