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issue. I went out and looked up at the top letter, and I mention it here only as another of the chimney: its funnel was joined in the instance of the tractability of smoke.* same stack with others, some of them short What is called the Staffordshire chimney er, that drew very well, and I saw nothing to (See the Plate, facing, page 396) affords an prevent its doing the same. In fine, after example of the same kind. The opening of every other examination I could think of, I the chimney is bricked up, even with the forewas obliged to own the insufficiency of my edge of its jambs, leaving open only a passage skill. But my friend, who made no preten- over the grate of the same width, and persions to such kind of knowledge, afterwards haps eight inches high. The grate consists discovered the cause himself
. He got to the of semicircular bars, their upper bar of the top of the funnel by a ladder, and looking greatest diameter, the others under it smaller down, found it filled with twigs and straw ce- and smaller, so that it has the appearance of mented by earth, and lined with feathers. It halfa round basket. It is, with the coals it conseems the house, after being built, had stood tains, wholly without the wall that shuts up empty some years before he occupied it; and the chimney, yet the smoke bends and enters he concluded that some large birds had taken the passage above it, the draft being strong, advantage of its retired situation to make because no air can enter that is not obliged to their nest there. The rubbish, considerable pass near or through the fire, so that all that in quantity, being removed, and the funnel the funnel is filled with is much heated, and cleared, the chimney drew well and gave of course much rarefied. satisfaction.
Much more of the prosperity of a winter In general, smoke is a very tractable thing, country depends on the plenty and cheapness easily governed and directed when one knows of fuel, than is generally imagined. In travelthe principles, and is well informed of the ling I have observed, that in those parts where circumstances. You know I made it descend the inhabitants can have neither wood, nor in my Pennsylvania stove. I formerly had a coal, nor turf, but at excessive prices, the more simple construction, in which the same working people live in miserable hovels, are 'effect was produced, but visible to the eye ragged, and have nothing comfortable about (Plate, figure 7.) It was composed of two them. But when fuel is cheap. (or where plates A B and Ć D, placed as in the figure. they have the art of managing it to advanThe lower plate A B rested with its edge in tage) they are well furnished with necessathe angle made by the hearth with the back ries, and have decent habitations. The obviof the chimney. The upper plate was fixed ous reason is, that the working hours of such to the breast, and lapped over the lower about people are the profitable hours, and they who six inches wide and the length of the plates cannot afford sufficient fuel have fewer such (near two feet) between them. Every other hours in the twenty-four, than those who have passage of air into the funnel was well stopped. it cheap and plenty: for much of the domestic When therefore a fire was made at E, for the work of poor women, such as spinning, sewfirst time with charcoal, till the air in the ing, knitting; and of the men in those mafunnel was a little heated through the plates, nufactures that require little bodily exercise, and then wood laid on, the smoke would rise cannot well be performed where the fingers to A, turn over the edge of that plate, de- are numbed with cold; those people therefore, scend to D, the turn under the edge of the cold weather, are induced to go to bed soonupper plate, and go up the chimney. It was er, and lie longer in a morning than they pretty to see, but of no great use. Placing would do if they could have good fires or therefore the under plate in a higher situa- warm stoves to sit by; and their hours of tion, I removed the upper plate CD, and work are not sufficient to produce the means placed it perpendicularly (Plate, figure 8) of comfortable subsistence.
Those public so that the upper edge of the lower plate A B works, therefore, such as roads, canals, &c. by came within about three inches of it, and which fuel may be brought cheap into such might be pushed farther from it, or suffered to countries from distant places, are of great come nearer to it, by a moveable wedge be- utility; and those who promote them may be tween them. The flame then ascending from reckoned among the benefactors of mankind. the fire at E, was carried to strike the upper I have great pleasure in having thus complate, made it very hot, and its heat rose and plied with your request, and in the reflection, spread with the rarefied air into the room. that the friendship you honour me with, and
I believe you have seen in use with me, in which I have ever been so happy, has conthe contrivance of a sliding-plate over the fire, tinued so many years without the smallest inseemingly placed to oppose the rising of the terruption. Our distance from each other is smoke, leaving but a small passage for it, be- now augmented, and nature must soon put an tween the edge of the plate and the back of end to the possibility of my continuing our the chimney. It is particularly described, and its uses explained, in my former printed * See Notes at the end of this paper, No. II.
correspondence: but if consciousness and nifest three ways. First, when the fire burns memory remain in a future state, my esteem briskly in cold weather, the howling or whistand respect for you, my dear friend, will be ling noise made by the wind, as it enters the everlasting
B. FRANKLIN. room through the crevices, when the chimney
is open as usual, ceases as soon as the plate
is slid in to its proper distance. Secondly, Notes for the Letter upon Chimneys. opening the door of the room about half an No. I.
