PLATES (PAGES) XXVII AND XXVIII. 



YELLOW MEDICINE, LYON AND LINCOLN COUNTIES, 1884. WARREN UPHAM. 



These counties span the interval between the crest of the Coteau des Prairies 

 and the Minnesota river, from southwest to northeast, and they present the same 

 succession of topographic features as Brown and Redwood counties. A minor portion 

 is drained toward the southwest and south, but the most of the whole area is drained 

 to the Minnesota river. Many streams take their source in the coteau, but these unite 

 at the foot of the plateau, constituting the Cottonwood, the Redwood, the Yellow Med- 

 icine and the Lac qui Parle rivers, which thence pursue winding ways across the flat 

 prairies to the Minnesota river. The unanimity with which the small streams unite 

 into these few trunk valleys, a feature which also extends further southeast as well 

 as northwest, indicates not only the wide expanse over which some powerful force 

 operated to control the surface topography and drainage, but points unmistakably 

 to the presence of the glacier as an obstruction to the separate continuance of these 

 small streams. It was while the third terminal (or Antelope) moraine was being 

 accumulated, a few miles northeastward from the foot of the coteau, that these 

 streams were received into a fluctuating lake or broad river-like expanse of water 

 lying approximately between the coteau and the Antelope moraine. On the retire- 

 ment of the ice from the Antelope moraine this lake was lowered, and the mingled 

 waters found the most accessible courses either northeast directly to the Minnesota, 

 or along the Antelope valley southeastwardly, the Cottonwood river being an illus- 

 tration of the latter. There are traces of this water not only in the smoothed con- 

 dition of the surface of the till, but in gravel-strewn, old water courses, the most 

 remarkable of the latter being that which extends through Wergeland and Burton, 

 and into Westerheim. This valley is distinct, twelve miles long, and from a quarter 

 to half a mile in width, lying thirty to forty feet below the flat surface of the till 

 adjoining. It was formed at the time of the existence of the ice-sheet along the 

 region to the northeast, and apparently connected a lake which was on the northern 

 slope, drained subsequently io the Minnesota valley by the Lac qui Parle river, with 

 another which extended southeasterly from Westerheim, and the stream which occu- 

 pied it must have been a large river. Another channel, which crossed this divide 

 at a later date, is in the town of Omro, and another, similar, in Stony Run. These 

 abandoned channels are comparable to that which exists between Big Stone lake and 

 lake Traverse, the chief difference being that the latter is the ultimate post-glacial 

 residuum of the Minnesota drainage system, and is still active on both sides of the 

 divide. 



