THE CLYDE TERRITORY. 413 



marine shells is overlain by 76 feet of Boulder-clay at a level of about 180 

 feet above the sea. In the basin of the Endrick draining into Loch Lomond, 

 Mr. R. L. Jack mapped shelly Boulder-clay up to a level of 320 feet. He 

 considered that the fragments of marine shells in the Boulder-clay had been 

 derived from a pre-existing inter-glacial deposit, formed when the sea stood 

 about 100 feet above its present level. 



Among the most interesting records of glacial time in the West of Scot- 

 land are the Arctic shell-beds of the Firth of Clyde. They have been 

 investigated and exhaustively described by Dr. Eobertson, Dr. Crosskey, and 

 Mr. James Bennie, whose researches have proved the Arctic character of the 

 fauna found in the marine clays. These deposits belong to the period of the 

 100-feet beach, though owing to denudation they occur now at lower levels. 

 The younger Raised Beaches at 50-feet and 25-feet levels are well developed 

 in the basin of the Clyde. From the deposits of the 25-feet terrace canoes 

 have been exhumed which point to the existence of neolithic man along 

 the shores of the estuary in post-glacial time. 



