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

a trifle greater. Other factors, telling in the favor of Mü-chu are the direction of
the joint valley, which is the same as that of Mü-chu, and the fact that the Bup-chu
forms small rapids at the junction, thus being situated at a somewhat higher level;
finally the name Mü-chu, belonging to the lower course of the north-western branch,
and remaining as the name of the joint river as well. Therefore the Bup-chu must
be regarded as a tributary, and it seems to be the greatest one of the whole system,
as the Raga-tsangpo has its sources in comparatively low mountains. During the
high-water period, when both the Mü-chu and the Bup-chu are very swollen, the
Mü-chu is said to be the greater of the two.

From the right or western side of the same section we notice the following
tributaries: Tagelung, Yondar and Rung, all with small brooks and fairly high
mountains in the background, just as the case has been with most other right trib-
utaries further south. Chupsang and Tugang are small valleys. Lenjo is a very
considerable valley, next after Raga-tsangpo the greatest of all from the west. The
view towards its upper reaches is soon closed by mountain shoulders cropping out
from both sides; one of its higher tributaries is called Shugelung. At least one third
of the volume of the Mü-chu comes from the Lenjo and its river has to be crossed
on a solid and well built bridge. Possibly this river also comes from the continental
water-parting, although the only information I could get about it stated, that a road
went from its upper course to Chang-la-Pod-la, and not to any other pass. Finally
Talung is a small tributary from the west.

The main valley itself is here deep cut and narrow between steep mountains
where living rock is very ordinary. Near Tongyang we have quartz-porphyrite, and
a little higher up plagioclas-amphibolite. Opposite Talung, at the left side, stands
diabas-porphyrite and ortoclas-porphyry in very steep, sometimes nearly perpendicular
walls, and a little higher up phyllitic schist appears; at a passage called Tigu-tang
quartzitic sandstone forms the rocks.

The terraces are as before. Near Tagelung they appear in three stories very
well marked at the right side of the valley, whereas at the opposite side the rocks
are clean. Sometimes the road is at the top of the highest terrace, 40 or 50 m,
with the river in its deep narrow bed below, but after a while it again approaches
the bottom of the valley or is built on the top of the lowest terrace, a few metres
above the river. The valley is full of gravel and blocks of all sizes. At Tigu-tang
near Linga, the road ascends above solid rock at the right side.

At Linga the height is 4 302 m.; thus the rise of the valley is on this section
somewhat steeper than before, and rapids are more common, although some quiet
and deep passages alternate with them. The breadth of the river remains very
much the same or about 20 m. At a place on the right side it was easy to see,
from water marks, that the high-water of Mü-chu used to rise more than 3 m. above
the level in the middle of April. Even if travellers and caravans, at this place,
have to walk through water one foot deep, they prefer the inundated road to the