On our right is the Chapel of the Choir, decorated by Giacomo della Porta. The mosaic altar-piece of the Conception is after Pietro Bianchi. Over the door, in the pier on the left of the chapel, is a niche closed with a wooden sarcophagus; here the body of the Pope is placed till his tomb is prepared. Opposite is the bronze memorial to Innocent VIII. by the brothers Pollaiolo. The spear-head held in the hand of the Pope refers to the spear which pierced our Saviour's side, it being presented to this Pope by the Emperor Bajazet II. On our right is a fine mosaic by Romanelli, the Presentation of the Virgin in the Temple. Beyond, on the left, is Canova's memorial to the "last of the Stuarts," who died in Rome, and are buried in the crypt below. It takes the form of an entrance to a tomb, which is guarded by beautiful genii. Over the door are the words--"BLESSED ARE THE DEAD THAT DIE IN THE LORD." Above are medallions of the Chevalier S. George, Prince Charlie, and the Cardinal York, the whole being surmounted by the British coat-of-arms, in which is quartered that of France. This monument was erected by George IV. Opposite, over the door leading to the dome, is the monument to Maria Clementina, wife of the Chevalier S. George, whose portrait in mosaic is by Barigioni. Beyond is the baptistery. The font is of red porphyry, which was once the top of the tomb of Otho II., and originally, it is said, of Hadrian. In front is Carlo Maratta's Baptism of Christ in mosaic; upon the left Peter baptizing the jailers in the Mamertine prison, a fiction from Passeri; and opposite is Procaccini's Baptism of the Centurion. This baptistery is said to be on the site of a temple to Apollo, upon what authority we cannot say. The nave has marked in the centre of its pavement the measurement of all the principal churches in the world, whereby it can be seen that S. Peter's is 93 feet longer than S. Paul's, London. The large porphyry circular slab is that upon which the holy Roman emperors were crowned, and where the priest who is made judge of ecclesiastical matters in the Roman Church is ordained. In a niche in each of the piers supporting the vault are colossal statues, 16 feet high, of the founders of the various religious orders; and in the piers of the dome are S. Longinus, the soldier who pierced our Saviour's side, S. Helena, who found the cross, S. Veronica, who wiped his face, and S. Andrew. Above are kept the relics of these saints, which are only shown to those who hold the title of a canon of the church. On the spandrels of the arches of the dome are four large mosaics, representing Matthew, Mark, Luke, and John, with their emblems. S. Luke's pen is 7 feet long, and the letters on the frieze are 6 feet high.