The baptistery erected by Pope Damasus after the discovery of the springs of the Aqua Damasiana, and restored by Leo III. (795-816), stood at the end of the north transept.[84] One of its inscriptions contained the verse-- "Una Petri sedes unum verumque lavacrum,"-- an allusion both to the baptismal font and to the "chair of S. Peter's," upon which the Popes sat after baptizing the neophytes. The cathedra is mentioned by Optatus Milevitanus, Ennodius of Pavia, and by more recent authors, as having changed place many times, until Alexander VII., with the help of Bernini and Paul Schor, placed it in a case of gilt bronze at the end of the apse. It has been minutely examined and described several times by Torrigio, Febeo, and de Rossi. I saw it in 1867. The framework and a few panels of the relic may possibly date from apostolic times; but it was evidently largely restored after the peace of the Church. The upright supports at the four corners were whittled away by early pilgrims. [Illustration: The Chair of S. Peter; after photograph from original--_A_ Oak wood, much decayed, and whittled by pilgrims. _B_ Acacia wood, inlaid with ivory carvings.] Another work of art deserves attention, because its origin, age, and style are still matters of controversy. I mean the bronze statue of S. Peter (see p. 142) placed against the right wall of the nave, near the S. Andrew of Francis de Quesnoy. Without attempting a discussion which would be inconsistent with the spirit of this book, I can safely state that the theories suggested by modern Petrographists, from Torrigio to Bartolini, deserve no credit. The statue is not the Capitoline Jupiter transformed into an apostle; nor was it cast with the bronze of that figure; it never held the thunderbolt in the place of the keys of heaven. The statue was cast as a portrait of S. Peter; the head belongs to the body; the keys and the uplifted fingers of the right hand are essential and genuine details of the original composition. The difficulty, and it is a great one, consists in stating its age. There is no doubt that Christian sculptors modelled excellent portrait-statues in the second and third centuries: as is proved by that of Hippolytus (see p. 143), discovered in 1551 in the Via Tiburtina, and now in the Lateran Museum, a work of the time of Alexander Severus.