GEOLOGICAL SURVEY OP THE TERRITORIES. 281 



Mississippi Eiver, consisting almost entirely of deciduous trees, such as 

 oat, elm, ash, &c. But this strip, as it approaches Iowa in its southern 

 extremity, is more or less broken up by prairie-belts, and there confined 

 chiefly to the river valleys. 



The remaining portion of the entire area lying west of this timber-line, 

 and extending to the base of the Eocky Mountains, consists of broad, 

 undulating, treeless plains, channeled by numerous streams, and dotted 

 in its eastern portion with numerous small lakes, which decrease in num- 

 bers and acquire a saline character as we move westward. This part 

 is, in fact, one section of the great plains of the interior, which stretch 

 northward from Mexico to Arctic America. 



The great uniformity in appearance and sameness of character of this 

 part of the country would apparently forbid any lengthened description 

 of its geographical features — and to a great extent this is true — yet there 

 are some facts and peculiarities worthy of our attention and study, 

 especially as there are some problems connected with these broad, open 

 areas which have not as yet been satisfactorily solved. "Why are they 

 devoid of forests? is a query often propounded, and, although approach- 

 ing solution, has not been answered to the entire satisfaction of our lead- 

 ing physicists. If we reject the view of Lesquereux, that the " prairies 

 are due to peat-growth," and the view of other physicists, that they are 

 due "to the texture of the soil," and also exclude as unworthy of con- 

 sideration the very general opinion that they have been i^roduced by the 

 annual bm^nings — for this applies only to their perpetuation and not to 

 their production — and accept the very plausable theory of Newberry, 

 Foster, Hayden, and others, that this condition arose from a want of 

 sufficient moisture, we have advanced but one step in the process of solu- 

 tion, and find ourselves confronted by another question equally difficult 

 to answer: What caused this lack of moisture on the plains I Aud why 

 are the prairies of ]!^ebraska, Kansas, and Dakota drier than those of 

 Iowa and Illinois? Doubtless the presence of the large body of water 

 in the lakes of the north — Suj)erior and Michigan — over which currents 

 of air already charged with moisture sweep down from the northeast, 

 the approximation of the Gulf of Mexico, and the Mississippi running 

 north and south along the border of the entire area, will go far toward 

 furnishing an answer to the latter inquiry. But it is not my iutention 

 to pursue this investigation at this time ; when I enter uj)on a discus- 

 sion of the climatology I may present some facts which I think bear 

 upon the subject. 



The water- drainage of Minnesota and Dakota forms one of the most 

 interesting and important features in the physical geography of this sec- 

 tion of the West. Although there are no marked or prominent water- 

 sheds here, yet the streams which originate in this limited area belong to 

 three different water systems or basins: that of Hudson Bay, the lake or 

 Saint Lawrence Basin, and the Mississippi or Gulf Basin — one draining 

 north, one east, and the other south, showing a higher geueral elevation 

 of the surface here than in either of these directions; that is to say, if 

 we move north, east, or south from this area, we descend. Professor 

 Wenchell makes the following statement in regard to the topography of 

 Minnesota : * 



The intimate relation subsisting between the geology and topography of the State 

 is more evident than in some of the other States in the Union. The causes which de- 

 termine the location of the great continental water-shed are those which determined 

 the existence of the Laurentian and Lake Superior ranges of igneous and metamorphic 

 rocks. The area of these rocks in Minnesota, as well as in Wisconsin and Michigan, 



* Geological and Natura.1 History Survey, Minnesota, (1873,) page 45. 



