or Blade Earth of Russia . 127 



mucks between that place and the mouth of the Don ; nor 

 indeed anywhere except in very limited patches along the sea 

 of Azof, or in other words on the southern face of the axis of 

 elevation between the Dnieper and the Don, which is a pro- 

 longation of the Carpathian chain, and constitutes what is com- 

 monly called the granitic Steppe. It occurs, however, in great 

 thickness on the slopes and plateaux on the northern side of that 

 axis, where, as it really surmounts the carboniferous limestone 

 with many seams of coal, a geologist who had not observed it in 

 other places might at first sight be led to suppose that the black 

 matter was due to the decomposition of the subjacent carbonaceous 

 strata.'" It lies, however, upon rocks of all ages, and the great 

 masses are included in the central region thus roughly defined. 

 Geologically considered, therefore, the Tchornoi Zem occupies 

 the centre of a great trough as large as an European empire, 

 having the detritus of the crystalline and older rocks for its 

 northern and the low granitic steppes for its southern limits. 



It is found at all levels, sometimes on plateaux, as on the right 

 bank of the Volga, high above the adjacent plains, in various paral- 

 lels, from 56J-° N. lat. to the high grounds extending to Saratof, 

 and at heights of not less than 400 feet above the valleys ; in other 

 places on slopes and undulations, and often in broad valleys, where 

 the rivers, having cut through the deposit, expose its thickness on 

 their banks. In the country where the southern limits of the 

 northern drift are traceable, it is interesting to observe that its 

 materials, reduced to small size, are overlapped by the black 

 earth. 



I may here remark, that on the plateaux and their sides, the 

 black earth, like all the other alluvia of Russia, is constantly cut 

 into by the ravines, called '•' avrachs " or '" baltas " by the Russians, 

 and which invariably show it to be the uppermost deposit. These 

 ravines have been mentioned in a former communication ; but the 

 attention of English geologists cannot be too frequently called to 

 them, as the rapidity with which they are laid open after the 

 ground has once begun to yawn, is something quite surprising 

 to those who have been accustomed only to survey the trodden 

 tracts of Europe and other parts of the world. 



Central Russia, indeed, may be described as consisting, to a 

 very great extent, of a series of undulations, composed of incohe- 

 rent materials, or, in other words, as a country so devoid of a 

 visible skeleton or framework, that the vast increment of clay, 

 sand, or mud, which occupies her surface, is easily denuded when 



* These coal-fields have since been described in the account of the gene- 

 ral structure of central and southern Russia, communicated by myself and 

 companions to th« Geological Society of London. 



