202 
THE GEOLOGIST. 
crystalline equivalents in Western Europe and tlie British Isles. 
In their small vertical dimensions they present to us, indeed, a 
very instructive lesson, for in passing from Norway, Sweden and 
Gothland into Russia, the distinguishing strata thin out, and 
losing their divisionary lithologieal characters, part also with 
many of their characterteristic shells. "When followed from 
one region to another, deposits of all ages exhibit hke con- 
structions and expansions, dependant on the forms of the ancient 
bays, the nature of the springs and currents, and the depth of 
the seas in which they were accumulatedf."'^ 
Devonian Rocks. — If the horizontal range of the Silurian rocks 
of Russia be considered large as respects our terms of compari- 
son, what will my associates say to the expanse over which the 
Devonian or next ascending group is spread, when I teU them it 
is much larger than the whole of the British Isles ? Reposing 
upon the low Silui'ian plateaus, this widely ranging deposit rises 
to heights of from 500 to 900 feet above the sea ; and it is very 
remarkable by being charged in many localities with ichthyolites, 
several species of which, hitherto considered peculiar to the 
Scottish Old Red Sandstone, are found associated with Mollusks, 
perfectly similar as a group, and often specifically the same, as 
those of the limestones of South Devon, the Boulonnais and the 
Eifel. The discovery of the intermixtm-e of Scottish Old Red 
Sandstone fishes and true Devonian shells in the same strata, 
was, you may believe, one of the most gratifying results of the 
recent explorations in Russia, as being confirmatory of the views 
of Professor Sedgwick, Mr. Lonsdale and myself respecting the 
divisions and equivalents of that member of the Palseozoic 
Rocks. In some parts of Russia, the Devonian rocks are red 
sandstones and marls ; but in an extensive central tract, 
where they rise into a dome which separates the northern from 
t Geological Researches in Russia (in the press) by Roderick Impey "Mur- 
chison, E. de Verneuil, and Count A. von Keyserling. assisted by Lieut. 
Kokshaiof, p. 40. 
