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 |
| Overland to India : vol.2 | |
| インドへの陸路 : vol.2 |
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引用情報
covered with blown sand, and he believes that the sandy expanse to the south-east derives its masses of sand partly from central Mongolia through the action of the prevailing west-north-west and north-west winds, partly from the dried-up beds. Potanin supposes that the south - west
winds prevalent in Ordos carry blown sand from the Nan-
shah all the way to the Kinghan mountains and Kerulen. Particularly interesting is Potanin's observation that
the sand of the desert belt in the northern half of Asia is 0
almost without exception piled up round lakes, and conse- quently in the lowest parts of the depressions where it
d t ti
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occurs. " Moreover, we find also that these sandy tracts always occur on the western or south-western shores of lakes ; this is the case with the lakes Balkash, Ala-kul, Ebi-nor, Ajar-nor, Orku-nor, Sajsan, Ulun-gur, Ubsa-nor, Durga-nor and Khara-nor lying to the east of Kirgis-nor." 1
From Tibet, where driftsand is very scarce, I will give
only one example. On the southern shore of the Bashkum- r1
kul and the stream which flows into this lake lies a very large belt of absolutely barren high dunes. Volumes might be filled with such examples, not only in Asia but also in Africa and other parts of the world.
It is too well known to need repeating that dunes are a function of weathering and the energy of the winds. A dry climate and a barren soil are also conditions for the production of dunes. If now all conditions are fulfilled, if weathering proceeds unhindered in a desert region unencumbered by vegetation, then the accumulation of driftsand and its movement must take place in different ways, depending on the character of the winds. If the prevailing wind is north-easterly, as in Russian Turkestan, the whole sandy waste moves south-westward. This is also the case with the immense collections of dunes I have described in Eastern Turkestan. If the wind blows from a different quarter in different seasons, the relief only of the dunes is changed, but the sandy area remains stationary. Dunes
1 In the first and second volumes of the Scientific Results of a Journey in Central Asia, 1899-1902, I have fully described the sandy seas of Central Asia, and I refer those who are interested in them to this work. I have also in the English translation introduced the result which the Russian explorer arrived at. The complete account will be found in vol. ii. pp. 38o et seq., from which the above excerpt is taken.
240 OVERLAND TO INDIA CHAP.
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