RESUME AND CONCLUSION. 
585 
however, have been soon after depressed, for the Devonian strata with their ich- 
thvolites are found resting on them. Again, we believe that the great central dome 
of the Devonian rocks of Orel was elevated not long after its formation, and, acting 
as a bar or line of separation in the waters, thus produced a distribution of sedi- 
mentary matter on its southern side very different from that upon its northern, 
and separated the great cretaceous and tertiary country on the one side from the 
palaeozoic rocks on the other. 
Looking to the differences, however partial, between the fossil floras of the car- 
boniferous and Permian rocks, we cannot but infer, that these plants were in exist- 
ence upon adjacent lands during each of these periods ; nor can we view the 
existence of the Jurassic series with its Ammonites and Belemnites, nor mark the 
great hiatus which exists between the base of this group and the Permian rocks 
beneath it, without believing, that broad and decided oscillations of sea and land 
took place both in and around these regions, which placed certain masses above 
the influence of the waters, during the very long interval of time which neces- 
sarily elapsed. 
Yet, after all, Russia in Europe constitutes but one huge depositary basin, 
surrounded on nearly all sides by plutonic, metamorphic and crystalline rocks. 
We readily therefore admit, that the various changes which took place in Scan- 
dinavia and Lapland on the north, in the Ural Mountains and Siberia on the 
east, in the Caucasus and granitic steppes on the south, and in the Carpathian 
and Silesian mountains on the south-west, may have considerably affected the 
conditions and influenced the relations of all the sedimentary accumulations of 
the low territories of Muscovy. Still, notwithstanding this admission, we dwell 
upon the fact, that such enormously wide horizontal deposits of different ages 
are nearly all conformable in superposition, and yet all clearly separable from 
each other by mineral characters and organic remains; — thus decisively showing, 
that old races of animals have disappeared and have been succeeded by others over 
vast regions, in which there never has been the smallest eruption of plutonic or 
volcanic matter. 
However we may explain its elevation to various levels, the ancient bottom of 
one great inland internal sea of brackish water, large as the present Mediter- 
ranean, which occupying, as we have stated, a vast depression in the earth s sur- 
face between the Caucasian chain and Russia, extended over enormous tracts of 
Asia, must be considered as having originated in great physical changes. In the 
