178 



THE GEOLOGIST. 



authors. The centre of Russia, between the parallels of 52 

 degrees and 54 degrees north latitude, is occupied by a dome 

 of Devonian rocks, which divides the empire into a northern 

 and southern basin, each characterised by marked geological 

 features, but most especially by all the good or workable coal 

 being confined to the southern basin. Over the whole area of 

 European Russia, however, whether it be traversed from 

 Archangel to the Black Sea, from its w^estern confines to the 

 foot of the Ural Mountains, or from St. Petersburgh to the 

 sea of Azof, the strata present a conformable succession and 

 nearly horizontal position, except in the coal regions north of 

 the sea of Azof, where the carboniferous beds are dislocated 

 and highly inclined, and overlaid unconformably by newer 

 deposits. The Silurian rocks do not occur within the flat, 

 central, and southern regions of Russia, but they exist exten- 

 sively in the Ural Mountains, and will be fully described in 

 future memoirs. The Devonian rocks forming the central 

 dome, before alluded to, differ lithologicaliy from the equiva- 

 lent strata in other parts of Russia, but they contain the dis- 

 tinguishing ichthyolites of the system, and the same testacea 

 which occur in the Devonian rocks of the south-west of Eng- 

 land, the Boulonnais, and the Eifel. They are, moreover, 

 surmounted along their northern frontier by the lowest strata 

 of the mountain limestone. The author's knowledge of the 

 carboniferous system of Russia was greatly extended during 

 their last expedition. In the northern region or basin, and 

 ranging from near Moscow to Archangel, it exhibits great 

 uniformity of character, consisting principally of a white lime- 

 stone, which often resembles the calcaire grossier of Paris, 

 and it contains only one thin bed of very impure coal; but, 

 in consequence of their extended researches, the authors show 

 that the system may be separated into three divisions, the 

 lowest being characterised by the great Productm hemisphe- 

 riais, the middle one by the Sjnrifer mosquensis, and many 



