746 
of eruptive matter and the abundance of metamorphic and metalli- 
ferous rocks. Thus in passing eastwards into Siberia on any paral- 
lel, from Bogoslofsk, Nijny Tagilsk, Ekaterinburg, Miask or Verch- 
Uralsk, no regular succession can be traced; as large zones of 
igneous and crystalline rocks intervene, and thus different members 
of the palzozoic series are met with upon the same strike. In some 
spots however, notwithstanding all this confusion, transitions can 
be traced from lower to higher formations. At Bogoslofsk, for ex- 
ample, a passage may be observed from Silurian to Devonian strata ; 
and though all the formations are not in apposition to the east of 
Ekaterinburg, the section of the river Isset clearly shows, that, after 
various undulations, the Devonian limestones and schists on the 
west are succeeded on the east by true carboniferous limestone 
with large Producti, this latter deposit being in some instances 
based upon conglomerates and grit. Whilst this succession is ex- 
posed in a region penetrated by many points of eruptive trap and 
porphyry, the whole of the less altered group reposing on nsica- 
ceous schists and other granitic rocks, a mass of Pentamerus lime- 
stone is thrown up in an insulated tract ata small distance ;. and 
as this limestone is quite dissimilar from any visible in the adjacent 
gorges of the Isset, where the Devonian and carboniferous lime- 
stones are fully developed, the authors conclude that it belongs to 
the Silurian epoch. 
On the eastern flank of the southern Ural the ancient sedimen- 
tary rocks occur in great undulations. At Troitsk in the steppes 
of the Kirghis, or beyond a chain of granite separated from and 
parallel to the Ural (see map), Silurian and Devonian limestones 
occur, whilst at Cossatchi Datchi, close to the eastern flank of the 
Ural, there is a small basin of palzozvoic rocks, the limestone of 
which is proved to be true carboniferous, by containing a vast pro- 
fusion of fossils, many of which are common to the Waldai lime- 
stones of Russia, and the mountain limestone of the British Isles and 
Belgium. In following southward the eastern slopes of the chain 
where they border on the river Ural, promontories of carboniferous 
limestone rise up in undulations, supporting troughs of the coarse 
carboniferous grits and conglomerates before alluded to; and on 
passing the axis of the chain between Orsk and Orenburg, where it 
dwindles to a small height, the same carboniferous group of lime- 
stones, conglomerates and grits is thrown off to the west upon the 
face of the igneous rocks forming the Guberlinsk hills. In 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- 
