EAST ANGELA DURING THE GLACIAL PERIOD. 203 



If the explanation offered be the true one, we have here a series 

 of river-gravel terraces occurring at all heights, from nearly the 

 bottom of the present valley up almost to the top of the Chalk 

 escarpment. 



Approximate Elevations {above the Cam) of two lines of 

 Gravel Patches. 



feet. feet. 



TheRivey 325 Balsham 370 



T , ,. , . , [270 Small patch W. of Balsham 250 



Intermediate patches | 20Q Gravel-pita 205 



Hildersham 125 (Possible continuation of the above.) 



{Indications of other 'patches between Gravel-pita N.W. of Dim- 1 ,^- 



the above.) gate J 



Wratting valley 110 



Ancient course of the Cam, 20 to 60 feet. 



EXPLANATION OF PLATE XV. 



Fig. 1. Map of a part of East Anglia, showing the Drift-deposits. Scale 8 

 miles to 1 inch. 

 2. Section from London-Clay escarpment to the Cambridge valley along 

 the line indicated on the map. Horizontal scale 4 miles to 1 inch ; 

 vertical scale 800 feet to 1 inch. 



Discussion. 



Prof. Duncan said that his impressions, formed twenty years ago, 

 agreed with those of the author. It was a very simple case of 

 geology complicated by geologists. He inquired whether the 

 author thought that such valleys as extend up to the Chalk from the 

 German Ocean were excavated before the Glacial period, or whether 

 they were then filled up and afterwards excavated. He also asked 

 whether the author was quite satisfied that all the gravels are water- 

 worn by tidal action. It seemed to him exceedingly interesting to 

 find that Mr. Penning pushed the ice-cap a little further back. 



Prof. Morris remarked that the valley of the Cam presents two 

 or three different conditions ; near Cambridge the river flows over 

 the Gault, cutting through the old gravel between Barnwell and 

 Chesterton. The valley was probably excavated in the Boulder- 

 clay, which occurs at higher levels, and once no doubt covered the 

 whole district. 



Mr. Jukes-Browne thought that the Boulder-clay did fill the 

 valleys, and that the boulders referred to by the author had been 

 derived from the Boulder-clay. One point of special interest in the 

 paper seemed to him to be that the author regarded the whole 

 Glacial series as continuous, in opposition to those who would place 

 the excavation of all the valleys in the Glacial period, while the 

 author considers them preglacial. At Cromer the so-called Middle 

 Glacial is nothing but blown sand. 



Mr. George Maw inquired as to the order of sequence of certain 

 beds known as Lower, Middle, and Upper Glacial, what evidence 



