| The mountains bounding the Amchok-tang to the east form a meridional range, which should, perhaps, be regarded as a southern ramification from the Pabla. On it the following mountains are observed: Togok, Shamda, and Chen-yangri, the last situated east of Amchok-tso ; Okchung and Okchen are two valleys from the east. The bed of the Kyam-chu, which is broad and shallow but sharply defined between its grass-covered banks, follows the foot of the western mountains. The western, or right, tributaries, Ngingri-changma and Ngingri-hloän, contain small brooks; near the latter the rocks consist of mica-porphyrite. Camp 157, Hramsang, is at a height of 4 87o m and near the N.W. corner of the Amchok-tso. Although this lake is situated south of the water-parting, it is some 150 m higher than the Shuru-tso, which belongs to the Chang-tang. In spite of this, the Amchok-tso was, on May 8, perfectly open, only a few blocks of ice being seen at the northern shore, this depending on the very hard and incessant S.S.W. wind which had been blowing during the last few days. The Kyam-chu goes out into the Amchok-tso at its northern shore, where it forms a wide-spread delta full of clay and sand. Farther east, a series of sand hills a few m high and with grass at the top, fall steeply down to the flat sandy shore. At the N.E. corner of the lake issues the effluent, Dongmo-chu. It receives a left tributary, Rong-serchang, and flows between high, snow-covered mountains which, as I have pointed out before, probably belong to the western end, or in fact are the western end of the Nien-chen-tang-la. Finally the joint river flows into the Raga-tsangpo. It leaves the lake from an inlet and is broad and shallow to begin with, but soon becomes narrow. In May it contains very little water. The natives asserted that the level of the lake stands much higher in summer, as could, too, be seen round the shore. During the rainy season the Kyam-chu brings heaps of clay and sand with it, and the northern part of the lake is therefore very shallow, being only half a metre deep even I oo m from the shore. When waves are raised by hard wind, as during my visit, the whole lake is grey with mud; the water had a temperature of 6.6° at noon; it is of course perfectly fresh and contains alga. The greatest depth I measured was only 3.66 m, so the Amchok-tso is extremely shallow. As a continuation of the lake to the north may be regarded the great plain of Amchoktang; to the west, south and east the lake is surrounded by hills. At some places, as at the N.W. corner, grey, fine-grained granite crops out. From Amchok-tso the road does not follow the Dongmo-chu down to Ragatsangpo, but turns west and S.W. to cross the range, at the northern foot of which the little lake is situated. The valley, followed by the road, is of a curious form; it is not broad, but along the middle is a ridge of gravel and shingle, separating the Serma-chu at the right side of the valley from the Pu-chu at the left. The Pu-chu comes from the mountains to the N.W. and W.N.W., beyond which is seen a snowy peak, Yarnjo, not very high. Serma-chu comes from the south. The two brooks do not join on their way to the lake. The Charung coming from the left | | |
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