206 
THE GEOLOGIST. 
or from their imbedded organic remains. In fact, he then di- 
stinctly acquainted us with what has now appeared in his work;, 
that, owing to the disturbed and convoluted condition of the 
strata, the want of persistency of mineral characters, and the ap- 
parent existence of similar species of shells throughout the series, 
it was impracticable to assign a base line to the deposits, or to 
trace their uppermost limits, still less a passage into any supe- 
rior formations. 
Now, as we have ventured to effect these objects, v/ith what 
success we must leave others to decide, I will here briefly state 
why I conceive M. Le Play did not arrive at similar results ; 
although he had in his own hands some means of proof, which 
through the short time at our disposal, we never obtained. 
No geologist, however practised, can, I venture to say, explain 
the structure of any complicated part of a distant country, unless 
he has made himself master of the clear succession of its normal 
formations. Long as I have been occupied in the study of the 
Palseozoic Eocks, I am confident that had my friend and myself 
been thrown suddenly into the chain of the Donetz, and had 
been desired at once to unravel its complexity, we should have 
reached no other geological result than that to which M. Le 
Play has attained, viz. of stating that the coal-seams are, as a 
whole, subordinate to the carboniferous or mountain limestone. 
We had, however, by two years of extensive comparative re- 
searches, obtained an intimate acquaintance, not only with the 
older Palaeozoic rocks of Russia generally, but, in reference to 
the carboniferous system, had convinced ourselves, that, through- 
out the enormous area over which we had traced it, the upper 
or coal group of western Europe was absent ; and that the cal- 
careous or lower group, occupying the w^hole carboniferous ho- 
rizon, was divisible into three stages, by help of certain fossils 
characteristic of each. Again, we had ascertained, by numerous 
sections on both flanks of the Ural Mountains, that in becoming 
part of a mountain mass, this system, so uniform and so pecu- 
