400 Sources of the ConstiUients of Minnesota Soils. 



XIX. Light gray sandstone, Dresbach ; analysis by Profes- 

 sor J. A. Dodge. 



XX. Red sandstone, Fond du Lac, analysis by Professor J. 

 A. Dodge. 



XXL White, friable sandstone, Jordan ; analysis by Profes- 

 sor J. A. Dodge. 



XXIL Gray slaty quartzite, Wauswaugoning bay, Lake 

 Superior; Professor C. F. Sidener. Geol. & Nat. Hist. Survey 

 Minnesota 13th an. rep. 1885, p. 100. 



Silica Si- 



Alumina AI2O3 . . . . 

 Ferric oxide FcaOa. 

 *CaCarb. CaCOs. .. 

 tMgCarb. MgCO:,. 



Potash K2O 



Soda NasO 



Water H2O 



XVI I XVII XVIIII XIX XX XXI! XXII Aver 



84.52 



12.33 



2.12 



0.55 



O.II 



0.34 



98.69 



1.06 



0.75 



0.22 



0.17 



97.67I81.47 

 8.90 



1. 31 

 0.55 

 0.74 

 0.44 

 0.02 

 0.15 



78.24 



10.88 



81.19 

 10.44 



1. 00 

 0.84 

 3.60 

 0.66 



81.86 

 9.87 

 1.44 

 0.82 

 1.70 



•45 

 1. 61 

 1-43 



86.23 

 7.83 

 I -13 

 1.28 

 1.05 

 1.43 



Total I 99.97 100.69 100.8897.3799.67 97-731 lOi -54 99-43 



^Recalculated from calcium oxide. 

 fRecalculated from magnesium oxide. 



The soil qualities of sandstones and qnartsites. — The sand- 

 stones and quartzites alone make a most barren soil ; they are al- 

 most entirely destitute of the essentials of plant food. Almost en- 

 tirely silica in their chemical composition, very nearly insoluble 

 in water, hard and extremely obstinate in their physical character, 

 they are most forbidding to all forms of vegetable life. Yet, in 

 soils the contents of these rocks have their uses. Their debris 

 does not pack into such an impervious mass as does clay, nor be- 

 come crystalline and compact like the carbonates, but the grains 

 lie loosely upon each other permitting free circulation of water, 

 and in this way serving the double purpose of draining away the 

 superfluous waters of level tracts, — preventing stagnation on the 

 one hand, and on the other aiding in securing a supply of water 

 from great depths through capillary action in time of drought. 

 In the Gulf States there are large tracts of sandy soil. With 

 the abundance of rain which annually falls in that section large 

 crops are produced on land which in the upper Mississippi valley 

 would be almost barren. In this state a sandy soil is not desirable 

 for farming purposes. The sandy plains existing are due to the 

 distribution of the disrupted sandstone and quartzite formations 

 through the agency of the glaciers of the successive stages of the 

 glacial invasion. 



