PREFACE. 
IX 
Novogorod and St. Petersburg]!, confirmed on another parallel the 
conclusions they had arrived at by their north-eastern traverses, of a 
general ascending succession of deposits from the Silurian on the north, 
to the Carboniferous basin of Moscow ; and convinced them that those 
two systems were clearly separated from each other by a full develop- 
ment of Old Red Sandstone, as abundantly charged with ichthyolites as 
in Scotland, and containing also many of the same species of shells as in 
Devonshire and the Rhenish Provinces. 
Through these researches, as well as those of Colonel Iielmersen and 
his associates in the Valdai Hills and around Pskoff and Dorpat, the 
chief physical relations of these palaeozoic rocks of the northern and 
central provinces were placed beyond all doubt. 
On his return to England, Mr. Murchison exhibited to the British 
Association for the Advancement of Science a first geological sketch map 
of the regions examined, and read a memoir thereon to the Geological 
Society of London in the name of M. de Verneuil and himself, explaining 
the conclusions at which they had then arrived. 
Shortly afterwards Professor Eichwald published his work on the 
Silurian organic remains of Esthonia 1 ; and in the course of the ensuing 
winter, Colonel Helmersen, grouping together all the information ob- 
tained from the earliest to the most recent researches, produced a small 
general geological map of Russia, very superior to any one which had 
preceded it. But although a good aperpu of the true succession of the 
older palaeozoic rocks in Russia had thus been obtained, — though the 
volumes of the Imperial School of Mines had laid before the public many 
materials concerning the mineral structure of distant and important 
tracts, — though, in short, Rose was then preparing to publish his elabo- 
rate description of the crystalline rocks and minerals of the Ural Chain, 
and Dubois de Montpereux had already given a clear geological ensemble 
to the Caucasus and Crimsea, and had described the tertiary strata of 
1 Esthlands Silurische Schichten System. M. Eichwald obligingly furnished the authors with many 
Silurian fossils. 
