Phineus, grateful for the relief afforded to him by the Argonauts, forewarned them of the dangers of their voyage and of the precautions necessary for their safety; and through his suggestions they were enabled to pass through the terrific rocks called Symplêgades. These were two rocks which alternately opened and shut, with a swift and violent collision, so that it was difficult even for a bird to fly through during the short interval. When the Argô arrived at the dangerous spot, Euphêmus let loose a dove. which flew through and just escaped with the loss of a few feathers of her tail. This was a signal to the Argonauts, according to the prediction of Phineus, that they might attempt the passage with confidence. Accordingly they rowed with all their might, and passed safely through: the closing rocks, held for a moment asunder by the powerful arms of Athênê just crushed the ornaments at the stern of their vessel. It had been decreed by the gods, that so soon as any ship once got through, the passage should forever afterwards be safe and easy to all. The rocks became fixed in their separate places, and never again closed.[558] [558] Apollodôr. i. 9, 22. Apollôn. Rhod. ii. 310-615. After again halting on the coast of the Mariandynians, where their steersman Tiphys died, as well as in the country of the Amazons, and after picking up the sons of Phryxus, who had been cast away by Poseidôn in their attempt to return from Kolchis to Greece, they arrived in safety at the river Phasis and the residence of Æêtês. In passing by Mount Caucasus, they saw the eagle which gnawed the liver of Prometheus nailed to the rock, and heard the groans of the sufferer himself. The sons of Phryxus were cordially welcomed by their mother Chalciopê.[559] Application was made to Æêtês, that he would grant to the Argonauts, heroes of divine parentage and sent forth by the mandate of the gods, possession of the golden fleece: their aid in return was proffered to him against any or all of his enemies. But the king was wroth, and peremptorily refused, except upon conditions which seemed impracticable.[560] Hêphæstos had given him two ferocious and untamable bulls, with brazen feet, which breathed fire from their nostrils: Jasôn was invited, as a proof both of his illustrious descent and of the sanction of the gods to his voyage, to harness these animals to the yoke, so as to plough a large field and sow it with dragon’s teeth.[561] Perilous as the condition was, each one of the heroes volunteered to make the attempt. Idmôn especially encouraged Jasôn to undertake it,[562] and the goddesses Hêrê and Aphroditê made straight the way for him.[563] Mêdea, the daughter of Æêtês and Eidyia, having seen the youthful hero in his interview with her father, had conceived towards him a passion which disposed her to employ every means for his salvation and success. She had received from Hekatê preëminent magical powers, and she prepared for Jasôn the powerful Prometheian unguent,