THE GEOLOGY OF THE BERWICK COAST LINE 85 



on a hill, and between this place and Burnmouth I could 

 show you, not far off, at least three places where the old 

 red conglomerate sticks yet to the Silurian. Denudation has 

 been a most mighty agent in reducing and moulding the 

 surface of the earth as we have it, a fact which is now 

 accepted, but until comparatively recent years was not 

 sufficiently understood. 



I must now say a few words about the intrusive basaltic 

 and the glacial era which I mentioned. Illustrations of 

 both are not far to seek. There, on the southern horizon, 

 we catch sight of the Fames, with a glimpse, on a clear 

 day, of Grace Darling's famous lighthouse. Nearer, the 

 castles of Bamburgh and Holy Island are prominent objects. 

 All those places, and more which I cannot stop to enumerate, 

 are, or rest upon those intrusive igneous rocks which are 

 well-known phenomena all over Borderland. The effects of 

 a glacial era, when that land was covered with a thick, 

 enormously thick, blanket of ice, are seen, too, in the Till, 

 Drift, or Boulder clay, which, in various degrees of thickness, 

 is a familiar object to everyone, though everyone may not 

 be aware of its origin. I walked up the Bowmont valley 

 above Yetholm the other day, for a few miles, and marked 

 how the modest little stream, though formerly a large river, 

 with intervening lakes, had eaten its way down through the 

 boulder clay. But we need not go so far as that for an 

 example, for we stand on it ; it is all around us ; yon 

 promontory, as you see, is capped with many feet of it ; 

 every river or burn side brings it into view- It is, so to 

 speak, geological flour ground in the glacial mill. The 

 glacial era was the latest geological era. As the ice sheet 

 and the glaciers slid along in their movement towards the 

 sea, they ground up the surface on which they moved into 

 powder of every degree of consistence, mixed with stones of 

 every sort and size. This, though it may be, and generally 

 is, perfectly dry, is boulder clay. 



