112 DR. J. A. SMYTHE ON 



changes brought about by the agency of ice and drifted 

 material may not be out of place. The existence of several 

 large pre-glacial valleys in the south-east, completely choked 

 with drift, has already been recorded [17 and 18], and to the 

 number may be added that of the Delf Burn, which apparently 

 continued its southerly course from Rothley and discharged 

 into the Wansbeck a little to the east of Wallington. Complete 

 obliteration of a pre-glacial valley by drift, as has already 

 been pointed out [18], is favoured by a situation at right 

 angles to the direction of ice-movement. When similar con- 

 ditions only lead to the partial filling up of a pre-glacial valley, 

 the drift is thickened on the lee-side of the valley, with the 

 result that the modern stream is displaced towards the other 

 bank. This disposition, noted by Hugh Miller [5], is well 

 shown in the Spartley Burn below Haseltonrig, the Forest 

 Burn at Ward's Hill, the Font near Nunnykirk and Pigdon 

 Banks, and the Redewater above East Woodburn, and results 

 frequently in the cutting of a rocky channel at the edge of the 

 drift-filled valley. 



Of the streams which flow in valleys of pre- and post-glacial 

 ages, some evidence has been brought forward in the pre- 

 ceding pages to show that the change from the one to the 

 other course is occasionally the result of diversion by ice. 

 This has been rendered probable in the case of Dewley Burn 

 [18] and the Ouseburn, Blyth, Wansbeck, and Hartburn. The 

 post-glacial denes in which these streams flow are, on this 

 view, swires, which instead of being left dry on the melting of 

 the ice, have been so placed that they have become permanent 

 drainage-outlets. 



Smaller effects due to the ridging of the drift are frequently 

 noticeable. The many feeders of the Houxty Burn, for 

 example, flow E.S.E. along lines determined by the drumlins. 

 Near the coast, the long line of the Bradford kaims has 

 diverted the Warren Burn northwards into Budle Bay, and the 

 Crowden Hill drift-ridge which runs parallel to the railway 

 from the Coquet to the Wansbeck, though it has been breached 

 by the Lyne Burn, has diverted the Brock's Burn southwards 



