He gnashed his teeth; and thrice he compassed round
With winged speed the circuit of the ground.
Thrice at the cavern's mouth he pulled in vain,
And, panting, thrice desisted from his pain.
A pointed flinty rock, all bare and black,
Grew gibbous from behind the mountain's back;
Owls, ravens, all ill omens of the night,
Here built their nests, and hither winged their flight.
The leaning head hung threatening o'er the flood,
And nodded to the left. The hero stood