An important development of this craft was the manufacture of coloured glass for churches and cathedrals. In the Peninsula, the earliest introducers of this branch of glass-making were principally natives of Germany, France, and Flanders, who came to Spain at the beginning of the fifteenth century.[108] Many of the oldest windows executed by these foreigners, or by the Spaniards who were taught by them, are still existing in the cathedrals of León, Toledo, Burgos, Barcelona, and the Seo of Zaragoza. León has several windows which date from as far back as the thirteenth century, and in which the glass is in small pieces, arranged as though it were mosaic. Some of the later and larger windows in the same cathedral are thirty-five feet high, and one, dating from the sixteenth century, is believed to have been presented to this temple by Mary of England, prior to her marriage with Philip the Second. [108] Before this time, however, Aymerich had written, in or about the year 1100, that sixty large windows in Santiago cathedral were closed by glass, which probably was coloured. We also hear of Francisco Socoma, who made or fitted windows of coloured glass at Palma, in the island of Majorca, in 1380, and of Guillermo de Collivella, who, in 1391, fitted at Lerida the glass which had been coloured for the cathedral of that town by Juan de San-Amat. It was, however, in the twelfth and thirteenth centuries that the custom became general, in Spain as in other lands, of colouring the surface of white glass by partial fusing--a process which is mentioned in the treatise of Abolais, to which I have referred repeatedly. Between the eleventh and the thirteenth centuries the coloured windows of Spanish temples were still composed of pieces of glass united in the manner of mosaic, forming ornamental patterns of stars and similar devices; but subsequently to this period the decorative themes are said to be painted _en caballete_, and consist of figures, or the representation of scenes from Scripture. In Spain, and dating from the twelfth century, the workshops for preparing this coloured glass were commonly situated within the precincts of important temples, such as Toledo cathedral, or else, as was the case at Burgos, in separate buildings and _dependencias_. Here, in the square ovens characteristic of that age, and before it was mounted in the ponderous leaden frame, the glass was coloured with exquisite solicitude and patience by the hand of the master-craftsman, sometimes with a colour upon one of its surfaces alone, sometimes with the same colour upon both, or sometimes with a different colour upon either surface. The cartoons from which such windows were constructed, and which were often designed by painters of renown, were usually three in number. The first contained, upon a reduced scale, a coloured outline of the window; the second, drawn to