259. The method of manufacturing tiles for floors and wainscots, etc. is similar to that described under "Terra Cotta," but as these uses of tiles are in the nature of finishing processes, analogous to plastering on walls, the subject is considered separately from terra cotta.

260. Tiles are used very extensively for flooring aisles and passages in churches, office buildings, the floors of waiting rooms in railway stations, and also for vestibules, bathroom floors, hearths, borders, and backs of fireplaces in dwellings. Very artistic effects may be produced by use of different colors and shapes; and for wainscots, by use of the great variety of plain and decorated tiles. Tiles are of every color, and are made as large as 6 inches square, but it is not recommended that pieces of this size be used for flooring, as they are likely to break or become loose, unless very carefully laid.

261. The art of laying mosaic floors was known to the Romans, by whom the component parts were termed tes-serse, from the word meaning tcsselated, or checkered. These consisted of small pieces of hard material of various colors, bedded one by one in a layer of cement, each piece being leveled with the others; and on the completion of the work any irregularities were corrected by rubbing the whole to a plane surface.

The modern tile floor is composed of pieces cut by dies; the pieces are thus uniform in size, and fit closely together, having an almost imperceptible joint. As a guide in setting, a colored drawing of the intended design is usually made. The full-sized pattern is laid out on a perfectly level cement floor, upon which the tesserae are placed, the workmen being guided in the arrangement of colors, etc. by the drawing. The pieces are afterwards joined together by a layer of cement applied to the upper surface, and in this way can be formed into slabs of convenient size, which, when hard, are ready for use, and can be easily laid, either as centerpieces, borders, or pavements.

262. Tiles may be laid directly on the concrete of any of the fireproof floors before described; but when the floor is framed with wooden beams, the foundation course is brick, set edgeways on short pieces of board, laid on strips nailed to the sides of the beams; but to save material the bricks are sometimes laid flat. The average thickness of the tiles is 1/2 inch, although they often run 5/8 inch, so that the top of the brick should be 3/4 inch below the finished floor. The top of the beams should stand in the same relation to the tile that they would to the top of a wooden floor, in order to avoid differences in level at the junction of the wooden and tile floors. In the case of a single wooden floor, the distance will be 7/8 inch, and in a double floor, 1 3/4 inches.

After the brick are laid the brick surface should be swept clean, and well dampened. The tiles should also be soaked in water for some time before they are used. If this precaution is not taken, the brick or tile will absorb water from the thin layer of cement between them, making it powdery and useless. The best Portland cement, only, should be used, the American brands, when fresh, being equal to most of the English. The cement should be mixed rather thin, without sand.

263. The pattern - when the tiles are laid with a centerpiece - should be commenced at the center, the position of which should be accurately ascertained by previous measurement. Straightedged strips of board should be put down as guides for each day's work, not only for regulating the lines of the pattern, but also for securing a uniform surface, which is done by first setting the strips carefully, and then laying the tiles by aid of a straightedge resting on the strips. Each tile is set on a bed of cement spread for it, and beaten down to the proper level by the wooden handle of a trowel. When a sufficient number of tiles has been laid, the joints may be grouted with liquid cement, which must, however, be immediately wiped off the surface of the tiles, since it is difficult to remove when dry.

If the cement used is good, the tiles cannot, after a few days, be removed without breaking, so that too much care cannot be exercised in placing them properly at first. When the pattern reaches the edges, it is usually necessary to cut many of the tiles. This can be done by soaking them well in water, and then scoring a line with a sharp chisel, where the separation is to be made; by placing the chisel exactly on the line, a sharp blow will effect the separation. Wide chisels should be used, and the tiles must be well soaked, for unless this is done they are likely to fly into fragments.

After the floor is finished, it is covered with sawdust an inch or so deep, and planks are laid over the tile, to walk on. When there is a baseboard and wainscot, whether of wood or stone, it is then fitted down upon the tiling.

264. If marble tiling is used in place of terra-cotta tile, the laying should be done in the same way, on bricks set on edge. The marble tiling is considerably thicker than the clay tile, generally from 7/8 to 1 1/4 inches, and the guide strips should be set accordingly. The under side of the marble is usually quite rough, and the laying is easier than that of clay tile. Mortar of cement, lime, and sand, made in equal parts, may be used.