The imprisonment of Peter, and his deliverance by the Angel, were incidents so important, and offer such obvious points of dramatic effect, that they have been treated in every possible variety of style and sentiment, from the simple formality of the early mosaics, where the two figures—Peter sitting on a stool, leaning his head on his hand, and the Angel at his side—express the story like a vision,[184] down to the scenic and architectural compositions of Steenwick, where, amid a vast perspective of gloomy vaults and pillars, a diminutive St. Peter, with an Angel or a sentinel placed somewhere in the foreground, just serves to give the picture a name.[185] Some examples of this subject are of great celebrity. Masaccio, in the frescoes of the Brancacci Chapel, has represented Peter in prison, looking through his grated window, and Paul outside communing with him. (The noble figure of St. Paul in this fresco was imitated by Raphael in the ‘St. Paul preaching at Athens.’) In the next compartment of the series, Masaccio has given us the Angel leading forth Peter, while the guard sleeps at the door: he sleeps as one oppressed with an unnatural sleep. Raphael’s fresco in the Vatican is not one of his best, but he has seized on the obvious point of effect, both as to light and grouping; and we have three separate moments of the same incident, which yet combine most happily into one grand scene. Thus in the centre, over the window, we see through a grating the interior of the prison, where St. Peter is sleeping between two guards, who, leaning on their weapons, are sunk in a deep charmed slumber;[186] an angel, whose celestial radiance fills the dungeon with a flood of light, is in the act of waking the apostle: on the right of the spectator, the angel leads the apostle out of the prison; two guards are sleeping on the steps: on the left, the soldiers are roused from sleep, and one with a lighted torch appears to be giving the alarm; the crescent moon faintly illumines the background. The deliverance of St. Peter has always been considered as figurative of the deliverance of the Church; and the two other frescoes of this room, the Heliodorus and the Attila, bear the same interpretation. It is worth while to compare this dramatic composition of Raphael with others wherein the story is merely a vehicle for artificial effects of light, as in a picture by Gerard Honthorst; or treated like a supernatural vision, as by that poet, Rembrandt. Those historical subjects in which St. Peter and St. Paul figure together will be noticed in the life of St. Paul. I come now to the legendary stories connected with St. Peter; an inexhaustible source of popular and pictorial interest.