ship of Zeus with mortals, of which Io was one of the first recipients. Hence the significance of her appearance in the "Prometheus Bound." She, like the Titan, resisted the divine will, and, like him, must suffer the penalty of her rebellion; accordingly the account of her sufferings, as, wailing and distraught, she pursues her toilsome wanderings, serves to heighten the impression of the cruel tyranny of Zeus, which it is the object of that drama to produce.
In "The Suppliants," however, Zeus appears in relation to Io, not as the obdurate tyrant, but as the beneficent deity, whose severest judgments issue in blessings to the individual and to mankind. Doubtless, under this aspect he would have been represented in the third member of the Promethean trilogy.
Herakles inquires from Prometheus his way to the gardens of the Hesperides; the Titan, in reply, describes his journey thither, and announces the dangers which he will have to encounter. Forthwith the eagle appears, winging its flight towards Prometheus: Herakles utters the exclamation, "Archer Apollo, surely guide mine arrow," draws his bow, and slays the pest.
In what manner the subsequent liberation of Prometheus was effected we have no means of determining; whether Herakles himself unloosed his chains, or whether this was accomplished through the intervention of Hermes, or some other divinity; whether Herakles prevailed upon Zeus to accept Cheiron as a substitute for Prometheus, and whether Cheiron voluntarily
