Dr. H. Trautschold—Periodical Movement of the Ocean. 491 
of this layer after the water had risen above the region of the Stig- 
maria swamps up to that of fir trees. The reason that the older 
Mountain Limestone of the government of Toula and other places is 
not covered by Jurassic sediments is due to the fact of the more 
considerable height of those localities than that of the greater part of 
' the government of Moscow and Riasan, where the newer Mountain 
Limestone is covered by Oolitic rocks. The circumstance, that the 
newer limestone of the Carboniferous system of Russia has been 
deposited in the lower part of the central marine basin, indicates 
by itself the receding movement of the Paleozoic sea. I have 
endeavoured long ago in several of my former papers to show, that 
the lower position of the newer sediments on undisturbed rocks 
affords one of the principal proofs of the general retreat of the 
ocean. 
The process in the formation of the Jurassic or Oolitic sediments 
in Russia is therefore simply as follows: When the Russian plain 
was submerged, the waves of the shallow sea stirred the peat mud of 
the Stigmaria swamps, mixed it with the underlying Permian clay 
and formed a black mud, which we now call Moscow Oolite, because 
it contains Oolitic animal remains. When the sea of that time rose 
still more, it overflowed wood-covered spots of the former continent, 
which furnished to the Ammonites virgatus stratum the above-men- 
tioned pieces of wood; at the same time the decomposition of 
amphibolic rocks gave the material for the formation of glauconite, 
which is the essential compound of the layers of the Upper Jura 
with Amm. virgatus and Amm. fulgens. Small prominences of syenitic 
rocks are found amidst the strata near Paulowsk in the government 
of Voronesh, where they are denuded by the river Don; it is more 
than probable, that these rocks, everywhere hidden by newer sedi- 
ments, have there a great extension. 
The sediments of the Cretaceous period have not the same exten- 
sion in the northern part of European Russia nor those of the Jurassic 
period. The last indications of them do not go further to the north 
than the 58th degree of latitude. If we do not admit that the Cre- 
taceous deposits everywhere towards the north are destroyed, we must 
acknowledge that a new receding movement of the ocean had begun 
at the end of the Cretaceous period in this part of the earth. But 
though the destruction after the retreat of the sea has been very 
considerable, and though a great part of the greensand of the 
Moscow Oolite and of the Cretaceous strata have been changed by 
prolonged trituration into alluvial sand, and the sediments of 
Gault, Upper Greensand, and Chalk Marl have undergone similar 
changes, we must still say, that in those places where these deposits 
have existed before, some remains of them have been conserved here 
and there, as sufficiently proved by the outliers of Gault, Upper 
Greensand, and Chalk Marl: in the Government of Moscow, that 
have escaped the general destruction. 
If the absence of several systems of marine sediments speaks in 
favour of the existence of a long continental period in Russia, in the 
Government of Moscow, from the end of the Carboniferous period 
