NATURE 
237 
THURSDAY, JULY 15, 1886 
GEOLOGY OF TURKESTAN 
II. 
Turkestan ; a Geological and Orographical Description 
based upon Data collected during the Fourneys of 1874 
to 1880. By J. V. Moushketoff. Pp. 714. With Map 
and Engravings. Russian. (St. Petersburg, 1886.) 
HE view taken by M. Moushketoff and other modern 
explorers of the region, as to the Aral-Caspian 
basin having consisted of several large lakes, or rather 
seas, connected together by outlets, is, in our opinion, the 
only one which can adequately explain the ulterior 
changes undergone by the basin during historical time ; 
and it is also fully in accordance with the orographical 
configuration of the region. These outlets have gradually 
dried up, and it is probable that the Aibughir and the 
Balkhan outlets both existed during the historical period. 
The basin of the Aral and Sary-kamysh was long main- 
tained by the inflow of water received by the Amu and 
the Sir. There may have been a period when both 
joined together before entering the great lake ; but later 
on, the Amu entered the Sary-kamysh, or western part of 
the double lake ; while the Sir flowed into its eastern or 
Aral part. As the Amu, undermining the Sultan-uiz-dagh 
hills, gradually moved further east, and finally, finding 
its way through this range, began to flow into the Aral, 
the Sary-kamysh lakes, deprived of its water, dried up 
much more rapidly. The Aral basin, in the meantime, 
may have increased in size. 
As to the Uzboy, which was considered by the earlier 
explorers as a former bed of the Amu-daria, M. Moush- 
ketoff, in accordance with the majority of the more recent 
explorers, considers it a marine outlet which connected 
both the great lakes ; and the absolute want of any river- 
deposits and the wide extension of Caspian shells up the 
Uzboy serve to confirm this view. The drying up of the 
Aral goes on now very rapidly. The disappearance of 
the Aibughir gulf ; the conversion of the Sary-cheganak 
gulf into a mere lake; as also that of the Kamyshly- 
bash, which the Kirghizes remember to have been con- 
nected with Lake Aral ; together with the numerous facts 
mentioned by MM. Severtzoff, Borschoff, Meyendorf, 
Maksheeff, and Schultz, are well known. The obser- 
vations of MM. Kaulbars and Dorandt furnish most 
valuable data of the same kind for other lakes of the 
region: the Sary-kamysh, now 50 feet below the level of 
the Caspian, covered a surface of no less than 4400 square 
miles. And we may add that these facts are not iso- 
lated ones, but that the same rapid drying up is going on 
throughout Western Asia: it is the characteristic of the 
geological epoch in which we now live. 
Many most interesting pages are devoted by M. 
Moushketoff to wind-agencies and to moving sands. 
His observations on dunes and analogous sand-hills, 
accompanied by several drawings, will assuredly be most 
welcome to geologists. M. Moushketoff distinguishes 
between two different kinds of sand-hills: the dunes, 
arising on the shores of lakes, and the darkhans. Wind 
* Continued from p. 119. 
VOL. XXXIV.—No. 872 
is a powerful agency in the formation of both. Recent 
meteorological observations have shown that north and 
north-east winds are much more prevalent than any 
others in the Turan region. On the lower Amu-daria 
and at Tashkend they are from 50 to 60 per cent. As to 
the rains they are so scanty that throughout the year their 
aggregate amount hardly reaches 69 millimetres at Petro- 
Alexandrovsk, and 73 at Nukus. The evaporation, as 
appears from M. Stelling’s work, is exceedingly great. 
Thus, while at Kishineff, for instance, the annual evapora- 
tion exceeds the annual amount of rain by only one-fifth, 
it is five times greater than the amount of rain at Astra- 
khan, three times greater at Tashkend, twenty-seven 
times at Nukus, and thirty-six times at Petro-Alexan- 
drovsk. The yearly amount of rain being represented by 
a column 69 millimetres high at Petro-Alexandrovsk, the 
evaporation is so great that a column of water 2320 milli- 
metres high would be evaporated every year; at Nukus 
the respective figures are 71 and 1928 millimetres. These 
climatic conditions would suffice, in M. Moushketoff’s 
opinion, to explain the geographical distribution of the 
moving sands which appear more especially to the south 
of Lake Aral. 
Now, among these moving sands two different kinds 
of moving hills should be distinguished; the dunes 
and the darkhans. The former are indebted for their 
origin to the combined action of water and wind ; they 
are disposed in long waves along the shores of the lakes 
or rivers—these last (the river-dunes) being local and 
never reaching more than Io or 15 feet in height. The 
marine dunes, attaining as much as 50 feet—not more— 
have lengths reaching to about 7oo yards. They arose in 
consequence of the retiring of the Aral Sea and the pre- 
vailing winds. These dunes have the most varied 
directions, according to the local direction of the former 
shore-line. 
As to the darkhans they are indebted for their origin 
to the agency of the wind alone. They can arise only 
under certain climatic conditions, and may appear cover- 
ing any geological formation, like the moving sands o 
the Ili River, which are due to the destruction of massive 
crystalline rocks, or the sands of the Sahara, which are a 
result of the disintegration of basaltic rocks. Their outer 
shape is quite characteristic, being always that of a 
crescent, or, to use Middendorff’s comparison, it resembles 
the hoof of a horse. Sometimes two, three, or four 
barkhans are connected together, and then they appear 
like a succession of crescent-shaped conical hills, con- 
nected by their respective horns. Their height is usually 
from 30 to 40 feet; there are, however, much smaller 
ones, and a few reach as much as 80 and even Ioo feet. 
The sand of which they consist varies according to the 
nature of the rocks to whose disintegration they are due ; 
the angles of inclination of their slopes also vary between 
30° and 4o° on the side turned to the wind, and between 
6° and 16° on the opposite side. 
On the whole, on seeing these hills, one would 
refuse, according to M. Moushketoff, to recognise in 
them a formation due to the sole agency of the wind, but 
one must witness a storm in the desert to recognise its 
full force. Still, during a very strong storm, M. Moush- 
ketoff did not see the wind moving particles of sand more 
than 1 to 2 millimetres in diameter. 
M 