inch, and holding your hand against the openThe latest work on architecture that I have ing, near the top of the door, you feel the cold seen, is that entitled Nutshells, which appears air coming in against your hand, but weakly, to be written by a very ingenious man, and if the plate be in. Let another person sudcontains a table of the proportions of the open- denly draw it out, so as to let the air of the ings of chimneys; but they relate solely to the room go up the chimney, with its usual freeproportions he gives his rooms, without the dom where chimneys are open, and you immesmallest regard to the funnels. And he re- diately feel the cold air rushing in strongly. marks, respecting these proportions, that they Thirdly, if something be set against the door, are similar to the harmonic divisions of a mo- just sufficient, when the plate is in, to keep nochord.* He does not indeed lay much stress the door nearly shut, by resisting the pressure on this; but it shows that we like the appear of the air that would force it open; then, ance of principles; and where we have not when the plate is drawn out, the door will be true ones, we have some satisfaction in pro- outward cold air endeavouring to get in to
forced open by the increased pressure of the ducing such as are imaginary.
supply the place of the warm air, that now No. II.
passes out of the room to go up the chimney. The description of the sliding plates here in our common open chimneys, half the fuel promised, and which hath been since brought is wasted, and its effect lost; the air it has into use under various names, with some im- warmed being immediately drawn off. Se material changes, is contained in a former let- veral of my acquaintance, having seen this ter to James Bowdoin, Esq. as follows: simple machine in my room, have imitated it
at their own houses, and it seems likely to beTo James Bowdoin, Boston.
come pretty common. I describe it thus parLondon, December 2, 1758.
ticularly to you, because I think it would be I HAVE executed here an easy simple con- useful in Boston, where firing is often dear. trivance, that I have long since had in specu Mentioning chimneys puts me in mind of lation, for keeping rooms warmer in cold wea- a property I formerly had occasion to observe ther than they generally are, and with less fire. in them, which I have not found taken notice It is this : the opening of the chimney is con- of by others; it is, that in the summer time, tracted, by brick-work faced with marble slabs, when no fire is made in the chimneys, there to about two feet between the jambs, and the is, nevertheless, a regular draft of air through breast brought down to within about three feet them, continually passing upwards, from about of the hearth. An iron frame is placed just un- five or six o'clock in the afternoon, till eight der the breasts, and extending quite to the back or nine o'clock the next morning, when the of the chimney, so that a plate of the same current begins to slacken and hesitate a little, metal may slide horizontally backwards and for about half an hour, and then sets as forwards in the grooves on each side of the strongly down again, which it continues to do frame. This plate is just so large as to fill till towards five in the afternoon, then slackthe whole space and shut the chimney entirely ens and hesitates as before, going sometimes when thrust quite in, which is convenient a little up, then a little down, till, in about when there is no fire. Drawing it out, so as half an hour, it gets into a steady upward curto lcave a space between its further edge and rent for the night, which continues till eight the back, of about two inches; this space is or nine the next day; the hours varying a sufficient for the smoke to pass; and so large little as the days lengthen and shorten, and a part of the fijnnel being stopt by the rest of sometimes varying from sudden changes in the the plate, the passage of warm air out of the weather; as if, after being long warm, room, up the chimncy, is obstructed and re- should begin to grow cool about noon, while tarded, and by that means much cold air is the air was coming down the chimney, the curprevented from coming in through crevices, rent will then change earlier than the usual to supply its place. This effect is made ma- hour, &c.
This property in chimneys I imagine we * Upon comparing these proportions with those aris: might turn to some account, and render imhappens that the first answers to unisons, and although proper, for the future, the old saying, as ușethe second is a discord, the third answers to the third less as a chimney in summer. If the opening minor, the fourth to the third unajor, the fifth to the of the chimney, from the breast down to the fourth, the sixth to the fifth, and the seventh to the oc. ."-NUTSHELLS, page 85.
