Sources of the Constituents of Minnesota Soils. 



39^ 



characters it touches on the rock below, in other characters it is 

 closely related to the soil above. A loam, a clay, a sand, or a 

 gravel bed beneath a cultivated field is sure to make its imprint 

 upon the crop raised. The reason for this is not far to seek; 

 it lies within the observation and every-day experience of every 

 one. Water will disappear by the barrel in sand and gravel; 

 while it will lie imtil it dries up when the bottom of the pool is 

 clay or mud. 



The underlying rock is compact and firm, never fresh and 

 unshattered, and never yielding to the urgent demands of the 

 growing trees for root space or support, unless it has first yielded 

 to the action of water and the crustal movements of a changing 

 globe. The varying proportions of the soil to the sub-soil, and 

 the sub-soil to the underlying rock are often noted. They lie in 

 the varying conditions under which soils are formed and retained 





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i^^^i^^iitniwia 



Figure 2. The decomposition of glacial drift, till, and the forma- 

 tion of soil. This is the type of rock alteration and soil build- 

 ing most extensive in Minnesota. Drazvn by F. W. Sardeson. 



in place. Upon hillsides there is a constant transport of material 

 towards the bottom. If the slope be gentle, this transport is slow, 

 and in any case it is the finest particles that are carried farthest. 

 This movement while slow and insignificant in itself, is of mo- 

 ment since it forms the record of a slow and almost imperceptible 



