Geological Society. 499 



of ice to heights: of 20 or 30 feet above its ordinary level, they had 

 at once a solution of the phenomenon ; for the blocks of white lime- 

 stone had evidently formed parts of the subjacent strata, which, 

 projecting into the mud and water on the edge of the Dwina, had 

 been first entangled in ice, and rent off at their natural joints upon 

 the expansion of the ice by which they were upheaved into their 

 present position, taking their present irregular talus shape when the 

 ice melted away from them. Believing, therefore, that the angular 

 ledges on the lake of Onega were similarly formed, the authors see 

 in them the proofs of the lakes of Northern Russia having formerly 

 stood at much higher levels, from which the waters, they suppose, 

 have been let off by successive elevations of the land ; and they fur- 

 ther think, that the diminution of shallow lakes, and the conversion 

 of marshes into land within the historic period in Northern Russia, 

 strongly corroborate the rise of this portion of the earth. 



Conclusion. — In recapitulating the chief point of the first and prac- 

 tical part of their Memoir, wherein they establish, they trust, on a 

 sound basis, the general classification of the Palaeozoic Rocks of 

 Russia in Europe, the authors remark, that the fact of some of the 

 deposits of such high antiquity being found to stretch in horizontal 

 and almost unbroken sheets over spaces of a thousand miles in length, 

 in a very slightly solidified or lapidified state, is the more interesting 

 when coupled with the absence, throughout the same regions, of all 

 plutonic or igneous rocks. This phenomenon must, it is conceived, 

 exercise considerable influence upon geological theory, it being now 

 apparent, that the lithological nature of the most ancient subsoil of 

 Russia in Europe is such as to compel geologists to reject the con- 

 clusion, that in proportion to their antiquity the strata have been 

 hardened or crystallized by any general radiation of central heat ; 

 for in these wide tracts such crystalline and hardened state is clearly 

 seen to be purely metamorphic, and dependent exclusively on the 

 vicinity of rocks of igneous protrusion, in receding from which to 

 the South all the strata described are at once found in their normal 

 soft condition. 



In taking leave of the Society, the authors explained some of the 

 chief objects of their journey to the Ural Mountains, Orenburg, &c, 

 on which they were about to proceed. 



Note. — After these sheets were sent to press, Mr. Murchison re- 

 ceived letters from his friends and fellow-travellers, the Baron A. de 

 Meyendorf and Count A. Keyserling, in which the researches of 

 these gentlemen in the South of Russia are explained. These let- 

 ters communicate important additions to the results already offered 

 to the Geological Society, particularly in regard to the extension 

 and development of the carboniferous system. The geological map 

 which has been prepared by their labours, and from those of other 

 Russian authorities, agrees with that of Mr. Murchison and M. de 

 Verneuil, exhibited to the Society, in the fundamental classification 

 of the rocks which occupy the northern and central governments of 

 Russia, and in the lines of demarcation between the Silurian, Devo- 



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