25 
SILURIAN ROCKS OF THE BALTIC PROVINCES. 
with some exceptions not far removed from this northern frontier line, all the great 
transverse dislocations cease in the succeeding sedimentary formations ; for in 
tracing the Devonian and Carboniferous rocks from the slopes of the Valdai Hills 
to the mouth of the great Dwina, no great upheavals have occurred ; and with this 
absence of elevation no transverse fissures are visible, and the whole region is void 
of a trace of eruptive rocks. To feebler exertions of the same influence whereof 
we have been speaking, we shall, however, presently advert in describing the Silu- 
rian strata near St. Petersburgh (see p. 31). 
Silurian Roclcs of St. Petersburgh and the Baltic Russian 'provinces (see Map, 
PL VI., with tabular view on the right, and Section across Russia beneath). — The 
oldest rocks in Russia containing organic remains form one great series, whose 
different members have a certain affinity in their zoological contents, yet exhibit 
marked distinctions, and are clearly separable from each other by superposition, 
imbedded fossils, and lithological characters. In the north-western regions of 
Russia they are composed of three zones, synchronous with those rock-systems of 
the British Isles and Western Europe to which the terms Silurian, Devonian, and 
Carboniferous, have been applied. A fourth system of this series, largely spread 
out over the eastern countries of Russia in Europe, is that which we have termed 
Permian. Our actual knowledge of these rocks in other parts of the world has 
been sketched in the first chapter; and in the sequel we shall describe their 
succession in order of time, as well as their passage from inferior to superior 
formations, each characterized by typical fossils. The complete description, 
however, of these remains, particularly in reference to many species not pub- 
lished by other authors, will form the chief part of the appendix to this volume, 
and the third part or second volume of our work. In the meantime, the remain- 
der of this chapter is devoted to the consideration of the oldest or Silurian groujj 
of these deposits, as developed in the Baltic provinces of Russia. 
The geologist who has formed his ideas of the older palaeozoic rocks from the 
splendid examples they offer to his inspection in the British Isles, where they 
attain a vertical thickness of several thousand feet, may well be disappointed when 
he first surveys their equivalents in Russia. Instead of the mountain masses, fre- 
quently in a subcrystalline condition, and often highly dislocated, to which he has 
been accustomed, he sees before him very low undulating hills only, whilst ravines 
of little depth occasionally expose horizontal beds of soft clay, incoherent sand- 
stone, and slightly consolidated limestone and shale ; the whole differing little in 
