Ἀλεξάνδρου ἀνάβασις 5.7.3

5.7.3

καίτοι ταχυτάτη γε ὧν ἐγὼ οἶδα Ῥωμαίοις ἡ γεφύρωσις ἡ διὰ τῶν νεῶν γίγνεται, καὶ ταύτην ἐγὼ ἀφηγήσομαι ἐν τῷ παρόντι, ὅτι λόγου ἀξία. αἱ νῆες αὐτοῖς κατὰ πόρου ἀφίενται ἀπὸ ξυνθήματος, οὐκ ἐπʼ εὐθύ, ἀλλὰ καθάπερ αἱ πρύμναν κρουόμεναι. ταύτας ὑποφέρει μέν, οἷα εἰκός, ὁ ῥοῦς, ἀνέχει δὲ κελήτιον ἐπῆρες, ἔστʼ ἂν καταστήσῃ ἐς τὸ τεταγμένον χωρίον· καὶ ἐνταῦθα ἤδη καθίεται πλέγματα ἐκ λύγου πυραμοειδῆ πλήρη λίθων λογάδων ἀπὸ πρώρας ἑκάστης νεώς, τοῦ ἀνέχειν τὴν ναῦν πρὸς τὸν ῥοῦν.

In what manner Alexander made his bridge over the Indus neither Aristoboulos nor Ptolemy, the authorities whom I chiefly follow, have given any account; nor can I decide for certain whether the passage was bridged with boats, as was the Hellespont by Xerxes and as were the Bosporos and the Istros by Darius, or whether the bridge he made over the river was one continuous piece of work. I incline, however, to think that the bridge must have been made of boats, for neither would the depth of the river have admitted the construction of an ordinary kind of bridge, nor could a work so vast and difficult have been executed in so short a time. But if the passage was bridged with boats I cannot decide whether the vessels being fastened together with cables and anchored in a row sufficed to form a bridge as did those by which, as Herodotos the Halikarnassian says, the Hellespont was joined, or whether the method was that which is used by the Romans in bridging the Istros and the Keltic Rhine, and by which they bridged the Euphrates and the Tigris as often as necessity required. Since, however, the Romans, as far as my knowledge goes, have found that the bridging of rivers by boats is the most expeditious method of crossing them, I think it worth a description here. The vessels at a preconcerted signal are let go from their moorings and rowed down stream not prow but stern foremost. The current of course carries them downward, but a small pinnace furnished with oars holds them back till they settle into their appointed place. Then baskets of wicker work, pyramid-shaped and filled with rough stones, are lowered into the river from the prow of each vessel to make it hold fast against the force of the current. As soon as one of those vessels has been held fast another is in the same way anchored with its prow against the stream as far from the first as is commensurate with their bearing the strain of what is put upon them. On both of them beams of wood are rapidly laid lengthwise, and on these again planks are placed crosswise to bind them together. In this manner the work proceeds through all the vessels which are required for bridging the passage. At each end of the structure firmly fixed railed gangways are thrown forward to the shore so that horses and beasts of burden may with the greater safety enter upon it. These gangways serve at the same time to bind the bridge to the shore. In a short time the whole is completed amid great noise and bustle, though discipline is by no means lost sight of as the work proceeds. In each vessel the occasional exhortations of the overseers and their rebukes of negligence neither prevent orders from being heard nor the work from being quickly executed.