Geological Society. 491 



further testified their warm thanks to the Russian minister, the 

 Count de Cancrine, who specially aided this geological inquiry, and 

 they also acknowledged their obligations to Count Nesselrode, Count 

 Alexander Strogonoff, Baron Humboldt, Baron Brunnow, and Gene- 

 ral Tcheffkine. They further expressed their sense of the value of 

 the services of a zealous young geologist, Lieutenant Koksherof, 

 without whose aid the authors could not have accomplished their 

 task. A geological map and sections illustrated the description, and 

 the characteristic fossils of each group were laid upon the table. 



Crystalline Rocks, Metamorphic Rocks, Trap Rocks, Physical Geo* 

 graphy, #c. — Before they proceed to describe the sedimentary de- 

 posits in their order from S. to N., or from the older to the younger 

 strata, the authors mention some peculiar varieties of gneiss which 

 occupy the little islands of the White Sea near Onega, one of which 

 is charged with garnets. They then give a brief sketch of the 

 altered condition of the sedimentary strata on the western shore of 

 the lake Onega, where they are pierced by masses of greenstone and 

 trappean conglomerate. 



A few words explain how the Waldai Hills, the great watershed 

 of Central Russia, afford the best means of reading off the succes- 

 sion of the older strata. The rivers Msta, Wolkoff, Siass, &c, 

 which flow from the south to the north, having short courses, neces- 

 sarily occupy deeper rents, and therefore expose on their banks 

 better sections than those streams, which, descending on the other 

 side of the crest, glide along on a very slightly inclined plane to the 

 south. By examining the banks of the north-flowing rivers, the 

 older formations were found to succeed each other in the following 

 ascending order :— 



1. Silurian Rocks. — The oldest sedimentary deposits of Russia 

 (those on which St. Petersburgh is situated) are clays, sandstone, 

 limestone and flagstone, which from their position and organic re- 

 mains are considered the equivalents of the Silurian system of the 

 British Isles. The detailed order of these beds was long ago given 

 by Strangways ; but at the early day when he wrote, the study of 

 organic remains was not sufficiently advanced to enable him to de- 

 termine the exact place of these beds in the geological series, nor to 

 point out their true relations to the adjacent masses. Many of the 

 fossils have since been described by the native authors, Pander and 

 Eichwald, and recently some very characteristic forms by M. de 

 Buch. 



The Silurian deposits consist in ascending order of blue clay, inter- 

 mediate grit, and overlying limestone, &c. In the first of these no 

 organic remains have yet been found ; and the intermediate sand- 

 stone or grit is alone distinguished by a remarkable form unknown 

 in western Europe (the Ungulite), which the authors consider to be 

 nearly allied to Or this. They likewise discovered in this grit one 

 small shell resembling a Pecten. In the limestones, and certain 

 overlying flagstones first described on this occasion, organic remains 

 abound ; and they agree well in the leading characters on which the 

 Silurian system was established, viz. that the forms of Trilobite, 



