Passage 7.23.3
ἐς λήθην ἄγει τὸν ποταμὸν Ἀργυρᾶς. ἤκουσα δὲ καὶ ἄλλον ἐπʼ αὐτῷ λόγον, τὸ ὕδωρ τοῦ Σελέμνου σύμφορον καὶ ἀνδράσιν εἶναι καὶ γυναιξὶν ἐς ἔρωτος ἴαμα, λουομένοις ἐν τῷ ποταμῷ λήθην ἔρωτος γίνεσθαι. εἰ δὲ μέτεστιν ἀληθείας τῷ λόγῳ, τιμιώτερον χρημάτων πολλῶν ἐστιν ἀνθρώποις τὸ ὕδωρ τοῦ Σελέμνου.
The Argyra river leads into forgetfulness. I have also heard another story concerning this river, that the water of the Selemnos is beneficial both for men and for women as a remedy for love, and that those who bathe in the river experience forgetfulness of passion. If there is any truth to this story, the water of the Selemnos would be more precious to humankind than much wealth.