\ 



GENERAL PHYSICAL FEATURES. H9 



Stratified clay.] 



Kandiyohi and Stearns counties. They are, however, in that case so grouped 

 as to suggest a former direction of drainage of the local water-courses dif- 

 ferent from that of the present. In most cases this gravel-and-sand deposit 

 lies on the till, and in numerous instances it is covered by a finer sand into 

 which it sometimes graduates by imperceptible changes, which sand in the 

 same manner also graduates into fine clay. 



Besides these plains of superficial gravel and sand there are extensive 

 beds of the same material embraced lenticularly within the till. These are 

 specially frequent, and constitute a large portion of the drift in the rolling 

 or broken tracts which cross the state, including the Leaf hills, the Mesabi 

 Ji it/Ms and the Gateau des Prairies. They are the open mouths of water- 

 reservoirs which penetrate within the drift-sheet and below it, and give rise 

 to the artesian wells that occur on the lower till-covered portions, and from 

 which issue the springs that feed the highest sources of the great rivers 

 of the state. 



Stratified clay. If the loam which covers the southeastern portions of 

 the state, including the counties of Houston, Winona, Wabasha, with por- 

 tions of Goodhue, Olmsted and Fillmore, be included under such designa- 

 tion, the most important and extensive tracts of stratified clay are found 

 to occur in the most widely separated corners of the state, viz: the north- 

 western and the southeastern. These clays, however, which have been 

 deposited by the Red river of the North and by the Mississippi, respectively, 

 at some former higher stage, exhibit very different chemical and physical 

 characters. That of the Red river valley is gray, or blue, when 

 unweathered, is compact and impervious without noteworthy exceptions, 

 and lies on a great thickness of blue till, from which, however, it is some- 

 times separated by an ancient soil-surface or by a bed of vegetable remains. 

 While its largest constituents are alumina and silica, its differential charac- 

 ters are due to the presence of a considerable percentage of the alkaline 

 earths and alkalies, which give a peculiar nature not only to the soils, but 

 also to the waters that are associated with it. That of the Mississippi 

 valley below St. Paul, and especially below Red Wing, is of a yellowish, or 

 yellowish-red color, or like powdered impure limonite, is not conspicuously 

 laminated, though it is so quite distinctly in some places, and frequently 

 becomes so sandy as hardly to justify the name of day. It lies generally 



