104 DR. J. A. SMYTHE ON 



fluent, this position would be along the junction. Once 

 cleavage of the ice-sheets has taken place, the position of 

 their edges and the contours of the ice-free land lying between 

 would alone determine whether ice-dammed lakes could be 

 formed along the edges of all, some or none of the sheets. 

 The position of the glacial lakes, as indicated primarily by 

 their overflow-channels or swires, thus enables one, in cases 

 where the contour of the land is favourable, to determine the 

 lines of confluence of ice-sheets at the period of melting 

 and to trace various stages in the retreat of the sundered 

 sheets. 



In the accompanying map (No. i) the swires are lettered 

 A to E; those which are produced by the same ice-flow bear 

 the same letter, and the numbers attached refer to the probable 

 order of formation. 



The Glacial Lakes South of the Coquet. — South or the 

 Coquet the northern and western sheets held sway at the 

 close of the glacial period. The first evidence of cleavage is 

 in the Pont valley near to Dissington, the lake held up by the 

 northern sheet overflowing through the gap Ai (height of 

 intake 400 feet).* The western sheet in its retreat south of the 

 Wansbeck was unable to obstruct the drainage, the northern 

 one, on the other hand, was in a favourable position with 

 reference to the contour, and lake-conditions were prolonged. 

 The "Pont Lake" [18] thus shifted its position slowly from 

 west to east, its level becoming lowered owing to the erosion 

 of its overflow-channels ; and new outlets A 2, A3, A 4, at 

 progressively lower elevations (340, 298, and 268 feet) were 

 cut when the containing ridge became bared of ice below 

 the level of the next higher notch [18]. It seems probable 

 that when the Pont lake was draining towards the Ouseburn 

 valley through A 4, it was receiving water from the Wansbeck 

 valley through A 5 (345 feet) and a small lake, impounded 

 near Newbiggin, overflowed into the Ouseburn through A 6 



* The contrast in composition of the Eachwick and Kirkley kaims noted 

 above, and the coincidence of their positions with those of the ice- edges 

 postulated here seems to be more than accidental. 



