ABSTRACT
T h e Tigris-Euphrates valley has far less unity than the valley o f the Nile. Its lower reaches, Babylonia proper, roughly from the level o f Baghdad to the Persian Gulf, are indeed economi
cally dependent on the rivers; only their waters, by natural inunda tion or canalized irrigation, make settled life possible in those latitudes. This economic unity had eventually to find its political expression as it did at last under Hammurabi. But further north the lowland plain is traversed by other streams-the Diyala and the two Zabs, flowing into the Tigris, the Khabur and the Balikh, tributaries o f the Euphrates-each an economically independent system. And here, too, in Assyria and Syria, the rivers traverse a zone still visited by winter rain-storms from the Atlantic sufficient to make cereal cultivation without irrigation possible if slightly precarious.
