150 THE GLACIAL LAKE AGASSIZ. 



that direction along the front of the ice-sheet and the Dovre moraine, 

 flowing into Lake Agassiz in the northwest part of township 129, range 49. 

 The belt of stratified gravel and sand, 1 to 2 miles wide, which there and 

 for a distance of 15 miles . southeastward constitutes the border of this 

 lacustrine area,^ seems to have been deposited by this great river, while 

 the ice-sheet lay on its northeast side, terminating where the edge of this 

 level or somewhat undulating tract descends like a terrace and is bordered 

 by the slightly lower Herman and Norcross beaches. Since the deposition 

 of these stratified beds, the River Warren, outflowing from Lake Agassiz, 

 has eroded and carried away their continuation across an extent of several 

 miles southeast to a remnant of the same gravel and sand which, with 

 underlying till, forms the plateau cut by the Fargo and Southern (Chicago, 

 Milwaukee and St. Paul) Railway in the southeast part of township 128, 

 range 47, Traverse County, Minn., abput half way between White Rock 

 and Wheaton. The outline of the ice margin along the extreme south- 

 western edge of this glacial lake at the time of its accunuilating the Dovre 

 moraine and forming the northeast bank of the glacial Sheyenne River at 

 its entraiice to the area of Lake Agassiz may therefore be somewhat confi- 

 dently traced around the little plateau between the Bois des Sioux and 

 Mustinka rivers and southward by Wheaton to the rolling land about the 

 Tokua Lakes at Graceville. The prominent morainic hills west of Taylor 

 Lake, according to this interpretation of our observations, were massed in 

 an angle of the ice margin, the usual place for plentiful drift accumulations. 

 Windy or Airy Mound, on the northern end or Head of the Coteau 

 des Prairies, close south of the line between North and South Dakota, is a 

 slight elevation above the general surface of this chift-covered Cretaceous 

 ridge. Its height is about 1,950 feet above the sea, and by estimate 100 

 feet lower than the crest of this ridge a few miles fiirther south. Thence 

 gentle slopes descend 750 feet to Sprague and Skunk lakes, near the north- 

 ern base of this highland; and the whole view east, north, and west from 

 Windy Mound sweeps over a broad, nearly flat expanse of till and lacus- 

 trine silt, ranging in altitudie from 960 feet at Wahpeton to 1,250 feet at 

 Forman and 1,300 feet on the area of Lake Dakota adjoining the James 



' U. S. Geol. Survey, Bulletin No. 39, pp. 38-40. 



