Southern Tibet : vol.7 / 492 ページ（カラー画像）

0492	Southern Tibet : vol.7
南チベット : vol.7

330

Sinian System. The Nien-chen-tang-la was the continuation of Huc's Tang-la, not of
the Aling-gangri. Richthofen never suspected that Aling-gangri and Nien-chen-tang-la
could be one and the same mountain fold, and, losing hold of the eastern fixed point,
he had no possibility of interpolating the Central Transhimalaya. On his maps he draws
his Aling-gangri Range far to the east and has even three parallel ranges north of
the Tsangpo, but they are, as he says, perfectly conjectural, and otherwise he has not
a word to say of them.

I do not know whether Saunders has been influenced by Richthofen. Richt-
hofen had made extensive journeys in Se-tchuan just east of Eastern Tibet. He knew
better than any living man the eastern continuation of these Tibetan Mountains and
he knew some of the rivers which take their rise from them. On Saunders' map
the Gangri Mountains are orographically in connection with the Nien-chen-tang-la,
whereas both are, on Richthofen's map, orographically and geologically independent
of each other. That Richthofen did not get any impression whatever from Hodgson's
map, is obvious from the fact that Richthofen has three parallel ranges north of the
Tsangpo, whilst Hodgson has only one.

In our days it has been proved by the journeys of Rockhill, Wellby,
Bonvalot, Dutreuil de Rhins and Grenard, as well as by the Pundit A— K—
and others, that Richthofen's Tang-la does not exist, and that the Sinian System, so
far as Tibet is concerned, was merely a hypothetical construction. The S. W. to N. E.
stretching of a whole series of ranges, as Richthofen would have it, is altogether
against the orographical structure of this part of Tibet. The folds seem to be as
regular here as in the rest of Tibet, although all of them make a sharp bend, turning
down to the S. E. and south, more or less as the rivers do.

There must, of course, be an elevation on the eastern border of the »Highland
of Khora, or as we prefer to call it now, the plateau-land of Central Tibet, the Chang-
tang. There is the extremely irregular water-parting between the self-contained basins
of the interior, having no outlets to the sea, and, on the outer side, giving rise to
the great Indo-Chinese Rivers. But this line of water-parting, divortia aquarum
as Humboldt says, is crossed at almost right angles by the mountain folds. It is
a water-parting of the same kind, but on an incomparably greater scale, and of much
greater geographical importance, than those which are so common on the highlands
themselves, where you cross them every time you go from one basin to another. We
have another example of the same kind of water-parting in south-western Tibet, namely
between the western-most feeder of the Tsangpo and the eastern-most source of the
Tage-tsangpo, that is to say, a low threshold in a latitudinal valley.

There is a good deal of precipitation even on the western side of the East-
Tibetan water-parting. There are high mountains to catch the humidity. But by far
the greatest part of the humidity is condensed on the mountains around and east of

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