CHAPTER XVIII.
THE LOP-NOR PROBLEM. - RICHTHOFEN AND
PRSCHEVALSKIJ.
In the preceding chapter I have confined myself to giving some idea of the manner in which, and of the practical conditions under which, my survey of the Desert of Lop was carried out, reserving for a subsequent chapter the full analysis of the results obtained. The two lines along which I crossed the Desert start from the ruins of Lôu-lan, and proceed south, but in such a manner that the western line forms a gentle curve to the west and the eastern line a similar curve to the east, so that after at first diverging, later on they converge again, the maximum distance between them in the interval amounting to 29 km. And yet, although the distance between the two lines is thus everywhere short, the desert nevertheless exhibits very great differences along the two routes, — except as regards the one feature of level. Everywhere along the western route we had the clay desert, traversed by wind-eroded gullies and jardangs, with a north-east and south-west direction; all the way until we reached the northern margins of the newly-formed desert lakes. The schor formation was only visible a long way off to the south, and even then was of small extent. Along the eastern route however the clay was confined to the northern half of the desert, while the southern half consisted of nothing but schor. On the western route the vegetation, or more accurately the remains of the toghrak forests, tamarisk steppes, and kamisch-fields were rather plentiful, although they decreased as we advanced south. On the eastern route these same species of plant-life thinned out before we had gone ten kilometers, and soon afterwards came altogether to an end; and the broad schor desert was as destitute of plant-life as the belt of schor which forms the southern border of the Kara-koschun. On the former route we entered in amongst the sand-dunes the very first day out from Lôu-lan, and the dunes continued to increase in size as we advanced, nor did they begin to decrease until we carne into the immediate vicinity of the Kara-koschun. On the east the sand was absent, with the exception of trifling quantities which had gathered under the shelter of the jardangs and the tamarisk-mounds in the south. But though we are warranted in concluding, from what we know otherwise about the western parts of the Desert of Lop, that the
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