578 THE HYPSOMETRICAL RELATIONS OF THE TARIM BASIN.
regard to its contour-lines in the same rough way as the other parts of the Lop region. And yet how inconceivably complicated are the contour-lines precisely along that line, as they are indeed for the matter of that in any of the other sand-free parts of the Lop Desert! To reproduce that complexity is of course quite impossible. It is only necessary to imagine a jardang extending for kilometers, being in general 2 to 3 m. high, along the sides of which the contour-lines would run for hundreds of meters! Then, bearing in mind that the entire desert is crammed with jardangs, and it is possible to conceive what the resulting map would be like. In order to render this still clearer I have on Pl. 6o at great pains drawn the meter contour-lines to a rather large scale, and have further had regard to the decimeter contour-lines as well. The positions of the curves outside of the ascertained line are idealised in the light of the experience that I possess as to the plastic features of the desert. They represent the jardangs and the hollows between them; they may in reality be longer or shorter than I have drawn them, but the chief object was of course to give a general idea of their arrangement. For the sake of simplicity I have made the line straight on north and south, although in reality it is somewhat convex towards the east. Further, I have made all the distances equally great, that is to say 200 m., although towards the south they actually amount to 282 m. Finally, I must remind the reader that in this little sketch I have considered that there is only one wind-eroded gully between every pair of measured points, whereas in point of actual fact as many as 5o gullies may be embraced within a distance of 200 m. So that in order to correspond to the reality, the sketch ought to possess as much detail in the drawing, but to be fifty times longer. It is a bold thing to lay down these contour-lines on the strength of only one measured line, but my only object is, as I have said, to give an idealised picture. The parts coloured blue are those that lie below the level of the Kara-koschun. From that it will plainly be seen, that on several occasions I crossed over narrow projecting bays and arms of the lake pointing towards the north-west. Had they been followed up westwards they would have been found to terminate in what were at that time vast expanses of open water. In the jardang desert all the points I measured stand on the top of the jardang ridges; but in the schor desert the lines run more simply. Pl. 6o ought to be compared with Pl. 36 and PI. 37.
If any one, after reading my description of the wind-eroded gullies and jardangs in the preceding pages, and after seeing the photographs I have given, should still entertain any shadow of doubt as to the mode of their formation, PI. 6o will, I am sure, infallibly convince him, that it is solely and alone the wind, using sand as an abrasive, that can have given rise to the remarkable regularity of the relief.
On the little sketch-map on Pl. 41 I have drawn a parallelogram, a study of which will still further help to elucidate the hypsometrical relations in the Desert of Lop. In the preceding chapter we have already seen how the surface of the Tschertschen Desert rises from north to south, as also how the Kuruk-darja, the Kontschedarja, and the Tarim show a constant fall towards the south-east. The Tschertschendarja falls towards the north-east. If the line which represents the second of the rivers just mentioned, the Kontsche-darja, be prolonged, and if at the same time the line of the Tschertschen-darja also be prolonged, these two lines will intersect one another in
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