Burn. 
older rocks emerge, for instance Tamdi-Tau, Bukan-Tau, 
Sultan Uis Dagh, now isolated mountainous masses consisting 
of various slates and erystalline rocks which as a result of 
greater denudation are now more cut up than the rocks of 
Thianshan. 
The deposits from the Cretaceous and Tertiary periods 
are of great thickness, attaining 5000 feet in Ferghana for 
instance. They consist of diverse coloured strata of marl, 
limestone, ferruginous sandstones, gypsum, clay &c. They are 
not identical everywhere but change according to the near- 
ness of the mountains: At the foot of the mountains, mar- 
ginal deposits are found, such as shelly limestones, conglo- 
merates, clay with gypsum and rock-salt, while, out on the 
flat land, sand and clay are found deposited in deeper water 
(ROMANOWSKI, MUSHKETOW). 
The Tertiary deposits, however, are rarely visible, as they 
are almost everywhere covered by newer deposits partly de- 
rived from them. Of these the most important are: the moving 
sands, the Aralo-Caspian deposits and the loess. 
Deserts of moving sand cover, according to RODSEWITCH, 
about 88 per ct. of the lowland. The sand is of varied origin. 
In the northern part it is derived from old Aralian sea-coast 
dunes and is white or grey. As this sand originates from the 
old Aralo-Caspian Basin, it has much the same distribution 
as the Aralo-Caspian deposits mentioned below. 
Throughout the rest of the moving-sand territory, the 
dunes (‘‘Barchans’’) are genuine inland deposits which owe 
their origin purely to the wind. The wind carries off every- 
thing available, all that mechanical disintegration provides 
for it. Thus the Aralian dunes, the Aralo-Caspian deposits 
and the older rocks contribute to the formation of the “Bar- 
chans’’. Illustrations of the effects of the levelling process 
will be found in BERG.-— The Barchans are of a dirty yellow 
colour, they have the shape of a crescent, generally quite 
regular. The convex part faces the wind, the inclination of 
the surface is here 6—16°, while on the lee side it is 30—38° 
(MusakETOW). The crest is a sharp and regular line, which 
from the highest point curves downwards and away from 
the wind. How the crescent shape is produced has been ex- 
