MOSAIC. This very elegant production is a species of inlaid or tessellated work, made with minute pieces of coloured substances, generally either marble or other coloured stones, or else glass more or less opaque, and of every variety of hue which the subject may require. The former mode was that chiefly employed by the Romans for their costly tessellated pavements, many of which have at various times been discovered in England. Mosaics of this description, that is, for pave ments, generally consist only of a series of ornamental borders inclosing one or more compartments containing some figure or device, or occasionally a group or subject. Others consist entirely of a pattern, generally in two colours, sometimes in three--black, white, and red. Examples of pavement mosaics in each of these modes have been discovered at Pompeii. Mosaic continued to be used both for pavements and ornamenting walls to a late period in the middle ages, and was greatly practised in Byzantine buildings, and by Byzantine artists who were also em ployed in Italy.
A kind of mosaic or coloured inlaid,work was occasionally employed in Italy during the middle ages for external decorations 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.
Although nearly similar as to their process, mosaio picttres, especially some of those of later times, may be considered as a distinct branch of the art. Whether actually employed as pavements or inserted in walls, mosaics of this class consist chiefly of ornament and pattern, executed in few and simple colours, with hardly any attempt at variety of tints and due graduation of tones, even in the figures, human or animal, occasionally intro duced in them. For a long period after the decline of the arts, mosaic painting continued to be employed in Italy, both and internally, for the decoration of churches, as for instance, on the facade as well as within the basilica of St. Mark at Venice. Some
have supposed that such productions were entirely the work of Byzantine or Greek artists, but the contrary opinion is maintained by Cicognara, who asserts that mosaic was practised by native Italians, and that it was well known to the earliest Venetians.
Copies of celebrated works by Raphael and other masters have been executed in mosaic, and have the effect of paintings produced in the usual way, though they are attended with infinitely greater cost, and are beyond all comparison more laborious and tedious in their process. As each separate piece of glass is of the same colour throughout, the gradua tion of tints, the melting off of any one colour from its highest light to its darkest shadow, can be obtained only by an immense number of small pieces, of which those contiguous to each other exhibit scarcely any perceptible difference to the eye. The sole advantage, in any degree proportionate to the cost attending it, is the extreme durability of the work when once accomplished.
Similar mosaic is employed sometimes on a miniature scale, for pictures on the lids of snuff-boxes and articles of that kind, or tablets in chimney-pieces, which are at the best mere curiosities and very laborious trifles. Florentine Work may also be mentioned as a species of mosaic, chiefly used for in:aying or veneering marble slabs for tables and de corative purposes of that sort, upon a mode rate scale.
The Mediaeval Exhibition of 1850 presented many beautiful specimens of mosaic, mostly on a small scale. In our own day, the chief mosaic work produced is in the form of tessel- ' lated tiles for pavements.