446 
ORSK AND ITS JASPERS. 
strong ledges, which containing Encrinites and Cidaris, and having the same north- 
north-west strike, dip still more sharply towards the chain or west-south-west. 
Hereabouts, and at Orlofskaya 1 , the porphyries are occasionally black and slaty, 
with acicular crystals of felspar ; the red porphyry has a coarsely granular base, 
and greenstone porphyry is not uncommon. Towards Orsk, the country gradu- 
ally lowering into a steppe, the limestone is no longer visible, but wherever the 
porphyritic or other igneous rocks do not prevail, the intermediate spaces are 
occupied by dark grey coarse grits and conglomerates which have the same strike 
and high inclination as the limestone, and, together with the interjacent ridges ol 
porphyry, proceed excentrically from the Ural chain, striking from north-north-west 
to south-south-east (see Map). We believe that these grits, sandstones and con- 
glomerates form the upper member of the carboniferous group, an inference which 
is sustained by the section from Orsk to Orenburg. In approaching the axis 
(as between Burmaya and Orsk), these grits have more of the true meridian strike 
than when examined further from the chain. 
Transverse Section of the South Ural from Orsk towards Orenburg (PI. HI. fig. 3). 
— Orsk has doubtless been fixed upon as the Russian advanced post towards the 
steppes of the Kirghis, on account of the insulated hill called Preobrajenski-gora, 
which rises up in the low country on the right bank of the Or, at its confluence 
with the river Ural. This hill, on which the church stands, is chiefly composed 
of an eruptive rock, which M. Rose describes as greenstone porphyry. 
Hofmann, Helmersen and Rose have described various quarries of ribboned 
and other jaspers, both to the north of the citadel, and also eastwards of it in the 
river Or, and in all cases they are directly in contact with greenstone porphyry. 
In the Preobrajenski-gora, the schists through which the intrusive rock rises, are 
highly altered and jaspidified at and near the contact, but at a certain distance 
from it they are nothing more than hardened grauwacke. We are entirely of the 
same opinion as M. Rose, that the jaspers are simply altered schists : we further 
believe that they are of the carboniferous, or certainly not older than the upper- 
most Devonian age, because they are succeeded on both flanks by carboniferous 
limestone, shale and conglomerate All the jaspideous bands near Orsk have, in 
1 Once for all it may be stated, that certain places in Russia are occasionally cited by us in the text 
with the termination ay a, some of which on reference to the Map are inseited without it. 1 his termination 
ought not, rigidly speaking, to be employed in a foreign language, for it is only employed by the Russians 
in an adjective sense to signify the post, station, forge, &c. of the place in question. 
