Date Mosaic, Gr.Date Mosaic 1100391 , belonging to the muses, polished, elegant, or well wrought), the representation of a design by fitting together on a ground of cement numerous small pices of stone and glass, of various colors, and generally cubical. Although one of the most mechanical of the fine arts, it is entitled to rank as a style of painting, from the fact that it requires the preparation of a cartoon or colored design, as in the case of a fresco or an elaborate oil picture, and no inconsiderable knowledge of form, color, and composition. Dating from a remote period, it has been transmitted to the present time, and in modern Italy has been carried to a higher degree of perfection than it attained at periods when it was almost the only species of pictorial art in vogue. Of the mechanical process employed, the following description of the practice in the establishment at the Vatican in Home will convey an adequate idea: "The slab upon which the mosaic is made is generally of Travertine or Tibertine stone. In this the workman cuts a certain space, which he encircles with bands or cramps of iron.

Upon this hollowed surface mastic or cementing paste is gradually spread as the progress of the work requires it. thus forming the adhesive ground or bed on which the mosaic is laid. The mastic is composed of calcined marble and finely powdered Travertine stone, mixed to the consistence of paste with linseed oil. Into toil paste are stuck the smalti or small cubes of colored glass which compose the picture, in the same manner as were the colored glass, stone, and marble sectilia and tesserce of the ancients. The smalti are vitrified but opaque, partaking of the nature of stone and glass, or enamels, and are composed of a variety of minerals and materials, colored for the most part with different metallic oxides. They are manufactured in Rome in the form of long, slender rods, like wires, of different degrees of thickness, and are cut into pieces of the requisite sizes, from the smallest pin point to an inch. When the mastic has sufficiently indurated (and it acquires in time the hardness of stone), the work is susceptible of a polish like crystal. Care must be taken, however, that by too high a polish the entire effect of the work is not injured, as innumerable reflected lights in that case would glitter in every part of the picture.

When the design is to be seen at a very considerable distance, as in cupolas or flat ceilings, the work is generally less elaborately polished, as the inequalities of the surface are then less distinguishable, and the interstices of the work cannot be detected by the spectator." By this process many copies of large pictures by Raphael, Domenichino, and other old masters in the Vatican have been executed, occupying periods of from 12 to 20 years, and requiring from 10,000 to 15,000 different shades of the primary colors for the purposes of the work. In 1853 Pope Pius IX. sent to the crystal palace exhibition of New York a mosaic copy of Guercino's " St. John the Baptist," valued at $60,000, which at a'short distance it was impossible to distinguish from a highly finished oil painting. This, however, was a work of small importance in comparison with others preserved in the cathedrals of Europe. Two other species of mosaic work are carried on in Tuscany (whence the name, Florentine mosaics), the pietre dure and pietre commesse, both of which are employed for ornamental purposes, and represent fruit, flowers, birds, etc. The former gives the objects depicted in relief in colored stones.

The latter consists of precious stones, as agates, jaspers, lapis lazuli, etc, cut into thin veneer and carefully inlaid. - The employment of mosaics, which have always possessed a certain value, as well from their imperishable nature as from their intrinsic merits as works of art, originated probably among those eastern nations by whom so many of the arts have been transmitted to Europe. The Romans acquired a knowledge of the process from the Greeks, who had borrowed it from the Asiatics; and by all of them it was originally applied as an ornament for pavements, the close imitation of inanimate objects scattered apparently over the floor being the chief aim of the artist. Large historical compositions, of which the mosaic representing the battle of Issus from the casa del Fauno in Pompeii affords a felicitous example, succeeded; and under the first Roman emperors the art attained a considerable degree of refinement, though still used chiefly as an adornment for pavements. The Romans made it coextensive with their civilization, and from Britain to the Euphrates remains of ancient Roman mosaics have frequently been exhumed.

