320 
SALT OF THE STEPPES FORMED AT DIFFERENT PERIODS. 
certain amount of salt is disseminated, and it is after copious rains only and in cer- 
tain seasons that they give off a saline effervescence. In many cases they appear to 
be the mere residue of salt marshes, which had been formerly overflowed by the sea. 
Pallas has, indeed, pointed out the distinction between these two classes ol salt de- 
posit. “ None of the salt lakes and marshes on the western coast of the Caspian 
Sea have such a stratified incrustation of salt, gradually increasing, as may be ob- 
served in the lakes of Bogdo, Elton and Indersk, near the river Yaik. Thei6 the 
ample store is continually supplied and increased by rich salt springs ; whilst all 
the saline particles of the other salt lakes are completely dissolved by the rains of 
autumn and winter 
To the clear distinction thus drawn by the great naturalist, before geology was 
a science, we have to add, that the copious perennial springs of the steppe of 
Astrakhan are derived from residual subterranean phenomena of oceanic character, 
accomplished during the palaeozoic sera, when intense mutations were brought about, 
and vast masses of crystalline rock-salt were formed, whilst the saliferous efflo- 
rescences of the marine mud of the steppes of the Caucasus are simply what we 
might expect to find in the retentive portions of the bed ol a retired sea 1 2 , particu- 
larly in the contiguity of the great eruptive chain of the Caucasus 3 . 
We believe that all the lowest part of this vast steppe of the Caucasus bears the 
same relations to the younger tertiary rocks of the Crimsea and the Caucasus, as 
the low steppe of Astrakhan to the adjacent promontories in the south of Russia. 
We have therefore laid these tracts down upon our Map under one common 
tint (10'), intending thereby to convey the idea, that the waters once covered a 
sinuous tract between the Caucasus and Southern Russia, uniting the Caspian with 
the Sea of Azof and the Black Sea on the one side, and the Caspian with the Aral 
on the other, at a period when other beds of the same inland sea (the steppe lime- 
stones) had been elevated and formed to a great extent their shores. At the same 
time we are ready to admit, that a portion of the steppe of tue Caucasus may have 
1 Pallas’s Travels through the Southern Provinces. English edition. 4to. p. 305. 
a In the expedition of General De Berg from the Caspian to the Aral, the greatest obstacles to the 
passage of the guns and heavy baggage were similar oases of marine mud to the north of the Ust-Urt, 
which were not frozen hard, even when the thermometer stood many degrees below zero. 
» In his work upon the Caucasus, M. Dubois has shown, that masses of rock-salt have been formed 
even in the tertiary deposits, by a conjunction of volcanic eruptions with the desiccation of ancient sea 
bottoms. The same results are indicated in the Isle of Tchelcken in the Caspian, where the springs of 
naphtha and salt issue from beneath the marine mud. (bee I elkener ut supra, p. 310.) 
