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character; the process was commonly adopted and employed in northern Europe from the twelfth to the fifteenth century, after which they fell into disuse.

The process of manufacture which, as it is supposed, was commonly employed, may be described as follows:

The thin squares of homogeneous clay having been moulded and allowed to dry gradually until of the proper firmness, a design in relief was impressed upon them, leav ing the ornamental pattern in cavetto; into the hollows or depressions thus left upon the face of the tile, clay of another color was impressed; the clay usually employed for the last operation was white, or pipe-clay.

The tiles were fully and carefully dried, and then partly burned, after which they were finished by covering them with a thin surface of metallic glaze, which was of a slightly yellow color, and, in the subsequent process of fixing this glaze in the furnace, the white clay beneath the glaze was tinged, and the red clay received a more full and rich tone of color.

To facilitate the equal drying of the tiles, as well as the burning, deep scorings or hollows were made on the reverse side, and in addition the pavement was more firmly held together by the cement, the bond being much stronger for it.

The sizes of these tile varied from about four inches square to six inches square, and their ordinary thickness was about

one inch.

It was necessary that the shrinking nature of the clay should be about equal, and there is not the least doubt but that ingredients were used to act as a check upon the more

fatty clays, or otherwise most of the designs would be full of cracks from unequal shrinking, or the surfaces would bulge and be thrown upwards. Imperfections of these characters are not wanting; but their general infrequence would go to prove the employment of ingredients to equalize the shrinkage in drying and in burning.

Occasionally, either from the scarcity of white clay of suitable quality, in some locations, or for the sake of variety, glazed tiles of this character occur which have the design left hollow, and not filled in according to the usual process; but a careful examination of the disposition of the ornament will frequently show that the original intent was to fill these vacant cavities, as in other specimens.

But instances also occur where the ornamental design was evidently intended to remain in relief, the field and not the pattern being left in cavetto.

Among some of the oldest specimens of glazed tiles employed in England, may be mentioned the pavement discovered in the ruined priory church at Castle Acre, Norfolk, a portion of which is in the British Museum.

These tiles are ornamented with scutcheons of arms, and on some appears the name of "Thomas." They are exceedingly coarsely executed; the cavities are left unfilled with clay of a different color, and they are very much inferior to the Norman tiles of the same period.

It has been stated that glazed tiles of superior make and finish have been discovered in the priory church at West Acre, Norfolk; this priory was founded by Ralph de Tony, in the reign of William Rufus, for Canons of the Order of St. Augustine; this at the suppression was valued at three

hundred and eight pounds, nineteen shillings, and eleven pence half-penny. There was a close figuring for the ninth pound.

Malkin's process is now largely employed for the manufacture of inlaid as well as plain tiles; dried slip in the place of soft-tempered clay being used.

A brass plate, one-eighth of an inch thick, is used to produce the pattern, a separate one being used for each color. Thus, if it consists of an ornament in red and white on a blue ground, one plate is perforated, so as to enable the red portion of the clay powder to be filled in; another is cut for the white portion, and a third for the blue ground; when all are filled, the tile is subjected to an enormous pressure in a screw-press, the glazing being sometimes done in the first firing, and sometimes in a separate operation, as has been explained.

Encaustic tiles of one color are also now made of dried slip; these tiles are made by subjecting the powdered and colored clay to a great pressure in steel-lined moulds, having a raising plate bottom and an accurately fitting plunger; in this way one and one-quarter inch of fine loose clay is compressed into a little more than one-half solid tile.

SECTION II. THE MANUFACTURE OF MOSAICS AND IMITATION INLAID, OR INTARSIA SURFACES.

Mosaics are often formed with tiles, made as described in the last paragraph of Section I. of this chapter, in which a great variety of forms and colors are employed to develop the pattern.

The Russian artists have of late years produced some beautiful specimens of mosaics in glass; the pieces of every shade and color are technically called smalts; they are generally opaque, and are set in cement the same as tiles.

In Greece, inlaid pavements of variously colored marbles were among the sumptuous decorations of the time of Alexander of Macedon. These were for the most part of fret work or geometric patterns, and known as the Opus Alexandrinum, but among the earliest mentioned, by Pliny, are those lithostrata formed of colorless tesseræ, the work of one Sosos of Pergamos, whose master-piece was the "Asaroton Econ" or the "Unswept Hall," a representation of the crumbs and fragments which would be found on a floor after a banquet, together with a cantharus or two-handled vase from which a dove was drinking, while others were pluming and basking in the sun. By the third century B. C., the art had so far advanced, that, according to Athenæus, floors were laid down in the great ship of Hieron II. which were composed of small cubes of stone of every color, so as to represent the entire history of the siege of Troy; a work, the execution of which occupied three hundred workmen an entire year.

From Greece, the art was carried by Greek workmen to Rome, where it was known as Opus Musivum, expressing decoration produced by placing together small portions of stone, marble or glass, colored, either naturally or by art. It here acquired universal favor, and soon came to be applied not only to floors, but to walls and ceilings. The small pieces of which they were composed (from their resemblance to gamblers' dice, were called by the Romans tes

selæ or tessaræ, from the Latin Tesselatum), were imbedded in cement in accordance with a predetermined design, and when the surface had been thus smoothed and polished, a reproduction of the design was there formed in a material as far as possible, exempt from change or ordinary decay. Pavements of this description are found wherever the Romans settled, no less than in Rome itself-in Asia Minor, Spain, Gaul, and England, and not only in large cities as in Carthage or London, but in the remotest villages and wayside villas. Scarcely a house of any size in Pompeii appears to have been without its mosaic pavement.

In the Middle Ages, this kind of work continued to be used in Italy, and some other parts of the Continent. The favorite pattern in the mediæval pavements is called " Opus Alexandrinum;" which was chiefly used in the twelfth and thirteenth centuries.

In England, it was never extensively employed, though used in some parts of the shrine of Edward the Confessor, on the tomb of Henry III., and the paving of the choir of Westminster Abbey, and Becket's crown at Canterbury, where curious patterns may be seen.

Mosaic-work of all kinds is still executed at Rome and Florence by the Italians, who display great skill in their combinations and colors.

Inventions are now being developed by which mosaics can be cheaply worked, which, of course, while the work does not compare in merit to that of Italy, and Russia, is at the same time suitable for many purposes of domestic ornamentation.

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