THE JUMALAK-DARJA TO TOKUS-KUM. 1~9
which is reached and covered by the perodical overflows of the Tarim, constitutes at each meridian a perfectly horizontal region, with an extremely gentle slope towards the east, there is nothing surprising in the water, and the channels which it follows, being alike extremely sensitive to even the very smallest changes of level. And such delicate variations are called into being by the river itself, partly through the sediment it deposits, partly through the belts of vegetation to which it gives rise. Those parts of the area of inundation, which at times fail to be reached by the water, dry up, and so become a comparatively easy prey to the winds. In this way the level is mechanically lowered by the transportation of the loose surface material; and whilst it is true, that the absolute change of level is per se insignificant, still the river is sufficiently sensitive to respond to even that slight alteration, and it does alter its course accordingly. These laws are operative on a much greater scale, and in a more conspicuous manner, in the lowermost reaches of the Tarim, and we shall therefore have an opportunity to study them more closely on a future page.
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