ORIGIN OF SALT SOURCES. 
197 
We shall hereafter show, that all this low tract was once occupied by a Caspian 
Sea, and endeavour to give some proof of the high level at which its waters once 
stood ; but we again insist, that the salt springs to which we have alluded, are com- 
pletely independent of any such comparatively recent cause, and are derived from 
a subsoil formed in the earlier zones of the earth’s crust. If we mistake not, a 
great number of the saline lakes of Eastern Russia and Siberia will be found to 
owe their qualities to the lodgement of water in depressions fed by salt springs 
or communicating with masses of rock salt '. However this may be, the facts to 
which we have adverted in Russia proper, may be turned eventually to national 
advantage, in a country where nearly horizontal strata occupy vast, regular depres- 
sions ; for wherever salt sources have their natural outbreak at the edges of such 
basins, we may feel certain, that artesian wells sunk in favourable places within 
their area, might raise salt to the surface, in districts removed at inconvenient 
distances from the usual marts of this indispensable commodity. A hint on this 
point is sufficient for the intelligent administration of the Imperial Mines. 
1 have been recently informed by M. Ilommaire de Hell, an enterprising French engineer, who has 
prepared for publication a Map of Southern Russia, that, in the southern steppes which we did not 
visit, between the Black and Caspian Seas, there is a very general occurrence of clay impregnated 
with saline particles, though the ordinary sandy superficial covering of the country yields fresh water. 
In dry seasons no salt is procured ; but when the inferior clay has been saturated by heavy rains, 
lakes are formed, which, on evaporating, leave considerable saline incrustations. The saliferous pro- 
perty of this steppe is considered by M. Hommaire to be a residuary phenomenon, due to the desic- 
cation of the once submarine tract which connected the Black and Caspian Seas (see Map). We may 
return to the consideration of this subject in a future chapter, when we treat of recent changes ; and, in 
the mean time, we simply remark, that if the inferences of M. Hommaire be admitted, they do not 
in any way interfere with our geological facts, as to the ancient origin of the permanent salt sources 
to which we have adverted. 
Formation of Ice in the Cave of Illetzkaya-Zastchita explained. 
Since the preceding pages were printed, Professor Wheatstone has called our 
attention to a memoir of Professor Pictet of Geneva, explanatory of the formation 
and conservation of summer-ice in natural caverns 1 . These caverns, near Be- 
sancon and in the Jura, occur in tracts where the mean cold is above the freezing 
point, and it is also said of them, as of Illetzkaya, (p. 1 86), that the hotter the 
summer the greater is the quantity of ice they contain. The grotto of La Baume 
near Besam^on presents, indeed, a close analogy to our Russian example, as it lies 
1 See Edinburgh Phil. Journ., vol. viii. p. 1, and Bibliotheque Universelle. 
2 D 
