lb 



ihe drift upon which it has been develo])e(l. It should be ])ointed out 

 that Hopkins and Pettit's investigation was not planned to answer this 

 question, but to determine the general character of Illinois soils, their 

 data being reported by glaciations arranged in order of age, in order to 

 bring out any relation existing between the age and the chemical com- 

 position. While they report no ])hysical constants the omission of 

 these is not very serious, as the soils alluded to in table 2 appear to all 

 have been silt loams or clay loams of loessial origin. 



The composition does not appear definitely dependent u]Don the age 

 of the drift except that the Late Wisconsin soils are in general richer 

 in potash than those of the earlier formations. This relationship is 

 confined to the prairie soils, there being none within the timbered 

 uplands. Hopkins and Pettit explain this by the assumption that ero- 

 sion keeps a comparatively fresh and unleached stratum constantly 

 near the surface in the case of the latter. 



In a recent study of Iowa soils very similar in conception to that of 

 the Illinois workers. Brown (9) compares Late Wisconsin drift soils 

 with the Kansan drift soils lying just to the east. Following the prac* 

 tice of Iowa geologists, he designates as lowan the drift sheet which 

 Leverett regards as an integral part of the Kansan. Like Hopkins and 

 Pettit he divides his soil column into three sections, soil 0-6^ inches, 

 subsurface soil 67^3-20 inches, and subsoil 20-40 inches. He reports 

 neither anv physical constants of his samples nor the soil types from 

 which they were taken, most of them probably being taken from unsur- 

 veyed counties. 



The Late Wisconsin soils were collected from three dififerent 

 counties — Clay, Kossuth and Boone — and the Kansas from six differ- 

 ent counties^Cerro Gordo, Floyd, Bremer, Blackhawk, Buchanan and 

 Delaware. Thus the most easterly of his Kansas fields were about 200 

 miles east of his most westerly Late Wisconsin field. 



Table 3. — Difference in composition of lozva soils on Kansan (or loivan) 

 and Late JVisconsin drifts, as shoum by data of Broivn. 



A summary of his data is reported in table 3. He finds the Late 

 Wisconsin soils much richer in total lime, from 60 to 1100 per cent in 

 all three levels, while the carbonates differ little except in the lowest 



