said to have been erected by Constantine. Eight columns of porphyry support a cornice, upon which are eight smaller columns; these sustain the cupola. The font is of green basalt. A tradition says Constantine was baptized here, though Socrates says he received Christian baptism at Nicomedia just before his death. Gibbon says Rienzi bathed in the font on the night before he was made a knight. The two side chapels, dedicated respectively to John the Baptist and John the Evangelist, are said to have been made out of the house of Constantine. The mosaics are of the fifth century, after the arabesque paintings in the Baths of Titus. _Adjoining_ is the Oratory of S. Venantius, in which is a mosaic of the seventh century--our Saviour in the act of giving his blessing. Two grand porphyry columns, supporting an entablature, formed the portico of the baptistery, opposite side to where we entered. There is a mosaic vault of the sixteenth century in the left chapel of this portico, and in the opposite one a good S. Philip Neri by Guido. _On our left of the obelisk is_ THE LATERAN PALACE. From the time of Constantine to 1377 this was the palace of the popes. In 1843 Gregory XVI. founded the museum. The original palace was destroyed by fire in the time of Clement V., and the present pile was built from the designs of Fontana in the pontificate of Sixtus V. It was subsequently used for many years as an hospital. _On our left is the entrance to_ THE LATERAN MUSEUM. _Ring the bell on the right in the passage, if the custodian is not at the door. The custodian will conduct you over, if desired; and he can give a good account of the objects of interest. It is open every day from 9 till 3, and is comprised in sixteen rooms. Fee, half a franc each person. The principal objects are as follows_:-- FIRST ROOM.--Bas-reliefs: Procession of Lictors and Senators, with figure of Trajan, found in his forum; Dares and Entellus, boxers, a fragment, found near the Arch of Gallienus; part of a sarcophagus, with the history of Mars and Rhea Sylvia, Diana and Endymion; a Circus Race; Helen and Paris; Soldier and Wife Parting; Leucothea feeding the Infant Bacchus. Bust of Marcus Aurelius; pavement mosaic of Boxers, from Baths of Caracalla. SECOND ROOM.--Portions brought from the Forum of Trajan, representing arabesques, children, chimeras, griffins. FOURTH ROOM.--Faun of Praxiteles, copy; bust of the Young Tiberius; bas-reliefs, Medea and Pelias's Daughters; statue of Mars; Germanicus; sepulchral cippi and bas-reliefs, found on the Via Appia. FIFTH ROOM.--Stag in gray marble; a Cow; Mithraic group; mutilated figure of a lynx; bust of Scipio; an altar with bas-reliefs, one representing cock-fighting.