326 
LEVEL AND CONTOUR OF THE ARAL SEA. 
us compel us to reduce to more moderate limits than we assigned to them, the 
oscillations to which the bottom of the old and extended Caspian has been sub- 
jected. According to M. Basiner, the deposits charged with true Caspian shells, 
as seen on the western shores of the Aral, do not rise to more than 1 50 or 200 
feet above that sea, and form a sort of undercliff or low buttress between it and 
the higher plateau of the Ust-Urt. This elevation agrees with that of the steppe 
limestone which we observed on the shores of the Sea of Azof and Black Sea. 
We willingly take this opportunity of thanking Colonel Helmersen for his timely 
correction of our ideas concerning a region as yet unknown personally to any prac- 
tical geologist ; and in referring to a memoir which he is preparing, in illustration 
of the geological fruits of M. Basiner’s journey, we also beg to say, that to his 
friendly communication we owe our first acquaintance with the existence of a band 
of eruptive rock (Shik Djeli) on the right bank of the Oxus, to the north-east of 
Khiva. To this important feature a reference will be made when we come to con- 
sider the true southern prolongation of the great Uralian chain. 
In reference to the real level of the Aral, it is right to observe, that some Rus- 
sian travellers, particularly M. N.Khanikoff, who has obligingly communicated to us 
his views, are of opinion 1 , that the determination of the height of that sea by mere 
barometrical observation is not to be depended on a . From a general survey of the 
surrounding regions, including an estimate of the fall of the Oxus from its sources 
to its mouth, and from the level of the country between its western hank and the 
Caspian, M. Klianikoff is of opinion, that there is no material difference between the 
level of the Aral and the Caspian, and that the former, like the latter, will be found 
to lie in a depression of the earth’s surface. In our previous reasoning we took 
the usually recognised data, and simply followed Humboldt. But even should 
M. Khanikoff’s view be substantiated, our general reasoning respecting the oscilla- 
tions of the bottom of the great former Caspian, and its brackish inhabitants, will 
not be affected, though the intensity which we have assigned to such vibrations 
must be diminished. 
1 See M. N. Khanikoff’s work on Bukhara, with maps. St. Petersburgh, 1843. 
5 There is a prevalent opinion among those who have travelled into the steppes, that the barometer is 
not to be there trusted as a test of height. Without again alluding to the error into which geographers 
were led as to the real depression of the Caspian, it is said that from a mean of twelve observations in 
the Siberian steppes, an observer recently obtained for a result, that the ground between the Ui and the 
Tobol rivers was beneath the ocean , and yet these streams have a course of hundreds of miles before they 
reach it ! 