hearth, be closed by a slight moveable frame
or two, in the manner of doors, covered with ing through the house, as they should choose; canvass, that will let the air through, but keep and the same, though reversed in its current, out the flies; and another little frame set with- during the stillest night. in upon the hearth, with hooks on which to I think, too, this property might be made of hang joints of meat, fowls, &c. wrapt well in use to miners; as, where several shafts or pits wet linen cloths, three or four fold, I am con- are sunk perpendicularly into the earth, comfident, that if the linen is kept wet, by sprink- municating at bottom by horizontal passages, ling it
nce a day, the meat would be so cooled which is a common case, if a chimney of thirty by the evaporation, carried on continually by or forty feet high were built over one of the means of the passing air, that it would keep a shafts, or so near the shaft, that the chimney week or more in the hottest weather. Butter might communicate with the top of the shaft, and milk might likewise be kept cool, in ves- all air being excluded but what should pass sels or bottles covered with wet cloths. A up or down by the shaft, a constant change of shallow tray, or keeler, should be under the air would, by this means, be produced in the frame to receive any water that might drip passages below, tending to secure the workfrom the wetted cloths. I think, too, that this men from those damps which so frequently property of chimneys might, by means of incommode them. For the fresh air would be smoke-jack vanes, be applied to some mechani- almost always going down the open shaft, to cal purposes, where a small but pretty constant go up the chimney, or down the chimney, to power only is wanted.
go up the shaft. Let me add one observation If
you would have my opinion of the cause more, which is, that if that part of the funnel of this changing current of air in chimneys, of a chimney, which appears above the roofof it is, in short, as follows. In summer time a house, be pretty long, and have three of its there is generally a great difference in the sides exposed to the heat of the sun succes warmth of the air at mid-day and mid-night, sively, viz. when he is in the east, in the and, of course, a difference of specific gravity south, and in the west, while the north side in the air, as the more it is warmed the more is sheltered by the building from the cool it is rarefied. The funnel of a chimney, being northerly winds; such a chimney will often for the most part surrounded by the house, is be so heated by the sun, as to continue the protected, in a great measure, from the direct draft strongly upward, through the whole action of the sun's rays, and also from the cold- twenty-four hours, and often for many days ness of the night air. It thence preserves a together. If the outside of such a chimney middle temperature between the heat of the be painted black, the effect will be still greater day and the coldness of the night. This mid- and the current stronger. dle temperature it communicates to the air contained in it. If the state of the outward
No. III. air be cooler than that in the funnel of the It is said the northern Chinese have a me chimney, it will, by being heavier, force it to thod of warming their ground floors, which is rise, and go out at the top. What supplies ingenious. Those floors are made of tiles, a its place from below, being warmed, in its foot square and two inches thick, their turn, by the warmer funnel, is likewise forced corners being supported by bricks set on end; up by the colder and weightier air below, and that are a foot long and four inches square; so the current is continued till the next day, the tiles, too, join into each other, by ridges when the sun gradually changes the state of and hollows along their sides. This forms the outward air, makes it first as warm as the a hollow under the whole floor, which on one funnel of the chimney can make it (when the side of the house has an opening into the air, current begins to hesitate) and afterwards where a fire is made, and it has a funnel ris
The funnel, being cooler than the ing from the other side to carry off the smoke. air that comes into it, cools that air, makes it The fuel is a sulphurous pitcoal, the smell of heavier than the outward air, of course it de- which in the room is thus avoided, while the scends; and what succeeds it from above be- floor, and of course the room, is well warmed. ing cooled in its turn, the descending current But as the underside of the floor must grow continues till towards evening, when it again foul with soot, and a thick coat of soot prehesitates and changes its course, from the vents much of the direct application of the change of warmth in the outward air, and the hot air to the tiles, I conceive that burning nearly remaining same middle temperature in the smoke, by obliging it to descend through the funnel.
red coals, would in this construction be very Upon this principle, if a house were built advantageous, as more heat would be given behind Beacon-hill, an adit carried from one of by the flame than by the smoke, and the floor the doors into the hill horizontally, till it meet being thereby kept free from soot would be with a perpendicular shaft sunk from its top, more heated with less fire. For this purpose it seems probable to me, that those who lived I would propose erecting the funnel close to in the house would constantly, in the heat even the grate, so as to have only an iron plate beof the calmest day, have as much cool air pass- I tween the fire and the funnel, through which
plate, the air in the funnel being heated, it pense of wood, and the stove-room kept conwill be sure to draw well, and force the smoke stantly warm; so that in the coldest winter to descend, as in the figure (Plate, figure 9.) nights, they can work late, and find the room where A is the funnel or chimney, B the graté still comfortable when they rise to work on which the fire is placed, Cone of the aper- early. An English farmer in America, who tures through which the descending smoke is makes great fires in large open chimneys, drawn into the channel D of figure 10, along needs the constant employment of one man to which channel it is conveyed by a circuitous cut and haul wood for supplying them; and route, as designated by the arrows, until it the draft of cold air to them is so strong, that arrives at the small aperture E, figure 10, the heels of his family are frozen while they through which it enters the funnel F. G in are scorching their faces, and the room is both figures is the iron plate against which never warm, so that little sedentary work can the fire is made, which being heated thereby, be done by them in winter. The difference will rarefy the air in that part of the funnel, in this article alone of economy shall, in a and cause the smoke to ascend rapidly. The course of years, enable the German to buy out flame thus dividing from the grate to the right the Englishman, and take possession of his and left, and turning in passages, disposed, as plantation. in figure 13, so as that every part of the floor Miscellaneous Observations. may be visited by it before it enters the fun
CHIMNEYS, whose funnels go up in the north nel F, by the two passages E E, very little of wall of a house, and are exposed to the north the heat will be lost, and a winter roorn thus winds, are not so apt to draw well as those in rendered very comfortable.
