It is navigable from Diabekr in the north, for its entire length.

Large rafts may be floated down from Mosul to Baghdad and Basra, and even small steamers have ascended as far north as Nimrud.

The Tigris, then, in contrast to the Euphrates, is the avenue of commerce for Mesopotamia, forming the connecting bond between it and the rest of the ancient world,--Egypt, India, and the lands of the Mediterranean.

Owing, however, to the imperfect character of the means of transportation in ancient and, for that matter, in modern times, the voyage up the stream was impracticable.

The rafts, resting on inflated bags of goat or sheep skin, can make no headway against the rapid stream, and so, upon reaching Baghdad or Basra, they are broken up, and the bags sent back by the shore route to the north.
The contrast presented by the two rivers is paralleled by the traits distinguishing Upper from Lower Mesopotamia.