Of the varieties in use among the ancients, the principal were the pavimenta sectilia, consisting of- floors formed of pieces of stone of different colors, cut geometrically and cemented together; the pavimenta tessellata, or floors inlaid with small cubes of stone forming a colored design; the opus vermiculatum, and the opus musimun, in which colored cubes of clay or glass of every conceivable tint, set up very much as types are by compositors, were employed to produce elaborate finished pictures. The first three were included under the general name lithostrotum. With the overthrow of paganism and the establishment of the Christian religion commenced a new and grander era in the history of the art; and mosaics, from being used almost exclusively in pavements, were transferred to the walls and ceilings of sacred edifices. The connecting link between the mosaic pavements of Pompeii and the mosaics of Christian origin is so slight, that Dr. Kugler is "almost tempted to believe that historical mosaic painting of the grander style first started into life in the course of the 4th century, and suddenly took its wide spread." For nearly 1;000 years from this period it was almost exclusively employed for mural decoration, and from its durability has preserved a knowledge of the arts and in some degree of the religious ideas of the middle ages.

From the 7th to the 9th century the most important and interesting remains of pictorial art are the mosaics in the churches and the manuscript illuminations; and the most ancient representations of the Virgin Mary now remaining are the old mosaics in the churches of Rome, Pisa, and Venice, referred to the latter half of the 5th century. - Christian mosaics admit of two general divisions, the later Roman and the Byzantine styles, the materials in use being in general cubes of colored glass, inlaid, in the Roman school, on a ground of blue or white, and in the Byzantine school on a gold ground, although in the latter the tesserm are frequently irregular in size and the workmanship coarse. The former style flourished in Italy chiefly in the 5th and 6th centuries, the most splendid specimens of it being found in the churches of Rome and Ravenna. The churches of Sta. Maria Maggiore in the former city and of San Vitale in the latter contain perhaps the finest. When in the 5th century the arts and sciences were driven out of Italy by the distracted state of the country, they found refuge in Constantinople, where about the commencement of the 6th century arose that peculiar style pervading many branches of the fine arts, to which the general name of Byzantine has been applied, and which for five succeeding centuries had a predominant influence throughout Europe and among many eastern nations.

The first and greatest example of it is the celebrated church of St. Sophia, built by Justinian about the middle of the 6th century, and adorned with an almost incalculable wealth of mosaics, of which only a few colossal seraphim and the traces of a figure of the Madonna have escaped the effects of Mohammedan iconoclasm. By the middle of the 7th century it gained a foothold in Rome, where the native school of mosaics had lapsed into decay; and subsequently it came into competition with the Lombard, Norman-Byzantine, and Romanesque styles, each of which betrays the influence of the parent Byzantine. The mosaics in the church of St. Mark in Venice, executed between the 11th and 14th centuries, are perhaps the purest specimens of the style in Italy. They cover a surface of about 40,000 square feet of the upper walls, wagon roofs, and cupolas, and are laid upon a gold ground. Others, in a different style, were executed as late as the 16th century, Titian, Tintoretto, and contemporary masters, in some instances furnishing the cartoons; and the whole is fitly described as "a gigantic work which even all the wealth of Venice spent six centuries in patching together." In the 12th century a new or Romanesque style, founded upon Byzantine traditions, arose in Italy; and early in the 13th century the Italians in northern and central Italy, renouncing their dependence on Greek artists, began to execute mosaic work for themselves according to original conceptions of nature.

Andrea Taffi, one of the earliest and most famous of the Italian mcsaicisti, produced a figure of the Saviour 14 ft. high, which, Vasari says, spread his fame throughout Italy. Contemporary with and immediately succeeding him were Jacopo da Turrita, the Gaddi, Giotto, and others, of whom the last executed the celebrated navicella, now in St. Peter's in Rome. Among the latest of the mosaicisti, who worked from their own or original designs, were Baldovi-netto, Gherardo, and particularly Ghirlandaio, the master of Michel Angelo, and Muziano, who brought the art to great perfection. At the commencement of the 17th century Clement VIII. employed numerous artists to decorate the interior of the dome of St. Peter's with mosaic copies of the works of eminent masters, and each succeeding century has added to the immense wealth in works of art of this description deposited in the church. In the 18th century Pietro Paolo Cristofori founded a school for mosaic in Rome, where the art is now practised on a grander scale than in any-other part of the world.