IIIF Color HighRes
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| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.4 |
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Citation Information
1i
450 EXPLORERS' JOURNEYS IN HIGH TIBET.
the Tang-la Mountains, flows across the highlands of northern Tibet, and waters China proper, where it soon assumes gigantic proportions. Its flow is very rapid.
At the confluence of the Naptschitaj-ulan-muren its breadth reaches 228 m.; but in the summer, during the rainy season, it is four or five times as big. Its valley is however only 2 versts broad, and through it runs the road to Tibet, keeping beside the river almost all the way to its sources in the Tang-la Mountains. The Blue River formed the limit of our journey in Central Asia.»*
In his third journey (1879-8o) Prschevalskij traversed a considerable part of north-eastern Tibet, but also to the east of my itinerary of 1900. If we confine the term Central High Tibet to that part of the country which possesses no outlet to the sea, then Prschevalskij did not, on this occasion either, touch the region in question, but he kept principally to the upper basin of the Jang-tse-kiang. Prschevalskij summarises the general characteristics of the physical geography of north-eastern Tibet in the following words: »The Tibetan mountain ranges are distinguished by the following properties: they run parallel to one another from east to west, and notwithstanding the great height above the sea the individual peaks reach but an insignificant relative altitude. Setting aside the snowy summits, they form dome-like swellings, with gentle gradual slopes. The mountains consist generally of gravel, sand, limestone, and schists. Snowy mountains occur in the Tang-la and Marco Polo ranges, and also on the mountains between these ranges and beside the upper course of the Yellow River. The lower glacier margin coincides here, as it does on the Nan-schan Mountains, with the mean snow-line. According to our observations, the latter begins on the Tibetan mountains at an altitude of 495o to 5100 m. Between the mountain-ranges stretch plains with a clay surface. There are no loess formations of any extent, and drift-sand is equally scarce. On the other hand saline formations are common. The water, including sometimes even the water of the rivers, has a brackish taste. The lacustrine region extends from the Tengri-nor to Lake Panggong. In the eastern part of the high plateau rise the Hwang-ho, the Jang-tse-kiang, and in the south-east the two Indo-Chinese rivers, the Salwen and the Mekong. The north Tibetan rivers mostly flow towards Tsajdam and generally terminate in salt marshes. The streams which have their sources on the northern slopes of the Tang-la, the Dung-bure, the Koko-schili, and the Marco Polo Mountains, empty themselves into the Mur-usu (upper Jang-tse-kiang).
As for the climate, the result of our hasty observations goes to show that, notwithstanding the southerly situation, there exists a remarkably low temperature, violent tempests, great aridity of atmosphere in the spring, autumn, and winter, and heavy rains in the summer. The low temperature is explained by the great altitude of the country and by the fact that it is bordered on all sides by lofty mountains, in part snow-clad. In spring and summer rapid changes of temperature take place. The autumn is the best season of the year in Tibet, for the atmosphere is then for the most part clear, the temperature equable, and storms seldom. The late autumn is mild, but the winter cold. Although snow falls very frequently, the amount is insignificant, for it is soon swept away by the storms or melted by the sun. The
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* General Prschevalskij's forskningsresor i Centralasien, Swedish translation by Sven Hedin (Stockholm, 1891); — N. Prjevalski, Mongolie et Pays des Tangutes (Paris 188o).
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