ACROSS THE JARDANG DESERT TO ALTMISCH-BULAK. 69
so that a region which is now furrowed by small and narrow grooves may in the future exhibit broader and bigger ones — gullies — after several of the smaller ones have, through continued erosion, become joined together.
Generally speaking, these gullies lie at an acute angle to the line of the Kurukdarja. But as the river meanders along a serpentine course, those parts of its bed which have lain open to the wind have undoubtedly been still further widened by its agency. Considering the incessant filing to which it has been subjected by the drift-sand, it might be expected that the river-bed would ere this have been totally obliterated. I have said that we saw the last portion of it at Camp No. XI, and consequently I have assumed that that was the point of its embouchure into the former lake. Still it is quite conceivable that it may have continued yet farther towards the east, but that its farther eastward extension has been blotted out. As a general rule, it may be said that the Kuruk-darja grows less distinct as it proceeds towards the east, and for two different reasons. Its transformation into desert has advanced from its lower part to its upper part. When the water ceased to flow, it was of course the parts around the river-mouth which were the first to suffer, whilst the higher parts of its course were still reached by the dwindling current, so that there the transformation into desert was delayed. Thus the more easterly portions of the river-bed have been longer exposed to the levelling operations of the wind. The second cause is the decrease in altitude of the Kuruk-tagh from west to east, so that the northeast and east-north-east winds have freer play towards the east, and consequently they sweep more unchecked over those parts of the desert than over its western parts, which are relatively better protected by the mountains and the detritus slope with its terraced foot.
Fig. 62. RAMISCH STUBBLE IN THE DESERT.
All the same, the river cannot have proceeded very much farther than the point which I regard as its termination beside Camp No. XI. This is also proved by the change in the surface conditions beyond that point, the thinning out of the dead forest, and in places its entire cessation, the abundance of mollusc shells, the presence of kamisch-fields. With regard to the last-named, their existence would appear to militate against my contention, that the wind planes away the clay surface layer by layer. But no; the position of the kamisch-fields constitutes on the contrary one of the most convincing proofs of the deportation of material. For, as may be seen from the accompanying illustration (fig. 62), the stubble of the dead kamisch is always found on the platforms and elevated parts of the clay. Wherever it has grown, and bound the soil together with its roots, or still does so, even though its roots are now withered, the wind is unable to carve out gullies, and the soil remains at its original level, or shows only an extremely small and imperceptible decrease. On the other hand, those parts which are free from reeds have been excavated all the deeper,
IIIFカラー高解像度
