444 
OLD KIRGHIS FRONTIER. — VERCH-URALSK TO ORSK. 
be considered an extension of that of the Ilmen Hills, is prolonged into the low 
chain, which under the names of Djahyk Karagai and Kara-Edir-tau, runs parallel 
to the Ural, and constitutes a well-marked watershed between the affluents of the 
river Tobol and those of the Ural. It is the same embranchment which, still 
further to the south, is confluent with the southern extremities of the axis of the 
Ural Mountains. In this eastern parallel, rocks similar to those in the adjacent 
and higher Ural (chlorite and talc schist, quartz rock, clay-slate and limestone, 
with hornstone, jasper, dolomite, &c.) succeed on either flank of the chief axis of 
eruption. Again, as in the Ural, encrinites have been traced in the intercalated 
limestone, which Colonel Helmersen is even disposed to consider of the carboniferous 
age. We have attempted to lay down the features of these wild tracts of the Kirghis 
in a general manner upon our Map, and will now merely say, that according to 
Captain Tchaikovsky, the granite, as at Ekaterinburg, is the youngest of all the 
eruptive rocks, dykes of it having been found to traverse greenstone, which, to- 
gether with greenstone porphyry, serpentine, &c., are repeated over and over amidst 
countless bands, which we can only consider as metamorphosed palaeozoic strata 1 . 
Eastern Flank of the South Ural between Verch- Uralsk on the north and Orsk upon 
the south. — Before we describe the other transverse sections across the South Ural, 
we beg to offer a very brief description of the geological features of its eastern flank 
between Verch-Uralsk and Orsk, i.e. along the course of the river Ural, or what is 
called the Old Line of the Cossacks. Of Verch-Uralsk, as the point which con- 
nects the Uralian and Siberian regions (see PI. IV.), we shall have again to speak, 
when detailing the great transverse section from thence to Sterlitamak. Covered 
with black earth and morass, no rock is visible near Verch-Uralsk, and it is only 
on advancing from thence to Spaskaya, that round-backed stony hills set in. In 
one of these, grey subcrystalline limestone appears, which is penetrated by green- 
stone and porphyry, and near the upper part of that village, a thick-bedded lime- 
stone dips 18° to the south-west 2 . 
The dominant eruptive rock in this tract is a red felspathic porphyry, the 
' Reise nach dem Ural, und dem Kirgisen Steppe, p. 217 et seq. The road along the new Russian fron- 
tier, or the new line of the Cossacks, which passes direct from Orsk to Troitsk, embraces nearly all this 
steppe region, and traverses the watershed in question a few stations to the north-east of Orsk (see 
Map, PI. VI., in which we have inserted the chief features noticed by Colonel Helmersen). 
4 We found a chambered shell in this rock very much resembling an Ammonite, but unfortunately it 
has been lost. Whatever this shell may have been, we could not when on the spot dissociate the rock 
which contained it from the enerinite limestone. 
