204 
THE GEOLOGIST. 
Of the latter, the extensive tracts in the south of Russia, occu- 
pying from lOjOOO 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 limestone, very analogous 
to those rocks which abound in the western dales of Yorkshire. 
These strata, based upon the crystalline rocks of the southern 
steppes, constitute a greatly disturbed region, and, owing to 
numberless convolutions, 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 acquaintance with the types in their nor- 
mal condition, we were enabled to trace the sequence, from con- 
glomerates and sandstones at the base of the carboniferous lime- 
stone, up to the equivalents of the Magnesian 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 
E-ussie Meridionale,^ 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 produced a work so replete 
with well-digested details, collected, not only from observation of 
the natural features of the region and the mines which have 
already been commenced in it, but also by numerous 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 fostered these 
inquiries. 
In a large geological ma]), iu which the demarcations of the 
