国立情報学研究所 - ディジタル・シルクロード・プロジェクト
『東洋文庫所蔵』貴重書デジタルアーカイブ

356

THE ROAD TO PORU-TSO.

are visible well marked beach lines. At the left side of the valley there is a hot spring, called Chuka-chusän. The road slowly diverges from the brook and ascends the southern hills with the little pass Chuka-la, 5 320 m. high. Just south of the pass, Camp 427, in the valley Tokya, is at 5 307 m. Quartz-porphyry and por-

phyrite prevail.

Along the foot of the mountains on the southern shore of Poru-tso, the road proceeds W.S.W. The beach-lines are sharp drawn the whole way, especially on the

slopes exposed to the west. The valley Tavuk is crossed. At Camp 428, Shaktik,

the height is 5 202 m. The rock is quartz-porphyrite. From a point a little above Camp 428, where the highest beach-line is well marked, to the shore of Poru-tso,

the distance, to the N. i 5° W., amounts to r 866 m in a straight line. On this line there are 35 well preserved beach-lines. The highest is io8 m above the present surface of the lake, and is at the same time the one best developed, showing that the lake remained at that level for a comparatively long period. When standing

at that level the Poru-tso may have possessed an effluent to some neighbouring depression, for not the slightest shore-lines could be seen above the i o8 m beach line. There are fish in Poru-tso, in spite of the very bad taste of the water, which is absolutely undrinkable, though there are freshwater springs along the shore. Poru-

tso is a small lake of elliptical form; the long axis in N.E.—S.W. The lake is hard-frozen in winter, and short-cuts are sometimes taken over the ice, which is never ventured over the Tarok-tso. The very mighty and massive meridional range west of the lake is covered with eternal snow, and has many small glaciers. I have called it the Surla range from the name of the pass I used.

The lake is at a height of 5 094 m; it is called Poru-tso, and sometimes Yeke- tso; the name of the district is Bongba-yeke; the Surla mountains are therefore sometimes called Bongba-yeke-gangri or simply Yeke-gangri. At their eastern side, W.N.W. from Camp 428, is a valley called Nashibuk. There is said to be a direct road to Tradum from Poru-tso, crossing the pass Yor-la, which is nearer Tradum than Poru-tso ; south of Yor-la is the district of Paryang. Some 3 days north is

41

Ka-la, a pass crossed by the serftun-lam. Five days N.W. there is a monastery called Marmik-gompa.

From Camp 428 the road descends W.S.W. to the very broad and open valley of the brook Nyapchu-tsangpo, which comes down from Men-la, and empties itself into the Poru-tso. So far as can be seen it comes from the south and turns to the N. 20° E.; in its upper course it is called Menle-chu. Men-la is seen to the S. 5° E. and is only one day's distance from our road. June the i 4 the river carried i I/2 cub. m water a second, and was perfectly clear. The ground is clay deposited on the old bottom of the lake ; there is some good grass. The river is broad and shallow between its low erosion terraces. West of it there is a salt-road between Hor and Tabie-tsaka, to which a march of 8 days is reckoned from here. Further W.S.W. is the entrance to the Sur-la valley where Camp 429 has a height of