In proceeding, as already proposed, to speak of the navigation of the Assyrians, it must be at once premised that it is not as mariners, but only as fresh-water sailors, that they come within the category of navigators at all.  Originally an inland people, they had no power, in the earlier ages of their history, to engage in any but the secondary and inferior kind of navigation; and it would seem that, by the time when they succeeded in opening to themselves through their conquests a way to the Mediterranean and the Indian Ocean, their habits had become so fixed in this respect that they no longer admitted of change.  There is satisfactory evidence which shows that they left the navigation of the two seas at the two extremities of their empire to the subject nations—­the Phoenicians and the Babylonians contenting themselves with the profits without sharing the dangers of marine voyages, while their own attention was concentrated upon their two great rivers—­the Tigris and the Euphrates, which formed the natural line of communication between the seas in question.

The navigation of these streams was important to the Assyrians in two ways.  In the first place it was a military necessity that they should be able, readily and without delay, to effect the passage of both of them, and also of their tributaries, which were frequently too deep to be forded.  Now from very early times it was probably found tolerably easy to pass an army over a great river by swimming, more especially with the aid of inflated skins, which would be soon employed for the purpose.  But the materiel of the army—­the provisions, the chariots, and the siege machines—­was not so readily transported, and indeed could only be conveyed across deep rivers by means of bridges, rafts, or boats.  On the great streams of the Tigris and Euphrates, with their enormous spring floods, no bridge, in the ordinary sense of the word, is possible.  Bridges of boats are still the only ones that exist on either river below the point at which they issue from the gorges of the mountains.  And these would be comparatively late inventions, long subsequent to the employment of single ferry boats.  Probably the earliest contrivance for transporting the chariots, the stores, and the engines across a river was a raft, composed hastily of the trees and bushes growing in the neighborhood of the stream, and rendered capable of sustaining a considerable weight by the attachment to it of a number of inflated skins.  A representation of such a raft, taken from a slab of Sennacherib, has been already given.  Rafts of this kind are still largely employed in the navigation of the Mesopotamian streams, and, being extremely simple in their construction, may reasonably be supposed to have been employed by the Assyrians from the very foundation of their empire.