59S COTTAGE, FARM, AND VILLA ARCHITECTURE. 1151 1152
the laths, which may be either of cast or wrought iron ; when of cast iron, they are four feet long, roach-bellied, that is, forming the segment of a circle on the under side, two inches broad at top, and a quarter of an inch on the imder edge ; when they are of wrought iron, they are one inch and a half broad (that breadth being necessary to form a bed for the tiles), and half an inch deep ; in this case the extended lengtli across the girders is from one of the kilns to the other : c c are the tiles pierced with holes, in the same manner as the tiles of malt-kilns, fig. 1 1 35, § 1 267. 1278. Construction. The exterior walls are of brick, with eighteen-inch footings, and are carried up . a foot or more of the width of fourteen inches, after which their width is nine inches, up to the eaves of the roof, which are eighteen inches above the drying-floor. The rafters are four inches by two inches at the bottom ; and three inches by one inch and a half at the top, where they abut against a circular curb or rim under the cowl. The furnaces or fuel-chambers are entirely of cast iron, and the ash-pits have iron doors. At the further extremity of the fuel-chamber there is an opening six inches square at top, through which the smoke and heat ascend into the flue. The flue for the first three or four feet is either built of fire-brick, or formed entirely of cast iron six inches in diameter ; after which its sides are formed of three bricks on edge, not plastered either outside or inside ; and its top is covered with two courses of tiles, breaking joint, six inches by three inches. The reason why narrow tiles are chosen is, that duty is saved ; and two courses breaking joint are employed, in order to prevent the risk of smoke getting through the joints into the dunge. The flues are svipported by piers formed of open brickwork on edge, and joined by arches four inches in thickness, beveled on the top so as to form the base of the flue. Two flues proceed from each fireplace, ascending at an angle of 15°, or more if the height of the dimge will permit, in the direction indicated by the arrows, meeting at e, in the plan fig. 1148, and each there returning over itself, and again meeting at the chimney shaft, /;. These flues may be easily cleaned by the removal, at short distances, of some of the covering-tiles ; or, what is a much simpler mode, by burning in the fuel-chamber a few handfuls of dry brushwood, or dried hop-bine, or any thing that will quickly create such a draught as will carry all the soot in the course of a few minutes out at the cliimney top. About London the washer- women clean the chimneys of their boilers on the same principle, by throwing in, in rapid succession, small quantities of gunpowder. The cowl should project about a foot on every side over the orifice in the summit. This orifice is, to that for the admission of air to the dunge, as one to one and a quarter. In the building of the walls of the kiln, in order to preserve them truly circular, an upright pole is fixed in the centre, and a guide-rod, fig. 1153, d, is framed on to it, of the requisite radius. The lower end of the central perpendicular pole is fixed in the ground, and the top kept steady by braces to other poles outside the circumference of the plan, so as not to interrupt the free revolution of the guide-rod. For every course of bricks laid on the wall, a course is also laid in mortar round the upright pole luider the guide-rod, so that the latter is always kept level. So rapidly can bricks be laid in this manner, that INIr. Read finds sue walling cost less than straight brickwork. The course of bricks innnediatcly under the flooring tiles, twenty inches from the top, ought to project an inch inwards for the tiles to rest on. The exterior opening to the dunge should be kept low, it being found that
