e ocean; while east of the same, in Persia, Kerman, Seistan, Chinese
Tartary, and Mongolia, the desert consists of a series of plateaux, having
from 3,000 to nearly 10,000 feet of elevation. The green and fertile region
which is thus interposed between the 'highland' and 'lowland' deserts,[3]
participates, curiously enough, in both characters. Where the belt of sand
is intersected by the valley of the Nile, no marked change of elevation
occurs; and the continuous low desert is merely interrupted by a few miles
of green and cultivable surface, the whole of which is just as smooth and
as flat as the waste on either side of it. But it is otherwise at the more
eastern interruption. Then the verdant and productive country divides
itself into two tracts, running parallel to each other, of which the
western presents features, not unlike those that characterize the Nile
valley, but on a far larger scale; while the eastern is a lofty mountain
region, consisting for the most part of five or six parallel ranges, and
mounting in many places far above the level of perpetual snow.

"It is with the western or plain tract that we are here concerned. Between
the outer limits of the Syro-Arabian desert and the foot of the great
mountain range of Kurdistan and Luristan intervenes a territory long famous
in the world's history, and the chief site of three out of the five empires
of whose history, geography, and antiquities, it is proposed to treat in
the present volumes. Known to the Jews as Aram-Naharaim, or 'Syria of the
two rivers'; to the Greeks and Romans as Mesopotamia, or 'the between-river
country'; to the Arabs as Al-Jezireh, or 'the island,' this district has
always taken its name from the streams which constitute its most striking
feature, and to which, in fact, it owes its existence. If it were not for
the two great rivers--the Tigris and Euphrates--with their tributaries, the
more northern part of the Mesopotamian lowland would in no respect differ
from the Syro-Arabian desert on which it adjoins, and which, in latitude,
elevation, and general geological character, it exactly resembles. Towards
the south the importance of the rivers is still greater; for of Lower
Mesopotamia it may be said, with more truth than of Egypt,[4] that it is
'an acquired land,' the actual 'gift' of the two streams which wash it on
either side; being as it is, entirely a recent formation--a deposit which
the streams have made in the shallow waters of a g