Mosaic, opus musivum, is a kind of painting made with minute pieces of colored substances, generally either marble or natural stones, or else glass, more or less opaque, and of every variety of hue which the subject may require, set in very fine cement, and which thus form pictures of different kinds, rivaling in color and hue those painted by the brush.

Early nations knew the art of mosaic, and it is supposed to derive its origin from Asia, where paintings of this kind were composed, in imitation of the beautiful carpets manufactured at all periods in those countries. The Egyptians employed it very probably for different purposes; no traces of it have, however, been found in the temples or palaces the ruins of which remain. There is in the Egyptian collection at Turin a fragment of a mummy case, the paintings of which are executed in mosaic with wonderful precision and truth. The material is enamel, the colors are of different hues, and their variety renders with perfect truth the plumage of birds. It is believed to be the only example of Egyptian mosaic.

The Greeks carried the art of mosaic to the highest perfection, assuming after the time of Alexander an importance which entitled it to be ranked as an independent art. Skillfully managing the hues, and giving to the figures in their compositions an exquisite harmony, they resembled at a slight distance real paintings. Different names were given to the mosaics, according as they were executed in pieces of marble of a certain size; it was then lithostroton, opus sectile; or in small cubes, in this case it was called opus tessellatum, or vermiculatum. The name of asaroton was given to a mosaic destined to adorn the pavement of a dining hall. It was supposed to represent an unswept hall, on the pavement of which the crumbs and remains of the repast which fell from the table still remained. It was said to be introduced by Sosus of Pergamus, the first mosaic artist of consequence of whom we hear.

Mosaic was used to adorn the pavements, walls, and ceilings of public and private edifices. The Greeks in general preferred marble to every other material. A bed of mortar was prepared, which served as a base, which was covered with a very fine cement. The artist, having before him the colored design which he was to execute, fixed the colored cubes in the cement, and polished the entire surface when it had hardened, taking care, however, that too great a polish, by its reflection, might not mar the general effect of his work. The great advantage of mosaic is that it resists humidity, and all which could change the colors and the beauty of painting. Painting could not be employed in the pavement of buildings, and mosaics gave them an appearance of great elegance. The mosaic of the Capitol, found in Hadrian's Villa, may give an idea of the perfection which the Greeks attained to in that art. It represents a vase full of water, on the sides of which are four doves, one of which is in the act of drinking. It is supposed by some to be the mosaic of Pergamus mentioned by Pliny. It is entirely composed of cubes of marble, without any admixture of colored glass. Mosaic of this kind may be considered as the most ancient; it was only by degrees that the art of coloring marble, enamel, and glass multiplied the materials suited for mosaics, and rendered their execution much more easy. It was then carried to a very high degree of perfection. The mosaic found at Pompeii, which represents three masked figures playing on different instruments, with a child near them, is of the most exquisite workmanship. It is formed of very small pieces of glass, of the most beautiful colors, and of various shades. The hair, the small leaves which ornament the masks, and the eyebrows, are most delicately expressed. What enhances the value of this mosaic is the name of the artist who worked in it—Dioscorides of Samos. Another mosaic found at Pompeii is the beautiful one of Acratus on a Panther. The subjects represented in mosaics are in endless variety, and generally are derived from mythology or heroic myths. Landscapes and ornaments in borders, in frets, in compartments, intermingled with tritons, nereides, centaurs, are to be found on them. The principal subject is in the center, the rest serves as a bordering or framework. In the Greek tessellated pavement found at Halicarnassus, the mosaic is of very fine workmanship, being composed of small cubes of white, black and red marble.

