IIIF Color HighRes
National Institute of Informatics - Digital Silk Road Project
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| IIIF Color HighRes |
| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.4 |
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Citation Information
HYPSOMETRY AND RELIEF OF THE TIBETAN PLATEAU.
583
lack of material. For instance, it is not possible to form any idea of the mean crest-altitude, although we may conjecture, that this does not in general exceed the mean pass-altitude by more meters than the mean pass-altitude exceeds the mean altitude of the nearest latitudinal valley, or by about 30o m. Equally impossible is it to determine the mean altitude of the insular, glacier-crowned summits, that is to say the mean altitude of the culminating points of the highlands. Other levels the mean values of which it must be left to the future to determine are the height to which the glacier-arms descend, the mean value of the absolute limits of vegetation, the mean altitude of the snow-line, and so forth.
J
For the time being there exists with regard to all these ample room for speculation and guess-work, and consequently it would at the present moment be anything but a grateful task to attempt to construct a hypsometrical map of the whole of Tibet. The white patches in the interior, and throughout the whole of the region north of the upper Tsangpo, are still far too big. Indeed, I will go so far as to declare, that, considering the knowledge which we at present possess regarding the altitudes, the hypsometrical map of the region between 86° and 92°, which has been traversed by several travellers, does not possess any special value. If the determinations of altitude along the meridional routes be used in the way in which I have attempted to use them in the last chapter or two, as a basis for calculating the mean altitude of identically the same range, then the mean altitude of that range may very readily be compared with the mean altitude of another range that is crossed by the same route; for the same errors are repeated in the same proportion in both ranges, and the result is therefore relatively permissible and reliable. But the case is quite different if we attempt to work out the mean altitude along a meridional line, because for that we have to use the route of one and the same traveller. If, for
r~
0
Fig. 370. I)EAP-CUT VALLEY IN NORTHERN TIBET.
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