When, in devotional pictures, St. Peter is accompanied by another apostle with no distinctive attributes, we may suppose it to be St. Mark, who was his interpreter, companion, and amanuensis at Rome. According to an early tradition, the Gospel of St. Mark was written down from the dictation of St. Peter.[166] In a miniature frontispiece to St. Mark’s Gospel, the evangelist is seated writing, and St. Peter stands opposite, as if dictating. In a picture by Angelico,[167] Peter is preaching from a pulpit to a crowd of people: Mark, seated on one side, is diligently taking down his words. In a very fine picture by Bonvicino[168] they stand together; St. Peter is reading from a book; St. Mark holds a scroll and inkhorn; he is submitting to St. Peter the Gospel he has just penned, and which was afterwards confirmed by the apostle. Lastly, a magnificent Venetian picture[169] represents St. Peter throned as bishop, with an earnest and rather stern countenance; he holds a book in his hand; two angels with musical instruments are seated on the steps of his throne: on his right hand stand John the Baptist, and St. Jerome as cardinal; on his left St. Ambrose; while St. Mark bends over a book, as if reading to this majestic auditory. * * * * * Those scenes and incidents related in the Gospels in which St. Peter is a principal or conspicuous figure, I shall enlarge upon when treating of the life of Christ, and will only indicate a few of them here, as illustrating the manner in which St. Peter is introduced and treated in such subjects. We have, first, the Calling of Peter and Andrew in a picture by Basaiti,[170] where the two brothers are kneeling at the feet of the Saviour; the fishing-boats and the Lake of Gennesareth in the background: and in the beautiful fresco by Ghirlandajo in the Sistine Chapel, where a number of contemporary personages are introduced as spectators. St. Andrew presenting St. Peter to our Saviour (as in a picture by Cavalucci, in the Vatican), is another version of the same subject; or St. Andrew is seen at the feet of Christ, while St. Peter is sitting on the edge of the boat, or descending from it in haste. ‘Christ walking on the Sea’ is a familiar and picturesque subject, not to be mistaken. The most ancient and most celebrated representation is Giotto’s mosaic (A.D. 1298), now placed in the portico of St. Peter’s, over the arch opposite to the principal door. The sentiment in the composition of this subject is, generally, ‘Lord, help me; or I perish:’ St. Peter is sinking, and Christ is stretching out his hand to save him. It is considered as a type of the Church in danger, assailed by enemies, and saved by the miraculous interposition of the Redeemer; and in this sense must the frequent representations in churches be understood.