Another and a still more remarkable mosaic was discovered in the House of the Faun, and is perhaps the most beautiful and magnificent specimen of the art that has yet been found. This mosaic, which is now preserved in the museum at Naples, is about eighteen feet long by nine broad. The subject represents a battle between Greeks and barbarians, the latter apparently of eastern race; but a variety of conjectures have been hazarded as to what battle is actually depicted. Some have seen in it the combat between Patroclus and Sarpedon, and the death of the latter; others have recognized in it the battles of the Granicus, of Arbela, of PlatÆa, of Marathon, etc. But the opinion most commonly adopted is that of Professor Quaranta, who refers the picture to the battle of Issus. The Grecian leader, supposed to represent Alexander the Great, is drawn with great beauty and vigor. Charging, bareheaded, in the midst of the fight, he has transfixed with his lance one of the Persian leaders, whose horse, wounded in the shoulder, had already fallen. The expression of physical agony in the countenance of the wounded man is admirably depicted. Another horse, which an attendant had brought for him, has arrived too late. The death of the Persian general has evidently decided the fortune of the day. In the background, the Persian spears are still directed against the advancing Greeks. But at the sight of the fallen general, another Persian leader in a quadriga, who, from the richness of his dress and accoutrements, the height of his tiara, and his red chlamys, is probably Darius himself, stretches forth his right hand in an attitude of alarm and despair, while the charioteer urges his horses to precipitate flight. Nothing can exceed the vigor with which both men and animals are depicted in this unequaled mosaic. If the Grecian hero really represents Alexander the Great, the mosaic may probably be a copy of a picture by Appelles, the only artist privileged to paint the Macedonian conqueror. It is unfortunate that the work has suffered much damage on the left side, or that which contains the Grecian host. It was, however, in this mutilated state when discovered, and seems to have been under a process of reparation. The border represents a river, apparently the Nile, with a crocodile, hippopotamus, ichneumon, ibises, etc.; whence some have been led to think that the mosaic is a copy of a picture on the same subject known to have been painted by a female Egyptian artist named Helena, and brought to Rome by Vespasian.

Painted floors were first used by the Greeks, who made and colored them with much care, until they were driven out by the mosaic floors called lithostrota. The most famous workman in this kind was Sosus, who wrought at Pergamus the pavement which is called asarotus oikos, the unswept hall, made of quarrels or square tesserÆ of different colors, in such a way as to resemble the crumbs and scraps that fell from the table, and such-like things as usually are swept away, as if they were still left by negligence upon the pavement. There also is admirably represented a dove drinking, in such a way that the shadow of her head is cast on the water. Other doves are seen sitting on the rim of the vessel preening themselves and basking in the sun. The first paved floors which came into use were those called barbarica and subtegulanea, which were beaten down with rammers, as may be known by the name pavimentum, from pavire, to ram. The pavements called scalpturata were first introduced into Italy in the Temple of Jupiter Capitolinus, after the beginning of the third Punic war. But ere the Cimbric wars began, such pavements were in common use at Rome, and men took great delight and pleasure therein.

For galleries and terraces open to the sky, they were devised by the Greeks, who, enjoying a warm climate, used to cover their houses with them; but where the rain waters freeze, pavements of this sort are not to be trusted. To make a terrace of this sort, it is necessary to lay two courses of boards, one athwart the other, the ends of which ought to be nailed, that they should not twist nor warp; which done take two parts of new rubbish, and one of tiles stamped to powder; then with other three parts of old rubbish mix two parts of lime, and herewith lay a bed of a foot thickness, taking care to ram it hard together. Over this must be laid a bed of mortar, six fingers thick, and upon this middle couch, large paving-tiles, at least two fingers deep. This sort of pavement is to be made to rise to the center in the proportion of one inch and a-half to ten feet. Being thus laid, it is to be planed and polished diligently with some hard stone; but, above all, regard is to be had that the boarded floor be made of oak. As for such as do start or warp any way, they be thought naught. Moreover, it were better to lay a course of flint or chaff between it and the lime, to the end that the lime may not have so much force to hurt the board underneath it. It were also well to put at the bottom a bed of round pebbles.

And here we must not forget another kind of these pavements which are called GrÆcanica, the manner of which is this: Upon a floor well beaten with rammers, is laid a bed of rubbish, or else broken tile-shards, and then upon it a couch of charcoal, well beaten, and driven close together, with sand, and lime, and small cinders, well mixed together, to the thickness of half a foot, well leveled; and this has the appearance of an earthen floor; but, if it be polished with a hard smooth stone, the whole pavement will seem all black. As for those pavements called lithostrota, which are made of divers colored squares or dice, they came into use in Sylla's time, who made one at PrÆneste, in the temple of Fortune, which pavement remains to be seen at this day.

It may be remarked here, that the Roman villa at Northleigh, in Oxfordshire, examined and described by Mr. Hakewill, abounded with beautiful pavements. The substratum of one of these, which had been broken, was investigated, when it was found that the natural soil had been removed to a depth of near seven feet, and the space filled up with materials which bear a near resemblance to those which Pliny recommends.

A specimen of the coarser sort of mosaic pavement is to be seen in the Townley Gallery, in the British Museum.