At the present time, the water-parting which
separates the northern part of the basin of the Caspian from the
vast plains traversed by the Tobol and the Obi, in their course
to the Arctic Ocean, appears to be less than 200 feet above the
latter. It would seem, therefore, to be very probable that,
under the climatal conditions of part of the pleistocene period,
the valley of the Obi played the same part in relation to the
Ponto-Aralian sea, as that of the Kishon may have done to the
great mere of the Jordan valley; and that the outflow formed the
channel by which the well-known Arctic elements of the fauna of
the Caspian entered it. For the fossil remains imbedded in the
strata continuously deposited in the Aralo-Caspian area, since
the latter end of the miocene epoch, show no sign that, from
that time onward, it has ever been covered by sea water.
Therefore, the supposition of a free inflow of the Arctic Ocean,
which at one time was generally received, as well as that of
various hypothetical deluges from that quarter, must be
seriously questioned.
The Caspian and the Aral stand in somewhat the same relation to
the vast basin of dry land in which they lie, as the Dead Sea
and the lake of Galilee to the Jordan valley. They are the
remains of a vast, mostly brackish, mere, which has dried up in
consequence of the excess of evaporation over supply, since the
cold and damp climate of the pleistocene epoch gave place to the
increasing dryness and great summer heats of Central Asia in
more modern times.
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