Passage 5.7.3
ταῦτα μὲν λόγου τοῦ ἐς Ἀλφειὸν †ἐς τὴν Ὀρτυγίαν †· τὸ δὲ διὰ τῆς θαλάσσης ἰόντα ἐνταῦθα ἀνακοινοῦσθαι τὸ ὕδωρ πρὸς τὴν πηγὴν οὐκ ἔστιν ὅπως ἀπιστήσω, τὸν θεὸν ἐπιστάμενος τὸν ἐν Δελφοῖς ὁμολογοῦντά σφισιν, ὃς Ἀρχίαν τὸν Κορίνθιον ἐς τὸν Συρακουσῶν ἀποστέλλων οἰκισμὸν καὶ τάδε εἶπε τὰ ἔπη· Ὀρτυγίη τις κεῖται ἐν ἠεροειδέι πόντῳ, Θρινακίης καθύπερθεν, ἵνʼ Ἀλφειοῦ στόμα βλύζει. μισγόμενον πηγαῖσιν ἐυρρείτης Ἀρεθούσης. κατὰ τοῦτο οὖν, ὅτι τῇ Ἀρεθούσῃ τοῦ Ἀλφειοῦ τὸ ὕδωρ μίσγεται, καὶ τοῦ ἔρωτος τὴν φήμην τῷ ποταμῷ πείθομαι γενέσθαι.
So much for the story regarding Alpheios and Ortygia. However, that the river passing through the sea arrives there and mixes its water with the spring, this I find impossible to disbelieve, knowing that the god at Delphi himself confirmed such a thing. For it was he who, when sending Archias the Corinthian to found the settlement at Syracuse, delivered these verses: "An isle called Ortygia lies on the misty sea, above Thrinacia, where the mouth of Alpheios gushes forth, mingling with the streams of wide-flowing Arethousa." Thus, because the waters of Alpheios indeed mingle with Arethousa, I accept also the tradition of the river's love.