38 
and highly important paper. He began by saying that Russia differed from other por¬ 
tions of Europe by its older sedimentary rocks being more continuous, and less 
broken up by the disruptions which have rendered examinations so difficult in 
other regions by the interruptions and even reversals of the series in limited areas. 
In Russia, these strata are spread in unbroken sheets, trending for 1,000 miles in 
one direction, with but few changes in its organic remains or mineral constituents. 
The only difficulties presented were in the slight elevation of their beds above the 
level of the sea, thus exhibiting but few, if any, mural escarpments / and the 
great thickness of the superficial detritus resting on the fundamental rocks. They 
were thus compelled to traverse great extents of country, along the river courses , 
where the only appearances of denudation could be expected. They accordingly 
extended their researches from the longitude of St. Petersburgh to Archangel, as¬ 
cended the Great Dwina to Ousting Veliki; thence to the south of Novogorod, 
and, finally, to the borders of Tambof, to determine the relations of the secondary 
rocks to those older deposites with which they had long been familiar. 
The formations succeed each other in the following ascending order: 
Silurian Rocks. —The oldest stratified deposites of Russia (those on which St. 
Petersburgh rests) are the clays, sandstones, limestones, &c., which, from their 
organic remains, are clearly the equivalents of the British Silurian system. The 
detailed order of these beds had been formerly observed, but, from a want of com¬ 
petent knowledge of fossilology, their proper place in the Geological series, and 
their relations to the superior orders, had not been defined. These Silurian rocks 
occupy several islands of the Baltic and the shores of Courland, and stretch in a 
broad band from west-northwest to east-northeast till they are lost under vast 
heaps of granitic detritus, between Lakes Ladoga and Onega; from these they are 
deflected north till met by great ridges of Trappean rocks. 
Old Red Sandstone , or Devonian Sandstone.-— They experienced no difficulty 
in identifying this system with an immense formation extending to the borders of 
Poland, and ranging over almost the whole of Lithuania. It stretches over a vast 
region to the Northwest, and constitutes much of the shores of the White Sea. 
This great system, consisting of clays, marls, cornstone, and flags, bears a strong 
resemblance to the deposites of the same age in the British Isles; differing from 
them, however, in abounding with saline springs and gypsum. This fact had 
induced previous writers to rank this formation with the new red sandstone , which, 
from its containing those minerals exclusively , had been termed in other parts of 
Europe the saliferous system. Its identity, however, with the old red sandstone 
is sufficiently established, it is thought, not only by its order of superposition, but 
also by its fossils, especially by its fossil fishes , among which are found the holop- 
tychus nobilisimus , (already mentioned,) as occurring in rocks of the same age in 
Scotland. These fishes have been traced several hundred miles, occupying seve¬ 
ral stages in the system. These views were confirmed before the Section by Pro¬ 
fessor Agassiz. It is also proper to remark that other fossils, never found in the 
carboniferous series , were here discovered in profusion—such, for instance, as 
occur in Devonshire, Belgium, &c. 
