22 
ANCIENT CRYSTALLINE ROCKS OF THE NORTH. 
intersect the wide and fiat regions of the governments of Vologda, Perm, and 
Orenburg, are there also respectively turned to the north or to the south by ele- 
vations like the Obschey Sirt, which are very slight in reference to the enormous 
spread of land by which they are surrounded. 
If it be asked, what is the direct connexion between these streams and a geolo- 
gical inquiry, the answer is obvious at least to every one acquainted with Russia. 
In other countries the upper lands often expose stony masses which emerge from 
beneath the soil as separate or continuous rocks, and afford the knowledge the 
geologist requires ; but here the round-backed plateau and loftiest elevation are 
so loaded with detritus of sand, clay, and far-transported blocks, that inspection 
of the concealed strata can seldom be obtained, except in the deep ravines which 
are daily forming on the sides of the valleys, or on the banks of rivers, where the 
subsoil is laid bare by denudations. The water-courses are, therefore, as truly the 
keys of the internal structure and mineral wealth of Russia, as they are the sinews 
of her commercial intercourse. 
Before, however, we describe the various sedimentary deposits watered by these 
streams, we must first give a brief sketch of their crystalline northern frontier. 
Crystalline Rocks of the North . — The fundamental rocks of Finland and Lap- 
land, consist, as in Scandinavia, of gneissose and granitic with plutonic rocks, 
many of which have been described by native writers, and some of the prominent 
varieties of which, in the region north of St. Petersburgh, were long ago made 
known to English geologists by Mr. Strangways 1 . By reference to the Map, 
PI. VI., it will be seen that such rocks, ranging from Norway and Sweden, spread 
out to the north-east over the vast territory which comprehends Finland, Russian 
Lapland, and large portions of the governments of Olonetz and Archangel. Having 
touched at intervals only upon the edges of this crystalline region, it is not in our 
power to describe it. We may, however, be permitted to say a few words upon 
certain small islands in the Bay of Onega, an arm of the White Sea, since no 
account of them has yet been published, whilst their description may serve to give 
the reader some idea of one of the classes of rock, so largely developed in these 
northern latitudes. 
Of the islands we examined, Ki-Ostrof is the principal, and lies a few miles 
north of the town of Onega. This narrow strip of rock, surmounted by a pictu- 
resque monastery, and affording barely sufficient soil to sustain a few fir-trees, does 
' Geological Transactions, vol. v. 1st series, and vol. i. 2nd series. 
