Ever since the re-discovery and exploration of the Catacombs in the sixteenth century they have been a vast treasury from which, as from an inexhaustible mine, have been derived innumerable relics of Christian antiquity, many of them of inestimable value. Among these are a number of gilt glasses of curious design and remarkable interest, lamps, vases, rings, seals, toys, trinkets, and various objects of domestic use or ornament. Collections of these relics are found in most of the great museums of Europe, especially in those of the city of Rome. An account of the more important of them will be given in the present chapter. Reference has already been made to the numerous fragments of gilt glass found in the Catacombs, which so remarkably illustrate Christian life in the primitive ages. In the last century, Buonarotti described all the specimens then known. The distinguished archæologist, Padre Garrucci, has recently exhaustively treated these remains of ancient art in his elaborate monograph on this subject.[614] They are also profusely illustrated in the magnificent pages of Perret.[615] These glasses are generally mutilated fragments, apparently the 363 bottoms of drinking-cups, and occasionally of the dish-like shape of the classic _patera_. They vary in size from about one to four or five inches in diameter. The design is executed in gold leaf on the bottom of the cup, so as to appear through the glass on the inside, and is occasionally beautifully relieved by a dark purple background. It is protected by a plate of glass, fused upon the lower surface so as to become a solid mass, like the glass paper-weights with enclosed ornamental designs which are so common. The pictures thus hermetically sealed are indestructible so long as the glass is not fractured. These vessels were apparently affixed at the time of burial to the soft plaster of the grave; but the thinner portion, standing out from the cement, has almost invariably been broken, while the thick part, imbedded in the plaster, has been preserved. Sometimes even the solid bottoms of these vessels were fractured in the effort to detach them from the walls, and frequently impressions in the cement indicate where they were affixed. They are rarely found _in situ_, having been destroyed or carried off by successive generations of explorers or plunderers. The most important collection is in the Vatican Library. In the British Museum are some thirty specimens; in the museums of Paris, Florence, and Naples, a less number; and a few others in various private collections. The entire number extant is only three hundred and forty. In the course of a quarter of a century De Rossi discovered but two fragments of these glasses. This extreme rarity is doubtless owing to their excessive fragility, and probably also to their being destroyed in large quantities to procure the gold they contain. In some of the extant examples portions of this gold has been