Vesuvius groans through all his echoing caves,
And Etna thunders o'er the insurgent waves."
When these were performed, he became deeply enamoured of Iole, daughter of Eurystheus, but she, being refused to his entreaties, he became insane a second time, and murdered Iphitus, the only one of the sisters of Iole who was willing to assist him in obtaining her.
After some time had passed, he was purified from this murder, and his insanity was at an end. However, the gods were not satisfied, but persecuted him still further, for he was smitten with an indisposition which compelled him once more to consult the oracle of Delphi.
Not being pleased with the manner in which his application was received, he resolved, in the heat of passion, to desecrate the sacred temple by plundering it, and carrying away the holy tripod. Apollo opposed him, and a fierce conflict ensued, to put an end to which, however, Jupiter interfered with his Thunderbolts.
Indignant at the insult offered to the sacred edifice, the oracle declared that it could only be wiped away by the hero becoming a slave, and remaining in the most abject servitude for three years.
In compliance with the decree, Mercury, by the order of Jupiter, sold him to Omphale, Queen of Lydia, as a slave. But his services to this queen so astonished her, that she freed him from his servitude and married him. When the term for which he had been sold expired, Hercules left her, and returned to Peloponnessus, where he re-established Tyndaris on the throne of Sparta.
After this, he became one of the numerous suitors of Dejanira, who had been promised by her father in marriage to that one who should prove the strongest of all his competitors. The most dangerous foe to Hercules was Achelous, a river god, who, finding himself inferior in strength, changed himself into a serpent, and afterwards into an ox. Serpent strangling was, however, nothing new to Hercules, and he had but little trouble with his enemy as an ox, until at last Achelous retired in disgrace to his bed of waters.