Fireplace

"[T]he flame and smoke will ascend and strike the top... which will thereby receive a considerable heat. The smoke, finding no passage upwards, turns over the top of the air-box, and descends between it and the back plate to the holes in the bottom plate, heating, as it passes, both plates of the air-box, and the said back plate; the front plate, bottom and side plates are also all heated at the same time. The smoke proceeds in the passage that leads it under and behind the false back, and so rises into the chimney."

"The air of the room, warmed behind the back plate, and by the sides, front, and top plates, becoming specifically lighter than the other air in the room, is obliged to rise; but the closure over the fire place hindering it from going up the chimney, it is forced out into the room, rises by the mantel-piece to the ceiling, and spreads all over the top of the room, whence being crowded down gradually by the stream of newly-warmed air that follows and rises above it, the whole room becomes in a short time equally warmed."

"At the same time, the air, warmed under the bottom plate and in the air-box, rises and comes out of the holes in the side plates, very swiftly, if the door of the room be shut, and joins its current with the stream before mentioned, rising from the side, back, and top plates."

"The air that enters the room through the air-box is fresh, though warm; and, computing the swiftness of its motion with the areas of the holes, it is found that near ten barrels of fresh air are hourly introduced by the air-box; and by this means the air in the room is continually changed, and kept at the same time sweet and warm."

"It is to be observed, that the entering air will not be warm at first lighting the fire, but heats gradually as the fire increases."

"Its advantages above the common fire-places are, 1. That your whole room is equally warmed, so that people need not crowd so close round the fire, but may sit near the window, and have the benefit of the light for reading, writing, needlework, &c. They may sit with comfort in any part of the room... 2. If you sit near the fire, you have not that cold draft of uncomfortable air nipping your back and heels, as when before common fires, by which many catch cold, being scorched before, and... froze behind. 3. If you sit against a crevice, there is not that sharp draft of cold air playing on you, as in rooms where there are fires in the common way; by which many catch cold, whence proceed coughs, catarrhs, tooth-aches, fevers, pleurisies, and many other diseases. 4. In case of sickness, they make most excellent nursing-rooms; as they constantly supply a sufficiency of fresh air, so warmed at the same time as to be no way inconvenient or dangerous. A small one does well in a chamber; and, the chimneys being fitted for it, it may be removed from one room to another, as occasion requires, and fixed in half an hour. The equal temper, too, and warmth of the air of the room, is thought to be particularly advantageous in some distempers... 5. In common chimneys, the strongest heat from the fire, which is upwards, goes directly up the chimney, and is lost; and there is such a strong draft into the chimney, that not only the upright heat, but also the back, sides, and downward heats are carried up the chimney by that draft of air; and the warmth given before the fire, by the rays that strike out towards the room, is continually driven back, crowded into the chimney, and carried up by the same draft of air. But here the upright heat strikes and heats the top plate, which warms the air above it, and that comes into the room. The heat likewise, which the fire communicates to the sides, back, bottom, and air-box, is all brought into the room; for you will find a constant current of warm air coming out of the chimney corner into the room. Hold a candle just under the mantel-piece, or breast of your chimney, and you will see the flame bent outwards; by laying a piece of smoking paper on the hearth, on either side, you may see how the current of air moves, and where it tends, for it will turn and carry the smoke with it. 6. Thus, as very little of the heat is lost, when this fire-place is used, much less wood will serve you, which is a considerable advantage where wood is dear. 7. When you burn candles near this fire-place, you will find that the flame burns quite upright, and does not blare and run the tallow down, by drawing towards the chimney, as against common fires. 8. This fire-place cures most smoky chimneys, and thereby preserves both the eyes and furniture. 9. It prevents the fouling of chimneys; much of the lint and dust that contributes to foul a chimney being, by the low arch, obliged to pass through the flame, where it is consumed. Then, less wood being burnt, there is less smoke made. Again, the shutter, or trap-bellows, soon blowing the wood into a flame, the same wood does not yield so much smoke as if burnt in a common chimney; for, as soon as flame begins, smoke in proportion ceases. 10. And, if a chimney should be foul, it is much less likely to take fire. If it should take fire, it is easily stifled and extinguished. 11. A fire may be very speedily made in this fire-place by the help of the shutter, or trap-bellows... 12. A fire may be soon extinguished by closing it with the shutter before, and turning the register behind, which will stifle it, and the brands will remain ready to rekindle. 13. The room being once warm, the warmth may be retained in it all night. 14. And lastly, the fire is so secured at night, that not one spark can fly out into the room to do damage."

