escarpment, the Tarim river, and the plains which spread at the foot of the Altyn-tagh, must have been occupied some time by a large basin, upon the shores of which stood that spot of the Lau-lan region, in which Dr. Hedin has found such interesting manuscripts. Later on, the lake occupied the eastern part only of that triangular basin; and now the lake Kara Koshun, or the Lob-nor of Prjevalsky, represents the southern trough of that depression, which continues still to be occupied by what has survived of the Lob-nor. At any rate, when the full reports and the levellings of Dr. Hedin are published, and the whole region is better explored, it will certainly appear that within this triangular depression (»Lob Nor desert= on Stieler's Atlas map) the lake was changing its position in proportion as it decreased, and it may change it several times more before the general desiccation of Central Asia, which is going on at great speed, will finally move the Tarim lake further south-westwards to meet the Cherchen, and finally reduce what will remain of the Lob-nor to the little lake Kara buran, which we see at the junction of the Yarkand-daria with the Cherchen.»
Prince Krapotkin commits here a double mistake. In the first place he removes the Lop-nor problem from the period of actual history, and regards it from the standpoint of geological history, carrying us back as far as the epoch at which the Asiatic Mediterranean was still in existence, forgetting that the Lop-nor problem belongs to the very latest phase of the Quaternary period. And when he converts the triangle between the lower Tarim, the Astin-tagh, and the »Altmisch-bulak escarpment» into an ancient great lake Lop-nor, and gives to the spring of Altmisch-bulak an altitude of 3600 feet or I i oo m., he forgets that the absolute altitude which he thus assigns to the northern shore of his imaginary lake would not allow the waters to remain within the boundaries he assigns to them. Such a lake as he supposes would extend a good bit west of Tschimen and Schah jar, and cut the existing Tschertschen-darja between Tatran and Boghuluk. To the north this immense lake would reach to within a short distance of the road running between Kutschar and Tschadir, would embrace Kara-schahr and the whole of the basin of the Baghrasch-köl, and eastwards would extend as far as Sa-tscheo. Under no other conditions would it be possible for the triangle in question to be under water. And this brings us to the question of the great Asiatic basin which Richthofen calls the Han-hai, and with regard to which he says inter alia:
»Nur ganz allgemein steht fest, dass das Meer am Ende der Kreideperiode das Han-hai erfüllte; dass es aus dem durch die Flüsse herzugeführten Material, insbesondere Sand und Geröll, Schichten absetzte, und sich in einer unbestimmten späteren Periode durch die Dsungarei zurückzog; und dass es dabei auf seinem früheren Boden ein grosses Binnenmeer zurücklies, welches durch allmälige Verdunstung in mehrere wassererfüllte Becken zerfiel, sowie dass auch diese allmälig an Grösse abnahmen, zum Theil ganz austrockneten, zum Theil aber noch in kleinen Ueberresten als Salzseen vorhanden sind.» And further: »Mag nun die Isolirung des centralasiatischen Mittelmeeres in einer etwas früheren oder späteren Epoche der Tertiär-periode erfolgt sein, so wird dasselbe immerhin noch als ein grosses Binnenmeer einen Bestand durch lange Perioden gehabt haben, ehe es zu geringen Dimensionen zusammenschrumpfte.»
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