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Digital Archive of Toyo Bunko Rare Books

The effect of their powerful erosive action can be traced all along the Su-lo-ho basin almost
as clearly as in the Lop depression. ⁸

Of the big mountain area drained by the Su-lo-ho, only the great alpine valley where
its headwaters gather far away to the south-east, and the ranges and
Headwaters of valleys south of An-hsi and Yü-mên-hsien came within the range of our
Su-lo-ho.
surveys. The former lying close to the Hoang-ho watershed and the
plateaus of the Koke-nôr region shares the physical character of the Central Nan-shan, as
described further on. The latter consist of a succession of parallel ranges, the southernmost
rising into peaks of 19,000-20,000 feet. ⁹ The broad valleys dividing them are very arid,
and the small patches of cultivation existing there owe their irrigation almost solely to springs
bringing subsoil water to the surface at the foot of the huge slopes of piedmont gravel. ¹⁰

Immediately to the east of the Su-lo-ho basin lies a much smaller drainageless area
which from its terminal depression may be called that of Hua-hai-
Hua-hai-tzu basin. tzu. ¹¹ As this by a curious bifurcation, mentioned already above,
receives also a small stream from the Su-lo-ho, it may conveniently find
mention here along with its big western neighbour. Sheets Nos. 40, 41 show the scanty
streams descending northward from that portion of the Nan-shan which divides the valleys
of the Su-lo-ho and Pei-ta-ho or Su-chou river; these have cut their way through a rugged
hill-range, apparently a continuation of the Ala-shan, and lose themselves in the depression
stretching north of the small oasis of Hua-hai-tzu or Ying-p'an to the foot of the Pei-shan.
The aridity of that hill-range as well as of the portion of the Nan-shan due south is so mark-
ed that irrigation in this area, too, is possible only from subsoil drainage. To the north-east
dune-covered or utterly waterless bare ground adjoins for a considerable distance; but even
the great physical obstacle thus created did not prevent the ancient Chinese Limes being
carried through it to the vicinity of the Pei-ta-ho. ¹²

Section VI.—FROM THE CENTRAL NAN-SHAN TO THE ETSIN-GOL BASIN

If we follow the high road south-eastwards from Yü-mên-hsien across the open
plateaus above the Hua-hai-tzu basin it takes us through the famous
Area drained by Chia-yü-kuan 'Gate' of the mediæval 'Great Wall' of China into the
Etsi -gol.
easternmost of the drainageless areas comprised within our surveys.
It extends from the headwaters of the Kan-chou river in the south-east (Sheet No. 46) to
the marshy lake-beds where terminates the Etsin-gol carrying the united waters of the rivers
of Kan-chou and Su-chou (Sheet No. 44). This great area divides itself into three well-
defined regions, all clearly marked by features which indicate transition to adjoining zones
of very different climatic conditions.

In the south we have the Central Nan-shan rising in three big ranges to snowy peaks
over 18,000 feet in height (Sheets Nos. 43, 46). In the wide valleys
Ranges of Central which divide them gather the headwaters of the rivers of Su-chou and
Nan-shan.
Kan-chou and of their principal tributaries. Other rivers which de-
scend in deep-cut valleys from the outer slopes of the Richthofen Range, the northernmost of
those ranges, also find their way into those two, after traversing the second, or submontane,
region to be presently mentioned.

All through the Central Nan-shan we find striking evidence of a climate far moister