4 
747 
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, the 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 Kaltchedansk, 
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 phanomena. 
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 M. G. Rose, this portion of their memoir is chiefly confined to 
a sketch of some striking phenomena 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 appears on or along the immediate flanks of 
the Ural ridge+. Whenever these greenstones and traps rise to the 
surface, the strata in their proximity are highly altered. Thus even 
when studied on a small scale on the western flank of the moun- 
tains, as at the baths of the Zavod of Sergiefsk, the sandstone in 
contact is altered into quartz rock, and the limestone so regularly 
bedded and full of fossils at a little distance, is converted into an 
amorphous, crystalline, splintery mass, charged with cross veins, and 
sulphureous saline waters flow from its base, the adjacent rocks 
being also much impregnated with iron ore. Similar but on a far 
grander scale are the phenomena of intrusion and metamorphism 
which are presented by the central axis of the Ural, and to a less 
* 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. 
+ The granitic region is in Siberia, to the cast of the Ural. 
VOL, II]. PART Il. oP 
