In 1292 the Grand Council, by a decree, ordered the removal of the glass-workers to Murano, and the destruction of the furnaces at Riva Alto. From the inauguration of this industry at Murano, the Government was extremely jealous in preventing the secrets of glass-making from being discovered by any strangers. From the year 1275 the export of lump glass, or of the materials used in its composition, and even of broken glass, was forbidden, and a heavy penalty attached to such acts; and from this time more stringent laws were made, and at length the manufactories were put in charge of the Council of Ten, so determined was the Republic to profit by the skill of its workers. These anxieties were not unreasonable, since it is known that men as high in position as the {127} ambassadors from France had a sort of police in their employ, who attempted to bribe the glass-workers, and to spy out the raw materials they used, and their manner of combining them. It appears most probable that to the original knowledge of the earliest Venetians some additions must have been made from the methods of the Oriental mosaic-workers, who were employed in San Marco as early as the tenth century, although later the productions of the Venetians were sought in the East, where the making of fine glass had come to be a lost art. That this is true is proved by an order still existing for four hundred mosque lamps, bearing verses from the Koran, in colored enamels, to be made for the Grand Vizier of the Sultan. The Arabic influence which is so clearly shown in Venetian glass is supposed to have come from the specimens of glass found in the Roman Campagna, and in many other places in Italy, such as Nola, Campania, and so on, which in all probability were used as models at Murano. Venice gained immense sums by her trade in glass beads alone. Their place in commerce is almost incredible, especially when they began to be covered with enamels, gold, and opaline colors. The Orientals exchanged for them silks, spices, precious metals, and all sorts of exquisite tissues. They found their way all over the world, and in modern days have been seen in central Africa, where they were used for money. The shrewd Venetians valued their exquisite pieces of glass, their vases, goblets, mirror frames, and ewers; but they were most jealous in the protection of their bead trade and manufacture. From the eleventh to the fourteenth century the preparation of enamel for mosaic work was the most important department of the glass-works at Murano, and the mosaic glass there made has never been equalled in beauty or durability elsewhere. Even pavements in San Marco, {128} made from this glass, and now five or six centuries old, are still perfect in color, joints, and setting. Salviati gives the name of glass to the Venetian manufacture alone, and applies "crystal or crystallified glass" to all other varieties, and Yriarte says:--