MOSAIC 851 concrete and cement were both set, the surface of the pave ment was rubbed down and polished. This kind of mosaic was largely used for floors of hypocausts ; the concrete bed was then supported on large tiles resting on numbers of short pillars. If used for upper floors very strong joists were re quired, and both Pliny (xxxvi. 25) and Vitruvius (vii. 1) recommend a double layer of boards, one crossing the other, on which the concrete and cement bedding was to be laid. The usual Roman pavement was made of pieces of marble, averaging from a half to a quarter of an inch square, but rather irregular in shape. A few other, but quite exceptional, kinds of mosaic pavements have been found, such as that at the Isola Farnese, 9 miles from Rome, made of tile-like slabs of green glass, and a fine " sectile " pavement on the Palatine Hill, made of various-shaped pieces of glass, in black, white, and deep yellow. In some cases e.g., in the " House of the Faun " at Pompeii glass tesserae in small quantities have been mixed with the marble ones, for the sake of greater brilliance of colour. Pompeii is especially rich in its mosaics both on floor and walls, almost every house having at least its vestibule paved in this way. In addition to graceful flowing patterns and geometrical de signs, picture-like subjects of great elaboration frequently occur: of these the most important is the large and minutely-executed scene of the battle of Issus, found in the House of the Faun. " It is of special value as being the chief classical historical picture still existing. It is a well-designed though somewhat crowded com position, representing the moment of Alexander s victorious charge against the cavalry of Darius. The expression of the faces and the characteristic dresses of the Greeks and Persians are repre sented with great skill (see fig. 2). The tesserae, as was always the case in this sort of work, are not all the same size, the smallest (only about one-tenth of an inch square) being reserved for the faces, where greatest refinement of detail was required. This was a floor- mosaic, though generally these minutely-executed works were affixed to walls. The most skilfully-executed of all existing mosaics of this pictorial kind is that known as "Pliny s Doves," found in Hadrian s villa at Tivoli, and now in the Capitoliiie Museum. It may possibly be the one so highly praised by Pliny (xxxvi. 25) as the work of Sosus, for, although he describes it as being at Pergamum, yet it was a common practice with the Romans to transport these mosaics from one place to another, arid this very celebrated one may well have been brought to Tivoli to adorn the emperor s villa. It is treated in a very realistic way : the light on the gold bowl, the plumage of the doves, and especially the reflexion in the water of the drinking dove, are represented with wonderful skill. It is, in fact, far too pictorial, and, like the late mosaics in St Peter s, Rome, is more remarkable for its technical skill than for any real artistic merit. This excessive realism, produced with great difficulty and cost, is a not uncommon fault of the more elaborate Roman mosaics, and was the inevitable result of the luxury and ostentation of imperial Rome, which made art the bond-slave of the wealthy, rather than the free and natural expression of a whole people, as it was among the earlier Greeks. Another interesting mosaic from the wall of a house at Pompeii, of extremely delicate work, is a rehearsal scene in a Greek theatre, where the choregus is instructing the actors : it is specially re markable from its being signed as the work of Dioscorides of Samos. Other figure-subjects are not uncommon, such as various representations of the victory of Theseus over the Minotaur, others of Achilles in Scyros, many hunting scenes, and the like, Throughout England, Germany, France, Spain, Asia Minor, and Northern Africa in no way have signs of Roman occupation been left so clearly and in so con spicuous a form as by the numerous large and generally well-preserved mosaic pavements which have at various times been discovered in all these countries. In many cases, long after all traces of the walls of the buildings have disappeared, owing to their being dug up and re moved for building purposes, the mosaics still remain to testify of the artistic power and mechanical skill of the Roman colonists. Few countries are richer than England in these remains ; the great pavements of York, Woodchester, Cirencester, and many other places are as elaborate in design and as skilfully executed as any that now exist even in Rome itself. In whatever country these mosaics are found, their style and method of treatment are always much the same; the materials only of which the tesserae are made vary according to the stone or marble supplied by each country. In England, for instance, limestone or chalk often takes the place of the white marble so common in Italian and North African mosaics ; while, instead of red marble, a fine sort of burnt clay or red sandstone is gene rally used ; other makeshifts had to be resorted to, and many of the Anglo-Roman mosaics are made entirely with out marble. It is perhaps partly owing to the great wealth of Northern Africa in marbles of many colours and of varying shades that the finest of all Roman mosaics have been found in Algeria and Tunis, especially those Fio. 2. Part of a Persian s Head from the Battle of Issus ; full size. from Carthage, some of which have been brought to the British Museum. See Archaeologia, vol. xxxviii. p. 202. The range of colour in the marble tesserae is very great, and is made use of with wonderful taste and skill : there are three or four different shades of red, and an equal number of yellows and greens, the last colour in all its tints being almost peculiar to this part of Africa, and one of the most pleasant and harmonious in almost any com bination. Deep black, browns, and bluish-greys are also abundant. The white marble which forms the ground of nearly all the designs is often not pure white, but slightly striated with grey, giving great softness and beauty of texture to the surface, and doing away with too great monotony of tone. The Roman practice, common to all their mosaics, of not fitting the tesserae quite closely together, but allowing the cement joints to show freely, was also of great value in giving effect to the general texture of the surface a point quite forgotten by some later mosaic-workers, who thought that the closer their tesserae were fitted together the better the mosaic would be. This remark does not apply to sectile mosaic, in which sufficient variety can be given by the markings and veins in each piece of marble. To return to the mosaics from Carthage, they are no less excellent in design than in
the richness and beauty of their materials. Large spaces