The colouring matter is produced from the oxides of various metals, as in the vitreous coloured glazes used in the enamels for glazed pottery. Vessels and objects in endless variety have been made by the Venetians, such as ewers, basins, drinking-glasses, bottles, standing cups, bowls, goblets, large and small candlesticks, beads, and mirrors, and were exported in great quantities to all parts by the Venetian galleys. Bead making at Venice was a separate trade, and was one of great importance in the sixteenth and two following centuries. The makers of the small beads were called the “Margariteri,” and those who made the large beads were known as the “Perlai.” The beads were made from small sections broken or cut off from rods or tubes of glass and placed in an iron pot that was made to rotate, so that the motion prevented the beads from adhering to each other, and at the same time formulated their spherical shape. Mirrors were made by the ancients of polished metal and from slabs of black obsidian—a kind of natural glass. In mediæval times they were made of clear glass behind which was placed a sheet of lead foil. Glass mirrors were made in Venice from the year 1507, when methods had been discovered of polishing the glass and of applying the “foglia,” or layer of metal leaf, to the back. After this date the making of mirrors soon developed into great importance, and the “Specchiai,” or mirror makers, had their own corporation. Like the other glass wares of Venetian manufacture, the mirrors were exported to all parts of Europe. Some good examples of sixteenth-century mirrors and mirror-frames in glass cut into ornamental shapes, with bevelled edges and engraved, are preserved in our museums and in old houses. Glass painting for windows was known and practised in Venice as early as the fourteenth century. The very early Italian stained glass used in windows is said to have been executed for Leo III. in 795. Besides the painted or stained glass used in church windows during the Middle Ages throughout Italy, there were glass manufactories in Rome, Verona, Milan, and Florence for the production of similar wares as those of Venice. In France and Spain glass making was carried on at various places from the days of the Romans; antique fragments of glass have been dug up in Normandy and in Poitou. In the latter province glass making flourished from a very early date up to the fifteenth century. It was revived in 1572 by the Venetian Fabriano Salviati, who came to Poitou and set up a glass workshop. At Paris, Rouen, Normandy, and in Lorraine glass was made prior to the sixteenth century. The Normandy glass was of a coarse kind, made chiefly for windows and common utensils, but many of the Venetian varieties were made at the other places named.