76 Horner^ s Geological Address. 



on the west and north by the granites of Sweden and Fin- 

 land, and on the north-east, east, and south-east, by the chain 

 of the Ural Mountains, which are mainly composed of plu- 

 tonic and metamorphic rocks. It consists, to a very great 

 extent, of a series of undulations, composed of incoherent 

 clays and sands ; but although in that unindurated state, not 

 consisting of modern detritus, but being very ancient depo- 

 sits that have undergone no consolidating process ; for the 

 whole of European Russia appears to have been exempted 

 from igneous agency. No eruptions have tilted up the beds ; 

 but the elevatory forces, to which, however, it has been indu- 

 bitably and repeatedly subjected, have raised the vast undu- 

 lating plains en masse, without a break. The oscillations of the 

 land having left the strike more or less horizontal, scarcely 

 any traces of unconform^bility of strata of different ages are 

 to be met with, and beds separated in time by vast intervals 

 are in the same parallelism of juxtaposition as if they were 

 the members of one group. Thus at the mouth of the Vaga, 

 a tributary of the Dwina, about 150 miles south of Archan- 

 gel, post-pliocene beds are seen resting conformably on lime- 

 stones with Producti and Corals of the Permian rocks ; and 

 an observer unacquainted with fossils might view the two 

 as parts of an unbroken series. 



We have some most instructive examples of similarity of 

 lithological characters between deposits of the most different 

 ages, consequent, perhaps, in some degree upon that absence 

 of consolidating processes to which I have alluded. A grit 

 occurs in Sweden, described as a recomposed granite or grani- 

 tic gneiss, which constitutes the base of the Silurian system 

 in that country, that can scarcely be distinguished in mineral 

 character from a tertiary grit in central France. Lower Si- 

 lurian deposits charged with fossils common to the crystal- 

 line slaty rocks of other regions often occur as greensands 

 and half-consolidated mud-like limestones. We have Silu- 

 rian bituminous schists that resemble the hard beds of the 

 Kimmeridge Clay. In one region a carboniferous limestone 

 has all the characters of a soft tertiary deposit ; in others, 

 Devonian, Carboniferous, and Permian rocks, are not dis- 

 tinguishable from the younger secondary or even tertiary de- 

 posits of Western Europe ; and even an oolitic rock of Mip 



