Page:Mongolia, the Tangut country, and the solitudes of northern Tibet vol 2 (1876).djvu/250

226 so materially retarded vegetation that its aspect differed very little at the end of the month from that which it had presented at the beginning. Although by the second week in March thirteen kinds of birds had made their appearance, it was only singly or in small numbers; and how rapid must their flight have been over the terribly cold deserts of Northern Tibet, where they could have procured neither food nor water!

We arrived on the shores of Lake Koko-nor in the middle of March and found the season as backward as it had been in Tsaidam a month earlier. The lake was entirely frozen over, and even the rapid Pouhain-gol was only here and there free from the ice, which in winter attained a thickness of three feet. Here, too, migratory birds were even less numerous than in Tsaidam. The cause of this difference in the climate of two countries lying in such close proximity to one another is, first, the great elevation of the Koko-nor basin, and, secondly, the influence which the great expanse of its waters exercises over the surrounding country. This sufficiently accounts for the contrast in the climates, which is so marked that it is even noticed by the inhabitants.

We determined to remain by the lake till the end of April to observe the flight of birds; and with this object in view we stationed ourselves at the mouth