THE SOURCE REGION OF CHAKTAK-TSANGPO.
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gangri is called Räruk. To the S.W., beyond a little valley, Nanchü-gongyonilungpa, the Chaktak-tsangpo pierces the Kanchung-gangri in a wild and narrow valley, which seems not to allow of any traffic; the high Kanchung peaks S.W. of Lapchung-tso are, therefore, left to the east by Chaktak-tsangpo. To the W.S.W. is a valley Luma-nakchen-nakchung and to the N.W. the valleys Salung-nakchung, Salung-nakchen and Pencha; a fairly large valley from the same direction is called Sosänang. Sago-gangri is a small and flat snowy massive to the N. 35° W., in the neighbourhood of which is situated the valley Tsalung-karpo. To the N. 30° W. a considerable valley opens out, called Gyandor-ngundor and leading to Gyandorngundor-la, which may be situated on the continental water-parting, for a road is said to lead over it to Teri-nam-tso. To the N. 5° W. is a small height with some snow, Sangmü-rigyü. From all the small valleys visible to the N.W., N. and N.E., brooks run down to the Lapchung-tso, and from this lake issues the joint river, Chaktaktsangpo. The sources of this river are thus situated on the southern slopes of the principal water-parting range, which I have called Lapchung.
The road follows the eastern shore of the lake northwards. There are many blocks of quartz-porphyry but no living rock; there are swamps and pools covered with thick ice, low, close grass, and, further north, the soil becomes sandy and more comfortable for the traveller. The northernmost part of the lake is narrow, and here the river enters which is formed by the several northern tributaries and in fact is the upper course of the Chaktak-tsangpo. The road crosses several small deep-cut brooks from springs; they go directly to the lake without joining the Chaktaktsangpo; the road keeps to the eastern side of the broad open valley, where there are rounded hills, separated from each other by small tributary valleys; the mountains at the western side are higher. The grass is fairly good. Some pasture grounds also have special names, probably from valleys from the eastern hills, such as Lapchungshungra, Dombe-hloma and Dombe-changma.
Camp 402 is situated in the entrance of the valley Sang-bertik or Sangmobertik at a height of 5 245 m. Its bottom was (May 9) full of solid, hard ice. It comes from the range with the continental water-parting. It is surprising to find just at the foot of this most important range a plain, so extensive and level as the one north of Lapchung-tso. But, on the other hand, this range has more of the Chang-tang character than of the peripheric accentuated sculpture. We found something of the same kind south of Angden-la, where, north of Amchok-tso there is another great plain.
From Camp 402 some interesting observations are made, as explained by my guides. To the N. 6 I° W. is a very low and flat threshold, Dicha-la, situated in the broad, long valley between Kanchung-gangri and Lapchung, through which a road proceeds to the N.W., reaching the lower Buptsang-tsangpo without crossing a single pass, and with only insignificant thresholds amongst hills. The Tibetans assert there is a longstretched tangy a or plain between the two ranges. West of Dicha-la a road
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