The great work, no doubt, of the Byzantines in the domain of glass is to be found in the manufacture of the mosaics with which they lined the walls of their churches, and when we hear that glass was made at Thessalonica, and again that one of the gates of the capital was named after the adjacent glass-works, it is of this branch of the art that we must first think.[66] Byzantine artists travelled to Cordova on the one hand, and to Damascus on the other, to work in mosaic for Mohammedan masters; we find them, too, at Rome, at Ravenna, and at Aachen. No doubt these _musivi_ took with them, at first at least, the materials with which they built up their pictures. For the use of coloured glass in the windows of churches, we may probably find a similar origin. In Justinian’s great church glass was not used for mosaics only; there were windows filled with stained glass, some of which may even now be in place. In the seventh century we hear of Greek workmen summoned to France for such work, just as from Merovingian France, as Bede tells us, Benedict Biscop obtained, a little later, skilled craftsmen to make the glass for his new church at Monk Wearmouth. [Illustration: _PLATE XI_ HANGING LAMPS OF SCULPTURED GLASS BYZANTINE. FROM TREASURY OF ST. MARK’S] In the ode that Paul the Silentiary wrote for the opening ceremony at St. Sophia (563 A.D.), he speaks of silver discs, hanging from chains and pierced to receive vessels of ‘fire-wrought’ glass, shaped like the butt of a spear (οὐρίαχος) (Lethaby’s _Santa Sophia_, p. 50 _seq._).[67] We have here in these lamps what is probably the first mention of a new use for our material—one which became before long, for a time, the dominant one. In the ‘spear-butt’ shaped lamps of St. Sophia we may see the prototypes of the conical oil-cups of the Saracens. Glass, however, was never held in great honour in the ceremonies of the Christian Church. Chalices and patens of glass are indeed mentioned in the _Liber Pontificalis_ as in use at the end of the second century: St. Jerome writes of ‘the Lord’s blood being borne in a vessel of glass,’ and some early miracles have reference to the making good of glass that had been broken. Of a ninth-century saint we are told that his Eucharistic vessels were first of wood, then of glass, and finally of pewter! In later times the use of so fragile a material fell out of use, and was even forbidden by the Church.