of the Vial Mountains. 129 



stones, conglomerates and grits is thrown off to the west upon the 

 face of the igneous rocks forming the Guberlinsk hills. Jn travelling 

 westwards to Orenburg, particularly from the limestone hills of 

 Gourmaya, the authors found a most instructive section, developing 

 the ascending order from the great carboniferous limestone through 

 the overlying grits, flagstone and calcareous grits with Goniatites, 

 into the beds with gypsum, which form the base of the Permian 

 system, the whole being distinctly overlaid by conformably inclined 

 strata of cupriferous grits, red sandstone, shale and limestones con- 

 taining fossils of the zechstein. 



Upon the eastern flanks of the Ural, on the contrary, granitic and 

 other igneous rocks rising (as before said) to the surface, that re- 

 gion is entirely void of all those strata which in Russia in Europe 

 are interposed between the carboniferous and Jurassic systems. 

 Beds belonging to the latter system have indeed been detected 

 at two very widely distant localities, the one in 65° N. lat. by 

 Capt. Strajefski, trie other forming a plateau in the southernmost 

 extremity of the chain north of Orsk, where they were first 

 observed by Col. Helmersen*. It must however be observed, 

 that the great mass of the chain is void of Jurassic strata, nor 

 have its eastern flanks afforded any evidences of cretaceous or ter- 

 tiary rocks, as identifiable by organic remains. From this last 

 remark, the authors would except certain grits which occur in 

 patches in the lower country of Siberia, notably at Kaltehedansk, 

 east of Ekaterinburg. These grits, which are largely quarried for 

 millstones, might almost be called " trachytic," as they resemble in 

 composition some of the rough trachytes of Hungary, and like 

 which they pass into an impure pitchstone grit. From the asso- 

 ciated amber and beds of clay, it may however be inferred, that 

 these rocks were formed under water, and that they owe the trachytic 

 aspect to their having resulted from the detritus of the quartzose 

 porphyries on which they repose. They are probably continuous 

 masses of the grits described by G. Rose, near Verkhoturie. Sec- 

 tions on the river Isset explain these phaenomena. 



Igneous, Metamorphic and Metalliferous Rocks. — As it formed 

 subordinate parts only of the objects of the authors, either to study 

 the details of the metamorphism of the sedimentary strata produced 

 by the intrusion of igneous rocks, or the associated simple minerals, 

 the relations of both of which have been so elaborately described 

 by Mons. G. Rose, this portion of their memoir is chiefly confined 

 to a sketch of some striking phaenomena of this class. No true 

 granite appears in the higher mountains, the syenite which is seen 

 at intervals being intimately allied to greenstone ; and the latter, 

 with its various modifications, is by far the most abundant of the 

 intrusive rocks which appear on or along the immediate flanks of 

 the Ural ridge f. Whenever these greenstones and traps rise to the 



* The authors did not visit the last-mentioned spot, but, from the com- 

 munication of their friend Colonel Helmersen, they have little doubt that 

 this deposit is a fragment of the Jurassic range which they traced to the 

 south and west of Orenburg. 



f The granitic region is in Siberia, to the east of the Ural. 



Phil. Mag. S. 3. Vol. 23. No. 150. Aug. 1843. K 



