With staff in hand across the cleft
The Challenger began his march;
And now, all eyes and feet, hath gain'd
The middle of the arch.
When list! he hears a piteous moan--
Again! his heart within him dies--
His pulse is stopp'd, his breath is lost,
He totters, pale as any ghost,
And, looking down, he spies
A Lamb, that in the pool is pent
Within that black and frightful rent.