north nave. The early windows are composed of series of medallions arranged in rows. Each medallion is made of small pieces of thick glass, deeply colored, particularly in reds and blues, bound together like mosaics with thin strips of lead. 13th-century windows The collateral chapels on the north side of the nave have some of the oldest existing windows. Some of these windows were funded by the guilds of craftsmen, and depict them at their work. Unusually, some of the windows, such as the Window of saint Joseph, are signed by the glass artist; the band in front of the Saint reads: "Clement, glassmaker of Chartres". The "Belles Verrieres" The "Belles Verrieres" are a group of windows located in the collateral chapels on the north side of nave and in the transept, containing some of the earliest stained glass in the cathedral. They are composed of early 13th century glass that was moved in the 15th century from its original locations in the south collateral chapels and reinstalled into new windows in the Chapel Saint-Jean, Chapel Saint-Severus, the Chapel of the Saint-Sacrament, and the Chapel of Saint-Pierre-and-Saint-Paul. The window in Bay 53 of the Chapel of Saint-Joseph-de-la-nef shows some of the craftsmen planning and building Rouen cathedral. 14th–15th century windows The windows of the 14th century began to look considerably different than the earlier windows. Glass artists had begun using techniques of silver stain and enamel paints baked on the glass to add greater detail and realism to the images. The windows looked less like mosaics, and increasingly resembled paintings, with the use of perspective and shading to suggest three dimensions. Fourteenth-century windows often depicted the subjects, usually saints and bishops, in architectural settings, surrounded and crowned by elaborate canopies and arches, to match the architecture of the cathedral. They also made greater use of grisaille, or a greyish or white glass, which surrounded and set off the figures and also brought increased light into the cathedral. One example from the mid-14th century is the Pentecost window in Bay 36, with an edge of grisaille bordered by angel musicians. Rose windows (15th c.) The rose window of the north portal is the only large rose window to survive in its original form. It was made by Guillaume Nouel at the end of the 14th century, and depicts Christ surrounded by the evangelists, bishops, kings and martyrs. Renaissance windows (16th century)