IIIFカラー高解像度
国立情報学研究所 - ディジタル・シルクロード・プロジェクト
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| IIIFカラー高解像度 |
| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.2 | |
| 1899-1902年の中央アジア旅行における科学的成果 : vol.2 |
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引用情報
334 THE LOP-NOR PROBLEM.
which occur in the Desert of Tschertschen, turn their steep faces towards the west-north-west, a result which we traced to the fact that the accumulations decrease in
height towards the south, in consequence of which they in that quarter advance more rapidly towards the west. On the whole the chain of bajirs which we followed led us south-south-west. If now this theory is sound, that the rate of progress of the dune-accumulations is proportional to their sand-mass, it might be expected that the bajirs in the Desert of Lop would stretch from the north-north-west to the south-south-east, or from the north-west to the south-east, because the volume of
sand in the Desert of Lop decreases from north to south. In that part of the sandy Desert of Lop which lies north of the newly formed lakes, they stretch on
the contrary from north-north-east to south-south-west, or in other words parallel to
the bajir depressions of the Desert of Tschertschen. At the same time it must be borne in mind, that the • bajirs of the Desert of Lop are rudimentary and only some
twenty or thirty meters in length, and that they are situated between individual dunes, not between dune-accumulations; moreover, as I have already stated, the sand in this part of the desert is probably affected by the jardangs and the wind-eroded gullies, so that the position which the sand assumes in relation to the wind is not normal.
Both the jardangs and the wind-eroded gullies decrease in number as well as in boldness of relief from north to south, a fact due in no slight degree to
the circumstance, that the sand which lies there neutralises the corrasion of the wind. The bajirs we observed between the western extensions of the northern desert lakes and the northern shore of the Kara-koschun are therefore disposed from north-north-west to south-south-east, or rather from north-west to south-east, as indeed might be expected from the direction of the prevailing wind.
These characteristic bajir depressions we regard as having been originated by the wind. While the masses of sand are effected by the prevailing winds, the bare
ground between the sand-waves is subjected to the influence of the meridional winds only; consequently the bajirs in the Desert of Tschertschen form spoon-shaped hollows, and these, if situated close to the right bank of the Tarim, get filled with water. The circumstances are no doubt the same in the Desert of Lop, although on a far smaller scale; indeed everything there is on a smaller scale.
Our investigations have brought us therefore to this point, that the bajir depressions are hollows on the lee side of the dune-accumulations, and consequently
form a system of depressions all more or less at right angles to the other system, namely
the depressions which are excavated directly by the wind. But, as we have seen, the bajir depressions are by no means parallel to one another, a consequence partly
of the mass of the sand, partly of the configuration of the ground. If we compare the positions which the bajirs occupy in different parts of the desert, we find them to be oriented in such a way as to suggest that the prevailing wind does not blow uniformly parallel to itself. A consideration of the wind-eroded gullies and jardangs in the Desert of Lop led us to the same conclusion, for in its north-east part they even lie north to south, then north-north-east to south-south-west, and north-east to south-west, suggesting that, while the wind blows from the north or the north-north-east in the northern part of the desert, it comes more from the east-north-
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