Chav. IV.

BRICKS AND TILES.

711

Tiles are formed of a reddish or grey-coloured clay, which fuses at a red heat: these claysare probably mixtures rather than compounds of silica, alumiua, and water.

The common kind of tiles is made of the blue clay, obtained near London at a greaterdepth than the ordinary brick earth ; this is excavated in the autumn, and exposed to the airdurin<r the winter, to properly temper it: after the tiles are moulded to their shape, theyare burnt in kilns, surrounded by a conical structure with an opening at top.

A kiln 20 feet square, with 3 furnaces, is calculated to burn about 34,000 tiles at onetime; the space which contains them above the arches of the fireplace being 14 feet 6inches square, and about 8 feet in height, this square chamber being open at the upper sur-face : around it is built the frustum of a cone, with a clear diameter of 32 feet at bottomand 3 feet at top, the wails of which are of brick, 18 inches in thickness at bottom, anddiminishing by three regular internal sets-off to 9 inches at the top : an entrance is usuallyleft at opposite sides for the charging and unloading the kiln, the bottom of which isgenerally sunk about 10 feet below the ordinary surface of the ground, and a vaulted pas-sage leads to the furnace, where the fuel is applied: such a kiln is adapted for the burningof bricks as well as tiles, and is found to answer for both admirably well.

The Earth used for making tiles should be pure and tough, and free from any foreignmatter : after constant turning over and tempering, it is brought to a proper consistenceand moulded into the desired shape.

Plain Tiles are usually made § of an inch in thickness, 10J inches long, and 6J wide,weighing from 2 to 2.} pounds each : these when laid lap over each other, and the partuncovered is called the gauge, which is generally 6£ inches: when so laid, 740 tiles willsuffice to cover 100 superficial feet; they are hung upon the lath by two oak pins in-serted in holes perforated by the moulders before burning.

Plain tiles are now made so that they may be placed side by side, in courses perfectlyflat, without overlapping: this is a far more economical method, decreasing the weightnearly half: a groove is run in the edges which receives a corresponding fillet, both at thesides and at the top and bottom, communicating with each other, and should any waterenter the joints it is carried down to the eaves in a continued line.

Pan Tiles , first used in Flanders, have a wavy or convex and concave surface one way,and are made \A\ inches in length and 10J inches in breadth ; their gauge is usually 10inches, and 170 are sufficient to cover 100 superficial feet; these tiles weigh from 5 to 5\lbs. each.

Ridge and Ilip Tiles are formed cylindrically, 13 inches in length, and girth 16, weighingon an average 5 pounds.

Gutter Tiles are nearly the same size and thickness.

Mathematical Tiles, for covering the upright surface of cottages, instead of lathing andplastering the outsides, are much in use in the counties of Kent and Sussex: these tiles areintended to resemble courses of brick, and are made to overlap each other; the face ofeach consists of two planes, the size of a common brick, and when placed in their properposition, they form a double thickness of tile; they are nailed on, and a fine mortar is in-troduced where they rest on each other, which is pointed in the same manner as ordinarybrickwork.

Weather Tiles differ from these : they lap over each other, and are made of variouspatterns, but having their size and thickness that of the common plain tile ; they resemblethe plates of chain mail, when in their position, and their exposed edges often receive avariety of outline, and form great diversity of pattern ; when put on with proper nails, theyare found very durable and keep out the weather. Various machines have been invented forthe manufacture of tiles, one of which, patented by Mr. Hunt, has two wooden cylinders,round which revolve bands of cloth, which press the clay into one regular thickness through-out ; this is conducted by a continued web over a covered wheel, curved on the rim, whichgives the cylindrical form to the tile; they then pass through iron moulds, and are cut offto the length required.

The Flat Tiles are made in somewhat similar manner: by this machine drain tiles, andthe sole pieces on which they rest, are moulded with the greatest correctness.

The Brick-making Machine , patented by the same inventor, has also two cylinders, eachcovered with an endless web, which are so placed that they form a sort of hopper on their twoupper cylindrical surfaces, the ends being enclosed by two iron plates: well temperedday from the pug mill is thrown into this hopper, and at the lower part it acquires the formand dimensions of a brick : beneath is worked an endless chain, by the movement of thecylinders, and at various marked intervals are laid the palette boards under the hopper;the clay is brought down by a slight pressure, and enters a frame, which has a wire stretchedacross it, which projects through the mass, and cuts off the requisite thickness; this isimmediately removed by the forward motion of the endless chain; and this operationis renewed as often as a new palette board is advanced under the hopper: such a machineproduces about 1200 bricks per hour, and is worked by two men and three boys.

Hrieks usually made with machinery are found to dry with more difficulty, in con-

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