See'st thou what sentinel Sits in the porch?
What presence guards the gate?
Know, that within, still fiercer and more fell, Wide-yawning with her fifty throats, doth dwell A Hydra.

Tartarus itself, hard by, Abrupt and sheer, beneath the ghosts in Hell, Gapes twice as deep, as o'er the earth on high Towers up the Olympian steep, the summit of the sky.
LXXVII.

"There roll the Titans, born of ancient Earth, Hurled to the bottom by the lightning's blast.
There lie--twin monsters of enormous girth-- Aloeus' sons, who 'gainst Olympus cast Their impious hands, and strove with daring vast To disenthrone the Thunderer.

There, again, The famed Salmoneus I beheld, laid fast In cruel agonies of endless pain, Who sought the flames of Jove with mimic art to feign, LXXVIII.

"And mocked Olympian thunder.