90 GRANITE AND CRYSTALLINE ROCKS OF THE SOUTHERN STEPPES. 
on the north, is upwards of 100 miles. Throughout this wide area all the rocks, 
with very slight exceptions, are of the carboniferous age, and they thus cover a 
surface of not less than 1 1 ,000 square miles. Occupying hills which have to some 
extent the character of low mountains, these rocks form a portion of the Upper 
Steppe, peopled hy the Don Cossacks and New Russians. 
This tract, which in reference to the southern steppes may he called elevated, is 
hounded on the east by the river Donetz, a partially navigable stream, along the banks 
of which, or of its tributaries, the strata are frequently exposed. Other rivers, which 
have their sources in the higher part of this territory, also offer good natural trans- 
verse sections ; such are the Krinka, the Miuss, and the Kalmiuss, which flow 
southerly into the Sea of Azof; the Toretz, the Bachmutha and smaller streams 
which run northwards, and eventually fall into the Donetz. We examined the 
hanks of all these rivers, and also those of the Voltchia, which, deflected by the 
granitic axis, flows northward and westward into the Dnieper, there to ascertain 
the western limits of the field. We also made various traverses across the central 
and eastern portions, and visiting most of the localities where coal is partially 
worked, and collecting many fossils, we hope to be enabled to give a definite idea 
of the general geological relations of the tract, and to point out an ascending order 
from the base of the Carboniferous system into the next overlying deposits. 
Though overlapped on their northern boundary by Permian, Jurassic, Cretaceous 
and tertiary deposits, which will be described in subsequent chapters, these car- 
boniferous rocks crop out again to the north, at points near Petrofskaya, and the 
real extent of country in that northern direction, in which they may form the chief 
substratum, is probably very considerable. 
To the south the carboniferous rocks are separated from the Sea of Azof by low 
hills, for the most part composed of tertiary deposits, and partially also by a narrow 
band of chalk (see Map). To the south-west they rest upon the eastern extre- 
mity of that vast mass of crystalline rocks, usually known under the name of the 
granitic steppe, which, extending from Volhynia and Podolia on the west-north- 
w^est, passes the Dnieper near Ekaterinoslaf, and disappears beneath the formations 
we are about to describe on the banks of the Kalmiuss. 
Axis of the South Granitic and Crystalline Rocks . — Before we proceed to describe 
the strata in an ascending order, we must say a few words upon the crystalline 
rocks which rise up from beneath this tract, and forming its axis, separate the 
Carboniferous districts from the Tertiary basin of the Sea of Azof and the Crimea. 
