entirely during both the twelfth and thirteenth centuries, and so darkened their interiors by heavily leaded mosaic glazing as to bring about, at the opening of the fourteenth century, a sudden revulsion in favour of better lighted interiors, which went so far as to produce the excessive light and glare observable at Sées, St. Ouen (Rouen) and Evreux. This sudden revulsion did not appear in England where, indeed, there were no grounds for it, because, as we have just seen, the glaziers had already thoroughly grasped the need for, as well as the value of, light-admitting grisaille. That they thoroughly mastered the technique of uncoloured glass we will readily conclude from the splendid monuments to their genius in the "Five Sisters" at York, and the grisaille in the south transept at Salisbury, ideal glazing for a land of infrequent sunshine. Turning from these untinted windows to those filled with colour, one notices at once that the early examples of the latter are made up of very small pieces of different hues bound together by winding strips of lead having little sunken channels on both sides to hold the glass in place. So small are these pieces that the windows seem to have been composed much in the same way that the diminutive cubes are assembled to make a mosaic. It is because of this striking similarity of method, that this early glazing, constructed of small fragments, is frequently referred to as "mosaic" glass. Another name which it often receives is also easily explainable. The stories on these early windows are told by groups of very small figures, and to prevent a chaotic multitude of these little persons spread over the glass, each episode or group is separated from the others by a frame of contrasting colour, thus breaking up the whole surface into medallions. For this reason, early mosaic glazing is sometimes spoken of as "medallion glass." Unfortunately for England, it possesses but few remains of this delightful product, and therefore suffers sadly by comparison with the great wealth of it to be seen in France. We shall find enough, however, at Canterbury and Lincoln to kindle our enthusiasm for the splendid jewelled glow which the glazier of that time, and of no other, knew how to make his windows produce. It will not take long for the intelligent observer to notice that this glitter is due partly to the fact that the glass is free from paint (except that used to delineate features, folds of garments, &c.), and partly because its surface is not regular as is ours to-day. Furthermore, the pieces were small, and the constantly recurring leadlines (breaking up and combining the rays of light coming through the little panes) assisted materially to produce the brilliancy and shimmer which so delight the eye. There is no doubt that the glazier thoroughly realised this, and availed himself of this mingling of the coloured rays to suit the purposes of his picture. We frequently see a