A. N. KRASSNOF THE RUSSIAN " BLACK EARTH." GO 



theory found adherents during the first half of the century, it was soon replaced by 

 another. 



This other theory, founded on the opinion of the people and set forth in a scien- 

 tific manner by Ruprecht in 1866, has recently been confirmed by stronger proof 

 furnished by Dokuchaef. It may at this day be regarded as accepted by most 

 Russian geologists. According to this theory, the chernozem is nothing else than 

 a vegetable earth formed by the roots of plants, which, in decaying, enriched with 

 organic substances the rock on which they had flourished. It differs from our soils 

 formed by this means only by its wealth in organic substances and in the mineral 

 salts that accompany them. It has nothing in common with the soils of the 

 marshes, because the humus of the latter has an acid reaction, while that of the 

 "black earth " is neutral ; moreover, it is not transformed into other substances by 

 desiccation, as happens with the soils formed out of peat. The substances of the 

 underlying rock or subsoil form the mineral skeleton of the " black earth," and 

 the relative quantity of organic substances in the vertical section of that soil be- 

 comes less and less as we go down, until at a depth of about two feet it becomes 

 zero. The " black earth " has been found on the most diverse rocks. Thus, neither 

 its structure nor its position has anything in common with the sedimentary forma- 

 tions produced under water ; and the remains of the solid parts of the graminacese 

 scattered here and there through the mass of humus afford another proof, of no 

 less weight, that this soil was formed by the roots of an herbaceous vegetation. 

 This theory, accepted, as I have said, by most Russian geologists, in these general 

 terms, leaves yet many questions in obscurity. 



If you cast a glance on the soil map of European Russia you will see that the 

 "black earth " there covers a very limited space ; it is a black band that begins on 

 the Austrian frontier, and may be followed to the Ural. Both the northwestern 

 and the southeastern portions of Russia are entirely devoid of "black earth." 

 Ruprecht, who was the first to give a scientific exposition of the theory of the 

 formation of the "black earth " by the roots of plants, at a time when the theory 

 of the glacial period had not yet become general, set forth these peculiarities in the 

 following terms : The whole northern and northwestern parts of Russia, at the be- 

 ginning of the Quaternary epoch, must have been a sea ; on the waves of that sea 

 floated the ice carrying the erratic blocks found here and there in northern Russia. 

 The northern boundary of the " black earth " was the shore of that sea. Accord- 

 ing to him, the limit of the erratic blocks coincides with the northern boundary of 

 the " black earth." Thus the erratic blocks in the north and the Aralo-Gaspian 

 sediments (with fossils of mollusks still living in the modern Caspian) in the south- 

 west were by him regarded as proofs that at a time not long ago the greater part 

 of Russia was covered by the sea. Only the region of the " black earth " was then 

 dry land, covered, as at the present day, by steppes. At this time the " black 

 earth " began to be formed. " In fact," says Ruprecht, " how will you explain that 

 the region of the chernozem lias a characteristic flora whose representatives are 

 Wanting in the northwest and southeast of Russia? How will you explain this 

 depth and this wealth in humus of this vegetal earth, if observation shows that mi 

 the kurgans or mounds erected in the midst of the steppes by the nomads, most of 

 which are more than a thousand years old, then- is yet found only a layer of soil 

 a few centimeters thick? Finally, why do these soils of the northwest and south- 

 east, of recent origin, bear so trivial a flora, in common with Scandinavia and the 

 Ural, while the chernozem is so rich in characteristic forms? We cannot but as- 



