The Georgics

Four chosen bulls of peerless form and bulk,
That browse to-day the green Lycaean heights

For seven whole months unceasingly, men say,
Beneath a skyey crag, by thy lone wave,
Strymon, he wept, and in the caverns chill
Unrolled his story, melting tigers' hearts,
And leading with his lay the oaks along

But when thou hast gripped him fast with hand and gyve,
Then divers forms and bestial semblances
Shall mock thy grasp; for sudden he will change
To bristly boar, fell tigress, dragon scaled,
And tawny-tufted lioness, or send forth
A crackling sound of fire, and so shake of
The fetters, or in showery drops anon
Dissolve and vanish. But the more he shifts
His endless transformations, thou, my son,
More straitlier clench the clinging bands, until
His body's shape return to that thou sawest,
When with closed eyelids first he sank to sleep."