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

Ki-chu with its tributaries is the greatest of all. The Shang-chu is considerably
shorter, and the Ta-nakbo-chu and Rung-chu still more so; the northern tributaries
to the Raga-tsangpo are mere brooks. There is only one exception: the Mü-chu.
But this is quite natural, for the Mü-chu is the only one of these rivers which is
strong enough to pierce the Nien-chen-tang-la, just as, further west, the Chaktak-
tsangpo pierces the Kanchung-gangri range. The Ki-chu, Shang, Ta-nakpo and
Rung have their sources on the southern side of the Nien-chen-tang-la, whereas
the Mü-chu comes from the southern side of the Pabla. The Bara-tsangpo and
Ota-tsangpo certainly come from the northern side of the range which continues
eastwards from Sela-la and which should be called Pabla in its whole length.

Regarding the whole profile from Ngangtse-tso to Ye the most striking thing
is the insignificant difference between the altitudes of the different passes. We have:
Pongchen-la 5 371, Sela-la 5 506, Shib-la 5 349, Chesang-la 5 474, Dangbä-la 5 250
and Ta-la 5 436 m. There is a difference of only 256 m between the highest and
the lowest. La-rok should not be considered, as it belongs to the very front to-
wards the Tsangpo where the great heights have ceased. The Pongchen-la belongs
to a small range just south of Ngangtse-tso. South of lower Tagrak-tsangpo there
is the range which I have called Ngangtse-range, for lack of a better name, and
which probably, more or less uninterruptedly, continues eastwards to the Tengri-nor;
if such be the case, it is pierced by Tagrak-tsangpo, Bara-tsangpo and Ota-tsangpo.
The Sela-la is on the continental water-parting and therefore the most important of
all, as well as the highest. The orographical rank of the Shib-la and Chesang-la
is difficult to determine. We only know that they are situated on ridges which
separate the tributaries of the Mü-chu from each other; and probably these ridges
are simply ramifications from a high swelling or mountain knot of the Pabla at about
88½° E. long. Dangbä-la, as shown above, is most probably situated on the S.W.
continuation of the Nien-chen-tang-la, and Ta-la on a southern ramification from
the same. Such is also the case with the La-rok. It should be added that the
Chesong-la may as well belong to a northern ramification from the Nien-chen-
tang-la.

On account of the general evenness, the relative altitude of the mountains as
compared with the valley decreases as we proceed upwards through the valley of
the Tagrak-Naong-tsangpo. On the south side of the water-parting these relations
cannot be noticed, as here we do not follow one valley down, but cross many valleys
at right angles. Therefore the difference of altitude between every single pass and
the valley below cannot be compared one with another. Taking the valleys south
of the passes we find Camp 118 at 674 m below Sela-la, Camp 119 350 m below
Shib-la, Camp 120 839 m below Chesang-la, Camp 122 341 m. below Dangbä-la
and Camp 123 at 1 092 m below Ta-la. Only in the case of Sela-la, Chesang-la
and Ta-la can an increasing relative altitude of the pass compared with the valley
south of it be noticed, or 674, 839 and 1 092 m.