Vol. 63.] ORIGIN OF CERTAIN CANOX-LIKE VALLEYS. 471 



essentially from the Midlaud type of valley with gently- sloping 

 contours, produced by the gradual and combined processes of 

 atmospheric and fluviatile erosion. 



Typical examples of each kind are here given. Fig. 1 (p. 472), from 

 a photograph taken a short distance above Bath, shows the valley in 

 which that city stands. Excavated out of the Jurassic limestone 

 of the Cotteswolds, it has rather a rapid fall, presenting, never- 

 theless, a characteristic example cf the older description. 



Fig. 2 (p. 473), an example of the second group, gives a distant 

 view of the entrance to the Ironbridge gorge, near Shrewsbury, 

 through which the Severn passes across a narrow ridge of Palaeozoic 

 rocks from the Cheshire plain to the south. The last-named has a 

 very modern look, reminding one of a recently made railway-cutting. 

 Time, edax rerum, has left no tooth-mark upon it. 



The lake-like basins described below are associated with and 

 drained by recent-looking gorges of the second type, cut down to 

 base-level across ridges of high land, and generally at right angles 

 to the natural direction of the drainage. The likeness which they 

 bear one to the other is very striking, suggesting that they originated 

 in a similar manner. 



Before discussing the subject in detail, it may be desirable to 

 sketch out, very briefly, the conditions which, in my opinion, may 

 have obtained in Central England in Glacial times, so far as they 

 bear on our present enquiry. 



Most glaciologists believe that this country was invaded by ice, 

 on the east from the German Ocean, and on the west from the Irish 

 Sea. 1 Crossing the Lincolnshire Wolds, 2 but (as I believe) at certain 

 points only, ice from the North Sea, augmented, I think, by that of 

 an inland glacier from the Yale of York, travelled towards the plain 

 of the lower Witham and the Fenland, whence it overspread a large 

 tract of country to the east, the south, and the west. To the east 

 it reached the Suffolk coast, to the south nearly to the valley of the 

 Thames, while to the west it filled those of the Welland, the Nene, 

 and the Ouse, overriding also the high land intervening. 



Another branch of the northern glacier, keeping to the west of 

 the Lincoln ridge, and reinforced by the North-Sea ice, moved 

 towards Doncaster and up the Trent basin to the vicinity of Derby, 

 where it met the Derwent glacier, and thence crept southward 

 along the valley of the Soar into Warwickshire 



On the west, the Cheshire plain was invaded by ice from the 

 Irish Sea which, diverting the glaciers descending from the 



1 Without any disrespect to the opinions of those who think otherwise, I 

 shall assume, in this paper, the correctness of the land-ice theory. 



2 See, as to this, W.J.Harrison, 'Sketch of the Geology of Lincolnshire' 1882, 

 p. 21, and W. Topley, Quart. Journ. Geol. Soc. vol. xli (1885) p. 132. Prof. 

 Kendall, moreover, has for many years held the opinion that the intensely 

 Chalky Boulder-Clay of Lincolnshire was due to ice crossing the Wolds from 

 the North Sea. See also, as to this, W. J. Harrison, Proc. Geol. Assoc, vol. xv 

 (1898) p. 405. 



