Page:An Encyclopædia of Cottage, Farm, and Villa Architecture and Furniture.djvu/314

 290 COTTAGE, FARM, AND VILLA ARCHITECTURE. seen. In kitcliens on the ground floor, it is a common practice, in many places, to leave an ash-pit under the kitchen range, three or four feet deep, covered with a wrought-iron grating, into which the ashes fall, and are only taken out when it is full, generally when the chimneys are swept. This practice is highly commendable, as saving the labour of daily carrying out and sifting the ashes, and bringing back the cinders. 602. The rounding of the chimney breast, and the contraction of tlte throat of the flue, whatever may be the kind of grate adopted, are points which contribute materially to the free draught of every chimney. The chimney breast requires to be rounded, in order to direct the current of cool air drawn from that of the room gradually upwards, so that it may mix in by degrees with the current of hot air ascending from the fuel chamber, instead of striking against it at right angles, which it must necessarily do when the chimney breast is not rounded. The object of contracting the throat of the chimney is to diminish tlie quantity of heat drawn from the room, by the current of air which is continually passing up the chimney ; but the same contraction, it is justly observed by Mr. Tredgold, often augments the draught to such a degree, as greatly to increase the consumption of fuel. The grand point to be attained is, such a di-aught as will do nothing more than carry off the smoke, and keep the fire clear ; because then there is the greatest radiation from the fire and fireplace, with the least waste of hot air from the room. The rounding of the chimney breast may either be effected by having a stone lintel or a cast-iron one. In countries where stone is so abundant that lintels of that material are thrown across the openings of the fireplaces, the under side may be rounded off as at a, in fig. 541, and the throat of the flue gradually contracted (as shown in the section from c to d, p. 113.), till, at the height of two or tlu-ee feet from the chimney breast, the superficial area, in ordinary cases, is not more than 90 or 100 square inches; this being found by experience to be a suitabley sized flue for an ordinary coal fire. When this contraction has been neglected in building the chimney, or done improperly ; or when it is found necessary to contract the throat still farther, to create a draught ; this may be done, in stone countries, by the piece of flag-stone, b, set on the surface, c, which may be moved backward or forward to adjust the draughts to the degree required. When fires are no longer wanted, this stone may be brought forward so as to lean against the breast of the chimney, as at d, to close up the flue ; or thrown back, as at e, when the chimney is to be swept. That this may be done with ease, and without dirtying the hands, the stone may be removed by inserting the points of the tongs in two holes cut in its face for that purpose. In countries where brick is the principal building material, the chimney breast, as we have seen, § 79, is built on an iron bar : this bar is generally flat, and about three inches broad ; consequently its inner edge pre- sents a sharp angle, instead of the rounded surface repre- sented in fig. 541 : to remedy this, a bar has been invented by Mr. Chadley, fig. 542, the cross section of which, taken at the centre of the opening, is shown at f; and another cross section, taken nearer the end, is shown at g. This is obviously an excellent bar, and its cost, for an opening three feet wide, is not more than the usual expense of a common wTought-iron bar, suitable for the same opening. " The contrivance for contracting or closing the throats of chimneys, itr brick-built buildings, is cither by a plate of cast iron, formed with a base so as to stand like the stone, d b 543 b, in fig. 541 ; or by what is called a register plate, fig. 543. In the latter case the plate is furnished with a turn latch, which may be worked by the tongs, so as to regulate the distance between its upper edge and the breast of the flue. It may