e their sources among the central glaciers, e.g. the
Malka, Baksan, Chegem, Cherek, Urukh, Ardon, all confined to deep narrow
glens until they quit the mountains. The Kuma, which alone pursues an
independent course through the steppes, farther north than the Terek,
has its sources, not in the main ranges of the Caucasus, but in an
outlying group of mountains near Pyatigorsk, the highest summit of
which, Besh-tau, does not exceed 4600 ft. But its waters become absorbed
in the sands of the desert steppes before they reach the Caspian. Of the
streams that carve into chequers the elevated plateau or highland region
of Daghestan four are known by the common name of the Koisu, being
distinguished _inter se_ as the Andian Koisu, the Avarian Koisu, the
Kara Koisu and the Kazikumukh Koisu, which all unite to form the Sulak.
The only other stream deserving of mention in this province is the
Samur. Both rivers discharge their waters into the Caspian; as also does
the Zumgail, a small stream which drains the eastern extremity of the
Caucasus range in the government of Baku.

_Volcanic Evidences._--Ancient, but now extinct, volcanic upheavals are
pretty common at the intersections of the main range with the transverse
ranges; of these the most noteworthy are Elbruz and Kasbek. The town of
Shemakha, near the eastern end of the system, was the scene of volcanic
outbreaks as late as 1859, 1872 and 1902; while in the adjacent
peninsula of Apsheron mud volcanoes exist in large numbers. All along
the northern foot of the system hot mineral springs gush out at various
places, such as Pyatigorsk, Zhelesnovodsk, Essentuki and Kislovodsk; and
the series is continued along the north-eastern foot of the highlands of
Daghestan, e.g. Isti-su, Eskiendery, Akhta. In this connexion it may
also be mentioned that similar evidences of volcanic activity
characterize the northern border of the Armenian highlands on the
southern side of the Rion-Kura depression, in the mountains of Ararat,
Alagoz, Akmangan, Samsar, Godoreby, Great and Little Abull, and in the
mineral springs of Borzhom, Abbas-tuman, Sleptzov, Mikhailovsk and
Tiflis. (J. T. Be.; P. A. K.)

_Geology._--The general structure of the Caucasus is comparatively
simple. The strata are folded so as to form a fan. In the centre of
the fan lies a band of crystalline rocks which disappears towards the
east. Beneath it, on both sides, plunge the strongly folded Palaeozoic
and Jurassic s