There existed up to the reign of Louis XVI. an elegant little sacristy upon the north-east side, having two storeys, in which were deposited deeds, charters, and gold and silver vessels for the use of the altar. In it was kept the splendid agate, now in the Bibliothèque Nationale, representing the Apotheosis of Augustus, which was absolutely presented to the people as a _pax_ upon great festivals, until de Peiresc, Councillor of the Parlement of Provence, about 1619, discovered the mistake, and the so-called "Triumph of Joseph" became acknowledged to be the "Apotheosis of Augustus." A careful drawing of the cameo was made by de Peiresc's friend Rubens, which was engraved by Luc Vosterman of Antwerpen. It was called in the inventory of the chapel _le Grand Camahieu_ and the _Agate de Tibère_; it is, indeed, the largest known, and is of most exquisite workmanship. The whole family of the Cæsars is represented; some on earth, some in Heaven. The cracks in it are mentioned in the inventory of 1480, and it is described as: _Item unum pulcherrimum camaut in cujus circuitu sunt plures reliquiæ._ The cameo is supposed to have been one of the treasures brought by S. Louis from Constantinople. In 1343, Philippe VI. sent it to the Pope who had desired to see it, but Charles V. restored it to the chapel in 1379, and then the chapter made their possession certain, by engraving upon the socle: _ce camaieu bailla à la Sainte-Chapelle du Palais, Charles cinquième de ce nom, roi de France, qui fut fils du roi Jean, l'an MCCCLXXIX_. The Byzantine mounting, described by Tristan de Saint-Amant, was melted up when the cameo was stolen, in 1804: _Car les quatres évangélistes sont représentés de part et d'autre du châssis ou tableau d'or, dans lequel cette pierre est enchâssée._ [Illustration] Another antique, an agate bust of Valentinian III.,[6] was metamorphosed into a S. Louis, and formed the crowning point of the precentor's mace. The clothing of this bust in silver-gilt drapery, the placing of a crown of thorns in the right-hand and a cross in the left, show the manner in which objects of Pagan art were adapted to Christian uses. That S. Louis should appear as a fat middle-aged man with a clean shaven face and cropped hair, was an anomaly of no consequence to the Mediæval artists. Another instance of the same _naïveté_ is the bust of Caracalla which formerly figured as a S. Peter upon the cover of a book of the Gospels, now in the department of manuscripts. The cover is of silver-gilt, Christ crucified with the Virgin and S. John upon either side, the amethyst bust being placed at the foot of the cross. Upon the other side is Christ enthroned, and an imitation emerald which no doubt represents some precious gem that has since disappeared. [Illustration: THE CHAPEL IN THE SIXTEENTH CENTURY.]