218 Capt. Koschkull on the Caucasus. 4 
mountain there are longitudinal valleys, the most important of — 
which are between the Elbruz and the Kazbek; the ae ; 
of Swanethi on the upper parts of the rivers Ingur and T 
nitz-I'skhale, the valley of Radscha on the Rion, and gene- — 
rally those inhabited by the Ossethes in the midst of the main — 
chain. In Daghestan and the Little Caucasus, there is no teg- 
ularity in their form or distribution. 
The principal range is bounded on the north and south by 
vast plains running parallel to the mountains, that is, north- 
northwest and south-southeast. The northern plain merges 
insensibly into the southern prairies of Russia, the southem 
serve to separate the two Isthmus ranges. 
By the north and south and north-northeast and south-south- 
west upheavals they are almost equally partitioned. The plat 
eau north of the Elbruz forms, on the northern plain, an eas 
ern division, along the valley of the river Terek, which belongs — 
to the basin of the Caspian sea, and a western division belong- 
ing to the Black sea. ae 
_ The southern plain is divided by the Karthlo-Imeritia mou 
tains into the valley of the Kur, in the Caspian basin, and ine 
plateau north of the Elbruz mainly caused the separation of 
these two basins which now show a very considerable different 
of level; for the surface of the Caspian is nearly 80 foot below 
the level of the Black sea, and the level of the latter 
looked for, some distance from the mouths of the rivers 
and Kouban. 
The sedimentary formations of the Isthmus of the | 
belong to the Jurassic, Cretaceous and Tertiary periods, ae 
corresponds to that of Germany, and, as a consequence; "ie 
the equivalents of the Oolite and Lias, both of which are io" = 
developed. The Wealden is wanting; the Crea 
talcose, and argillaceous. These latter are most 
