TCHORNOZEM OR BLACK EARTH OF RUSSIA. 
563 
so uniform in its colour over all northern and central Russia. By reference to the 
Map it will appear, that this shale, which formerly must have had a vast extension, 
has been most widely denuded. Nor could it have been otherwise, when exposed 
to those powerful currents (which as the superior stratum it must have been) that 
carried southwards the northern materials. Such currents may then, we believe, 
have moved on this fine sediment in solution to the very extremity of their in- 
fluence, and thus transported it southward of the limit of the northern boulders, 
there is another reason for supposing that the Jurassic shale has furnished a por- 
tion of the materials for the tchornozem, in the absence of that earth to the south 
of certain tiacts where we have reason to think that the former has never existed. 
In truth, it is in this respect exactly like the northern drift of Russia, which inva- 
riably contains many materials of the formation immediately north of it. Now, as 
there neither is nor has been much Jurassic shale north of Moscow, but abundance 
in the environs of that city, so it is only on passing the plateaux to the south of 
that parallel, that we find the first great spread of this singular black material. 
But even if this explanation of the chief derivation of the black earth be accepted 
in regard to European Russia, there are, we admit, difficulties respecting great masses 
of it in southern Siberia, over which no northern current transporting blocks has 
certainly ever swept. Granting, however, that the Siberian black earth had equally 
a marine origin, may not its materials have been carried northwards round the 
south end of the Ural chain ? Or may not a large portion of the low grounds of 
Siberia have been then under the waters of large lakes, whose bottoms would 
necessarily be muddy, as the whole region is void of coarse detritus ? 
Forbearing to speculate with our present knowledge upon the probable extension 
of hays of the ancient sea into those parts of Siberia, we cannot avoid alluding to 
a striking analogy between the deposition of the rich cotton soil of Hindostan and 
our Russian tchornozem. We learn from Captain Newbold, who described the 
“Regur” or Indian cotton soil some years ago 1 , that it is a dark-coloured silt 
which occupies the summits of plateaux at various elevations, and is spread out in 
separate broad masses, from the northern part of central India to the south of Tri- 
chinopoly, hut is unknown on the coasts. This Indian earth bears, indeed, a re- 
markable geological affinity to that of Russia in being never found to the north, or 
along the low country under the Himalaya Mountains, the great source of all the 
gravelly detritus of that peninsula. In Hindostan therefore, we believe, that this 
1 See Records of the Royal Society. The memoir was not printed. 
