XVII/4 Dante's powers of physical visualisation (in which he parallels his friend Giotto in his new bodying forth of the world's reality) are unprecedented in literature and one of his greatest achievements is the predictive description of flight which ends this Canto, complete with a conversation between Virgil and Dante that could be that between pilot and novice on a training plane. Flight and 'a flight of stairs' are joined as in a pun to recall Virgil's comment, `It's stairs like these we'll have to travel by. . .' This particular staircase is taken from a diagram in J. V. de Vries' La Perspective' of 1639 (via the TLS via the HRC, Austin, Texas), and also recalls the windingly vertiginous descent that Dante experiences on the back of Geryon. The flight of the little green plane (a rubber stamp from an educational set bought in Sao Paolo) follows the curve of the banister. The stem of the staircase has become the falling river of blood. Perhaps Dante's description here would qualify as an early example of Science Fiction, which would make the technical nature of the illustration that much more relevant. -- Source of annotation: Marvin or Ruth Sackner.