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.3 | |
| 南チベット : vol.3 |
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引用情報
| 218 | THE LATEST DISCUSSION ABOUT THE TRANSHIMALAYA. | ||
| Kara-korum, with the Kara-korum pass continue straight to the east to 85° E. and calls it »Snowy Range seen by Wellby». The map is too rough to be taken seriously. In another book ` Graham Sandberg makes some references to our mountain system. Speaking of Tengri nor he says:2 »Glacial drainage must furnish the bulk of the water-supply of this lake ; for all travellers concur in noting the size and number of glaciers along the northern slopes of the Noijin T'angla.» He quotes Hooker and Godwin Austen3 and comes to the conclusion that all the loftier ranges in Tibet are well stocked with enormous glaciers and snow-fields, several hundred feet thick. Old moraine and other signs of glacial action prove that the glaciers have formerly been very much larger than now. The present precipitation could not bring about such accumulations. Thus in »later centuries» the climate must have undergone a radical change and the present precipitation is infinitely less than formerly. He then draws the surprising conclusion: »However, so huge were these glaciers and other reservoirs of congealed water that, long as they have been furnishing the main demands of the great outflowing rivers, they are still large enough to maintain an adequate supply to them for an indefinite period to corne.» The drying up lakes prove that the glaciers that feed them are dwindling. The fall of rain and snow in the north and west are insignificant. But in central Tibet a fair quantity of both occur, giving rise to such great rivers as Yeru Tsangpo and at least two other outflowing rivers, which thus, as he says, pass regions with abundant rain. But he admits that even nowadays the annual renewal of nevée is an appreciable factor. »Some fresh snow — though only a moderate quantity — is still added yearly to snow-field and peak and does not melt. Comparatively scanty moisture reaches Tibet in modern times.» Great rivers reach India and China from Tibet and still the amount of snow and rain-fall in Tibet »is certainly, by itself, totally inadequate to produce such an out-flow». He correctly points out that the monsoon makes itself felt to a certain appreciable extent throughout Tibet. From the considerable volume of the northern tributaries to the Tsangpo Sandberg concludes that the northern watershed of this river must be set back many miles farther north than the actual valley line wherein the channel runs. He says it is a mistake to believe that »the massive mountain range, practically a continuation of Mount Kailas, known to geographers as the Gang-dis-ri range (really Gang Tise Ri) gives birth to these northern tributaries. This range passes eastward from forty to seventy miles north of the general line of our river, and in the main forms the southern watershed of the great lake plateau.» Now, he says, recent exploration shows that several of the northern feeders rise still further north than the Gang-dis-range, and even on the lake-plateau itself. But he omits to tell us which this recent ex- I Tibet and the Tibetans. London 1906. 2 Op. cit. p. 65. 3 Ibidem p. 23. | |||
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