SUMMARY. 



The thesis icpuris a study of the relation of the chemical com- 

 position and the physical properties of certain glacial soils of Minne- 

 sota to the age of the drift upon which they have heen developed. 

 The Helds sampled are in Rice county, for which detailed glacial and 

 soil surveys were available. This county is covered in ])art by the 

 latest drift, the l^te Wisconsin, and the remainder by the earliest 

 exposed in Minnesota, the Kansan, both derived from [)ractically the 

 same sources and both originally highly calcareous from the surface 

 downward while the southern tip of the deciduous forest, the Big 

 Woods of Minnesota, extended down into it from the north and occu- 

 pied extensive areas on both sides of the dividing line between the 

 two drift sheets. 



On each of three types, the loam and the silt loam of the Carring- 

 ton series and the silt loam of the Fargo series, representing, resp(;c- 

 tively, forest, upland grassland and lowland grassland, ten virgin 

 fields were sampled, five on the Late Wisconsin and five on the Kansan. 



All the fields sampled for the Carrington series were so situated 

 as to h.ave been fully exposed to the leaching effect of the portion of 

 the precipitation passing from the surface into the deeper subsoil. 

 The Fargo silt loam had developed under such poor natural drainage 

 conditions that on many of the fields of this ty])e there was little or 

 no leaching to be expected. 



The samples were taken to a depth of three feet in four separate 

 sections, the first six inches, the second six inches, the second foot, 

 and the third foot. In each field two sets were taken, these being- 

 composites from ten borings, and these two sets were combined to 

 form the field samples. Complete analyses were made of the com- 

 posites of the corresponding sections from the five fields on the same 

 type and the same drift, determinations of the phosphoric acid and 

 carbon dioxide of all the field samples, and of the moisture equivalent, 

 proportions of coarser rock fragments, nitrogen, color and reaction 

 by various methods of all the set samples. 



Five fields on a fourth soil type, Marshall silt loam, developed 

 only upon the loess overlying the Kansan till, were included in the 

 study and treated similarly insofar as part of the determinations are 

 concerned. Three of these were still in virgin forest, and two were 

 adjacent to land that had been cleared and given over to farming. 



The texture of the fine earth of each type, as indicated by the 

 moisture equivalent, is very similar on both drifts, but the proportion 

 of coarser fragments is lower in the soils on the Kansan than in those 

 on the Late Wisconsin. On the older formation, the original frag- 

 ments of the softer rock (limestones, shales, and cherts), have almost 

 entirely given way to the processes of weathering throughout a depth 

 greater than three feet. 



