AIR WATER SOILS. 925 



and underlying- drift and also from the lowan drift is briefly set forth. 

 Remarkable instances of the transportation without destruction of 

 stratification of limestone ledges occupying in some instances areas of 

 several acres are noted. Descriptions are given of well-defined soils 

 and weathered zones which occur between successive a(;cumulations of 

 drift, as well as of moraines and associated sheets of till, and there is 

 a general discussion on the influence of the drift on drainage systems. 

 The thickness of the lUinoisan drift is estimated at from 100 to 130 ft. 

 and its relation to the water supply is considered in detail. The essen- 

 tial conditions for obtaining artesian wells, as well as the occurrence 

 of g'as, are also considered. The sources of soil material are discussed 

 uid an attempt is made to classify the soils according to their origin 

 and physical characteristics. Eight classes are recognized as follows: 

 Residuary, bowlder-clay soils, gravelly soils, sand}" soils, blufi-loess 

 soils, silts slowly pervious to water, tine silts nearly impervious, peaty 

 or organic soils. A statement of the origin or mode of deposition and 

 the areal distribution of these soils is given in a table and their agri- 

 cultural value and importance are discussed. The loess soils are ol 

 particular interest. Typical soils of this class are found bordering the 

 rivers of the region, merging inland into less pervious white clays, one 

 class of which is known as gumbo. This is an adhesive clay varying 

 in color from ash or light gray to nearly black. The black portions 

 are heavily charged with humus. This gumbo soil contains a few 

 small pebbles which seldom exceed half an inch in diameter. It closely 

 resembles the gumbo of the Illinois and Mississippi River flood plains, 

 which is deposited by flooded streams in the portions of the flood 

 plains where there is little current. The origin of this deposit and its 

 time relations compared with the overlying loess and the underlying 

 till have not yet been satisfactorily worked out. 



The soil zones of European Russia in connection vrith the salt 

 content of the subsoils and v/ith the character of the forest vege- 

 tation, (t. Vissotski {Fochvovedenie [Pedologie], 1 {1899), pp. 19-26). — 

 It has been established that the soils of European Russia are distrib- 

 uted in zones in the following order, beginning at the north: (1) Podzol 

 (siliceous) soils, (2) gray forest soils, (3) chernozem (black earth) soils, 

 and (4) soils of the steppes — deserts. The quantity of the soluble salts 

 in the subsoils increases in the same order. In the first zone the salts 

 are entirely absent, in the second calcium carbonate is found, in the 

 third calcium carbonate and gypsum, and in the last calcium carbonate, 

 gypsum, sodium chlorid, potassium carbonate, etc. Conformably 

 therewith each zone is characterized by a specific vegetation. The 

 first is the region of mixed forests (fir, pine, birch, aspen, willow), the 

 second of oak forests, the third of shrubby plants of the steppes 

 (elder, hawthorn, spindle tree, cherry, privet, sloe, etc.), and the 



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