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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 Ihe 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 Ihe 

 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, alotte; the river courses, 

 where the only appearances of denudation could be expected. They accordingly 

 extended their researches from the longitude of St. Pctersburgh to .Archangel, as- 

 cended the Great Dwina to Ousting Veliki; Ihenco 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 lung been familiar. 

 The formations succeed each other in the following ascending order : 

 Silurian Rocks. — The oldest stratified deposites of Russia (those on which St. 

 Petcrsbuigb 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 Bailie and the shores of Courland, and stretch in a 

 broad band from west-northwest to east-northeast till they arc 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 salifcrous system. Its identity, however, with the old red sandstone 

 it sufficiently established, it is thought, not only by its order of superposition, but 

 also by its fossils, especially by i\» fossil fishes, among which are found the holop- 

 tychus ruibiliaimux, (already mentioned,) as occurring in rocks of the same age in 

 Scotland. These fishes have been traced several hundred miles, occupying sevp- 

 ral stages in the system. These views were confirmed before the Section by Pro- 

 fesxor Agassiz. It is also proper to remark that <rther fossils, never found in the 

 carboniferous series, were here discovered in profusion — such, for instance, as 

 occur in Devonshire, Belgium, Sec. 



