REVISION OF THE MAP OF LAKE AGASSIZ 781 



western part of the Lake of the Woods, at the present station 

 of Warroad. Through a distance of 18 miles next northward 

 from Red Lake this survey traversed a continuous swamp, called 

 on the profile "tamarack and spruce swamp," which includes the 

 divide between the basins of this lake and the Rainy River. The 

 depth of the mud and water throughout the swamp was from 5 to 

 15 ft., being mostly between 7 and 10 ft.; and in many places the 

 hard bottom was noted as gravel and sand. The highest part of 

 the surface of the bog or swamp on this line, forming the water 

 divide, some 5 to 6 miles north of Red Lake, has an elevation of 

 1,197 ft. above the sea, being 21 ft. above the lake. Westward 

 from this lowest part of the divide on the north side of the basin of 

 Red Lake and the Red Lake River lies the area of Beltrami Island, 

 of which the northeast margin was crossed by this railroad survey, 

 rising there to a height of 1,283 ft., or 107 ft. above Red Lake and 

 86 ft. above the eastern base of the island. 



The profile of the surveyed line shows a well-defined beach of 

 Lake Agassiz at 1,215 ft., this being the highest recognizable beach 

 ridge crossed by the survey. On the descent toward the Lake 

 of the Woods the profile crosses a succession of ten lower beaches 

 of the great glacial lake, their altitudes above the sea being 1,196, 

 1,172, 1,156, 1,143, 1^127, 1,116, 1,106, 1,099, T^P93, and 1,087 ft.' 



These beach ridges are clearly indicated by the profile, but 

 none are shown at higher levels. My conclusion from the profile 

 record, therefore, was that the series comprises the highest shore 

 and the successively lower shores of Lake Agassiz. The higher 

 part of the tract northwest of Red Lake was accordingly called an 

 island of that glacial lake, and was named, like the county in which 

 it mostly lies, for the exiled Italian author, Costantino Beltrami, 

 who in 1823 was one of the earliest white men to traverse and 

 describe this region. He was preceded only by the Canadian 

 geographer, David Thompson, in 1798. 



An elaborate map of this area, from Red Lake north to Rainy 

 River and the Lake of the Woods, with contour lines at intervals 

 of 10 ft., accompanies a report published in 1909,^ entitled "Drain- 



' Notes of this profile were published in Geology of Minnesota, IV (1899), 136-37. 

 ^ 6ist Cong., ist sess., H. R. Doc. No. 2^, 40 pages. 



