78 Horner 8 Geological Address. 



mentary palaeozoic deposits ; and through fractures in the 

 latter the igneous rocks were erupted, after having produced 

 in them those changes of structure which we call metamor- 

 phic ; that is, having caused them to change their original 

 chai*acters, and assume a crystalline aspect,^ — the force act- 

 ing with such intensity as in many places to overturn the 

 strata, and so invert the order of superposition on the flanks. 

 But it has not been by one great fissure only that the igneous 

 rocks have been erupted ; " other parallel outbursts and up- 

 heavals have taken place along the same line at subsequent 

 epochs ;" and the authors shew grounds for belief that the 

 present form of these mountains was the result of more than 

 one elevatory process, and that there was a period when, as 

 a low ridge, they formed the western shore of a great conti- 

 nent to the east, that now called Siberia, and even at so re- 

 cent a period as when that continent was inhabited by large 

 quadrupeds closely allied to existing species. The Urals ex- 

 tend from Nova Zemlia to the Caspian, through nearly thirty 

 degrees of latitude, in a direction nearly north and south, 

 but seuding oif branches to the east and west at both extre- 

 mities, one of which, on the north-west, the Timan range, was 

 first explored geologically by Count Keyserling in 1843 ; and 

 in no part of this long line are they divided by any great 

 transverse valleys, nor does their general altitude exceed 

 from 2000 to 2500 feet. No parts of the author's descrip- 

 tions are of higher geological interest than those in which 

 they speak of the Urals ; and to some of the more striking 

 features of that chain of mountains I shall afterwards more 

 particularly refer. 



The immediate substructure of the whole area of Russia in 

 Europe is composed of the palaeozoic rocks, which, on the 

 northern division, are covered by sand, clay, and blocks. A 

 narrow band of Silurian deposits, the older members of that 

 group, stretches along a great part of the shores of the Bal- 

 tic, succeeded eastward by Devonian and Carboniferous for- 

 mations, each occupying a vast extent of country ; and, lastly, 

 that highest member of the palaeozoic order of strata to which 

 the authors have applied the term " Permian System^'' the 

 most widely spread of all, occupying a region more than twice 



