6 THE GLACIAL LAKE AGASSIZ. 



soutliern New England and Long Island to North Dakota and Assiniboia. 

 The characters of other drift deposits point with equal certainty to a vast 

 sheet of land ice as their cause ; and the explanation accounts for this lake 

 in the Red River Valley, for similar lakes that were tributary to it from the 

 basins of the Soiu'is and South Saskatchewan rivers, and for the contempo- 

 raneous higher levels of the great lakes now discharged by the River St. 

 Lawrence. 



EARLV OBSERVATIONS OF LAKE AGASSIZ, 



The evidences of the former existence of a great lake in the Red 

 River Valley were observed in 1823 by Keating, the geologist of the first 

 scientific expedition to this district,-' in 1848 by Owen,^in 1857 by Palliser,^ 

 in 1858 by Hind,* and in 1873 by Dr. G. M. Dawson.^ Each of these 

 geologists explored considerable tracts of the lacustrine area, recognizing its 

 limits in a few places; and Hind especially described and mapped portions 

 of the lower beach ridges. Dr. Dawson's work was in connection with the 

 British North American Boundary Commission, and includes detailed notes 

 of the part of this area lying between the Lake of the Woods and the 

 Pembina Movmtain. Several references to these authors and quotations 

 from their reports are presented in later pages of this volume. 



The excavation of the valley occupied by Lakes Traverse and Big 

 Stone and the Minnesota River was first explained in 1868 by Gen. G. K. 

 Warren, who attributed it to the outflow from this ancient lake. He made 

 a careful sui-vey of this valley, and his maps and descriptions, with the 

 accompanying discussion of geologic questions, are most valuable contri- 

 butions to science.* After his death, in commemoration of this work, 



' Narrative of an Expedition to tlie Source of St. Peters River, Lake Wiuuepeek, Lake of the 

 Woods, etc., performed in the year 18:23, » » » under the command of Stephen H. Long, U. S. 

 Topographical Engineer. Loudon, 1825. Vol. II, p. 3. 



^ Report of a Geological Survey of Wisconsin, Iowa, and Minnesota. Philadelphia, 1852. P. 178. 



■'Journals, detailed reports, etc., presented to Parliament, 19th May, 1863, p. 41. 



* Report of the Assinihoine and Saskatchewan Exploring Expedition. Toronto, 1859. Pp. 39, 40, 

 167, 168. 



'Report on the Geology and Resources of the Region in the Vicinity of the Forty-ninth Parallel, 

 from the Lake of the Woods to the Rocky Mountains. Montreal, 1875. P. 248. 



•""On certain physical features of the Upper Mississippi River," American Naturalist, Vol. II, 

 pp. 497-502, November, 1868. Annual Rei>ort of the Chief of Eugiueers, United States Army, for 1868, 

 pp. 307-314. "An essay concerning important physical features exhibited in the valley of the Min- 

 nesota River, and upon their signification," with maps; Report of Chief of Engineers, 1875. "Valley 

 of the Minnesota River and of the Mississippi River to the junction of the Ohio; its origin cousid- 



