Yarkand, flows along the western and northern sides of the basin and drains over half its area. Because of the importance of this river, the region is often called the " Tarim basin." As this name applies to only the western portion of the country under discussion, it seems better to designate the basin as a whole by the name of its terminal reservoir, as is done in the case of the Aralo-Caspian basin, the Titicaca basin, the Great Salt Lake basin, and many others. Accordingly, I shall make little or no use of the term " Tarim basin," and shall use " Lop basin " as the name of the central basin of Asia. The Lop basin, thus defined, comprises the most western portion of the Chinese Empire. Together with the Turfan basin north of Lop-Nor, it forms what is known as Chinese Turkestan; and with the smaller regions of Ili and Dzungaria to the north, is comprised in the huge Chinese province of Hsin-Kiang, the "new province."
The most important factor in determining the character. of the vegetation, and hence of the animal and human life of a region, is, of course, its climate. The climate of the Lop basin depends upon the threefold fact that the basin lies first in the middle of the temperate zone, second in the centre of the largest of the continents, and third in the midst of a ring of lofty mountains which completely enclose it. The three factors combine to minimize the amount of precipitation, and to induce great extremes of temperature. From September, 1905, to March, 1906, during most of which time I was in the central part of the basin, I saw no precipitation whatever, though in mid-January, near Lop-Nor, I came upon two or three inches of snow which was
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