Engineering

"[I]n any chimney, the air over the fire is rarefied by the heat, becomes lighter, and therefore immediately rises in the funnel, and goes out; the other air in the room (flowing towards the chimney) supplies its place, is rarefied in its turn, and rises likewise; the place of the air thus carried out of the room, is supplied by fresh air coming in through doors and windows, or, if they be shut, through every crevice with violence, as may be seen by holding a candle to a key-hole."

"2. Heat may be separated from the smoke as well as from the light, by means of a plate of iron, which will suffer heat to pass through it without the others."

"1. Fire... throws out light, heat, and smoke (or fume.) The [first] two... move in right lines, and with great swiftness; the latter is but just separated from the fuel, and then moves only as it is carried by the stream of rarefied air; and without a continual accession and recession of air, to carry off the smoky fumes, they would remain crowded about the fire, and stifle it."

"If the room be so tight as that all the crevices together will not supply so much air as is continually carried off, then, in a little time, the current up the funnel must flag, and the smoke, being no longer driven up, must come into the room."

"If the Chimney is apt to smoke, it will sometimes be necessary either to lower the mantle or to diminish the height of the opening of the Fire-place, by throwing over a flat arch, or putting in a straight piece of stone from one side of it to the other, or... building a wall of bricks, supported by a flat bar of iron, immediately under the mantle."

"When the throat of a chimney is situated very high up above the mantle, and especially when the mantle and breast of the chimney, or the wall that reposes on the mantle, are very thin, workmen who are employed to alter chimnies, setting about the work with their minds strongly prepossessed with what they consider as the leading principle... that the throat of the chimney should not be more than four inches wide, they are very apt to bring the grate too far forward. In dropping their plumb-line from the breast of the chimney, they do not reach up high enough into the chimney, but take a part of the breast, where it still goes on to slope backwards, for the bottom of the perpendicular canal of the chimney. They also very often commit another fault, not less essential... in neglecting to bring down the throat of the chimney nearer to the fire, when... too high."

"1. The first of these methods has generally the conveniency of two warm seats, one in each corner; but they are sometimes too hot to abide in, and, at other times, incommoded with the smoke; there is likewise good room for the cook to move, to hang on pots, &c. Their inconveniences are, that they almost always smoke, if the door be not left open; that they require a large funnel, and a large funnel carries off a great quantity of air, which occasions what is called a strong draft to the chimney, without which strong draft the smoke would come out of some part or other of so large an opening, so that the door can seldom be shut; and the cold air so nips the backs and heels of those that sit before the fire, that they have no comfort till either screens or settles are provided (at a considerable expense) to keep it off, which both cumber the room, and darken the fire-side. A moderate quantity of wood on the fire, in so large a hearth, seems but little; and, in so strong and cold a draft, warms but little; so that people are continually laying on more. In short, it is next to impossible to warm a room with such a fire place; and I suppose our ancestors never thought of warming rooms to sit in; all they purposed was, to have a place to make a fire in, by which they might warm themselves when cold."

"[C]onsider the fire-places heretofore in use, viz. 1. The large open fire-places used in the days of our fathers, and still generally in the country, and in kitchens. 2. The newer-fashioned fire-places, with low breasts and narrow hearths. 3. Fire-places with hollow backs, hearths and jambs of iron, (described by M. Gauger, in his tract entitled La Méchanique de Feu,) for warming the air as it comes into the room. 4. The Holland stoves, with iron doors opening into the room. 5. The German stoves, which have no opening in the room where they are used, but the fire is put in from some other room, or from without. 6. Iron pots, with open charcoal fires, placed in the middle of a room."

"Savot pointed out the means for curing that domestic plague—a smoky chimney; and, like a true physician, set about investigating the causes of the disease."

"3. To remedy this, the Sieur Gauger gives, in his book, entitled La Méchanique de Feu, published in 1709, seven different constructions of the third sort of chimneys mentioned above, in which there are hollow cavities made by iron plates in the back, jambs, and hearths, through which plates the heat passing warms the air in those cavities, which is continually coming into the room fresh and warm. The invention was very ingenious, and had many conveniences; the room was warmed in all parts, by the air flowing into it through the heated cavities; cold air was prevented rushing through the crevices, the funnel being sufficiently supplied by those cavities; much less fuel would serve, &c. But the first expense, which was very great, the intricacy of the design, and the difficulty of the execution, especially in old chimneys, discouraged the propagation of the invention; so that there are, I suppose, very few such chimneys now in use. The upright heat, too, was almost all lost in these, as in the common chimneys."

"It is hoped that these amusing details will not make the book less interesting to those who seek to become acquainted with the beautiful laws on which warming and ventilation depend; the principle of the latter art being, in fact, identical with that by which nature ventilates our globe—a hot ascending current from the warm regions, while the cooler air streams in at a lower level from the temperate regions."

"In the mean time, very little is done by these chimneys towards warming the room; for the air round the fire-place, which is warmed by the direct rays from the fire, does not continue in the room, but is continually crowded and gathered into the chimney by the current of cold air coming behind it, and so is presently carried off."

"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:"

"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."

"6. Charcoal fires in pots are used chiefly in the shops of handicraftsmen. They warm a room (that is kept close, and has no chimney to carry off the warmed air,) very speedily and uniformly; but, there being no draft to change the air, the sulphurous fumes from the coals (be they ever so well kindled before they are brought in, there will be some,) mix with it, render it disagreeable, hurtful to some constitutions, and some times, when the door is long kept shut, produce fatal consequences."

