UNINHABITED REGIONS 
965 
temperature of the night ; and this is the most destructive 
of all the disintegrating agencies. Next after it ranks the 
wind, which carries away all the finer particles of detritus. 
Precipitation occupies here the third place ; it only falls 
during two months in the year — and not even then with 
absolute regularity — and falls in the form of rain. 
This type of valley is characteristic. A transverse 
profile would give a straight base-line (the sai), with the 
mountains shooting vertically down upon it from both 
sides, without any talus at their feet. 
The higher we ascended, the finer the gravel, until 
eventually its place w'as taken by coarse sand. The buran 
(storm) enveloped every feature of the landscape in its 
yellow haze. The horses speedily disappeared from sight. 
Even the camels and donkeys outpaced us that day, and 
their trail was already half obliterated as we rode along it. 
In the upper part of the valley we again turned towards 
the south. Immediately beside us the rock was black 
clay-slate ; but right ahead were tw'O isolated towering- 
masses of red sandstone, forming a gigantic gateway, and 
tow'ards them we steered our course. 1 hey marked the 
termination of the valley of Kara-muran. Beyond them 
lay a country of highly diversified featuies, much levelled 
down by denudation, a country corresponding to the trough- 
shaped catchment-basins in the mountain- chains of the 
Peripheral regions, only that this was shallow and of more 
than average width. The river did not originate in any 
definite head-stream, but was formed by a number of small 
rivulets or furrow's (then dry), which converged from every 
direction upon the chief catchment-basin of the valley. 
The ground at the foot of the w'estern mountains, that is on 
our right, was littered with huge fragments of rock fallen 
from the summits above, and strangely split and fractuied. 
forming a series of crenelations. Seen from a distance, 
they looked like big red cubes, but when we came nearer 
they assumed the climensions of houses of colossal size. 
South of the twin mountains of red sandstone w'e rode 
across a boundless arena -like plain, covered with sand, 
which was rippled on the surface, though without any 