"With all these conveniences, you do not lose the pleasing sight nor use of the fire, as in the Dutch stoves, but may boil the tea-kettle, warm the flat irons, heat heaters, keep warm a dish of victuals by setting it on the top, &c."

"We leave it to the political arithmetician to compute how much money will be saved to a country, by its spending two thirds less of fuel; how much labor saved in cutting and carriage of it; how much more land may be cleared by cultivation; how great the profit by the additional quantity of work done, in those trades particularly that do not exercise the body so much, but that the workfolks are obliged to run frequently to the fire to warm themselves; and to physicians to say, how much healthier thick-built towns and cities will be, now half suffocated with sulphury smoke, when so much less of that smoke shall be made, and the air breathed by the inhabitants be consequently so much purer."

"[T]he builder of chimneys has been left to grope his way in the dark without assistant; and in almost every instance his attempts to improve upon the practice of his predecessors, have been unsuccessful; so that the inhabitants of these countries, with justice, complain that the inconveniencies felt in new houses from this cause, usually are more than sufficient to counterbalance all the elegancies that modern refinement has introduced into the dwellings..."

"[T]he causes which produce smoke in rooms... may be all reduced to one of the three following general classes: 1. A faulty construction of the tube, vent, or chimney itself; 2. To some fault in the other parts of the building, and a wrong position of the chimney with respect to these; or, 3. To an improper situation of the house with respect to external objects."

"The earth is every where surrounded with a great body of air, that is called the atmosphere. This air is a thin elastic fluid, possessing some qualities peculiar to itself, but subjected in general to the same physical laws with other fluids; and of consequence it hath a constant tendency to preserve an exact equilibrium in all its parts; so that if at any time the weight of it at one place is diminished, the heavier air rushes from all sides towards that point, till the equilibrium be again restored."

"Many are the causes that may tend to destroy this equilibrium of the atmosphere; but the only one that it imports our present discussion to explain the effects of, is ."

"When heat acts upon the air, it immediately makes it expand to a great degree, so as that the same quantity of it occupies a much larger space than formerly. Hence... where a fire is kindled, the air immediately contiguous to it will be heated, and of consequence rarefied, and made lighter..."

"[A]s it is an invariable rule among all fluids, that those which are lightest rise upwards, and at length swim upon the top of such as are more weighty... so... that when any particles of the same fluid are... rendered lighter, or more weighty, than other parts... they either rise to the top, and give place to the more dense and weighty parts of it, or sink to the bottom, and force the warmer fluid to the surface."

"It is owing to this cause that the water at the top of a caldron, before it begins to boil, is always as warm, or warmer, than what is below:—for the particles of water that touch the bottom are no sooner acted upon by the heat below, than they become warmer, and more expanded, than those immediately above them, and therefore rise directly upwards, and give place to denser cold particles, which are forced in their turn to ascend in like manner towards the top."

"In the same manner... when the air contiguous to a fire is heated... it is immediately expanded very much; and therefore instantly rises upwards, till it reaches the higher regions of the atmosphere, or is cooled by gradually mixing with the denser air it meets with in its ascent:—and as its place contiguous to the fire is immediately occupied by the cold dense air around it, which rushes from every side towards that point, it is heated and rarefied in its turn, and ascends in the same manner, carrying the smoke that rises from the burning body along with it."

"It is in this manner that the constant suction of air towards every fire is produced; and from this cause proceeds the continual tendency of smoke to ascend from the surface of the earth, unless where some circumstance interrupts the course of nature."

"[M]en... disccovered, that when the fire was surrounded with a wall to any considerable height, the motion of the wind was interrupted by it, and the smoke allowed to rise upwards till it reached the top of the building.—The free ascent of this disagreeble vapour... was promoted by the addition of a roof... Hence... in every part of the globe the first and most simple huts... are circular buildings, with a conical roof; in the middle of which, for the most part, is left a hole for the emission of the smoke; the fire having been placed in the centre of the building immediately below the opening, which served instead of a window, as well as a vent-hole for the smoke."

