ON THE GLACIATION OF EAST LOTHIAN SOUTH OF THE GARLETON HILLS. 31 



ceases to be a well marked feature on crossing the 75-foot contour line, so that 

 high-water mark at Dunbar, when this channel was being cut, cannot have reached the 

 level of the 100-foot contour line of the present time, and probably did not surpass the 

 7 5 -foot contour. 



In the time at our disposal we were unable to follow up this promising line of 

 evidence, but a visit to St Abb's showed a very similar relation. Lying in the bottom 

 of the hollow which isolates the headland, is a well defined glacial drainage channel. 

 It cuts through rock covered with boulder clay, and is clearly recognisable well nigh as 

 far as the 50 -foot contour line. 



One further observation may be added which may some day prove of interest in 

 dealing with the raised beaches of the Forth. About half a mile south of the railway at 

 Prestonpans a clearly marked glacial drainage channel cuts through the 150-foot contour 

 line. It in part follows the course of an old glacial groove, but at the same time it 

 undoubtedly shows that the ice sheet at the time of its formation lay to the north and 

 not the south. We see, then, that the great ice sheet continued its process of shrinking 

 into the centre of the valley even to this late stage, and that the bed of the shallow 

 estuary of the Forth served as its last refuge when it had withdrawn from the coastal 

 regions of East Lothian. 



