Three different kinds of enamel are used in the decoration of the Ardagh Chalice, namely, (1) a peculiar variety of _cloisonné_ in which the compartments, or _cloisons_, are all cut out of a single piece of metal and the open framework thus formed is pressed into the surface of the enamel when soft until it rises up and fills each compartment; (2) a combination of _cloisonné_ and _champlevé_ enamel in which the compartments are all cut out of a single piece of metal, some being pierced right through and the remainder only sunk partially through the thickness of the metal; the framework is pressed into the enamel when soft, thus filling up the open compartments, as in the first kind just described, and the remaining dug-out compartments are filled with fusible enamel as in _champlevé_; and (3) a species of _champlevé_ enamel, in which the surface of a piece of glass was engraved with a design in _intaglio_ and the hollows filled up with an enamel of a different colour. The Celtic enamels of the Christian period usually occur in the form of small round bosses, of which there are good instances on the Ardagh Chalice, the Ardagh Brooch, the Tara Brooch, the Lismore Crozier, and the Cross of Cong. The use of bands of silver with borders of niello is well illustrated by the head of a crozier[435] formerly belonging to the late Dr. W. Frazer, M.R.I.A., of Dublin. Portions of the silver have been stripped, showing how the surface of the metal into which it was inlaid was roughened with a pointed tool to make the inlay adhere better. Niello is a black composition made of silver, lead, sulphur, and copper, which is reduced to powder and placed in cavities or lines cut for its reception in the surface of the metal, and afterwards incorporated with it by being passed through the furnace. Niello probably found its way to Ireland from the East. It was used by the Byzantines as early as the beginning of the ninth century.[436] [435] _Proc. R.I.A._, 3rd ser., vol. i., p. 207. [436] J. H. Pollen’s _Gold and Silver_, p. 53.