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

25.56 m., average depth 0.34 m., average velocity 0.50 m. and volume 4.37 cub. m.
a second. Thus the river carried 8.26 cub. m. a second.

A little north of the crossing point is a broad, open valley called Na-marding,
with a brook going to the Tage-tsangpo. Anak and Lingur are small valleys in
the neighbourhood. Some strange terraces are seen round Na-marding with perfectly
flat surfaces; they cannot possibly have anything to do with the lake, as they are
more than 200 meters over its present surface.

The road from Na-marding to Tokchen crosses a series of rolling hills sloping
down to the lake, and several ravines between them. Quarzite, sandstone and conglom-
erate predominate, but only once is sandstone found in situ dipping 21° N. 75° W.
The gravel is often wind-worn; no erratic blocks could be seen. A little quite sec-
ondary pass, Karpo-la, is 4,888 m. (16,032 feet) high. From these hills the road goes
finally steeply down to the valley of Samo-tsangpo, which, to judge from Ryder's map,
gets most of its water from the mountains south of Surnge-la. Tokchen, on the
tasam, is not always situated at the same place. When I passed in 1908 the tents
of Tokchen were pitched some 3 miles higher up in the valley. On July 25th the
Samo-tsangpo carried only 0.73 cub. m. a second with a breadth of 11.5 m. On
July 23rd, the following year, it carried 4.89 cub. m., with a breadth of 21.9 m.
But in 1908 the rain was much more abundant than in 1907.

Just south of the point where Samo-tsangpo enters the lake the breadth of
the almost horizontal shore plain may be 200 or 300 m. This plain becomes more
and more narrow to the south, but widens out very considerably to the north. South
of the river the plain is bounded to the east by a wall of gravel, and inside of it
is a belt of »vegetation hills» or low earth-cones, bound by roots, in sand.

A little north of the mouth of Samo-tsangpo is a comparatively great lagoon,
surrounded by swamps and excellent grass. Between the lake and the lagoon is a
narrow neck with a wall of gravel, some 3 m. high. The lagoon and its swamps are
fed by the rivulets coming down from the valleys Pachen and Pachung, both origi-
nating from the southern slopes of the Transhimalaya, west of Surnge-la.

The Pachen leaves its rocky valley at a height of 4,696 m. (15,402 feet).
The mountains consist of phyllite and sandstone dipping 24° N. 80° E. On August
19th, 1907, the Pachen carried 1.98 cub. m., but a mile below the mouth of the
valley only about half as much, which was on account of the water disappearing in
the gravelly ground and reappearing again round the lagoon as springs.

A few miles (5.3 km.) farther west the Pachung leaves its valley, which in
every respect is very like its Pachen neighbour. The same day the Pachung carried
2.36 cub. m. After having left the rocky valleys, the two rivulets cross the scree
of gravel and sand at the foot of the mountains, which slowly go over into
undulating ground, steppe, and »vegetation cones». Finally they enter the lagoon,
which also receives a small brook of 0.5 cub. m., called Lungnak, from another
lagoon situated a little to the west of the first. The eastern lagoon thus received