Notices of Memoirs — W, TJpham — The Glacial Lake Agassiz. 475 



Report of the Committee to conduct Archaeological Investigations in 



British East Africa. 

 Professor E. Guthrie Perry. — On a Recent Find of Copper Implements 



in Manitoba. 

 C. Hill-Tout. — Report on the Ethnology of the Okanagan. 

 Br. G. B. Gordon. — Ethnological Researches in Alaska. 

 Professor H. Montgomery . — Archaeology of Ontario and Manitoba. 



Section K. — Botany. 



J. Parhin. — The Evolution of Inflorescence. 



Br. Kidston, F.P.S., Sf Professor B. T. Gwynne -Vauyhan. — The 

 Ancestry of the Osmundaceae. 



II. — The Glacial Lake Agassiz.' By Wakken TJpham, A.M., D.Sc, 



St. Paul, Minn. 



DURING the final melting of the North American ice-sheet a glacial 

 lake, held by its barrier in the basin of the Red River and Lake 

 Winnipeg, extended from Lake Traverse, on the west side of Minnesota, 

 northward to the Saskatchewan and Nelson Rivers, and eastward on 

 the international boundary to and somewhat beyond Rainy Lake. 

 It attained thus an area of about 110,000 square miles, exceeding the 

 combined areas of the five great lakes tributary to the St. Lawrence 

 River. This glacial lake, named in 1879 Lake Agassiz, had a south- 

 wardly flowing outlet, called the Glacial River Warren, which took 

 the course of the present Minnesota River, joining the Mississippi at 

 Port Snelling. 



Beach ridges of sand and gravel, a few feet high, traced by levelling 

 along about 800 miles of the highest shore of Lake Agassiz, mark its 

 stage of greatest extent, and other similar beaches, at many successive 

 lower levels, record later stages of the lake, reduced in height by 

 erosion of a deep channel along the course of the outflowing river. 

 After the recession of the ice- sheet permitted drainage from the glacial 

 lake north-eastward into Hudson Bay, still lower beaches were formed, 

 until the complete uncovering of the area crossed by the Nelson 

 River reduced Lake Agassiz finally to its present representative. Lake 

 Winnipeg. 



In its earliest and highest stage. Lake Agassiz was nearly 200 feet 

 deep above Moorhead and Fargo ; a little more than 300 feet deep 

 above Grand Forks and Crookston ; about 450 feet above Pembia, 

 St. Vincent, and Emerson ; more than 500 feet above the site of the 

 city of Winnipeg; and about 500 and 600 feet respectively above 

 Lakes Manitoba and Winnipeg. The length of Lake Agassiz is 

 estimated to have been nearly 700 miles, and its greatest width more 

 than 200 miles. 



Reports on the explorations of this ancient lake have been published 

 by the Geological Surveys of Minnesota, the United States, and Canada. 

 In the present paper the latest explanations are reviewed to account 

 for the northward ascent of its beaches. 



1 Paper read before British Association, Section C (Geology), Winnipeg, 1909. 



