Enamel was employed, during the middle ages, for the decoration of metallic surfaces by means of various processes, distinct from one another, although they produce nearly one and the same effect. In some cases the different colours introduced were applied in a manner not very dissimilar to mosaic-work; slender lines of filigree were attached to the surface of the plate; these were bent and fashioned so as to form the outline of the design, the intervening spaces were then filled in with the desired colours, probably in a pulverized state, and the plate was then exposed to a degree of heat, sufficient to fuse the enamel-paste without affecting the metal. The face of the work was afterwards ground and polished down. The few existing examples of this mode of operation which remain, consist of enamels on gold, such as Alfred's jewel and a small number of specimens of various dates. In this process each colour was separated and kept distinct from that which adjoined, by means of the little metal thread which traced out every portion of the design; this operation must have been tedious and uncertain, and a similar effect was produced by another process which seems to have been most commonly adopted. It is termed in France technically, champ-levé, implying that the field of the metal was removed, or tooled out, leaving certain slender lines which serve in place of the filigree to keep one coloured enamel distinct from another, and to define the outline and chief features of the design. The metal plate in this instance, which in almost every known example is of copper, was chased out in the same manner as a wood-cut prepared for printing with letter-press; the casements or cavities excised on the face of the metal served to receive and hold firmly the enamel, with which they were filled by means of fusion; the face having been polished, the lines of metal were gilded, and thus produced an effective appearance as contrasted with the bright colours to which they served as an outline. The thickness of the metal gave great durability to enamelled works of this description, and unless the enamelled object or plate were bent or violently bruised, the colour could not easily be detached. Some examples are indeed to be seen in as perfect preservation as if they had only just been withdrawn from the furnace. The best works of this kind are those which were produced during the twelfth and thirteenth centuries. The next process, which forms properly the step of transition
