PLIOCENE PEEIOD IN ENGLAND. 495 



laying down the Chalky Clay over Norfolk, Suffolk, Essex, and East 

 Middlesex ; and, uncovering much of the moraine so laid down, had 

 cut through that part of it which had been deposited in the channels 

 and interspaces of denudation, and, deepening these, thus formed the 

 valleys of these counties, which it occupied to a depth, in the east 

 of Norfolk and North Suffolk, below their present bottoms. As the 

 valley of the Yare about Norwich affords the best evidence of this 

 action, I propose to trace it by evidence more particularly in that 

 part. 



In the year 1866 my coadjutor in the task of working out the 

 Pliocene structure of Norfolk, Mr. F. W. Harmer, discovered that 

 clay, similar to that which covered the high grounds through which 

 this valley was cut, rested in the bottom of the valley on glaciated 

 chalk. Hence, to distinguish it from the general outspread of the 

 Chalky Clay over the higher ground, and from the Cromer Till, he 

 called it a " third Boulder-clay ;" and this was communicated to 

 the Society*. 



Soon after this the progress of the excavations for the sewer- works 

 at Norwich brought to light the circumstance that morainic clay, of 

 the same physical character as that of the high ground, lay in asso- 

 ciation with sand beneath the gravel and alluvium, and much below 

 the level of the Yare river ; and this Mr. Harmer and I communi- 

 cated to the Society f. 



Shortly afterwards, in the formation of the branch railway to 

 Cromer, a cutting was made through the hill forming the northern 

 side of this valley, at Thorpe, near the well-known crag-pit of that 

 place, and also just above one of the two instances of this " third 

 Boulder- clay " to which Mr. Harmer had called attention ; and so 

 much of this cutting as had not been sloped, I have represented in 

 fig. XYIII. 



It is clear from this and from fig. IX. that, after d had been laid 

 in the way I have traced it upon c, in the fjord represented by the 

 first excavation of the Wensum-Yare valley out of 6 3 (and probably 

 hi also), it was ploughed off by the action of ice moving along the 

 valley, and a confused mass of sand and brickearth resulting appa- 

 rently from the forcing upwards of the beds 6i, hS^ and c, to the 

 place where this part of the clay resting upon c had previously been, 

 and so in a jagged way into the ploughed- off edge of the clay. A 

 very little way to the west of this section, and on the same slope of 

 the valley-side, was a pit, showing a deep section of the Contorted 

 Drift, much twisted about and forced into c ; and inasmuch as the 

 Contorted Drift is everywhere near Norwich free both from the 

 marl-masses and from the contortions produced by their introduc- 

 tion which are so abundant in Sheet 68, it is pretty clear that the 

 disturbance of that drift which is shown by this pit-section was 

 due, not to this cause, but to the same passage of the ice down the 



* Quart. Journ. Geol. Soc. vol. xxiii. p. 87. 



t Quart. Journ. Geol. Soc. vol. xxv. p. 445. I think now that this sand must 

 have been similar in position to that in fig. XX. 



