Note 634 — CANTO XXIV.

But Malebolge, etc.: Each Bolgia in turn lies at a lower level than the one before it, and consequently the inner side of each dividing ridge or wall is higher than the outer; or, to put it otherwise, in each Bolgia the wall they come to last—that nearest the centre of the Inferno, is lower than that they first reach—the one enclosing the Bolgia.