tile exposing a semicircular face to the weather. The semicircular portion has a drop flange, which catches over the

Fig. 128.

0.10

re-entering curves of the upper part, these curves having upturned flanges for that purpose. Whenever roof tiles are to be glazed, they are varnished after being burned; the glaze is then put on, and the tiles are then placed in a potter's oven and remain until the glaze commences to run. The glaze is usually made from what are called lead ashes, being lead melted and stirred with a ladle till it is reduced to ashes or dross, which is then sifted, and the refuse ground on a stone and resifted. This is mixed with pounded calcined flints.

A glaze of manganese is also sometimes employed, which gives a smoke-brown color.

For a black color iron filings are sometimes used; for green, copper slag; and for blue, smalt is employed, the tile first wetted and the composition laid on from a sieve.

At one time very inferior roof-tiles were made in England on account of the careless weathering or preparation of the clay employed; and in order to cure this a statue of Edward IV. required that all clay for tiles should be dug, or cast up, before the first of November, and not made into tiles before the March following.

The garden of the Louvre in Paris was called the Tuileries, as being a place where tiles were anciently made; a magnificent palace was begun there in 1564 by Catherine de Medicis, wife of Henry II., finished by Henry IV., and splendidly adorned by Louis XIV., but was sadly defaced in our times, during the Franco-Prussian war.

Modern tile-covered roofs add greatly to the picturesque appearance of buildings.

A portion of a roof covered with diamond-shaped tiles is shown in Fig. 129, and the form of the tile is shown in a section, and a plan of face and bed.

Fig. 130 shows a roof covered with tiles of various shapes, and Fig. 131 shows the six forms of roofing tiles in most common use in this country.

A great advantage for the tile roof is that it is a non-conductor, and, therefore, cooler in the summer season than any other kind of roof. The buff tile, being lighter in color, is the coolest, as it does not absorb the rays of the sun. Tiles are also a better protection against lightning than the lightning-rod, as the latter attracts electricity, while the former is a non-conductor. Insulators, made of pottery, are extensively used on telegraph lines in Europe and portions of America.

The rain water collected from a tile roof is much purer

Fig. 130.

and cleaner than from any other kind of roof, as the tiles are very smooth, and no dust or soot settles upon them.

Tiles are indestructible, and are not affected by heat or cold. They will not crack and slide off the roof, like slate, leaving the sheathing exposed, when subjected to sudden heat, as by the burning of an adjoining building.

After doing service on one structure, the tile can be taken off and used on other buildings. Tiles should not be put upon a roof that has less than one-quarter pitch (a slant of six inches to the foot), although we have seen some roofs of less pitch which are satisfactory. A roof to support tile should be somewhat stronger than for shingles. The rafters should be 2x 6, 18 inches apart, and well stayed, so that they cannot spread. The sheathing should be of soft wood, of even thickness, and close together. Generally felt or tarred paper is placed under the tile, although it is not necessary to make the roof water-tight, but it stops circulation and makes the roof warmer in winter, and adds but little to the cost.

SECTION II. THE PROCESS OF MANUFACTURING
ROOFING TILES.

When the process of manufacturing roofing tiles is conducted by hand, the method is nearly the same in this country as in England, and but few improvements have been made in this mode of production; but by the machine process we are enabled to manufacture very satisfactory roofing tiles at but a small cost.

The clay of which the tiles are made is dug and spread out in shallow beds to disintegrate, and a hot sun or dry frosty weather is best for this.

In all cases the clay should next be finely pulverized by passing through iron rollers or other suitable appliances, and too much care cannot be given to this branch of the preparation of the clay, as has before been observed.

The clay-mills shown in Chapter VI. can be used to advantage in pulverizing the clay.

A good pug-mill which can have the knives made larger at the top than at the bottom and used for tempering the clay when the tiles are made by hand, is shown in Chapter IV.

The usual form of pug-mill employed in England is generally six feet high, three feet in diameter at the larger or upper end, and two feet at the bottom.

The clay is kneaded and completely mixed by a revolving cast-iron spindle, which carries a series of flat steel arms, so arranged as to form by rotation a worm-like motion upon the clay, which is pressed from the larger to the smaller diameter of the tub in which the clay is confined, and finally comes oozing out of an aperture at the bottom; in this manner of tempering great cohesive power is given to the clay.

The clay is then ready to make roofing tiles, the moulding is usually conducted in a shed, and most of the manufacturers prefer to place their tiles in the open air, if the weather allows.

The moulding table or bench is supported on four legs, which are well under the table, leaving the two ends of the top of the table to project liberally. The coal-dust box, 14 x 8 inches, is at the left hand of the moulder, at the corner of the table, and the moulding board, 14 x 10 inches, is usually placed slightly to the right of the coal-dust box.