328 THE SIXTH CROSSING.
The pass is called Ding-la or Chargo-ding-la, and its height is 5 885 m. To the north the view is hidden by mountains close at hand. To the S.E., S. and S.W. is the not very high water-parting range of Surnge, with eternal snow on some of its peaks. Between the Ding-la and Surnge ranges the country is a confusion of hills and ridges. Comparatively near, to the S.E., is a group with eternal snow and small glaciers; S. 31° E. is the valley Shiri-marmo; S. 25° E. is the valley Tsomra; S. 2 2° E. a snowy peak; S. i 5° E. the ice-filled valley of Da-teri; direct south is the small lake of Argok-tso, and south of it opens a valley called Darkyang; west of the lake is the valley Tsalung, and in our vicinity, S. 20° W., a place called Dobo-martsong.
Ding-la lies in granitic porphyry; a little rock in the valley south of the pass consists of diabas-porphyrite; the descent is steep; from the left enter several tributaries, the greatest of which is Longgyo; they are all right tributaries to the Aong-tsangpo. To the S.W. appears a small snowy peak. Luma-nakpo, Camp 446, is at 5 138 m.
Just south of this camp the river Argok-tsangpo flows to the N. 24° W. It had (July 9th) 5 cub. m of water and receives a tributary of 21%2 cub. m from considerable snowfields and small glaciers on the S.W. side of the Ding-la range. The deep and narrow valley in which it pierces this range is visible to the N.N.W. It seems curious that the road does not follow that valley instead of forcing the high Ding-la pass, but either the valley makes too long a detour to the west, or it is impracticable for traffic.
The country between my sixth and seventh crossings is unknown, and I could not get any reliable information regarding the source of the Aong-tsangpo, the river which joins the Lavar-tsangpo. Some informants affirmed that the Argok-tsangpo joined the Aong-tsangpo at Aong-dunker, others that the Argok-tsangpo was the same river which lower down was called Aong, after having received some more tributaries. However, the Argok-tsangpo comes from the Argok-tso, a little lake which was left to the S.E. of our route, into which several tributaries seem to flow from surrounding mountains. The lake is surrounded by hills ; at the left side of the river is a terrace 5 m high. From the west a little river, Surnge-chu, enters the lake; on its bank, Camp 447 has a height of 5 155 m; the fresh-water lake Argok-tso thus still belongs to the hydrographical system of Nganglaring-tso.
The Surnge valley is broad and flat, between rounded hills covered with snow even in the middle of summer; the rise of the valley is very gradual and the river forms, as it were, a series of small lakes; from the sides enter several small brooks; at one place the valley is divided by a hill. From the N.W. enters a tributary, Takche, at the lower course of which Camp 448 has a height of 5 281m. The rock here is granitic porphyry, and the same rock prevails on the pass. This water-parting between the Satlej and the plateau-land is very extraordinary. Proceeding south-westwards from Takche one has the impression of going through a great open
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