208 
THE GEOLOGIST. 
completely confirmed of an avscending section from south to 
north. 
In fact, tlie examination of tlie carboniferous region of the 
Donetz is one of the best examples that can be adduced, of the 
paramount importance to the practical miner of the close study 
of organic remains, in reference to the normal position of the 
strata ; for, throughout deep sections in the northern part of the 
same territory, there is not a trace of this great Productus, whilst 
all the fossils of the middle and upper strata are present. Any 
one, therefore, who had felt as confident as we do, that this re- 
markable fossil was as clear an indication of a lower band as the 
Spirifer Mosquensis and Fusulings are of an upper, could not 
have doubted of the general relations and order of the strata in 
the chain of the Donetz. 
Agreeing in the correctness of the general parallel which M. 
Le Play has drawn between the deposits of the Donetz and the 
carboniferous limestones of Great Britain, Belgium and France, 
I do not believe that beyond this point his comparisons can be 
sustained. The coal fields, for example, of the Low Countries 
and of Diisseldorf, with which I am well acquainted, do not ofi'er, 
as he supposes, an analogy to those of the Donetz ; for in the 
former, coal-seams are in no instance inter stratified with the 
Mountain Limestone series of English geologists, but are inva- 
riably superposed to it. Again, in the Prussian and Belgian 
provinces, the mountain limestone with sands and shale, but void 
of coal, reposes on a fine succession of Devonian and Silm'ian 
rocks, loaded with typical fossils ; whilst the group of the 
Donetz, exclusively carboniferous to its base, rests at once either 
on very ancient cristalline rocks, or upon porphyries and other 
eruptive masses, to the agency of which is to be attributed the 
extraordinary contortions into which the strata have been thrown. 
The true analogy, therefore, of the coal of the Donetz, considered 
in reference to other deposits of the same age, is to be found in 
the north-western English districts of mountain limestone, in 
