THE SEVENTH OR DOVRE MORAIXE. 151 



River. After extending as a continuous massive ridge nearly 200 miles 

 from south-southeast to north-northwest thrc^ugh southwestern Mimaesota 

 and the northeast comer of South Dakota, with an elevation increasing 

 northward from 1,600 to 2,050 feet above the sea, the Coteau des Prairies 

 Ls thus terminated, and along the next 175 miles northward to the south 

 end of the Pembina Mountain escarpment no conspicuous rise of the sur- 

 face is observable from a great distance on the west side of Lake Agassiz 

 and the flat, low plain of the Red River Valley. There is, however, a 

 slow ascent of several hundred feet from this lacustrine area west to the 

 plain-like expanse of Cretaceous shales and overlying drift, which rises 

 northward from 1,200 to 1,300 feet above the sea in Sargent County to 

 about 1,500 feet in the region surrounding Devils Lake. 



Intf) this plain the Sheyenne and James rivers have cut narrow and 

 trough-like channels or valleys that vary from a third or a half of a mile 

 to commonly 1 mile and rarely 2 miles in width. These channels, like the 

 narrow morainic belts of knolls and low hills, are thus minor features of 

 the general topography. The Sheyenne channel or valley is 100 to 200 

 feet deep, mainly cut in the Cretaceous shales for its lower half or more, 

 though the faces of the bluffs are usually covered by a talus of drift, while 

 the James Valley, ranging from 75 to 125 feet in depth, is mostly eroded 

 in the drift sheet, there thicker than along- the Sheyenne. From the vicin- 

 ity of Valley City northward by Cooperstown to De\'ils Lake, Langdon, 

 and a large part of southwestern Manitoba, stretching west from the crest 

 of the Pembina Mountain, the depth of the drift is only from 10 to 50 feet. 

 Over extensive tracts of Griggs and Cavalier counties it varies from 10 to 

 30 feet. Its average northward on this belt is small, not probably more 

 than as 1 to 4 or 6 in comparison with its thickness in the Red River 

 Valley, throughout western and southwestern Minnesota and on most parts 

 of the great Cretaceous ridge of the Coteau des Prairies. 



Between the Dovre moraine and the compound moraine next west the 

 general level of the northwestern part of Sargent County and of south- 

 western Ransom County is diversified by three massive swells or hills, which, 

 like the suiTounding nearly flat country, have a smooth surface of till. 

 One of these, rising 75 to 100 feet and extending 2 or 3 miles from south 



