Vol. 59.] IN THE CHALK NEAR ROYSTON. 369 



This pit was figured by Penning, and my own notes are in practical 

 accordance with his. The pit has been worked farther to the south, 

 and the evidence of the arching over of the strata in that direction 

 is now apparent. 



There is a fifth pit a little west of the cross-roads north of Ther- 

 field, about 530 feet above sea-level ; and this showed Chalk-with- 

 flints having a slight northerly dip, with Boulder-Clay banked up 

 against the upper part on the northern side. Here we have a final 

 indication of the local disturbance. 



The fact that the Chalk is bent into a gentle anticline at Reed, 

 combined with other evidence, enables us to feel confident that 

 elsewhere the Chalk was similarly ridged up, and that nowhere are 

 the highly inclined strata overturned or inverted, though there may 

 be an overthrust in the Barkway pit. That the Chalk is so bent and 

 the flints in places so shattered might of course be due to sub- 

 terranean disturbance, as in the faulted and fractured Chalk of the 

 Purbeck coast, were it not that the disturbed Chalk near Royston, 

 with its fractured and displaced flints, occurs in conjunction with 

 the Boulder-Clay, and that we have a mass of Boulder-Clay beneath 

 a considerable thickness of disturbed Chalk. 



No other explanation is reasonable, and in my opinion none other 

 is possible, than that the Chalk was disturbed by the agent 

 which formed and distributed the Chalky Boulder-Clay. 



If I followed the dictates of prudence I might perhaps stop here, 

 but I am tempted not to leave my story without an end. 



It has been noted that Boulder-Clay occurs along the crest of the 

 high ground bounding the disturbed area, and in force to the south ; 

 but excepting on the spurs of this high ground, which extend 

 beyond the line of disturbance, the vale and undulating downs im- 

 mediately to the north are devoid of this Glacial Drift. This is a 

 remarkable fact, when we remember that in East Anglia (as Penning 

 observes) the Boulder-Clay ' caps the highest hills ' and sometimes 

 ' occupies the deepest valleys.' 1 There are broad hollows below the 

 Upper Chalk-scarp, in one or two instances, with somewhat narrower 

 outlets opening to the north, and calling to mind dwarfed forms of 

 corries. One such hollow may be noticed 6 furlongs north-east 

 of Therfield' Church; and a wider amphitheatre-like expanse, of 

 which mention has previously been made, opens out west of Barley, 

 and is prolonged through Wardington Bottom. 



The question arises as to whether a portion of the ice at the time 

 of maximum glaciation was arrested over the lower grounds, while 

 higher masses of ice were thrust forward against the scarp, bendiug 

 the Chalk and fracturing and disturbing its flint-layers, portions of 

 the ice finally overriding the crest and extending towards the 

 London Basin. 



1 Quart. Journ. Geol. Soc. vol. xxxii (1876) p. 195. 



