Canto XV. The high banks of the stream of tears protect our travellers from the burning sands and the rain of fire, until they encounter a procession of souls, each one of which stares fixedly at them.  One of these recognizes Dante, who in his turn is amazed to find there his old school-master Ser Brunetto, whom he accompanies on his way, after he learns he and his fellow-sufferers are not allowed to stop, under penalty of lying a hundred years without fanning themselves beneath the rain of fire.  Walking by his former pupil’s side, Brunetto in his turn questions Dante and learns how and why he has come down here, ere he predicts that in spite of persecutions the poet will ultimately attain great fame.

Canto XVI. Reaching a spot where the stream they are following suddenly thunders down into the eighth circle, Dante beholds three spirits running toward him, whirling round one another “in one restless wheel,” while loudly exclaiming his garb denotes he is their fellow countryman!  Gazing into their fire-scarred faces, Dante learns these are three powerful Guelfs; and when they crave tidings of their native city, he tells them all that has recently occurred there.  Before vanishing these spirits piteously implore him to speak of them to mortals on his return to earth, and leave Dante and Virgil to follow the stream to the verge of the abyss.  There Virgil loosens the rope knotted around Dante’s waist, and, casting one end of it down into the abyss, intimates that what he is awaiting will soon appear.  A moment later a monster rises from the depths, climbing hand over hand up the rope.

Canto XVII. This monster is Geryon, the personification of fraud, and therefore a mixture of man, beast, and serpent.  When he reaches the upper ledge, Virgil bargains with him to carry them down, while Dante converses with neighboring sorrowful souls, who are perched on the top of the cliff and hide their faces in their hands.  All these spirits wear purses around their necks, because as usurers while on earth they lived on ill-gotten gains.  Not daring to keep his guide waiting, Dante leaves these sinners, and hurries back just as Virgil is taking his seat on the monster’s back.  Grasping the hand stretched out to him, Dante then timorously mounts beside his guide.

    “As one, who hath an ague fit so near,
  His nails already are turn’d blue, and he
  Quivers all o’er, if he but eye the shade;
  Such was my cheer at hearing of his words. 
  But shame soon interposed her threat, who makes
  The servant bold in presence of his lord. 
    I settled me upon those shoulders huge,
  And would have said, but that the words to aid
  My purpose came not, ‘Look thou clasp me firm.’”