"[A]s luxury encreased, and the elegant arts became more common... fire places were contracted to a narrower size.——The grate, instead of being placed in the middle of a large area, with seats around it, was pushed close to the back wall. The width of the opening of the vent, was found to be sufficient if it contained the whole of the grate;—and as the fire warmed the room more effectually when it came well forward, the grate was brought as far into the apartment as could be done.—The pipe of the chimney was contracted to such dimensions as to admit of being contained within the thickness of an ordinary wall, and reduced to that elegant and commodious tube now known by the name of chimney."

"[H]igh [longer] chimneys... have a greater suction of air, and are less liable to vent ill, than low ones, and this is one principal reason why in the same house the chimneys in the garrets, and the higher stories, are more apt to vent ill, than those on the floor, where the chimneys are of necessity longer. A smoky chimney, therefore, may sometimes be cured, merely by raising it higher..."

"A chimney may not only be defective by having the mantle too high, or by being too wide from side to side, but also by being too deep between the fore-side and the back, as is often the case in very old houses. In this case, the distance between the fire and the mantle is so great, that much air passes up without being sufficiently rarefied... This fault may be sometimes cured, by bringing the grate a little forward, which, by making the fire act more powerfully upon the mantle, rarefies the air more in its passage."

"[W]hen the grate is brought forward, there is a great vacancy left between it and the back of the chimney, so... air passes under the grate, and ascends behind it very little rarefied; so... there will be as much lost in this way as will be gained in the other: and as there is not enough of heated air... to make the vapour ascend with rapidity, they are often choaked with thick fuliginous vapours hanging in them, almost in equilibrio with the rest of the atmosphere, so that the least puff of wind beats them down the chimney, and pushes the smoke into the room; whereas, when it is far back, it is driven down upon the hearth, and rises upwards again when the gust is over, and a great deal of it is catched within the mantle as it rises, which in the other case would have been dispersed through the room."

"When this is the case the most effectual method... is, to bring the grate forward till the forepart of it is immediately under the inner edge of the mantle; then build up the vacancy at the back of it, the whole width of the fire-place from side to side, raising it perpendicularly till it is as high as the back of the grate, and then bending it forward towards the mantle, as... fig 4. When it is as high as the workman can reach, let it be suddenly turned backward again, sloping a little upward... then fit a sheet of milled iron to the inside of the mantle, making it slant a little upward toward the back... a small distance above the new... masonry, and extending within a few inches of the back wall... By this construction all the air that enters into the chimney is made to pass immediately above the fire, between it and the heated iron... as the back of the fire-place is bent a little forward above the grate... the heat is likewise reflected into the room with the greater force... [I]f the smoke is accidentally beat down the chimney by a sudden gust of wind, it will be catched by the sheet of Iron, and prevented from coming into the room."

"[Y]ou desire me to give you... my thoughts upon the Construction and Use of Chimneys... I embrace willingly this leisure... to comply... as it will not only fhew my regard to... a friend, but may... be of some utility to others; the doctrine of chimneys appearing not to be as yet generally well understood, and mistakes respecting them being attended with constant inconvenience, if not remedied; and with fruitless expence, if the true remedies are mistaken."

"Having lit a pipe of tobacco, plunge the stem to the bottom of a decanter half filled with cold water; then putting a rag over the bowl, blow through it, and make the smoke descend in the stem of the pipe, from the end of which it will rise in bubbles through the water; and being thus cooled will not afterwards rise to go out through the neck of the decanter, but remain spreading itself, and resting on the surface of the water. This shews that smoke is really heavier than air; and that it is carried upwards only when attached to, or acted upon, by air that is heated, and thereby rarefied and rendered specifically lighter than the air in its neighbourhood."

"Smoke being rarely seen but in company with heated air, and its upward motion being visible, though that of the rarefied air that drives it is not so, has naturally given rise to... error."

