l68 NEW YORK STATE MUSEUM 



Into the sides of these moraines, shore lines have been cut at 

 definite levels, usually defined by cobble beach terraces. Steep, 

 exposed eminences have been washed bare of soil at the levels of 

 the ancient lake, and at such places they present rugged cliffs. In 

 more sheltered situations the action of the waters formed gentle 

 lines of sandy beach, or in the lee of reefs and islands built up 

 shoals and sand bars. The streams, too, at the levels where they 

 emptied into the ancient water body built deltas great or small, 

 according to their own size. Bottom deposits, also, were formed 

 and now give decisive evidence as to the extent and nature of the 

 water body in which they were laid down. 



4 GENERAL FEATURES OF THE CHAMPLAIN GLACIATION 

 At the end of the Pleistocene Glacial Epoch the latest or Wis- 

 consin stage was closed by a dwindling of the continental ice cap. 

 It shrunk from the mountain tops and higher areas where it had 

 been thinnest and came to occupy only the valleys and lowlands 

 between them. At that time a tongue of ice occupied the Cham- 

 plain valley and extended through the defiles of Lake George and 

 Wood creek and down the Hudson valley to the sea. Its retreat has 

 been detailed by Professor Woodworth in the paper mentioned 

 above. During the advancing and maximum stages of this Wis- 

 consin ice sheet practically all traces of former ice invasions were 

 obliterated, as well as the marks of its own advance. Thus we have 

 left at its disappearance only the phenomena made by the most 

 recent occupation in its waning stage. The scouring, striae and 

 grooves in the bedrock were usually buried beneath a blanket of 

 till. Its slow retreat was marked by retreatal and marginal 

 moraines. In the stagnant lobes at its end, rivulets from the melting 

 ice fell into crevasses and bored potholes at the bottom of deep 

 moulins (Barker, 1913 and Woodworth, 1905, p. 228). Where 

 the rock walls at the sides of the valley reflected the sun's 

 insolation the ice melted fastest, and here along the edges 

 of the ice tongue flowed glacial streams laden heavily with silt and 

 stones from the melting glacier. These streams flowed partly over 

 the ice and in part cut their channels into the valley wall leaving 

 scourways. At favorable places these streams widened out into 

 marginal lakes whence the impounded waters escaped to the next 

 lake of the chain at a level slightly lower. These marginal streams 

 carrying their loads of debris deposited some of it along the edge 

 of the glacier, which became lateral moraine terraces after the 



