STAGES OF GROWTH SHOWN BY MORAINES. 211 



Lake Traverse and the Bois des Sioux River, about 4 miles soutliAvest of 

 White Rock, lying 1()() feet below this gravel and sand bluff. The same 

 high tract was at that time continuous also southeastward across the present 

 valley, which is 4 miles wide, to the plateau in Traverse County, Minn., 

 between the Bois des Sioux and Mustinka rivers, which is crossed and cut 

 into by the railway in section 26, township 128, range 47. A thickness 

 of 12 feet of this delta of gravel and sand, having a surface 75 feet above 

 Lake Traverse, is shown by the railway excavation, without exposing its 

 plane of contact with the underlying- till, which forms the basal part of the 

 plateau and extended, before its erosion by the outflow from Lake Agassiz, 

 in an inclined plane gradually rising to the blufP of till, 100 to 110 feet high, 

 east of the northern end of Lake Traverse. In this incipient stage, con- 

 temporaneous with the accumulation of the Dovre moraine, Lake Agassiz 

 stretched nearly 30 miles from northwest to southeast, with a width varying 

 from 1 to 2 or 3 miles, being probabh' widest in the \'icinity of Wheaton, 

 Minn., at its southern end, Avhere the River Warren flowed away south- 

 westward. The lake in this stage was little more than a broad expansion 

 of the glacial representative of the Sheyenne River, which deposited its 

 delta sediments along the edge of the lacustrine area, being walled in by 

 the front of the ice-sheet. 



With the glacial recession thence to the Fergus Falls moraine (p. 158) 

 Lake Agassiz attained a length of about 120 miles from Lake Traverse 

 north to Ada, Caledonia, and Hillsboro, with a width of 40 to 50 miles, 

 occupying thus an area of about 5,000 square iniles (PI. XIX). Its depth 

 at Breckenridge and Wahpeton was approximately 100 feet; at Moorhead 

 and Fargo, 200 feet; and at Caledonia, 275 feet. 



In the earliest part of this extension of the lake its outlet by the River 

 WaiTen seems to have been for a short time about 25 feet higher than dur- 

 ing the later and much longer part of this stage of recession of the ice and 

 growth of the lake, as is shown by the Milnor beach, a less distinct shore 

 deposit than the Herman beach and 20 to 25 feet above it, which was 

 observed near Milnor, N. Dak., and along a distance of about 10 miles thence 

 northwest to the Sheyenne, but was not recognized farther north nor in 

 Minnesota. The Sheyenne at the time of formation of the Milnor beach 



