Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/516

Rh 466 BUILDING [BRICKWORK. Discharg ing arches under openings. Chimneys and flues. Chimney hopper. Pargetttn: of joints, which are composed of material that must both yield to pressure and shrink in drying. Some part of the ill effect attendant on this is obviated by the bond-stones, which tail in or run through the wall, and tend&amp;gt;to keep the discordant materials together; but still much of it remains. And besides this, the internal or cross walls, which have 110 stone in them, will either settle down and shrink away from the external walls, or drag them inward, as they happen to be well or ill bonded or tied. For these reasons, brickwork built in this manner with masonry should be executed with exceedingly well-tempered mortar, made with no more lime than is absolutely necessary to cement the particles of sand together, and the sand again to the bricks, worked as stiff as it can be, and laid in as thin courses as may be to answer the purpose required of it. Above all, work of this kind must not be hurried, but allowed time to dry and shrink as it goes on. In some- large edifices the brickwork is carried up and com pleted, and after a sufficient time has elapsed for the work to have settled, the ashlaring is carried up and worked in with the bond stones set in the brickwork for the pur pose. Discharging arches over vacuities having been disposed of incidentally, we have now only to speak of them under openings, in which situation their use is to distribute the superincumbent weight equally over the substructure, or along the foundation as the case may be. For this purpose the arch is inverted, as shown in fig. 4, Plate XXI. ; and by means of it the weight brought down by the piers is carried along the footings, which are thus equally borne upon throughout their whole length. Arches of two half bricks are indicated here, that being sufficient for ordinary purposes, and to develop the principle ; in large and heavy works, arches of three half bricks, and even greater may be judged necessary. Any arc between a quadrant and a semicircle may be used with advantage ; but an arc of less than 45 cannot be recommended for the inverted dis charging arch under piers. Arches require abutments whether they are &quot;erect or inverted; this is often forgotten when inverted arches are used. Not the least important part of the bricklayer s art is the formation of chimney and other flues. Great tact is required in gathering-over properly above the fire-place, so as to conduct the smoke into the smaller flue, which itself requires to be built with, great care and precision, that it be not of various capacity in different parts, in one place contracted to a narrow straight, and in another more widely expanded, and so on. There is now often introduced at the level of the mantel, a plate with an opening in it through which the smoke ascends. This, which is called a chimney-hopper or chimney lintel, is very useful not only to ensure the proper gathering of the flue, as the brickwork of the flue is formed at once upon it, but as a substitute for the usual register, and it also renders needless the usual iron chimney bar required to support the breast. It is absolutely necessary that flues be of a certain magnitude, but the bore should be regulated by the size of the fire place, or rather by the quantity of smoke to which it is required to give vent. For large kitchen fires it is con sidered best to have two flues. Practical men differ as to whether a tapering flue, or an enlarging flue is best for carrying away smoke. They are usually made of one size throughout. Of late years cylindrical earthenware tubes have been used with advan tage, and of a smaller bore than the common 9-inch by 14-inch capacity. With glazed tubes it has been found that the soot falls down with thunderclaps and other strong a mortar in which,. a certain proportion of cow-dung is mixed, which prevents it from cracking and peeling off with the heat to which it is exposed. The part brought out into the room from the wall, and over the opening, is called the breast. The flooring in the opening is called the hearth, fig. 8, Plate XXI. ; it is set on the bricks or stones of the wall, and is usually of stone, although cement and iron plate are sometimes used. The slab is that part of the floor of a room which is immediately before the fire-place, and along the extent of its front. In basement rooms, this slab is supported by a brick wall brought up from the ground ; but in upper rooms the slab is supported by a flat half brick arch called a brick trimmer, which is turned from the chimney breast under the hearth on one side to the trimmer joist on the other, which is generally made some what thicker than the other joists for this purpose. The chimney-piece which comes in front is fixed by the mason after the carpenter s work is done. The plate above mentioned assists in ensuring a proper Causes draught to the flue, and preventing a smoky chimney, smoky These are frequently caused by want of sufficient air to feed c &quot; imn the fire, which must be supplied from the room itself or by a tube brought from the outside of the building. Another cause of smoke is too short a funnel, especially if the flue be a large one, as formerly built for sweeping by boys. Every fire-place must have its own flue. Other causes are one fire overpowering the other, when there are two in one large room, or two rooms communicating by a door way, or when the tops of chimneys are commanded by higher buildings, or by a hill, so that the wind sometimes blows almost perpendicularly into the tops of the chimneys that lie in its way and beats down the smoke. A down draught is usually produced by the difference of the exter nal atmosphere from that in the room; this often brings down the smoke of a neighbouring chimney ; it can occasionally be obviated by raising one of them, or by fixing on it one of the exhausting pots now manufactured for the purpose. The bad construction of fire-places is another cause of smoky chimneys, the throat being too large for the fire. We shall not attempt to describe the many patent and other inventions submitted for curing these nuisances, but what is known as Billings s terminal must be exceptcd. It con sists of a low conical top about a foot high, placed on the flue, and screened on each side by a tcrra-cotta baffler, rising somewhat higher than the pot ; the wind striking the former is thrown upwards and assists in extracting the smoke ; the latter prevents the smoke of one flue being blown down the adjoining ones in the same stack. The common terra-cotta pot with louvre sides is also useful and ornamental. Brick and tile paving is performed by the bricklayer. Pavin Brick-paving is either flat or on edge, in sand or in mortar brick. or cement. Brick flat-paving in sand, that is, with the bricks laid on their broadest surfaces, and bedded in and on dry sand, is very slight and fragile, and brick flat-paving set and bedded in mortar is very little better ; for if the soil on which the paving is laid be light and sandy, the bricks are easily displaced by being pressed unequally ; and if it be clayey it will probably be moist, and the thin porous brick absorbing the moisture, will generally become saturated, and present a damp unwholesome floor. Paving with bricks on their edges, however, forms a much better floor, and is preferable to a stone paving, if the latter be laid on the ground without the intervention of footings. Brick-on-edge paving in sand is generally used in beer cellars, pantries, dairies, stables, &c., as its numerous open joints allow wasted or discharged fluids readily to escape ; and it is both cool and dry under ordinary circumstances. In mortar or cement, bricks on their edges form a sound, dry floor ; the smallness of the surface exposed by each brick in this manner leaves them, of course, less susceptible of partial pressures, and the depth from the soil to the
 * . vibrations. Flues of brick are plastered or pargetted with