102 = Results of a Second Geological Survey of Russia. 
In concluding, however, I must tell you of a very interesting discovery 
we made in returning from Taganrog to Petersburgh. Count Keyserling 
took the line of Voroneje and the Don, and M. de Verneuil and myself 
that of Koursk, Orel, and the river Oka, and on meeting at Moscow our 
results completely agreed.* It was, as you know, generally believed up 
to this moment, that central Russia presented a regular succession from 
older to younger deposits as you proceeded from north to south. This 
is not the case. A great axis of Devonian rocks or old red sandstone, 
having a width of at least 120 miles, rises in the heart of the country 
around Voroneje and Orel, and stretches to the W.NW.., in which direc- 
tion it probably connects itself with deposits of the same age in Lithuania 
and in Courland. This discovery seems, indeed, to have an intimate re- 
lation to one which we made in entering Russia early in the spring, near 
to Schavli in Lithuania, of much red ground anda band of upper Silurian 
rocks. In fact it also explains the cause of the great difference which 
exists between the deposits of the carboniferous basin of the Donetz and 
those of your Moscow region, now proved to constitute a vast basin. For 
as the two seas, in which these deposits were accumulated from high an- 
tiquity, were separated by the ancient lands in question, so must we in- 
fer that the conditions and nature of their shores, their rivers, their cur- 
rents and bottoms (on which of course the nature of marine deposits de- 
pend), must have been essentially different. 
This discovery also proves the symmetry of the opposite edges of the 
Moscow busin ; since in advancing from the governments of Tula and 
Kaluga on the south, we see the same ascending order as that which we 
before described in the Waldai Hills on the north. In both tracts the 
Devonian or old red rocks, with Holoptychius nobilissimus, and many 
fishes and shells of that system well known in the British Isles,t pass un- 
der the lowest stata of the carboniferous era, and serve as a base line to 
those thin beds of poor coal, associated with Unio sulcatus and Productus 
gigas (hemisphericus, Sow.) which are at present the subject of new re- 
searches on the part of the Russian Government. 
The enormous space we traversed and examined, in all between 13 and 
14 thousand miles, might well astonish you, if I did not assure you, that 
the arrangements for this journey, undertaken under the auspices of the 
Minister of Finance, Count de Cancrine, were admirably prepared by 
General Tcheffkine, whose clear directions, united to that spirit of hos- 
pitality which characterizes all Russians, and above all the inhabitants of 
the Ural and Siberia, rendered every enterprise feasible, and enabled us 
to overcome every obstacle. 
* Colonel Helmersen, so distinguished for his geographical and geological re- 
searches in Russia, and who aided us so much in both our surveys, also examined 
the tract near Orel in the course of the summer, and,had come to the same conclu- 
sions as our party. I was, however, unacquainted with his opinion when I wrote 
this letter.—R. I. M. 
+ See Silurian System, p. 599. 
