Page:Mongolia, the Tangut country, and the solitudes of northern Tibet vol 2 (1876).djvu/109

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ALPINE ZONES.

87

white, and lilac rhododendra and Caragana jubata, with an occasional patch of bright red flowers. But this does not last long. In July the rhododendra and Caragana jubata cease blooming, and early in August the morning frosts nip many of the herbs.

The luxuriance of the alpine meadows is limited to an elevation of 12,000 feet. The temperature above this is too cold, and winds and storms of too frequent occurrence, to allow of the development of vegetation, which becomes more stunted the higher we ascend, until it disappears altogether, and nothing is left but bare rocks, with an occasional patch of moss and lichen. Here the scientific observer may find an admirable illustration of the wasting, irresistible power of time, as it gradually wears down the hardest rocks and reduces to insignificance the loftiest cliffs.

Here, too, amid the loose débris, springs take their rise, at first trickling in feeble runnels, half hidden beneath the stones, soon to unite with other streams and descend in torrents down the rocky valleys.

As regards fauna that of the Kan-su mountains is richest in birds; of mammals we only found eighteen kinds, and fish and reptiles were very scarce. The small number of insects and almost entire absence of reptiles is due to the unfavourable climate.

The mammals belong exclusively to three orders, carnivora, rodents, and ruminants. We did not see a single specimen of the Insectivora or Cheiroptera.