In the eleventh century churches built in various places were decorated with discs and “ciotole” of glazed and painted terra-cotta. The researches of the abbé Cochet at Bouteilles have shown that glazed pottery was in use in the north of France in the Anglo-norman period of the thirteenth and fourteenth centuries, or perhaps even in earlier time. Examples of glazed and painted tiles of the fourteenth century are preserved in the British museum. As before stated, this glaze is composed of silica with varying proportions of potash or soda and of oxide of lead, by which addition it is rendered more easily fusible but remains transparent. To obtain a white surface was, however, desirable, the colour of the paste beneath the glaze being generally of a dull red or buff and ill-adapted as a ground for the display of coloured ornamentation. To supply this want, before the invention of the tin enamel, an intervening process was adopted. A white argillaceous earth of the nature of pipeclay was purified and milled with water, and thus applied over the coarser surface of the piece in the same manner as the glaze: again dried, or slightly fixed by fire, it was ready to receive the translucent coat through which the white “slip” or “engobe” became apparent. It is easy to conceive that by scratching a design or pattern through this white applied surface to the darker clay beneath, before fixing in the fire, a ready mode of decoration presented itself without the use of colour, to be covered with but visible through the glaze; hence the early incised or “sgraffiato” ware, one of the primitive modes of decorating glazed pottery. Passeri states that pottery works existed from remote periods in the neighbourhood of Pesaro, as proved by remains of furnaces and fragments of Roman time and tiles with the stamp of Theodoric; that during the dark ages the manufacture was neglected, but that it revived after 1300, and that it then became the fashion in that city to adorn the church towers and façades with discs and “bacini” of coloured and glazed earthenware; a practice which had been in use at Pisa and other cities as early as the eleventh century. The origin of this custom has been much discussed; and the reader will find an account of it in the introduction to the detailed catalogue of Maiolica in the South Kensington collection. Occasionally, or rather frequently, circular and square slabs of porphyry and serpentine were used on the same building, concurrently with the glazed earthenware, as on the tower of Sta. Maria Maggiore at Rome; and, indeed, this mode of enrichment attached to the architecture of the 11th, 12th, and 13th centuries is in accordance with that produced by the enamelled discs and inlaid stones on processional crosses and church plate of the same period.