Russia and the Ural Mountains. 529 
prevail, whilst in no part of the empire is there a trace of the over- 
lying deposits, with which we are familiar under the term of “ coal- 
measures.” Coal, however, does occur at intervals, both underlying 
the carboniferous limestone, as in Berwickshire, and alternating 
with its central and upper members, as in Northumberland, and the 
carboniferous valleys of our lake country. 
Of the latter, the extensive tracts in the south of Russia, occupying 
from 10,000 to 11,000 square miles, and usually known as the 
country of the Donetz, offer a very striking illustration ; containing 
in one district as many as seven good seams of coal, subordinate 
to sandstone, shales and limestones, very analogous to those rocks 
which abound in the western dales of Yorkshire. These strata, 
based upon the crystalline rocks of the southern steppes, con- 
stitute a greatly disturbed region, and, owing to numberless con- 
volutions, present the most remarkable contrast to the horizontal 
deposits of Central and Northern Russia. It is therefore difficult to 
observe the order of succession; but, owing to our previous acquaint- 
ance with the types in their normal condition, we were enabled to 
trace the sequence, from conglomerates and sandstones at the base 
of the carboniferous limestone, up to the equivalents of the Mag- 
nesian Limestone or Zechstein. 
Whilst thus briefly alluding to this tract, I must pass, for a time, 
from my own labours, and those of my friends, of the value of which 
you must judge when our work is completed, in order to mention the 
recent appearance of the fourth volume of the splendid work of M. 
Anatole Demidoff, ‘ Voyage dans la Russie Méridionale,’ which is 
entirely devoted to the description of the carboniferous region of 
the Donetz. M. Le Play, an eminent French engineer, happily 
selected by M. Demidoff to ascertain the true mineral wealth of the 
tract, and to describe its physical and geological structure, has pro- 
duced a work so replete with well-digested details, collected, not 
only from observations of the natural features of the region and the 
mines which have already been commenced in it, but also by uu- 
merous borings carried on by himself or his assistants during a 
period of three years, that the Imperial Government will doubtless 
feel grateful to the accomplished patron who has so liberally fos- 
tered these inquiries. 
In a large geological map, in which the demarcations of the car- 
boniferous and crystalline rocks, and also of the overlying secondary 
and tertiary deposits are given, M. Le Play has grouped under 
darker colours such parts of the tract as are known to be productive 
of coal, to distinguish them from those in which the mineral has not 
yet been discovered. ‘This method, doubtless, carries with it a 
certain amount of information, but is deficient in stratigraphical 
meaning, for some of the beds so marked are higher than others; 
in some the coal is interlaced with limestone, and in others it is 
almost entirely subordinate to sandstone and shale ; in one tract 
anthracite exclusively prevails, in another bituminous coal. By re- 
ference, however, to the explanation, and to a series of tables, this 
defect is obviated. These tables are, in fact, perfect models for the 
