328 THE UPPER TSANGPO TO CHÄROK.
Kakyu; S.3o°W. is the valley Tsagelung-kaleb; to the S.49°W. is Teboche a valley and a mountain; to the S.57°W. is a sand-covered hill situated in the broad valley Rongle with a road over Nangsa-la to Mogum in Nepal; S.75°W. is the valley Changma-lung; the near mountains to the N.W. are called Nendo or Mendo with a valley Mendo-bup.
The next day's march takes us N.W. The Gyang-chu and its right tributary Rong-kardum-chu soon disappear to the south. At the mouth of the northern tributary Rubi-naya the rock is plagioclas-amphibolite, granite and limestone-like mass. Rubi-la is a little threshold on the road, 4,675m. (i 5,334 feet), from where is seen to the S.38°W. a black promontory, just east of which the Gyang-chu is said to come out on the plain from its mountain passage. To the N.E. we see the Transhimalaya valley Hlalung with a road to the Tabie-tsaka of Chang-tang.
Sabsang-chu is a considerable tributary from the valley Kogung to the west; its bed is very broad and bounded by 6 or 7m. high erosion terraces, the right one in three stories; the brook was divided into three branches carrying 3.5cub.m. together; but great parts of the bed were still moist proving that only a few hours ago a much greater amount of water had come down from the northern slopes of the Himalaya. If such pulsations in the tributaries of the upper Tsangpo take place simultaneously, they must of course give rise to considerable oscillations in the main river as well.
The last bit of the road goes over the flat gravelly scree from the foot of the western mountains. At some distance to our right is the sharp limit between the brownish red scree and the green plain which follows the right bank of the Tsangpo. Going down the 6 or 7m. high terrace of the Tsangpo we camp at the bank of the river near Chärok, at a height of 4,657m. (15,275 feet).
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