18 



PROFESSOR P. F. KENDALL AND MR E. B. BAILEY 



station, before passing on to indicate other lines of evidence which point equally clearly 

 to the oscillations in which the great ice sheet effected its retreat. 



In the first place, still dealing, as at Upper Keith, with the deposits of the great 

 Lammermuir terrace, we may draw attention to the highly significant erosion forms 

 which they locally present. As already noticed at Woodhall, south of Spott, the 

 terrace has been so completely dissected by a series of glacially directed stream courses 

 that its sands and gravels have now assumed a kamiform aspect, and it is obvious in 

 the field that the ice sheet which directed this erosion must have re-advanced after a 

 retreat, until it actually came to stand upon the top of the spread of deposits which 

 previously had accumulated before it. 



But this is not the only way, or indeed the most important way, in which oscillations 

 of a retreating ice sheet may be recorded in the erosion effects which it determines, and 

 to make our line of argument more readily appreciated, we have inserted the following 

 explanatory diagram. 



-^5W^ 



600 A B 



_575_ 

 J550. 

 _525. 



500 __ 



Fig. 3. 



The contour map and section in fig. 3 show an ideal case of a spur reaching out 

 from a line of hilly country at right angles to the general trend of an ice margin 

 retreating towards the north. The ridge has been breached by two overflow channels, 



