APPROACHING THE BOGTSANG-TSANGPO. t 3 I
southern one is filled with ice and comes so near the threshold that it seems doubtful whether it flows to the north or the south of it. From the furrows in the ground, it even seems at highwater times to form a bifurcation. Camp LXXIX was placed in the very angle between two ice-filled beds, the southern of which also had running water. The joint brook flows to the S. 50° E. in a deep-cut valley, and is a left tributary of the Bogtsang-tsangpo. In the background to the S. 66° E., appeared a snow-covered peak belonging to a comparatively high range or group. To the S. W. and W. S. W. we are aware of a series of small steep peaks, pyramids or pinnacles which rise abruptly from the undulating grass-covered ground of detritus. They are not high, but very steep or perpendicular to the north or N. E. On the accompanying photograph they are clearly visible. This photograph should be compared with the panorama 9oA and 9oB, Tab. 15, where the same pinnacles are to be found from S. 52° W. to S. 8o° W. They consist of light reddish chalk-limestone. To the N. 82° W. we see the comparatively high mount which we left to our right when ascending to the pass. It is visible both on the panorama and on two photographs. The eastern slopes of this mount are furrowed by innumerable dry watercourses. The first-mentioned photograph is an excellent illustration of the general relief worked out by running water and erosion. In the lower part of the principal bed, situated close to Camp LXXIX, a part of the ice-sheet is readily visible. One even gets a graphic impression of the hopeless barrenness of the soil, which goes a long way to explain the cause of our heavy losses in caravan animals. Over the hills to the south, the road continues to a pass which we had to cross the next day. No nomads were in sight, the grass extremely poor, and dung very rare.
On December 5/11 our direction is nearly south for 12.2 km. From Camp LXXIX we have only to rise 27 m. to a flat threshold, 4,843 m. high, from which the ground slopes down to the bed of the Bogtsang-tsangpo, 4,710 m. in height. From the river we again slowly rise to Camp LXXX at 4,760 m.
The S. W. wind had been strong again. The temperature was -2 5.4°.
From the camp we have to cross undulating hills and rather deep-cut watercourses with gravelly beds here and there with small limestone knolls cropping up at the sides, and finally we follow a little watercourse which later on joins the brook at Camp LXXIX and originates from the pass. The latter is a flat saddle of quite secondary importance, but is still provided with two cairns and traversed by many paths of tame yaks and sheep. The living rock consists of grey quartz-amphiboldiorite-porphyrite ; below the pass the gravel was of dark grey dense aptien-limestone. Pan. 91, Tab. 15, shows the view to the south from this threshold. To the south the valley of Bogtsang-tsangpo is bounded by considerable mountains. Down in the valley, the river meanders in several branches all covered with ice. Exactly to the south of the pass the latitudinal valley of the river is very broad and more like a
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