Kendall 8f Muff- — Glacier Lakes in the Cheviots. 513 



the old bi-eccias with which I am acquainted ; but if the suggested 

 explauation be correct the gravels were formed during a period 

 of elevation of the land, whereas most or all of our older deposits 

 were formed during periods of slow subsidence. But, though the 

 explanation now suggested accounts for much of the problem 

 presented to us by the gravels near the Thames, it must be admitted 

 that there are certain facts which it does not explain. Thus, the 

 Corbicula fluminalis bed at Crayford and Grays bears so strong 

 a resemblance to deposits which have been clearly formed during 

 a long, slow depression of the surface, that I can only think that 

 at some time this particular part of the Thames Valley sank whilst 

 the remainder was either rising or, more probably, was lying 

 stationary during a period of repose. 



The deep channel of drift in the valley of the Cam described by 

 Mr. Whitaker ' also seems to me to point to an area of local 

 depression. 



The conclusions to which I have come are, therefore, four in 

 number : — 



1. That the gravels of which I have spoken are river gravels, 

 formed since the country last rose above the sea. 



2. That the process of elevation was not continuous, but that 

 short periods of rapid movement were separated by long periods 

 of repose. 



3. That the gravel-flats are the work of rivers during the periods 

 of repose. 



4. That the earth-movements did not affect the whole area 

 uniformly, and that local depression occurred. 



VIII. — Evidences of Ancient Glaciee-dammed Lakes in the 



Cheviots.* 

 By Percy F. Kendall, F.G.S., and Herbert B. Muff, B.A., F.G.S. 



IT is uncertain whether Cheviot itself was overridden by extraneous 

 ice, but striae on Thirl Moor and Baker Crag, recorded by the 

 Geological Survey, probably indicate that that portion of the 

 watershed was overridden by ice from the Tweed Valley, and 

 Professor James Geikie mentions the occurrence of till and striated 

 stones on the tops of the Cheviot Hills at 1,500 feet. The transport 

 of erratics shows movement along both sides of the axis of the 

 range from S.W. to N.E. at some stage of the glaciation. Across 

 the northern end and for at least ten miles down the eastern side, 

 however, a distribution of erratics from the Tweed Valley, together 

 with other indications to be mentioned, points to an ice-flow veering 

 round through easterly to a north to south direction. Our 

 observations go to confirm the above conclusions with respect to 

 the area north and east of Cheviot. 



During a few days spent in the district, we observed certain 

 features which throw much light on the later stages of the Ice Age 



1 Quart. Journ. Geol. Soc, 1890, vol. xlvi, p. 333. 



^ Bead before the British Association, Section C (Geology), Glasgow, Sept., 1901. 



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