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

prevails a long distance upwards; a nameless valley with a well developed fan cut
through by its brook; as a rule the mouth of every side valley is filled with and
sends out a fan of gravel and shingle, deposited at an earlier period, and cut through
at the present time; the front of every fan is generally steep as it has been eroded
by the main river. Shugutsar, Kita and Lungmar are small valleys in a region
where the living rock consists of diabas. Then follows the Samo valley.

The tributaries from the right or west side are, on this section of the road;
Jamo, of considerable dimensions, although short, and with a ridge of black mountains
in its background; Gumbu, a small valley; Panchung and Panchen, both coming from
a mountain covered with some snow; and finally Kating, where the height, at Camp
141, is 4 229 m.

On this section the Mü-chu runs from N.W. to S.E.; from Sirchung to
a little beyond Ghe it flows south, and then again S.E. to the junction with the
Raga-tsangpo. As a rule the Mü-chu here follows close to the left side of the
valley, where the mountains are steep and the side valleys short and insignificant
and generally without names. The terraces have the same characteristics as before,
30 to 40 m high, and best visible near the mouths of the tributaries. The road
often goes on the top of this terrace, which is cut through by many ravines. The
main valley is very narrow. Sand is common, but only on the leeside of such
objects as manis or edges of ravines, fragmentary dunes are formed, or rather
accumulations of sand.

On the next section, up to Linga, the mouths of the following left tributaries
are passed: Ngalung, a small valley, but with a considerable fan pressing the main
river over to the right side. This alternating of left side and right side fans pressing
the main river over to the other side, is a characteristic feature which becomes more
and more developed. Opposite every fan the side of the valley along which the
main river flows, is generally bounded by steep mountains. After a series of quite
small valleys follows the Tongyang which is considerable and has a brook cutting
a deep furrow through the fan; the upper part of this valley is bounded by high,
rounded hills. Then follows from the east the valley Gok-shung, and finally the
greatest of all the tributaries to the Mü-chu, perhaps with the only exception of
the Raga-tsangpo, namely, the Bup-chu, here also known under the name of Sha-
chu. The valley of Bup is broader and more open than the valley of Mü, which is
not surprising, as the Bup-chu is, undoubtedly, situated between and parallel with
two ranges, whereas the Mü-chu cuts its valley at right angles across the ranges.
Therefore the Bup-chu is chiefly a tectonic valley, whereas the Mü-chu is erosive.

Comparing the two rivers we find that the one comes from the N.W., the
other from the N.E., both having their sources on the continental water-parting of
the Pabla range and joining at Linga. Therefore it is hard to tell which of them
should be regarded as the main river. At the confluence the Bup-chu had, April 15,
a volume of 6.09 cub.m a second, and Mü-chu 6.29 cub.m. Thus the Mü-chu was