LOESS IN THE TIAN SHAN MOUNTAINS. 63 
shown at the end of the ride by the condition of our clothes, which had been 
carried in a well-wrapped valise, unwisely tied on at the back of our tarentass. 
The form and distribution of the drifts by Kara-bulak leaves no doubt as to 
the recent derivation of the loess from the plains on the west and northwest. Not 
only does the fan-like flood plain of the Kusak open in that direction, but the great 
sandy wastes of the lower Hi and Karatal, south of Lake Balkash, stretch for scores 
of miles beyond. All this gives further support for the supposition that, in this 
region at least, loess is not derived from mountains, but from the river plains. To 
be sure, the waste that is laid on the plains comes originally from the waste of the 
mountains, but in the mountains the slopes are often plant-covered, and are therefore 
better fitted to gather loess than to furnish it, as seems to be attested in the loess 
mounds that have been so manifestly laid up on the ridges over the Kok River 
above mentioned. It is not from ordinary river valleys that loess is best supplied, 
but from the open plains of aggrading rivers ; and, moreover, it is chiefly while the 
aggrading rivers are wandering over their plains that loess can be furnished in 
greatest quantity, as was pointed out in the notes on Fergana, above. The former 
broad valley floor of the Kusak by Kara-bulak, for example, is not to-day in condi- 
tion to furnish loess, because it has been plant-covered since the river has intrenched 
itself below the plain, and the river trench is as yet too narrow for the outspreading 
of silts. Further west, where the same river emerges from its trench to wander 
upon a broad plain, loess ma}' now be swept off in good quantity' by the westerly 
winds, to settle on the plant-covered hills. 
LOESS IN THE (western) KUGART VALLEY. 
The loess drifts of the Kusak valley-sides give me confidence to put on record 
certain notes made in the valley of the (western) Kugart, in the outer spurs of the 
Tian Shan, about 20 miles northeast of the town of Jellabad, in northeastern 
Fergana. The treeless hillsides seemed often to be loess-covered, and in many 
places the loess had slipped down, leaving a scar. Ravines were worn through 
the loess, hence it was not of verj- modern date. The loess and the \-alley floor 
were well covered with herbage. But the most significant feature was the drift-like 
appearance of the loess; it seemed to lie in pillow-like masses (fig. 64), whose lines 
of modeling were not down-hill, except where the drifts were gashed by ravines, 
but along the hillsides, as if here it had been wind-swept down the valley to the 
southwest. We asked our jiggits, who had been detailed by the native chief of tiie 
department to accompany us to the head of the pass, from what direction the wind 
blew in winter; and the answer was, "Strong from the northeast" 
The Kugart River is to- day intrenched from 300 to 400 feet below its former 
valley floor, which was here a mile or more wide. The terraced walls of the trench 
show the valley to have been heavily aggraded with gravels and sands. It is 
therefore probable that the loess on the hillsides was largely supplied from the 
valley floor during the period of aggradation, and that since terracing began the 
accumulation of loess has ceased. 
