322 
CHANGES OF LEVEL IN THE ARALO-CASPIAN DEPOSITS. 
date, was, indeed, likely to prevail, at a period when it was not ascertained, whether 
the fossils of the steppe limestone differed or not from the shells of existing na- 
ture ; and when, from the want of accurate admeasurements of the relative heights 
of land and water it was imagined, that the whole of this region was a depression 
on the surface of the earth ; the present Caspian Sea being supposed to he more 
than 300 feet below the level of the ocean. The Russian researches, to which 
allusion has been made, have, however, removed this obscurity. They have taught 
us that the Caspian is 83 - 6 English feet only beneath the Black Sea. It has been 
further ascertained, that the Caspian and Aral are separated by the broad and lofty 
isthmus of the Ust-Urt, which from its condition and contents must have been 
formed long antecedent to the historic sera ; and lastly, it is now supposed by 
other observers, that the Aral being 1 1 7 feet above the Caspian, is consequently 
33'4 feet above the Black Sea, Mediterranean and ocean (see section, p. 311). 
These great differences of level in masses of water, whose shores are occupied by 
limestones which must have been accumulated under the same inland sea, were 
clearly effected in very ancient periods ; for independent of the prodigious altera- 
tion in the physical outline of these countries, caused by the elevation of former 
sea-bottoms and their erection into barriers which now separate the Aral and 
Caspian seas, we find that a considerable proportion of the fossilized shells are no 
longer living in the adjacent Caspian, and thus, independently of the great muta- 
tions of surface, we are compelled to believe, that the steppe limestones are, in 
relation to our own age, of high antiquity. In like manner, though to a less ex- 
tent, we draw the same inference concerning the greater part of the low steppes ; 
for although from their relations and “ facies ” these sands have evidently been de- 
siccated at a period subsequent to the elevated steppe limestone which constitutes 
their shores, they contain some of its shells, and among them species now unknown in 
the Caspian. The calcareous hills, and the low, sandy and argillaceous bottoms of 
the steppe, we consider, therefore, to be signs of two retreats of the same pristine sea, 
the Caspian is 18 met. 30 cent., or GO' 04 English feet only lower than the Sea of Azof! (See Bull, de la 
Soc. Geol. de France, vol. xiv. p. 322.) This determination, with many other admeasurements, is about 
to appear in a work entitled “ Les Steppes de la Mer Caspienne,” some livraisons of which, already before 
us, do great credit both to the artistical and literary accomplishments of Madame Hommaire, who accom- 
panied her husband in his laborious survey of these Kalmuck steppes. With every respect however for 
this author, we really consider it impossible that his one line of observations can be placed in competition 
with the quadruple and closely compared data of the Russian mathematicians, to whose results, in com- 
mon with Baron Humboldt, we attach implicit confidence, feee this line of levels on Map. — May 1844. 
