IIIFカラー高解像度
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
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| IIIFカラー高解像度 |
| Southern Tibet : vol.7 | |
| 南チベット : vol.7 |
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引用情報
RICHTHOFEN.
33o
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. Richthofen 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 [)E 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 Khor», 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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