And we have seen a proof not only in the present times, but also more fully in antiquity, that the waters there are innavigable; for they say that Jason sailed into the Pontus by the 'Dark Rocks', while he sailed out of it by the Ister; and for this, besides alleging not a few other evidences, they point out altars set up by Jason in the country, and in one of the islands in the Adriatic a costly temple of Artemis erected by Medea.