have taken place.

The evidence of the general stability of the physical conditions
of Western Asia, which is furnished by Palestine and by the
Euphrates Valley, is only fortified if we extend our view
northwards to the Black Sea and the Caspian. The Caspian is a
sort of magnified replica of the Dead Sea. The bottom of the
deepest part of this vast inland mere is about 3000 feet below
the level of the Mediterranean, while its surface is lower by 85
feet. At present, it is separated, on the west, by wide spaces
of dry land from the Black Sea, which has the same height as the
Mediterranean; and, on the east, from the Aral, 138 feet above
that level. The waters of the Black Sea, now in communication
with the Mediterranean by the Dardanelles and the Bosphorus, are
salt, but become brackish northwards, where the rivers of the
steppes pour in a great volume of fresh water. Those of the
shallower northern half of the Caspian are similarly affected by
the Volga and the Ural, while, in the shallow bays of the
southern division, they become extremely saline in consequence
of the intense evaporation. The Aral Sea, though supplied by the
Jaxartes and the Oxus, has brackish water. There is evidence
that, in the pliocene and pleistocene periods, to go no farther
back, the strait of the Dardanelles did not exist, and that the
vast area, from the valley of the Danube to that of the
Jaxartes, was covered by brackish or, in some parts, fresh water
to a height of at least 200 feet above the level of the
Mediterranean. 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