There is, on carefully drawn maps of Mesopotamia, a pale undulating line (considerably to the north of the city of Accad or Agade), which cuts across the valley of the two rivers, from Is or Hit on the Euphrates,- the place famous for its inexhaustible bitumen pits,- to Samarah on the Tigris. This line marks the beginning of the alluvium, i.e. of the rich, moist alluvial land formed by the rivers, and at the same time the natural boundary of Northern Babylonia. Beyond it the land, though still a plain, is not only higher, rising till it meets the transversal limestone ridge of the Sin jar Hills, but of an entirely different character and formation. It is distressingly dry and bare, scarcely differing in this respect from the contiguous Syrian Desert, and nothing but the most laborious irrigation could ever have made it productive, except in the immediate vicinity of the rivers. What the country has become through centuries of neglect and misrule, we have seen. It must have been much in the same condition before a highly developed civilization reclaimed it from its natural barrenness and covered it with towns and farms. It is probable that for many centuries a vast tract of land south of the alluvium line, as well as all that lay north of it, was virtually unoccupied; the resort of nameless and unclassed nomadic tribes, for Agade is the most northern of important Accadian cities we hear of.