Vol. 6$.~] ORIGIN OF CERTAIN CANON-LIKE VALLEYS. 475 



understand that this could have occurred, if at that time the Welsh 

 ice could have followed an unobstructed course along low ground 

 towards the Bristol Channel. 



The conditions here sketched out, namely, of ice moving upon 

 Central England from the sea in a direction opposed to that of the 

 natural drainage, are precisely those under which Glacial lakes 

 with their accompanying overflow-channels would have naturally 

 originated. 



II. Lake Pickering and the Malton Gorge. 



Most of the Glacial lakes of the Cleveland district described in 

 the papers to which reference has been made are comparatively 

 small. There is one on a large scale, however, Lake Pickering, 

 which was caused, as has been pointed out, by the blocking of the 

 outlet of an important valley with ice and Glacial drift. 



Pig. 3 (p. 476), reduced by the kind permission of Messrs. J. 

 Bartholomew & Co. from one of their contour-maps, shows the 

 topographical features of this district and of the country surround- 

 ing it. 



The Pickering depression must have been formerly occupied by a 

 river flowing eastward, fed by affluents from the surrounding hills, 

 but of the valley in which this river ran no trace remains. The 

 basin has been levelled by the deposition of alluvium, and the 

 streams which now traverse it flow across a nearly featureless 

 plain. Its present drainage-system has no relation whatever to 

 that existing in pre -Glacial times. 



Occupying a faulted trough of Kimeridge Clay, the Pickering 

 basin is nearly surrounded by high land. An opening exists to the 

 west, into the Vale of York, near Gilling, but this Prof. Kendall 

 considers was blocked by the Teesdale ice at the period in question. 

 Comparatively low ground exists, however, to the south-west, 

 between Dalby and Settrington, through parts of which an overflow 

 from Lake Pickering may in the first instance have taken place. 

 As the level of the Lake was lowered, the escaping water was 

 confined to a narrower outlet, while, finally, the current becoming 

 more rapid, the excavation of the gorge from Malton to Kirkham 

 Abbey took place. 



While constructing a contour-map of England and Wales for the 

 purpose of tracing the movements of the Pleistocene ice-streams, I 

 was interested to find the special features of the Pickering region 

 reproduced in other parts of the country in a way which, I think, 

 cannot be accidental. Comparing some of the more important of 

 these cases with the former, as to the Glacial character of which 

 there seems to be no question, I shall endeavour to show that they 

 also may be explained in the way suggested by Mr. Fox Strangways 

 and Prof. Kendall. 1 



1 Most of the localities mentioned in the present paper may be found on one 

 or other of the maps published with it. 



