Passage 8.29.3
δράκοντας δὲ ἀντὶ ποδῶν τοῖς γίγασιν εἶναι, πολλαχῇ τε ὁ λόγος ἄλλῃ καὶ ἐν τῷδε ἐδείχθη μάλιστα ὡς ἔστιν εὐήθης. Ὀρόντην τὸν Σύρων ποταμὸν οὐ τὰ πάντα ἐν ἰσοπέδῳ μέχρι θαλάσσης ῥέοντα, ἀλλὰ ἐπὶ κρημνόν τε ἀπορρῶγα καὶ ἐς κάταντες ἀπʼ αὐτοῦ φερόμενον, ἠθέλησεν ὁ Ῥωμαίων βασιλεὺς ἀναπλεῖσθαι ναυσὶν ἐκ θαλάσσης ἐς Ἀντιόχειαν πόλιν· ἔλυτρον οὖν σὺν πόνῳ τε καὶ δαπάνῃ χρημάτων ὀρυξάμενος ἐπιτήδειον ἐς τὸν ἀνάπλουν, ἐξέτρεψεν ἐς τοῦτο τὸν ποταμόν.
That giants had serpents instead of feet has seemed, here as in many other places, an exceedingly foolish story. When the Roman emperor desired to sail upriver by ship from the sea to the city of Antioch upon the Orontes, the river of Syria, since the river did not flow at an even level all the way to the sea but rather descended abruptly from a steep cliff, he undertook with great effort and expense of money to construct a suitable artificial channel for sailing upstream, and diverted the river into this canal.