Of the so-called Cosmati mosaics, where the little triangular pieces of glass are inlaid in marble or wood, we have a good example in the thirteenth-century shrine of the Confessor in Westminster Abbey. At the same period a more elaborate means of decoration was obtained by painting the backs of little plaques of glass with gold and colours, and fixing them on the panels of pulpits, on the frames of the painted reredos, or even on secular furniture. I have seen examples of church furniture thus decorated at Aachen and in the Norman churches of Southern Italy—a pulpit at Bitonto in Apulia is a remarkable example. But we need not go far to find a still finer specimen of such work: the Gothic framework of the _retabulum_ that formerly was placed in front of the high altar in Westminster Abbey[102] is decorated with bosses of glass paste cut or cast _en cabochon_, with casts of antique gems, and, above all, with little plaques of blue and purple glass backed with silver foil. On the upper surface of these glass plaques a design in gold, consisting of small medallions with animals and twining branches, stands out in low relief. The pattern, says Viollet-Le Duc (_Dictionnaire du Mobilier français_, i. 338), was first painted on the glass with a mixture of red ochre, wax and turpentine, and over this, before it was dry, gold leaf was laid, the gold adhering only to the soft ground. The effect of this external decoration is heightened by the shadow which it throws upon the silver foil beneath. In other examples, the pattern is painted in various colours under the glass, and a leaf of gold, pasted beneath the more or less transparent pigments, shows through here and there. In all these instances the crude colour of the gold is lowered in places by coatings of varnish.