230 



THE GEOLOGIST. 



are also greatly altered by the prevalence of igneous rocks ; 

 and it was only along the western flank that the authors 

 were enabled to establish a clear succession of carboniferous, 

 Devonian, and Silurian deposits. The evidence on which 

 these inferences rest, is given at length in a series of detailed 

 sections obtained in river gorges and by other accessible 

 lines ; and, notwithstanding the greatly dislocated nature 

 of the strata, a clear passage is shown to exist from the 

 Permean beds, described in a former memoir, into the 

 carboniferous system, and thence into the Devonian, and 

 afterwards into the Silurian. Explanatory accounts of 

 variations of lithological character from the ordinary types 

 are likewise given, and a certain amount of specific dif- 

 ference in the organic remains is also enumerated; but 

 it is shown that the suites of testacea and other fossils, agree 

 with those of well determined carboniferous, Devonian, 

 and Silurian regions, and are totally distinct from the 

 organic forms of any other series of rocks. FuU descrip- 

 tions are given of the various igneous rocks, of their effects 

 upon the sedimentary strata, and of the metallic veins con- 

 nected with them. It may, however, be stated as an inter- 

 esting fact, that true granite is of very rare occurrence along 

 the axis of the chain. Another point of interest is con- 

 nected with the periods of dislocation, the change of relative 

 level of land and water, and of the protrusion of igneous 

 rocks. The authors offer in detail their reasons for con- 

 cluding that these phenomena were repeated at different 

 geological epochs. From the occurrence of cupriferous 

 minerals diffused throughout the Permean strata, they 

 infer, that anterior to the deposition of those beds, me- 

 talUc veins must have existed in the Ural Mountains ; and, 

 from the abundance of the remains of terrestrial plants in 

 the same deposits, that the chain must have been raised 

 to a certain extent above the level of the then existing 



