The sun sets (Canto viii.) and the shades join in the Compline hymn. At its conclusion, two angels clad in green robes descend, and take up their position on either side of the little valley. Dante, with his companions, goes down to join the “mighty shades,” and is met by one whom he at once recognises as an old friend, the Pisan noble Giovanni, or Nino de’ Visconti, “judge” or governor of the Sardinian province called Gallura, nephew of Count Ugolino. After some talk Dante notices the three stars spoken of above, and at the same moment Sordello draws Virgil’s attention to an “adversary.” They see a serpent making its way through the grass; and immediately the angels start in pursuit, putting it to flight. After this episode another shade announces himself as Conrad Malaspina, of the house with whom Dante was to find shelter during a part of his exile. The night wears on, and Dante falls asleep (Canto ix.). He dreams that he is being carried by an eagle up to the empyrean heaven. On awaking he finds that the sun has risen some time, and learns from Virgil that at daybreak St. Lucy (who has already come under notice as taking an interest in his welfare) had appeared and borne him to the place where they now are, in front of the gate of Purgatory. This is approached by three steps of variously-coloured stone. The first is white marble, the second a dark and rough rock, the third blood-red porphyry, indicating probably the three stages of the soul’s progress to freedom through confession, contrition, and penance. On the topmost step sits an angel, who having marked seven P’s (_peccata_ sins) on Dante’s forehead, admits them within the gate. Thus far, except in the passage, Canto viii. 19 sqq., to which Dante himself draws the reader’s attention, the allegorical interpretation has not afforded any very great difficulty. With this particular passage readers will do well to compare _Inf._, ix. 37 sqq., where a very similar indication is given of an underlying allegory, and draw their own conclusions. But on the whole, the main interest of the first nine cantos of the _Purgatory_ is more of a personal nature. Sordello alone may give an excuse for a good deal of historical research. For example, no one has yet explained Dante’s reasons for so distinguishing a person who, from all the records that we have, does not seem to have made any great figure in the eyes of his contemporaries. It will hardly be necessary to follow Dante step by step through the stages of the mountain of purification. We shall probably do best to consider the general plan on which Purgatory is arranged, the nature of the various penances, with their adaptation to the offences which they expiate, and the light thrown in this division of the poem on Dante’s opinions about the elements of political and moral science.