"[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."

"Nothing is so effectual to prevent Chimnies from smoking as diminishing the opening of the Fire-place in the manner here described, and lowering and diminishing the throat of the Chimnney; and... a perfect cure may be effected by these means alone, even in the most desperate cases."

"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."

"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 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."

"The width between the jambs was reduced to 3 feet; the jambs from the mantel were to be carried up sloping to the waist, or where the flue begins to be of uniform width, and the opening of the fire-place was formed like an arch."

"[I]t is... probable that the combined heat can only be communicated to other bodies by actual contact with the body with which it is combined; and... the rays... communicate or generate heat only when and where they are stopped or absorbed. ...[T]hey seem to bear a great resemblance to the solar rays. ...I must not enter too deeply into... the nature and properties of... radiant heat."

"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."

"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."

"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."

"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 ."

"[A] great improvement was made in France in fire-places by Louis Savot (born 1579 ; died 1640), a licentiate in the Faculty of Medicine at Paris."

"[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."

"For this reason the throat of the chimney should be contracted until it is no larger than is sufficient to carry off the products of combustion. A similar contraction throughout the entire length of the flue would be desirable, were it not that an allowance must be made for clogging up by soot, and for the resistance by friction to the passage of the air offered by the rough walls of the flue."

"Vitruvius... thus describes the construction of the or stove for heating the or sweating room of a bath. The floor is made inclining, so that a ball placed on any part of it would roll towards the fireplace, by which means the heat is more equally diffused in the sweating-chamber. The floor is paved with tiles... and on these are built brick pillars... two feet high, and cemented with clay and hair mixed together. The pillars are placed at such a distance, as will allow tiles to be laid on them to form the ceiling of the hypocaust, and support the pavement of the caldarium. The air to the caldarium, or room over the hypocaust, is admitted through an aperture in the centre of its roof, from which a brazen shield is suspended by chains. By raising and lowering this shield, which opens or shuts the aperture, the heat of the caldarium is regulated. For heating the water to supply the baths, there are to be three caldrons... the arched cavities in which they stand are to be heated by one fire. After such minute instructions how to form the stove in which large quantities of wood were to be consumed, it is singular that he should omit to notice in what way the smoke produced was to be conveyed into the atmosphere. From this silence, it has been inferred that he was ignorant of what Anderson calls "the elegant and commodious tube now known by the name of a chimney.""

"[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..."

"The rays that are sent off from the burning fuel, generate heat, only when and where they are stopped, or absorbed, consequently they generate no heat in the air in the room, in passing through it, because they pass through it, and are not stopped by it, but, striking against the walls of the room, or against any solid body in the room, these rays are there stopped and absorbed, and it is there that the heat found in the room is generated. The air in the room is afterwards heated by coming into contact with these solid bodies. Many capital mistakes have arisen from inattention to this most important fact."

"Longlande, in Pierce the Plowman'sVision, feelingly alludes to the change as prompted by a mean and selfish wish to abridge the ancient hospitality observed towards the poor. "Elynge is that halle eche day in the wyke, Ther the lorde ne the lady liketh nat to sitte. Nowe hath eche ryche a reule to eten by hym silve In a privey parlour for pore mennys sake; Or in a chaumbre wyth a chymney, and leve the cheef halle That was mad for melis men to eten inne." The chimneyed chamber was spacious and lofty, and usually formed with a large bay window, looking into the court of the castle."

"[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]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."

"[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 the smoke and hot vapour which rise from a fire naturally tend upwards, the proper place for the throat of the Chimney is... perpendicularly over the fire."

"The strong hold of Conway is further remarkable for exhibiting another domestic refinement, not found, except at , in any contemporary building. A hearth is recessed into the wall, and has a rising from it for the passage of the smoke into the air. It is true, that after this period, flued fireplaces were sometimes made in rooms that had been erected without them, but the chimney in Conway Castle, and a similar one at Kenilworth [Castle], appear as if they had formed part of the original edifices."

"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."

"[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 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..."

"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."

"But ...how far above the burning fuel... ought [the throat] to be placed."

"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."

"The register-plate was described at the close of the fifteenth century by Alberti... and by others who wrote afterwards. Were this simple and cheap smoke-valve introduced into every cottage chimney, it would save the heat of [5] or [6] millions of tons of coals that is now annually wasted and thrown away."

"An ironmonger in London, however, assuming a good deal of my pamphlet, and working it up into his own, making some small changes in the machine, which rather hurt its operation, got a patent for it there, and made, as I was told, a little fortune by it. And this is not the only instance of patents taken out of my inventions by others, though not always with the same success; which I never contested, as having no desire of profiting by patents myself, and hating disputes."

"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."

"[O]f above an hundred and fifty Fire-places which have been altered in this city, under my direction, within these last two months, there is not one which has not answered perfectly well. ...the saving of fuel, arising from these improvements of Fire-places, amounts in all cases to more than half, and in many cases to more than two thirds of the quantity formerly consumed."

"The use of these fire places in very many houses, both here in Pennsylvania, and the neighbouring states, has been, and is, a great saving of wood to the inhabitants."

"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."