292 THE GLACIAL LAKE AGASSIZ. 



the draiuage from it ceased, these plains are left far from any important 

 stream. Similarly, on the west side of Lake Agassiz, a large delta extending 

 southward from the Elk Valley was deposited by a proportionally large 

 river flowing from the ice-sheet, but no considerable river now enters the 

 lake area there. 



Opposite to the Buffalo delta, within a distance of about 30 miles to 

 the east, the ice front was indented by a great embayment or reentrant 

 angle at the time of formation of the eighth or Fergus Falls moraine. 

 While the ice border was receding from the seventh or Dovi-e to the Fergus 

 Falls moraine, the conditions of its melting were probably unfavorable for 

 the formation of deltas in this glacial lake; but during the accumulation 

 of the Fergus Falls moraine the drainage from the ice border converged 

 toward the Buffalo River and caused its delta to be formed. Again, when 

 the ice-sheet had retreated another stage and was forming its ninth or Leaf 

 Hills moraine, this indentation of the ice front, having fallen back about 

 40 miles northward from its former position, sent its glacial streams to the 

 Sand Hill River, and a second delta was brought into the lake. 



In the same manner, the much larger Sheyeune, Elk Valley, Pembina, 

 and Assiniboine deltas, brought into Lake Agassiz from the west and hav- 

 ing likewise the height of the early Herman beaches, are referable chiefly 

 to the drainage from the melting ice-sheet, and in less measure to erosion 

 of the river valleys. The material of all the deltas of this lake is princi- 

 pally modified drift, rather than allu%'ium like that which the streams now 

 transport and spread over their bottom-lands at every stage of flood. 



FROM MUSKODA NORTH TO TUE SANU HILL RIVER. 



(PLATE XXV.) 



In the next 2 miles north of IMuskoda the crest of the Herman beach 

 ridge ranges mainly from 1,113 to 1,125 feet above the sea; at its lowest 

 depression, about 1 mile north of Muskoda, its height is 1,105 feet; at 

 William Perkins's house, in the southeast quarter of section 30, Cromwell, 

 1,122 feet; an eighth to a third of a mile south-southeast from Mr. Per- 

 kins's, 1,130 feet. A nearly or quite continuous depression, from a fifth to 