"[A]ir is a which has weight as well as others, though about eight hundred times lighter than water; that heat makes the particles of air recede from each other and take up more space, so that the same weight of air heated will have more bulk [volume] than equal weights of cold air which may surround it, and in that case must rise, being forced upwards by such colder and heavier air, which presses to get under it, and take its place."

"That air is so rarefied or expanded by heat, may be proved to... by a lank blown bladder, which laid before a fire will soon swell, grow tight, and burst."

"Another experiment may be, to take a glass tube... open at both ends, and fixed upright on legs, so that it need not be handled, for the hands might warm it: at the end of a quill, fasten five or six inches of the finest light filament of silk, so that it may be held either above the upper end of the tube or under the lower end, your warm hand being at a distance by the length of the quill. If there were any motion of air through the tube, it would manifest itself by its effect on the silk [Fig. I]; but if the tube and the air in it are of the same temperature with the surrounding air, there will be no such motion. ...Warm the tube, and you will find as long as it continues warm, a constant current of air entering below and passing up through it, till discharged at the top; because the warmth of the tube... rarefies that air, and makes it lighter than the air without, which therefore presses in below, forces it upwards, follows and takes its place, and is rarefied in its turn."

"[N]o form of the funnel of the chimney has any share in its operation or effect respecting smoke, except its height. The longer the funnel if erect, the greater its force when filled with heated and rarefied air, to draw in below and drive up the smoke (if one may in compliance with custom use the expression draw), when in fact it is the superior weight of the surrounding atmosphere that presses to enter the funnel below, and so drives up... the smoke and warm air..."

"I have been... particular in explaining these first principles, because for want of clear ideas respecting them, much fruitless expence has been occasioned... whole stacks having been pulled down and rebuilt with funnels of different forms, imagined more powerful in drawing smoke, but having still the same height and the same opening below, have performed no better than their predecessors."

"What is it then which makes a smoky chimney..? The causes of this effect which have fallen under my observation, amount to nine..."

"Smoky chimneys in a new house are [as] such frequently from mere want of air. The workmanship of the rooms being all good... true and tight... The doors and the sashes too, being worked with truth, shut with exactness so that the room is as tight as a snuff-box."

"Now, if smoke cannot rise... unless other air be admitted to supply its place; and if therefore no current of air enter the opening of the chimney, there is nothing to prevent the smoke coming out into the room."

"If... a column of air, equal to the content of the funnel, must be discharged, and an equal quantity supplied from the room below; it will appear absolutely impossible that this operation should go on if the tight room is kept shut: for were there any force capable of drawing constantly so much air out of it, it must soon be exhausted, like the receiver of an air-pump, and no animal could live in it."

"Those therefore who stop every crevice in a room to prevent the admission of fresh air, and yet would have their chimney carry up the smoke, require inconsistencies, and expect impossibilities."

"I have seen the owner of a new house in despair, and ready to sell it for much less than it cost, conceiving it uninhabitable, because not a chimney in any one of its rooms would carry off the smoke, unless a door or window were left open."

"Much expence has... been made to alter and amend new chimneys which had really no fault: in one house... of a nobleman in Westminster, that expence amounted to... three hundred pounds... and after all, several... alterations were ineffectual, for want of understanding the true principles."

"When you find... that opening the door or a window enables the chimney to carry up all the smoke, you may be sure that want of air from without was the cause of its smoking: I say from without, to guard you against a common mistake of those who may tell you, the room is large, [and] contains abundance of air sufficient to supply any chimney... These reasoners are ignorant, that the largeness of a room, if tight, is... of small importance, since it cannot part with a chimneyful of its air, without occasioning so much vacuum..."

"It appearing plainly... that some of the outward air must be admitted, the question will be, How much is absolutely necessary? ...To discover this quantity, shut the door gradually, while a middling fire is burning, till... the smoke begins to come out into the room; then open it a little, till you perceive the smoke comes out no longer: there hold the door, and observe the width of the open crevice... thence... your room requires an entrance for air equal in area.. I have found ...thirty-six square inches, to... serve for most chimneys."

"High funnels, with small and low openings, may indeed be supplied through a less space [in area]; because... the force of levity being greater in such funnels, the cool air enters the room with greater velocity, and consequently more enters in the same time. This, however, has its limits..."

