The modern Italian musaicisti have reached almost the perfection of technical and manipulative dexterity. Their mode of working differs, however, little in principle from that of the mediaeval workers in mosaic. They employ for the ground of their work a plate of metal or a alab of travertine, the size of the picture, and this is surrounded by an iron frame. In this bed is spread a cement or stucco, com posed of mastic, powdered travertine, and carbonate of lime, mixed with linseed oil, so as to form a paste. The tessera, or amalti, of which the picture is composed, are imbedded in the cement, which is only laid as far as the musaicisti are ready to proceed at one time, as it remains but a short period in a fit state for working on, and eventually hardens to the consistency of stone. When the whole picture is completed the surface is rubbed smooth to remove all inequalities, and brought to a polish, or left dull, according to the position the picture is intended permanently to occupy. The smalti are of opaque glass, coloured with metallic oxides and pre pared in a peculiar manner. They vary in size from an inch square to a pin's head. The medimval mode of working and materials, will be found described in Mrs. Merrifield'a Ancient Practice of Painting,' v. L, p. Ili. &c.
Something akin to mosaic or coloured inlaid-work was occasionally employed in Italy during the middle ages for external decoration also ; as an instance of which the facade of the Duomo at Pisa may be mentioned, where, though the pattern is chiefly in black and white, brilliant reds and blues are intermixed at intervals, a species of external decoration supposed by some to have been derived from the practice of pagehromy among the Greeks. (Potecnnorre.) This is much the
character of the Oriental mosaic, of which the mosques of Cairo and Damascus afford very beautiful examples. On the resemblance between Oriental and Byzantine mosaic work, and the characteristics-of the former, see Hessemer's Arabische mud Alt-Italienische Bau-Ver zierungen.' Pietra Dura, or Florentine work, is a kind of mosaic, in which by pieces of coloured stones and marbles, figures or patterns are formed on marble slabs for tables and decorative purposes. An imitation of it is manufactured to some extent with Derbyshire marbles at Matlock, Derby, and Buxton. There is a fine sort of Florentine work, called in Italy, Pictra Commesse, which is executed with agates, jasper, and other precious stones, cut into various shapes and sizes; it is an elegant but very costly style of ornamentation.
What was called Persia work, or Tarsiatara, was a kind of mosaic in wood, by which landscapes and patterns were inlaid in walnut panels, by means of small pieces of wood of various shades and colours. A very humble imitation of it is the inlaid toy-work kilown as Tunbridge ware.
(Furietti, Dc Musiris Roma (1i53); Ciarnpini, Vetera Monimenta ; )tazoia, La Reines de Pompei ; Donaldson, Pompeii ; Laborde, Mos. &Italica ; Miller, Handbuch der A rehtiologie ; and Archiiol. der Alien Kuria ; .'Agincourt, Hat. de I'Art, tab. 13, &c. ; Merrifield, Ancient Practice of l'ainting, vol. L ; N. D. Wyatt, Specimens of the Geometrical Mosaic of the Middle Ayes ; Secchi, e1alook° Anton:ion° descriito c Illus trate ; Kreutz, La Basilica di San Marco in Venezia, esposta ne suoi Mosoici ; pruner, The Manic, of the Cupola, in the Cappello Chigiuni' of &a. Maria del Popolo in Rome, designed by (taffaello Sanzio d'Urldno.)