70 PROCEEDINGS OF WASHINGTON MEETING. 



sume that the region of the chernozem, from the earliest times, since the end of 

 the Tertiary, was a steppe covered by a characteristic steppe vegetation under which 

 the chernozem was slowly formed." 



But this view, which to the modern geographer may seem somewhat crude, could 

 find adherents only up to the day when the glacial theory became dominant among 

 geologists and geographers. At the present day, after the researches of our glacial- 

 ists, Krapotkin, Nikitin, and others, we know that the youngest formations bearing 

 erratic blocks are of the same origin in our land as in Germany ; that they are the 

 moraine of the Scandinavian glacier, the traces of which are found not only in the 

 region of Ruprecht's sea but farther southward under the " black earth," as well as 

 in the governments of Poltava and Voronesh. Professor Dokuchaef having at the 

 same time found several points where the " black earth " covered Caspian sediments, 

 it became necessary to give another explanation of the peculiarities of distribution 

 of the " black earth" than that given by Ruprecht. At the present day the expla- 

 nation given by Mr. Dokuchaef and his school is regarded as the most probable. 



According to him, climatic conditions, as well as the character of the vegetation, 

 imparted to the region of the " black earth " its peculiar contours. The properties of 

 the "black earth," he says, depend on the relative age of the ground, on its sub- 

 soil, on the climate, on the relief, and on vegetation. But since vegetation, too, de- 

 pends on climate, the latter is to be regarded as the main factor in the formation of 

 this soil. 



In fact, nothing but the vegetation of the steppes covered by herbaceous plants 

 can form the chernozem. Submerged and marshy ground forms and accumulates 

 organic substances of an entirely different character. Forests are incapable of 

 producing " black earth." Numerous observations show that everywhere under 

 the shade of forests there is formed a gray soil, made up of pieces of the size of a 

 walnut, containing not more than 2 to 3 per cent of organic substances. This soil, 

 having very considerable thickness, was observed everywhere beneath the forests 

 of Russia and Denmark, and a series of special labors were devoted to this subject. 

 Observation even shows that forests taking root on the " black earth" decompose 

 it and gradually transforms it into the gray soil peculiar to forests. Thus it is the 

 condition favorable to the steppe and its vegetation that presents the best combina- 

 nion of heat and humidity necessary for the formation of the " black earth." In 

 fact, the numerous excursions and analyses made by Dokuchaef and confirmed by 

 myself in central Asia and Turkestan bear out this idea with striking exactness. 



By means of comparison of " black earth " specimens taken in various localities 

 of Russia whose relief and subsoil were analogous, Professor Dokuchaef has pre- 

 pared a diagrammatic map of the variations in the quantity of organic matter of the 

 "black earth." This map shows that in the eastern parts of the region of the 

 chernozem, in the provinces of Penza, Samara and Simbirsk, we find the soils most 

 rich in organic substances. Toward the northwest from this 2>art of the region 

 spoken of, in proportion as the climate becomes colder and moister the soil becomes 

 less rich in humus, and is gradually transformed into the vegetal earth or sod of 

 the north, or makes room for the soils formed by forests, which begin to domi- 

 nate beyond the northern boundary of the "black earth." The same thing may 

 1)0 observed toward the southeastern boundary of our region. There, too, the soil 

 becomes poorer in humus, but, according to Dokuchaef, it is the dryness of the 

 climate, unpropitious to the steppe vegetation, that prevents the formation of the 

 chernozem. Dokuchaef's map also gives a series of approximately concentric 



