VOL. XVII. (2) NORTH AND MID COTTESWOLDS 271 



mostly fragmentary and it is possible that some of them 

 may have been derived from Glacial beds in the Upper Severn 

 Valley.^ 



Rivers. — Mr S. S. Buckman has suggested that the Lower 

 portion of the Moreton gravels are of fiuviatile origin and of 

 Pliocene age and that the upper portion is composed of material 

 introduced by a river in Glacial times — the vertical position of 

 the larger stones suggesting that they were " conveyed by 

 floating ice and dropped as the ice gradually melted."^ The 

 vertical position may, I think, be explained by the supposition 

 that there has been a settlement of the gravel owing to the 

 elimination of a part of the soluble constituents. 



Glacial Lakes. — It has been suggested that the North 

 Cotteswold and Vale of Moreton Drift was transported by ice- 

 floes on the waters of a glacial lake extending from the melting 

 front of the eastern glacier to a barrier in the Bristol Channel 

 or the Avon Plain. 



Although the drainage of the Severn Basin may have 

 been obstructed by ice advancing up the Bristol Channel 

 from the Irish Sea or crossing from Central and South Wales,^ 

 it seems improbable that a dam thus formed would raise the 

 level of the lake sufficiently high to allow the floating of bergs 

 into the Vale of Moreton about 500 feet O.D. or, if Tangley 

 be included, about 650 feet O.D. There are no signs of the 

 presence, in Pleistocene times,* of so large a body of water in 

 the Severn Plain. 



As an alternative to an invasion of the eastern ice-sheet, 

 Mr F. W. Harmer suggests that " the overflow from a Glacial 

 lake, then filling a part of the basin of the Avon, carried Bunter 

 pebbles and Lincolnshire flint towards the south." ^ 



The principal objection to the lake-hypothesis is the 

 absence of any signs of an efficient dam in the Avon Valley, 

 which is the normal course of the channel by which drainage 

 from the eastern ice would flow towards the Severn. When, 



I Proc. Cottesw. Nat. F.C., vol. .xiv., pp. 184-7. 2 ibid., pp. 113-8 ; Quart. Journ. Geol. Soc, 

 vol. Iv., p. 220. ^ ^. . 



3 F. W. Harmer, Quart. Journ. Geol. Soc, vol. l.xiii., p. 474 ; H. C. March, Proc. Dorset. Nat. 

 Hist. F.C., vol. xix., p. 136. The subject will be further discussed in dealing with the Severn Valley 

 deposits. 



4 A reference to the formation of " Lake Bosworth " will be found m Harrison s chapter on 

 the " .\ncient Glaciers of the Midland Counties," in the Geologr\- of the Birmingham District, p. 94. 

 and in Kelly's Director\- of Warwickshire, p. 20. See also Prof. P. F. Kendall, Quart. Journ. Geol. 

 Soc . vol. Iviii., p. 568.' 5 Quart. Journ. Geol. Soc, vol. Ixiii., p. 500. 



