It is not our purpose to trace the history of window glass, but it would seem that, according to the best documentary evidence, before the fourteenth century but little if any white glass was used for windows.
According to M. Le Vieil, painting on glass was discovered in the twelfth century. The first windows are said by him to have been painted for the St. Denis Abbey. This, however, appears to be an erroneous statement, for several monuments had been decorated with painted windows before this. Among others the Abbey of Leroux, in Anjou, France, dating from 1121; in Bavaria, in the Abbey of Tegernsee, where window frames are preserved dating from the tenth century. Glass painting, with vitrifiable colors, according to several authors, was discovered about the tenth century.
In Europe window glass is made in two ways, crown and cylinder glass. Crown-glass making is almost abandoned, with the exception of a few factories in England; it is an awkward and unprofitable way of manufacturing, and is not, I believe, practiced anywhere in this country. Cylinder-blowing being more economical and producing a better quality of glass, this method has been adopted all over the world. The Venetians and Bohemians blew cylinders for the windows of the twelfth and thirteenth centuries. Cylinder-blowing was introduced in France from Bohemia in the beginning of the eighteenth century.
France now manufactures a large quantity of window glass, one factory alone, La Compagnie des Verreries de la Loire et du Rhône, producing annually 590,000 square yards, and 89,000 yards of colored glass. In the north of France 25 to 30 furnaces of 8 pots produce from 4,500,000 to 5,000,000 square yards. The annual production, according to the official statistics of 1873, is put down at $4,400,000; for 1878, $3,000,000. In France, as in other countries, glass manufactories are to be found mostly near the coal fields.
Belgium has 60 window-glass factories, with 213 furnaces, containing each from 6 to 8 pots. These factories are mostly located near Charleroi and Jumet; a few, however, are to be found near Mons. Owing to the general commercial depression now existing, about one-third of these factories are idle. The annual production, notwithstanding this reduction, has fallen off but little, owing to gradual improvements which have been introduced in the methods of working and
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