"It remains then to be considered, how and where this necessary quantity of air from without is to be admitted, so as to be least inconvenient. For, if... the air proceeds directly to the chimney, and... comes cold to your back and heels, as you sit before your fire you feel the... inconvenience."

"Various have been the contrivances to avoid this: such as bringing in fresh air through pipes, in the jams of the chimney, which, pointing upwards, should blow the smoke up the funnel; opening passages into the funnel above, to let in air for the same purpose. But these produce an effect contrary to that intended; for, as it is the constant current of air passing from the room through the opening of the chimney into the funnel, which prevents the smoke coming out into the room, if you supply the funnel by other means, or in other ways, with the air it wants, and especially if that air be cold, you diminish the force of that current, and the smoke, in its efforts to enter the room, finds less resistance."

"The wanted air must... indispensibly be admitted into the room to supply what goes off through the opening of the chimney. M. Gauger... proposes, with judgment, to admit it above the opening of the chimney; and to prevent inconvenience from its coldness, he directs its being made to pass in its entrance through winding cavities made behind the iron back and sides of the fire-place; and under the iron hearth-plate; in which cavities it will be warmed, and even heated, so as to contribute much, instead of cooling, to the warming of the room. This invention is excellent in itself, and may be used with advantage in building new houses; because the chimneys may then be so disposed as to admit conveniently the cold air to enter such passages: but, in houses built without such views, the chimneys are often so situated as not to afford that convenience, without great and expensive alterations. Easy and cheap methods, though not quite so perfect in themselves, are of more general utility; and such are the following:"

"Few can imagine the difference of climate between the upper and lower parts of such a room, who have not tried it by the thermometer, or by going up a ladder till their heads are near the ceiling. It is then among this warm air that the wanted quantity of outward air is best admitted."

"This may be easily done by drawing down about an inch the upper sash of a window; or, if not moveable, by cutting such a crevice through its frame... it will be well to place a thin shelf... to conceal the opening; and sloping upwards, to direct the entering air... In some houses, the air may be admitted by such a crevice... near the ceiling and over the opening of the chimney. ...[T]he entering cold air will there meet with the warmest rising air from before the fire, and be soonest tempered by the mixture. The same kind of shelf should also be placed here."

"Another way... is to take out an upper pane of glass in one of your sashes: set it in a tin frame, giving it two springing angular sides, and then replacing it with hinges below [Fig. 2], on which it may be turned to open more or less above. ...By drawing this pane in more or less, you may admit... air... Its position will naturally throw that air up and along the ceiling."

"A second cause of the smoking of chimneys is, their openings in the room being too large... Architects... have no other ideas of proportion in the opening of a chimney, than what relate to symmetry and beauty... while its true proportion, respecting its function and utility, depends on quite other principles... The proportion then to be regarded, is what relates to the height of the funnel. For... funnels in the different stories of a house are necessarily of different heights or lengths... [T]he openings of the longest funnels may be larger, and that those of the shorter funnels should be smaller. For if there be a large opening to a chimney that does not draw strongly, the funnel may... be furnished with the air it demands by a partial current... on one side of the opening... the other side free of any opposing current, may permit the smoke to issue there into the room."

"Much... of the force of draft in a funnel depends on the degree of rarefaction in the air it contains; and that depends on the nearness to the fire... in entering the funnel. If it can enter far from the fire on each side, or far above the fire in a [too] wide or high opening, it receives little heat in passing by the fire, and the contents of the funnel is by that means less different in levity from the surrounding atmosphere, and its force in drawing consequently weaker."

"Those who have any doubts respecting the very great change of air or ventilation which takes place each time the door of a warm room is opened in cold weather, need only set the door... wide open for a moment, and hold two lighted candles in the door-way, one near the top of the door, and the other near the bottom... The violence with which the flame of that above will be driven outwards, and that below inwards by the two strong currents of air which, passing in opposite directions, rush in and out of the room at the same time, will [convince them] that the change of air which actually takes place must be very considerable... and these currents will be stronger, and consequently the change of air greater, in proportion as the difference is greater between the temperatures of the air within the room and of that without."