SECONDARY ROCKS. 
JURASSIC OR OOLITIC SYSTEM. 
CHAPTER XI. 
Jurassic System of Russia. — Range and uniformity of Composition of the lower Divi- 
sion, from the Northern Sea to the Lower Volga.— Basins of the Middle Volga, 
the Oka, and the Moskwa. — Iron Sands and Grits with Plants in Russia and 
Poland compared with their equivalents in England. —Large Basin of the Lower 
Volga, Simbirsk, Saratof, fyc. — Jurassic Rocks of Orenburg, and their peculiar 
mineral aspect. — Upper Division of the Group on the river Donetz in Southern 
Russia, and at Cracow in Poland. — The whole of the Jurassic Rocks of Russia 
on the parallel of the Oxford Clay, Calcareous Grit and Coral Rag of England, 
or “ Terrain Oxfordien” of France. — Suppression of the Trias, Lias, and Lower 
Oolite in Russia. — Occurrence of the Oxford Formation in Asia and Africa . — 
Conclusion. 
Throughout the Paleozoic series of which we have just taken leave, there 
exists, as has been shown, a vast succession of deposits, which, covering an enor- 
mous superficies, are linked on to each other by regular transitions and organic 
contents. Far different is the system which next presents itself upon the surface 
of Russia. Occurring at remote intervals only, the strata immediately oveilying 
the red formation last described, contain a class of organic remains entirely distinct 
from any hitherto named, and occupy isolated basins, patches, or stripes, the 
beds of which have no natural connection with the deposits beneath them. As 
the rocks of these countries are less disturbed than those of any portion of the 
globe which geologists have examined, and as the Palaeozoic series is complete, 
we were at first naturally induced to look also for a full succession of secondary 
deposits, similar to that with which we were acquainted in other countries. In 
vain however, we sought for fine escarpments, like those of our oolites in En- 
2 H 
