Silver stain (oxide of silver) introduced at the beginning of the 14th century is largely used in stained glass, and usually on the back thereof. According to the different degrees of heat in the firing, a pale yellow or deep orange of great transparency is produced. Coloured glass was made by the Egyptians 4000 years ago, but the earliest stained glass windows recorded, were those of Brionde A.D. 525. None however are known to be in existence prior to those of St. Denis A.D. 1108. Other examples are found in Norman windows, with small medallions of figures and ornament of a decided Byzantine type, extremely deep in colour, being, by its style of treatment, termed mosaic glass. The 13th century, or early Gothic period, has single lancet lights, with medallions containing small figures surrounded by the typical 13th century foliage; or the windows were entirely of ornament in _grisaille_, arranged symmetrically, having narrow bands of ruby or blue, with wide borders. These _grisaille_ windows are of a greenish white glass, with the ornament in outline, and the ground hatched with brown enamel in fine cross lines (fig. 1-2). The north transept window at York cathedral, called the five sisters, is typical of this grisaille glass. The finest examples however, are at Salisbury and Chartres cathedrals. Later in the period, single figures were introduced under a simple canopy or gabling, plain or crocketed, with an ordinary trefoil arch. [Illustration: 13TH CENTURY GLASS. CHARTRES CATHEDRAL.] “Quarry glass,” square or diamond in shape, with brown enamel details, was frequently used, where simple masses were desired. In the 14th century, the figures were larger and placed under canopies in each light of the mullioned windows, such figures in rich colours forming a bright belt across the window, surmounted by the canopies, cusped and crocketed, and in strong yellow pot metal, or yellow-cased glass. The borders were narrow, with a somewhat natural rendering of the rose, the maple and the oak. In the 15th century, a further change took place, figures became more numerous and the canopy or shrine larger, and chiefly in white glass, with the crockets and finials tipped with yellow stain. The coloured border of the earlier glass is entirely absent, its place being taken by the shaft of the canopy, and the crockets, finials and ornaments are square in treatment and based chiefly on the vine leaf. [Illustration]