Very few, if any, pictures in mosaic have been found in England ; but num bers of pavements of Roman origin hare often been, and still arc continually dis covered. Those necessarily differ con siderably from the delicate and beautiful works already noticed; and yet the neat ness of their component parts, and the elegance of their figures, obtain and de serve admiration. Of all the pavements in mosaic left in English churches, not one can be compared with that placed by Richard Ware, Abbot of St. Peter's, W est minister, before the high altar of the church, in 1272, which is thus described by Malcom, in the first volume of " Lon dinium Redivivum." " The materials are lapis-lazuli, jasper, porphyry, alabaster, Lydian, and serpentine marbles and touch stone. The centre of the design is a large circle, whose centre is a circular plane of porphyry, three spans and a pouter in diameter; round it stars of la pis- laz ul i, p ea-gree n,red and white, which being of most beautiful colours, have been subject to depredations ; those enclosed by a band of alabaster; and without, a border of lozenges, red and green ; the half lozenges con tain triangles of the same colours. A dark circle held brass letters, the places of which may be seen, but are now reduced to six:R .E.C)2M T The extreme lines of this great circle run into font smaller circles facing the cardi nal points : that to the east, a centre of orange and green variegated : round it a circle of green and red wedges ; without that, lozenges of the same calours ; and completed by a dark border. To the north, the circle has a sexagon centre of variegated grey and yellow ; round it a band of porphyry and a d ark border. The west circle nearly similar. The south, a black centre within a variegated octagon. A large lozenge encloses all the above circle, which is formed by a double bor der of olive-colour; within which, on one corner only, are 138 circles intersecting each other, and each made by four oval pieces, enclosing a lozenge. The other parts vary in figure ; but would take ma ny pages to describe.
The above lozenge has a circle on Bach of its sides, to the north-west, south-west, north-east, and south-east. The first con tains a sexagon, divided by lozenges of green ; within which are forty-one red stars. In the intersections red triangles. Green triangles form a sexagon round every intersection. The second contains a sexagon; within it seven stars of red and green, forming several sexagons, containing yellow stars. The third has a sexagon, formed by intersecting lines in to sexagons and triangles; within the for mer stars of red and green. The latter sixteen smaller triangles of red, green, and yellow. The last a sexagon, with thirty-one within it, filled by stars of six rays, green and yellow. The space with in the great lozenge round the circles is composed of circles, stars, squares, lo zenges, and triangles, the component parts of which are thousands of pieces of the above shapes. The whole of the great lozenge and circles is enclosed by a square; the sides to the cardinal points.
It has held other parts of the inscription : of this U and t' only remain on the eastern side, N 0 on the south, none on the west, and on the north. The four outsides are filled by parallelograms and circles of considerable size, all divided into figures nearly similair to those described." The above descriptions of mosaic pic tures and mosaic pavements will convey a competent idea of the nature of the art. The manner in which they are com posed is explained by Keysler, whose ac curacy is almost proverbial. According to this valuable author, persons were constantly employed at Rome in making copies, in mosaic, of those excellent pie tures which adorned the walls of St. Pe ter's church, to replace the latter, as the damps of the building were annually and gradually destroying them. The mate rials used in his time were small pieces of glass, tinted with different gradations of colours, in the manner of the fine wor sted used for needle work. The glass was cast in thin plate, and afterwards cut into pieces of different lengths and breadths : some of those intended for the composition of figures to be placed on vaults and ceilings were above half an inch in width ; but those used for subjects situated near the spectator were formed by pieces not thicker than a common pin, of which two millions are said to be ne cessary to compose a portrait four feet square. The substance prepared to re ceive these shreds of glass is a kind of paste, composed of calcined marble, fine sand, gum tragacanth, the white of eggs, and oil. As some time elapses before the ground hardens, there is no difficulty immediately arising from the act of plac ing the glass properly, or in removing those which may be found misplaced ; bot after a certain interval it becomes so extremely solid, that nothing less than violence has any affect upon it. Keysler mentions, that "the paste is first spread in a frame of wood, which must not be less than a foot in breadth and thickness, if the piece be any thing large." The frame is secured by brass nails to a plane of marble or stone : and as some of the most important subjects are twenty feet in length, and fifteen in breadth, an idea may be formed of their very great weight. The fragments of glass are arranged in their proper gradations in cases, which are placed before the artist in the manner the types are set before compositors in printing. The former were so very accu rate in imitating the most beautiful strokes of the pencil, that the difference, accord ing to Keysler, seems to consist only in the colours of the copy being more vivid and rrilliant than those of the painting. When the copy is completed, they polish them in the same manner usual with mir rours ; and after this operation is per formed, it is almost impossible to discover that they are composed of an infinite number of fragments, as they rather re• semble rich pictures covered with glass. Those pieces intended for distant view are never polished.