GENERAL PHYSICAL FEATURES. 129 



Soils' and Bubsoils.] 



found throughout -Ho iston, Winona, Wabasha and most of Goodhue coun- 

 ties, and the eastern portions of Washington, Dakota, Rice, Olmsted and 

 Fillmore. Such soils are remarkable for their mellowness and their diver- 

 sified capabilities. 



(2) The local modifying circumstances. The local circumstances, due 

 mainly to differonce of drainage, sometimes so modify the primary drift soils 

 dependent on the nature of the original drift, as to completely mask their 

 essential arid characteristic qualities. If the natural drainage has been 

 imperfect for a long period of time the original soil will become blackened 

 by accumulated carbonaceous matter, or whitened by the evaporation of 

 calcareous waters, or reddened by iron from chalybeate waters. If these 

 processes be carried on to excess, the resultant material is a peat, a marl, 

 or a bog-ore. There are all shades of gradations between these substances 

 and the original soils which they modify, and though they occupy but a 

 comparatively small portion of the area of the state, they are distributed 

 from north to south throughout its whole extent. The peaty, or mucky, 

 soils are more extensive than the others, and are found both in the rolling 

 timbered parts, and in the prairies. The accumulated vegetation some- 

 times blackens the loams and the subsoils to the depth of six, or even ten, 

 feet. This is due not alone to the growth and decay of vegetation on the 

 spot, but also to the inflow of carbon by surface washing from the surround- 

 ing areas. Calcareous or marly soils, are frequently found in the region ot 

 the upper Mississippi, and in regions where the drift contains much lime- 

 stone gravel and stones. Strongly alkaline soils are found in low grounds 

 in the region of the unmodified blue till, and reddened or ferruginous soils 

 occur in the eastern part of the state where waters draining from non- 

 calcareous gravels and sands, evaporate in lower grounds. 



In addition to the influence of natural drainage on the original soils, 

 another important cause has operated to blacken and enrich the soils of the 

 entire prairie region of the state. The fires which have destroyed the grass 

 of the prairies for many successive years, have annually deposited on the 

 surface a residuum of charred unconsumed matter, which has entered within 

 the soils and blackened them to varying depths, so that nearly everywhere 

 the surface soil of Minnesota is a rich black loam, the same fires having 



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