Southern Tibet : vol.7 / 453 ページ（カラー画像）

0453	Southern Tibet : vol.7
南チベット : vol.7

0453

Southern Tibet : vol.7

南チベット : vol.7

facts he asks: how was this large lake formed: where would have been the outlet
and is there any sign of a dam? Drew supposes the plain once drained to the
Eastern Kara-kash, and later on it was dammed. »It is possible that at different
times the dam may have been at different spots . . . . If, as is possible, the lake
existed during part of the glacial period, then a glacier itself, with its moraines —
perhaps a glacier occupying the head of Eastern Karakash Valley — may have
formed the dam.»

In his résumé Drew gives the boundaries of the two basins and adds that to
the north JOHNSON had shown »how the ridges and the valleys lessen in height
till the plains of Khotan are reached». To the west was HAYWARD'S Kara-kash
and high ground extending to the Kara-korum Pass and Suget-davan. To the east
the country had never been explored. Drew thinks there is a bounding ridge of
mountains on the east as there is one on the west. At the north-western corner of
the basin of the lake or lakes he thus has an opening for former drainage between
the Kwen-lun and the western ridge. This opening is now closed by alluvial accu-
mulations. It was formerly probably obstructed to a much greater height than now,
perhaps by glaciers and moraines, as glaciers at that time »were more numerous
and larger than now». He also thinks a dam existed at the south-western corner.

From the highest margin-marks he finally draws the conclusion that at one
time the whole Lingzi-tang and Kwen-lun Plains formed one great lake 60 by 20
miles and stretching to the very foot of the Kwen-lun Mountains. The subsequent
sinking of the water and drying up of the lake he attributes to a change of climate.
At a certain period of the desiccation the lake must have been separated into two parts.

Drew also visited some of the great Kara-korum glaciers.¹ In the Skardu tract
he found lacustrine and glacial remains as GODWIN-AUSTEN and THOMSON had
done before. He went up the Basha and Braldu streams. From Arundo he made
an excursion and covered 3½ marches on and alongside the glacier. At the irregular
edge the ice seemed about 200 feet high, and higher up probably thicker. The
lower end was 1½ mile broad and covered all over with débris. The débris con-
tinued for some miles up. Still higher up clear ice appears between hills of moraine.
Drew reached a point 20 or 25 miles from the end. He estimates the whole glacier
at 30 miles.

As far as Drew could make out there was no possible way to the head of
the glacier and over the watershed. But he says:²

A way from Skardu to Yarkand used in former times to lead travellers for some
distance up the Baltoro Glacier, and then across the range, here called Mustagh, by one
of the northern tributary glaciers. From certain ice-changes that road becoming too

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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