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WATER' SYSTEM LAKES UBSA AND KOSO. 95
THE EKTAG ALTAI AND TANNU-OLA RANGES.
Owing to the greater elevation of the Mongolian plains, the southern slopes of
the Altai have a lower relative elevation than those facing northwards. Here, also,
the snow-line is higher, rising to about 8,700 or 9,000 feet, altitudes reached by
few of the northern crests, except in the west on the Kobdo plateau. In this region
of Central Asia the most humid atmospheric currents are those which come from the
nearest marine basin ; that is, from the Polar Sea. Hence the rain-bearing and
fertilising winds blow from the north-east. But these winds discharge their
moisture on the northern slopes of the Altai, so that those facing Mongolia are
mostly destitute of vegetation. In several places the contrast is complete between
the two sides dense forests on the north, mere scrub and brushwood on the south.
The two chief ranges branching from the Altai into Mongolian territory are
the Ektag Altai and the Tannu-ola. The former, sometimes also called the " Great
Altai," runs north-west and south-east parallel with the course of the Black Irtish
and Uluugur. Some of its crests rise above the snow-line, whence the term Ektag,
a dialectic form of the Turki Ak-tagh, or " White Mountains." But the range
is pierced by deep depressions, through which the Russian caravans easily reach
the Kobdo plateau from the Irtish valley. The range itself, as shown by the
recent explorations of Potanin, is continued south-eastwards far beyond the
meridian of Kobdo, after which it trends eastwards under the name of the Altai-
nuru. In this recently discovered section some of the peaks attain an altitude of
10,000 feet, and the Olb'n-daba Pass, crossed by the Kobdo-Barkul route, is no less
than 9,400 feet high.
Farther east other ranges run parallel with the Ektag and Tannu-ola that is,
north-west and south-east ;
but these are everywhere cut up into irregular masses
by erosion. Here is apparently the culminating point of the Altai' system, crossed
by Ney Elias at the Bayan-ingir Pass (over 9,000 feet) on the route from Kobdo
to Biisk. A snowy peak rising immediately north of the pass seemed to this traveller
to have an elevation of 12,000 feet, or 830 more than the Bielukha, highest summit
of the Russian Altai'.
The Tannu-ola, or eastern chain of the Kobdo plateau, stretches far east of the
Altai to the head-streams of the Selenga. Although some of its peaks pass the
snow-line, the Tannu-ola is in many places but slightly elevated above the
surrounding plains. From its base the plateau stretches for 120 miles southwards
to the Khangiii range, above whose wooded slopes several snowy crests are said to
have an elevation of 10,000 feet. Between the Kinghai and the Altai'-uuru the
>t>'ppe has a mean altitude of from 5,000 to 6,000 feet.
WATER SYSTEM LAKES UBSA AND Koso.
All the depressions of ihe plateau comprised in the vast quadrilateral of the
Mongolian Altai' arc occupied by lacustrine basins. One of these is the saline
Ubsa-nor, one of the largest lakes in the Chinese Empire, with an area of at least