ns with Dante down a declivity, where the stones, unaccustomed to
the weight of mortal feet, slip and roll in ominous fashion. This
passage, Virgil declares, was less dangerous when he last descended
into Hades, for it has since been riven by the earthquake which shook
this region when Christ descended into hell.

Pointing to a boiling river of blood (Phlegethon) beneath them, Virgil
shows Dante sinners immersed in it at different depths, because while
on earth they offered violence to their neighbors. Although anxious to
escape from these bloody waters, the wicked are kept within their
appointed bounds by troops of centaurs, who, armed with bows and
arrows, continually patrol the banks. When these guards threateningly
challenge Virgil, he calmly rejoins he wishes to see their leader,
Chiron, and, while awaiting the arrival of this worthy, shows Dante
the monster who tried to kidnap Hercules' wife.

On drawing near them, Chiron is amazed to perceive one of the
intruders is alive, as is proved by the fact that he casts a shadow
and that stones roll beneath his tread! Noticing his amazement, Virgil
explains he has been sent here to guide his mortal companion through
the Inferno, and beseeches Chiron to detail a centaur to carry Dante
across the river of blood, since he cannot, spirit-like, tread air.
Selecting Nessus for this duty, Chiron bids him convey the poet safely
across the bloody stream, and, while performing this office, the
centaur explains that the victims more or less deeply immersed in
blood are tyrants who delighted in bloodshed, such as Alexander,
Dionysius, and others. Borne by Nessus and escorted by Virgil, Dante
reaches the other shore, and, taking leave of them, the centaur "alone
repass'd the ford."

_Canto XIII._ The travellers now enter a wild forest, which occupies
the second division of the seventh circle, where Virgil declares each
barren thorn-tree is inhabited by the soul of a suicide. In the gnarly
branches perch the Harpies, whose uncouth lamentations echo through
the air, and who greedily devour every leaf that sprouts. Appalled by
the sighs and wailings around him, Dante questions Virgil, who directs
him to break off a twig. No sooner has he done so than he sees blood
trickle from the break and hears a voice reproach him for his cruelty.
Thus Dante learns that the inmate of this tree was once private
secretary to Frederick II, and that, having fallen into unmerited
disgrace, he basely too