EUSSIAN SOIL INVESTIGATIONS. 709 



River), tind Argentina. In the open orass plains, .such as tlie Hungarian, 

 Russian, and Siberian steppes or American prairies in the northern 

 hemisphere, and tlie eastern provinces of Argentina (Entrerios, Cor- 

 rientes, Buenos-Ayres) in the southern hemisphere, occur the soils of 

 the chernozem group. In Asia, Europe, and North America between 

 the chernozem and tundra soils those of the fifth and sixth group are 

 situated. In the southern hemisphere there is no such complete 

 grouping of soils as in the northern. This is due to a different con- 

 figuration of the southern continents. 



The system of soil zones enumerated above is only an ideal general 

 scheme. In reality no one of these zonal types of soils embraces the 

 continental surface of the globe in a continuous belt. All of them 

 extend in interrupted bands and spots, now expanding enormously in 

 breadth, now becoming narrow, now intermixing with one another at 

 their boundaries, now forming circumscribed areas separated by 

 greater or smaller distances from the principal zones. The reason for 

 this is found in the effect of local orographic, geological, and climatic 

 peculiarities, which interfere with the development or cause a dis- 

 placement of certain soils.' 



The division into types distributed in zones or belts does not begin 

 to exhaust the whole \'ariety of natural soils. As stated above, among 

 the soil-forming factors there are some which maA' individualize them- 

 selves by diverging from the concordant action of the other factors. 

 Thus, for example, a particular composition of the parent rock may 

 retain its influence on the soil and thus impart special features which 

 are not proper to the dominant zonal type; a similar effect may be 

 caused by the local saturation of soils with water, due to the config- 

 uration of the surface. Humus soils of this second class may be called 

 intrazonal or semizonal. They are dispersed among the main zones in cir- 

 cumscribed areas and spots, occurring chiefly, although not exclusively, 

 in connection wiih some of the zones. Certain types of the intrazonal 

 soils are met with in those zones whose general conditions fa^or the 

 most or interfere the least Avith the action of the individualizing factor. 



There are undoubtedly very man}- types of intrazonal soils. We shall 

 mention the following as examples: (1) Alkali soils, which form when 

 the parent rock contains soluble salts and the drainage is poor. Since 

 the salt contents of the rock may depend on causes purely geological, 

 ha\'ing no direct connection with the other soil-forming factors, there 

 is, generally speaking, no zonal regularity to be observed in the distri- 

 bution of alkali soils. However, they occur mostly in the arid regions 



^In Russia, e. g., the soils of the steppes deserts extend to the south and south- 

 east of the chernozem, and in North America to the west and southwest (in con- 

 f(jrmity with the increasing aridity of the chniate). It may he added that vertical 

 zones may also be observed on broad slopes and plateausi which appear in a measure 

 as local repetitions of the horizontal zones in an analogous order. 



