105 



Devonian and Silurian rocks, loaded with -typical fossils; whilst 

 the group of the Donetz, exclusively carboniferous to its base, 

 rests at once either on very ancient crystalline rocks, or upon por- 

 phyries and other eruptive masses, to the agency of Which is to be 

 attributed the extraordinary contor-tions into which the strata have 

 been thrown. The true analogj'^, therefore, of the coal of the Do- 

 netz, considered in reference to other deposits of the same age, is to 

 be found in the north-western English districts of mountain lime- 

 stone, in which several workable seams occur ; though in this com- 

 parison it must be stated, that the Russian beds contain much more 

 coal than the British strata. But even if we admit that, to some 

 extent, there is a similarity in the carboniferous rocks of South 

 Russia and the Low Countries, in their being both flanked by cre- 

 taceous deposits, we must also not omit to recognise a great dis- 

 crepancy, through the presence in the one case of overlying strata of 

 the age of the Zechstein, and in the other by the total absence of 

 that deposit. 



To considerations of theoretical importance concerning the 

 changes which the surface of Southern Russia may have undergone, 

 and which are ably put forth by M. Le Play, I will not at present 

 advert ; reserving my views on these points for the concluding 

 chapters of the work upon Russia, when all the elements which my 

 friends and myself can bring together shall have been laid before our 

 readers, to enable them to see the grounds upon which the conclu- 

 sions are based. 



For the present, then, I take leave of this volume of M. Le Plaj'-, 

 which, though it contains some views of positive geology from which 

 I differ, must still be regarded as an important addition to the re- 

 cords of physical science, and as possessing much more the charac- 

 ter of a good monographic description of a given tract in Russia, 

 than anything vvhich, from the extensive nature of our i-esearches, 

 my friends and myself will ever be enabled to offer. 



Permian Rocks. — On its eastern frontier, far removed from the 

 tract to which allusion has been made, the uppermost member of 

 the carboniferous limestones of Northern and Central Russia, di- 

 stinguished by the presence of multitudes of the io\&\n\miev Fusu- 

 lina, is succeeded by the most widely spread of the Russian systems ; 

 to which, from its occupying the whole of the ancient kingdom of 

 Permia, we have assigned the name of Permian. You have been 

 told, that this vast group is composed of limestones, marls, great 

 masses of gypsum, rock-salt and repeated alternations of cupriferous 

 strata ; and that it contains a flora and a fauna of characters inter- 

 mediate between those of the Carboniferous and Triassic periods. 

 The shells are, to a great extent, those of our Magnesian Limestone 

 or Zechstein ; and, like the conglomerate of that deposit near Bris- 

 tol, the Permian rocks are distinguished by the presence of The- 

 codont Saurians. The interest attached to these vast deposits, which 

 have been spread out on the western flanks of the Ural Mountains, 

 is increased by the inferences Avhich have been drawn, that springs 

 and currents holding much copper in solution must have flowed 



VOL. IV. PART I. I 



