The finest grisaille windows in England or, for that matter, in the world, are the five immense lancets which fill the end of the north transept of York Minster and are known as "the Five Sisters." Their date is probably about 1260. The iron-work in them is straight-barred, and the massive main bars, placed every 3½ feet or so, divide the space between the broad borders into a succession of squares, one above the other, each one of which is occupied by a medallion--a different shape in each light--outlined with a narrow band of colour, and having bosses of colour at the centre and between the medallions. One hardly can trace the plan of the painted pattern on the white, which besides is much confused with centuries of breakage and repair, and one is only conscious of it as texture, which indeed is its _raison d'être_. Five feet wide, and towering to a height of more than 50 feet, each "sister" is a shimmering mass of pearl and silver, delicately veined and jewelled with colour to give quality to its whiteness. [Illustration: PLATE XXI THE NATIVITY, UPPER PART OF EAST WINDOW OF NORTH AISLE, ALL SAINTS', NORTH STREET, YORK Fourteenth Century] [Sidenote: "Quarries."] The same tendency that caused the artist to substitute mosaic diaper for the scroll work in the setting of his medallions in coloured windows led him in time to fill large spaces of his grisaille windows with painted "quarries." "Quarries" (from the French _carré_) are small diamond-shaped panes, and were then the quickest and most economical way of glazing any given space. Sometimes towards the end of the century the painted pattern ran over the quarries independently of them, but more often in the thirteenth century each quarry was a repetition of the next, the whole thus forming a regular diaper. Sometimes each quarry has a thick black line painted parallel to two, or sometimes all four, of its sides at a distance of three quarters of an inch or so, leaving the space between it and the lead blank while the rest of the quarry is patterned. The effect of this when glazed together is that of interlacing white bands on a ground of pattern. Apart from economy, the principal motive for the use of grisaille in windows was, as I have said, the need for light. In the Cathedral of Chartres, where there is no grisaille except that in the chapels already mentioned, and where practically all the other windows are filled with richly coloured glass, it is quite difficult to read in the nave on a dull day. It is possible, therefore, that in some churches a certain number of windows may have been deliberately reserved for grisaille. [Sidenote: Combination of grisaille and figure work.]