Second Geological Survey of Russia in Europe. 67 



times upon an adjacent peat bog in North Wales specially affected 

 and impregnated the vegetable fibre in preference to the accom- 

 panying soil, so is it conceived that the forests washed into the sea 

 in which the Permian deposits were accumulated, attracted around 

 them the cupriferous matter contained in the transporting currents. 

 This point will be reverted to in the subsequent sketch of the Ural 

 mountains. 



The general succession of these Permian deposits is then described 

 on several parallels of latitude between the Ural and the Volga, and 

 also their outliers in the steppe between Orenburg and Sarepta ; 

 and it is shown, that this vastly extended and diversified system, 

 containing not only copper deposits but also large masses of gyp- 

 sum, rock-salt and copious salt-springs, lies in an enormous trough 

 bounded on the north and east, and south-west, by the carbonife- 

 rous limestone on which it reposes. 



By their examination during the past year, the authors have 

 cleared away some difficulties which obscured their former views. 

 By reference to the abstract of their first memoir (vol. xix. p. 492), it 

 will be seen, that they considered (though with much hesitation) 

 certain limestones and beds of gypsum which occupy cliffs upon the 

 Dwina to the south of Archangel, and extend to Pinega and to- 

 wards Ust Vaga, to be upper members of the carboniferous lime- 

 stone. By a comparison of the Producti and other fossils, and 

 the great masses of gypsum which they contain, these northern 

 beds are now brought into direct identification with the true Per- 

 mian or Zechstein deposits. In the south-western termination 

 of this vast basin near Samara, the Permian rocks, particularly 

 at Usolie, rest in patches of a dolomitic conglomerate upon the 

 steep escarpments of the carboniferous limestone, out of the mate- 

 rials of which they have been formed, and do not present that 

 regular succession which they exhibit when followed westwards 

 from the slopes .of the Ural chain. It is also observed, that though 

 gently undulating or horizontal over all the lower regions, these 

 rocks, on approaching the Ural mountains, are occasionally thrown 

 into anticlinal axes of some length, parallel to the direction of the 

 palaeozoic rocks of the adjacent chain. 



In a sketch of the outliers in the Steppe of the Kirghiss, the base 

 of the insulated hill of Monte Bogdo is shown to consist of a mem- 

 ber of the Permian group, surmounted by fossiliferous limestone 

 which probably belongs to the Jurassic system ; and it has before 

 been shown that the rock-salt of Iltetzkaya Zatchita*, south of 



the magnesian limestone it appears, from Professor Sedgwick's description 

 of the latter, that traces of lead ore and also of copper, are found in it in 

 small quantities, which that author considers to have been derived from the 

 large mineral masses of the same in the surrounding and more ancient car- 

 boniferous limestones. Lead is also worked in the dolomitic conglomerate 

 of the Mendip Hills, where it is associated with calamine. See memoir of 

 Mr. Conybeare and Dr. Buckland, Geol. Trans., 2nd Series, vol. i. part 2. 

 p. 293 ; also Mr. Weaver's memoir, ibid. p. 367. 



* Proceedings, vol. iii. p. 695, [or Phil. Mag. S. 3. vol. xxi. p. 357.1 



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