134 On the Tclwrnoi Zcm, 



that such vegetables may have been entirely decomposed ; for in 

 the deep denudations which expose 15 to 20 feet of this matter, 

 surely some remains of the forests or bogs would be found in 

 the lowest parts of the solid earth, just as we find roots and 

 branches of oak, pine, birch, and hazel in our peat bogs. 



But if, for these reasons, it be impossible to adopt the hypothesis 

 of simple terrestrial origin, and that we consider it a subaqueous 

 deposit, with what known accumulation shall we compare the 

 black earth? 



Having referred to some of the difficulties which are to be over- 

 come before the practical farmer can avail himself of the lesson 

 which is offered to him in the crucible of the chemist, I will 

 (claiming the forbearance of agriculturists) say a few w^ords on the 

 geological relations of this Russian earth, and conclude with an 

 attempt to explain the cause of its colour. With what known 

 superficial deposit, then, are we to compare it? Is it to be placed 

 in parallel with the equally finely levigated silt which the Ger- 

 mans call Loss, or with the upper diluvial mud which in Belgium, 

 France, and Germany is said to bound the northern drift? 

 Though this comparison is made by M. A. Erman, and has been 

 alluded to by the eminent geologist M. E. de Beaumont, I do not 

 conceive that it can be sustained. With the ordinary diluvial or 

 drift clay the black earth has, indeed, nothing in common; for it 

 does not contain a single transported pebble. Besides, it overlaps, 

 and is never mixed with, that drift which occupies such large 

 tracts of northern Russia. Again, the composition of the 

 ''Tchornoi Zem" is most distinct from the Loss of Germany, 

 which light-coloured, sandy, calcareous mass is abundantly filled 

 with terrestrial and lacustrine shells in perfect preservation, 

 clearly indicating that it was accumulated on the sides of an- 

 cient, wide, lacustrine rivers, which were barred up so as to 

 form lakes in the way described by Mr. Lyell, just before the 

 present configuration of the land was completed. The fact, also, 

 that the Loss has not yet been seen on high plateaux, but occu- 

 pies the sides and bottoms of the great valleys in which rivers 

 flow, is in itself sufficient to prove that, although it may have been 

 accumulated at nearly the same epoch, it cannot be considered as 

 the exact equivalent of the " Tchornoi Zem," which contains no 

 terrestrial and fluviatile remains, and is found at all levels without 

 any relation to the existing water-courses. 



Debarred, by the absence of any. portions of plants in its com- 

 position, from referring it to the decay of ancient forests, and 

 unable to compare it with any known deposit, from the absence of 

 all organic remains, let us see whether the very peculiar nature of 

 the physical, geographical, and geological conditions of Russia 

 may not help us to a solution of the problem. 



