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

sion in the prolongation of the north-western corner of the lake we recognise the
place where the Satlej formerly used to flow out of the Rakas-tal. It is not like a
river bed. The ground is dry clay, and no fluviatile terraces or river banks are
visible. Some springs rising in the depression run into the lake. But all this is in
perfect agreement with the circumstances which must have prevailed when the Satlej
left the Rakas-tal. For the low clay ground was then inundated at a considerable
distance westwards, and only at some distance further N.W. could one expect to
find any traces of an old bed.

On September 6th, 1907, I made an excursion to the dry bed of the Satlej
which I reached at a point some 7km. N.W. of the one where I had first crossed it.
About 1km. S.E. of this western point some comparatively large pools of stagnant
water filled a part of the bed. They are formed by springs and probably brackish
as they did not contain any vegetation. Here the bed is sharply bounded by old
river terraces, though very much deformed since water flowed through. One could
see that the bed had been partly filled with clay and sand, swept down by temporary
water-courses after heavy rains, and in these alluvia secondary terraces and furrows
had been modelled by the wind. The vegetation and innumerable rabbit-burrows
had also destroyed the fresh appearance of the bed. Such changes as these do not,
however, require a long time, and the old river bed is always very easy to
recognise as such. A little farther N.W. the rounded sand terraces are 4 and
5m. above the bottom of the bed.

This second point in the bed must be its highest, or a few metres above the
Rakas-tal. Continuing north-westwards in the bed one comes to some large
fresh-water pools. From the last of them a little brook flows north-westwards, so
here at any rate the culminating point of the bed has been passed and the definite
regular slope to the Indian ocean has begun. The watercourse enters a large pool
filling the whole bed. A little lower down where the bed enters a real valley,
Laling-tak, bounded by rocks on both sides, a spring rises from the ground and
forms a little brook, surrounded by good grass and streams down the valley. At
Dölchu-gompa one is already 72m. below the surface of the Rakas-tal. The
question when the Rakas-tal last sent an emissary through the bed cannot be
answered with any degree of certainty. And it is of course impossible to know
whether this will be the case again. Remembering the general desiccation which
the whole of Tibet is undergoing, it seems unlikely that the Rakas-tal will rise above
the highest threshold in the bed. But we have seen that the Manasarovar has
been able to send, in 1909 to 1911, an effluent through the bed of Nganga or
Ganga, and the possibility is not excluded that this might be the case with the
Rakas-tal as well, provided a sufficiently wet climatic period entered during a
few years.

At the entrance of the valley, Laling-tak, the rocks are of limestone and lime-
spar in 9°N. and in 12°N.73°W.