If the advance of the Kara-korum glaciers is really a fact, one would expect to find a period of growing and strong effluence from the two lakes, or at least from the Manasarovar. But such a period can hardly be found in the list given above, unless we go back to 1846 and 1848 and admit that the effluence may have continued for several years after the visit of the Stracheys. We must also consider that between 1868 and 1900 there is a gap of 32 years which may easily have contained a maximum.
Still, comparing the two lists, some conclusions may be drawn. In 1780 there was a flood in the Shayok proving that the valley had been closed by the glaciers. This agrees well with the lakes, for all reports we possess from the time before 1780 indicate effluence from both lakes. From 1848 till 1863 the Kumdan route was closed by the glaciers, which agrees with the observations of the Stracheys in 1846-48, when the Manasarovar had even effluence. Then follows the period from 1865 till 1902 when the Kumdan road was almost always open, which is in excellent agreement with the lakes which from 1865, or earlier, till 1908 had no effluence, except in 1904, although doubtful. From 1903 to 191i the Kumdan route has been closed, a fact for which we do not find any correspondence in the oscillations of the lakes, though we again have to remember the gap from 1868 till 1900. The rise of the lakes which carried with it an effluence in 1909, 1910 and 1911 will, if it continues sufficiently long, probably be followed by a new closed period on the Kumdan route, after a certain elapse of time.
The results I have obtained from this examination at least show that the variations in the rainfall directly and periodically influence the hydrography of the two lakes, as well as certainly all other lakes in Western Tibet, and the movements of the glaciers. In the old moraines we find the mile-stones on the way of post-glacial desiccation. Therefore a ftriori a diminution in the effluence from the lakes must have taken place during the same period. The 200 years, within which we possess the only reliable dates regarding the lakes, probably indicate a period of much lower degree than the general post-glacial desiccation. And therefore we have no cause to exclude the possibility of the Satlej's flowing out again from the • Rakas-tal.
The climatic variations which have taken place during the last 200 years have, of course, not had the slightest influence on the conditions of the nomads, as a whole. From Father DESIDERI's narrative we find that the nomads lived, in 1715, exactly as nowadays. But, on the other hand, even periodicities of such a low degree as those which I have called the Manasarovar period, for instance from 1907 to 1909, influence the nomads so far, that 1907 was regarded as an unfavourable year, as no rain fell and the grass remained very sparse and bad, from which the sheep, yaks and horses had to suffer. In 1908 the conditions were already improved and in 1909 and 19 i o were very satisfactory. During such years the flocks are kept in excellent condition and the wealth of the nomads increases. During a period of several dry years their life becomes a hard struggle. Therefore it may with some reason be said that the changes in rainfall also give rise to variations in the conditions of life amongst the Tibetans.
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