KI L
87
K I L
measure, wlneli contains twoTwo kilderkins make a barrel,
Keys are used for the purpose of preventing boards fromharping.
Dado, when made of broad boards, glued together, shoulda h\'ays be keyed. See Dado.
KEY-STONE, of an arch or vault, the last stone placedthe top thereof; which, being wider and fuller at the top,,‘ ari at the bottom, wedges, as it were, and binds in allrest.
. M. Belidor makes the thickness of the arch-stones of ato ge ’ one twenty-fourth part of the width of the arch; but. lr> Gautier, another experienced engineer, makes their. ea gth, in an arch 24 feet wide, 2 feet; in arches, 45, 60,, 5 . 90 wide, 3, 4, 5, 6 feet respectively; and it is observedy Mr. Muller, that the thickness allowed by Belidor is notufficient to prevent the weight of the arches from crushing11 e key-stones to pieces by their pressure against one
another.
, The name key-stones, or arch-stones, is sometimes also® lv en to all the stones which form the sweep of an arch, orau 't> answering to what the French more distinctly callv °Ussoirs.
Kilderkin, a liquid measure, which
‘ ‘ins, or eighteen gallons.
four a hogshead.
KILN , a kind of oven, or stove, for admitting heat, in^ner to dry substances of various kinds, as corn, malt, hops,C- It also signifies a fabric or building constructed for therifpose of burning limestone, chalk, and other calcareousin°3^ S ’ ‘ nto hme. Kilns are of different kinds, and formeddifferent ways, according to the purposes for which theyr ®designed.
8t . LN > Hop, a stove or kiln for the purpose of drying or°l in g hops.
v Kiln, Lime, a sort of kiln constructed for the purpose ofding lime. The operation called burning lime, consists inO t^ 0s ‘ n g marble, limestone, chalk, oyster - shells, or any? r carbonate of lime, for some time to a white heat, by8 , lc d means the carbonic acid and water contained in thesel; ar stan ces are expelled ; and the earth, which lias the pecu-?. Paracters assigned to lime, is left behind in a mass whichder c °herence, an d is therefore easily reduced to pow-| p re ' It is usually called quick-lime after calcination. NewlyI o ne P r d - K absorbs water with great avidity; it will absorbf ~ ° Ut 'th of its weight of that fluid, and still remain per-it tL dt T" II a sufficient quantity of water be poured uponin’j tle iime falls into powder ; some of the water is convertedUjji v apour by the disengaged caloric of that part whichthe 68 vv 'th the lime ; this is called the slacking of lime : ifPla qUantit y slacked be considerable, and performed in a darkof ''glit will be observed as well as heat. Kilns are built
Mii ', erent forms or shapes, according to the manner in6, t)nl tPe y are t0 b e wrought, and the kinds of fuel to befj a | °y e d. It may be remarked, that, in places where mate-v.-fj are dear, from their being fetched from a distance, andi s ® re tlie fuel is coals, and also expensive, the form of a kilnCo tiv° S • °I an inverted cone, a form which has its in-
is D et "ences ; but in districts where the art of burning limeh a ‘ “ctised with superior attention and correctness, the formel|; . Kte years been gradually changing from conical toof a Jp a L Some writers are of opinion, that the best formday . Un c-furnace, in the established practice of the presentI'lit l V d * at °I an egg placed upon its narrower end, havinglts broader end struck off, and its sides somewhatI'lw ® ss ed, especially towards the lower extremity; theIp . a ~pl°t or bottom of the kiln being nearly an oval, with* ’ or draft-hole, toward each end of it. It is supposed
that two advantages are gained by this form, over that of thecone. By the upper part of the ‘kiln being contracted, theheat does not fly off so freely as it does out of a spreadingcone. On the contrary, it thereby receives a degree of rever-beration, which adds to its intensity. But the other, and stillmore valuable effect, is this : when the cooled lime is drawnout at the bottom of the furnace, the ignited mass, in theupper parts of it, settles down, freely and evenly, into thecentral parts of the kiln ; whereas, in a conical surface,the regular contraction of its width, in the upper as well asthe lower parts of it, prevents the burning materials fromsettling uniformly, and levelling downward. They hang uponthe sides of the kiln, and either form a dome at the bottomof the burning mass, with a void space beneath it, therebyendangering the structure, if not the workmen, employed ;or, breaking down in the centre, form a funnel, down whichthe underburnt stones find their way to the draft-holes.And the contraction of the lower part of the kiln has not thesame effect; for, after the fuel is exhausted, the adhesionceases, the mass loosens, and, as the lime cools, the less roomit requires. It therefore runs down freely to the draft-holes,notwithstanding the quick contraction of the bottom of thekiln or surface.
Lastly, with respect to the lime-furnace, the fire requiresto be furnished with a regular supply of air. When a kilnis first lighted, the draft-holes afford the required supply.But after the fire becomes stationary in the middle, or to-wards the upper part of the kiln, (especially of a tall kiln,)while the space below is occupied by burnt lime, the supplyfrom ordinary draft-holes becomes insufficient. If the wallsof the kiln have been carried up dry or without mortar, theair finds its way through them to the fire. In large deepkilns that are built with air-tight walls, it is common to formair-holes in their sides, especially in front, over the draft-holes. But these convey the air, in partial currents, to oneside of the kiln only, whereas that which is admitted at thedraft-holes passes regularly upward to the centre, as well asto every side of the burning mass ; and, moreover, tends tocool the burnt lime in its passage downward, thereby contri-buting to the ease and health of the workmen. Hence, it isto be observed, the size of the draft-holes ought to be pro-portionate to that of the kiln and the size of the stones takenjointly, (air passing more freely among large than amongsmall stones,) and the required supply of air should be whollyadmitted at the draft-holes. By a sliding or a shifting valve,the supply may be regulated, and the degree of heat be in-creased or diminished, according to circumstances.
The most ancient kind of lime-kiln is probably that whichis made by excavating the earth in the form of a cone, ofsuch a size as may be necessary ; and afterwards building upthe sides, or not, according to the circumstances of the case :the materials being then laid in, in alternate layers of fueland stone, properly broken, until the whole is filled up. Thetop is then covered with sods, in order that the heat may beprevented from escaping : and the fire lighted at the bottom,and the whole of the contents burnt, in a greater or lessspace of time, in proportion to the nature of the stone, andthe quantity that is contained in the kiln. From the circum-stance, of the top parts of these kilns, in some districts,being covered over, and the sides sometimes built up withsods, they are termed sod-kilns, in order to distinguish themfrom the other sorts. When the whole of the contents ofsuch kilns are grown cold, they are drawn or taken out fromthe bottom ; and the kiln again filled, if necessary. Thesekilns are obviously intended for burning only one kiln-fullat a time. But as the burning of lime in this way is tediousand uneconomical, other methods and forms of kilns have