One of the very curious cases of the employment of a purely secular Roman gem for ecclesiastical uses is offered by the exceedingly beautiful convex blue aquamarine engraved with the head of Julia, daughter of Titus, a fine work of the Augustan Age, now in the French Cabinet des Médailles in Paris. This was donated in the ninth century by the Carolingian emperor, Charles the Bald, to the Treasury of St. Denis, after it had been given a setting of pearls and precious stones. In St. Denis it was placed at the apex of a reliquary, which became known as the Oratorium of Charlemagne, and the head of the vain and worldly princess is said to have been venerated by the pious monks and priests as that of the Virgin Mary. As a work of portrait art this gem is one of the finest examples from classic times.[522] The strange decadence and the conventionalized but profoundly earnest quality of Early Christian art is shown in an intaglio gem of the Royal Numismatic Museum in Munich. This is a dark-hued sardonyx of two layers, and the engraving depicts a bearded Christ, enthroned and accompanied by the twelve apostles, six on either side, four of them beardless while the remainder are represented with beards; they are all gazing reverently upon the central figure, behind whose head appear the arms of the cross and above them the letters _I̅C̅_ _X̅C̅_ Ἰησοῦς Χριστός.[523] Another somewhat similar Early Christian gem is a cameo cut in a sardonyx of three layers, the groundwork being a brownish-black, and the figures of a light-bluish hue, the upper parts yellowish-brown. Here also we have an enshrined Christ; above his head two angels hold a diadem. This is of superior workmanship to the intaglio gem just described.[524] There is a sardonyx cameo showing a rude figure of the Prophet Daniel, a lion on either side of him, and inscribed with his name in Greek letters. This is of Byzantine workmanship.[525]