a south wall; because, when rendered cold No. IV.
by those winds, they draw downwards, PAGE 404. Few can imagine, &c. It is
Chimneys, enclosed in the body of a house, said the Icelanders have very little fuel, are better than those whose funnels are exchiefly drift wood that comes upon their posed in cold walls. coast. To receive more advantage from its
Chimneys in stacks are apt to draw better heat, they make their doors low, and have a that have constant fires in them warm the
than separate funnels, because the funnels, stage round the room above the door, like a gallery, wherein the women can sit and work, others, in some degree, that have none. the men read or write, &c. The roof being
One of the funnels, in a house I once octight, the warm air is confined by it and kept cupied, had a particular funnel joined to the from rising higher and escaping; and the cold south side of the stack, so that three of its air, which enters the house when the door is sides were exposed to the sun in the course opened, cannot rise above the level of the top of the day, viz., (Plate, figure 12.) the east of the door, because it is heavier than the side E during the morning, the south side S warm air above the door, and so those in the in the middle part of the day, and the west gallery are not incommoded by it. Some of side W during the afternoon, while its north our too lofty rooms might have a stage so con- side was sheltered by the stack from the cold
winds. structed as to make a temporay gallery above,
This funnel which came from the for the winter, to be taken away in summer. ground-floor, and had a considerable height Sedentary people would find much comfort above the roof, was constantly in a strong there in cold weather,
drawing state day and night, winter and No. V.
Blacking of funnels, exposed to the sun, Page 410. Where they have the art of would probably make them draw still stronger. managing it, &c. In some houses of the low In Paris I saw a fire-place so ingeniously er people, among the northern nations of Eu- contrived as to serve conveniently two rooms, rope, and among the poorer sort of Germans a bedchamber and a study. The funnel over in Pennsylvania, I have observed this con- the fire was round. The fire-place was of struction, which appears very advantageous. cast iron (Plate, figure 13.) having an up(Plate, figure 11.) A is the kitchen with its right back A, and two horizontal semicircular chimney; B an iron stove in the stove-room. plates B C, the whole so ordered as to turn on In a corner of the chimney is a hole through the pivots D E. The plate B always stopped the back into the stove, to put in fuel, and that part of the round funnel that was next to another hole above it to let the smoke of the the room without fire, while the other half of stove come back into the chimney. As soon the funnel over the fire was always open. By as the cooking is over, the brands in the kitchen this means a servant in the morning could chimney are put through the hole to supply the make a fire on the hearth C, then in the stustove, so that there is seldom more than one dy, without disturbing the master by going fire burning at a time. In the floor over the into his chamber; and the master, when he stove-room, is a small trap-door, to let the rose, could, with a touch of his foot, turn the warm air rise occasionally into the chamber. chimney on its pivots, and bring the fire into Thus the whole house is warmed at little ex- I his chamber, keep it there as long as he want
ed it, and turn it again, when he went out in- seems to have been formed on the same printo his study. The room which had no fire in ciple, and probably from the hint thereby it was also warmed by the heat coming given, though the French experiment is not through the back plate, and spreading in the mentioned. This book being scarce, I have room, as it could not go up the chimney. translated the chapter describing the stove, viz.
“ Vulcanus Famulans, by John George Description of a new Stove for burning of
Leutmann, P. D. Wirtemberg, 1723.
“ On a Stove, which draws downwards. TOWARDS the end of the last century an in “ HERE follows the description of a sort of genious French philosopher, whose name I stove, which can easily be removed and again am sorry I cannot recollect, exhibited an ex- replaced at pleasure. This drives the fire periment to show, that very offensive things down under itself, and gives no smoke, but might be burnt in the middle of a chamber however a very unwholesome vapour. such as woollen rags, feathers, &c. without “ In the figure, A is an iron vessel like a creating the least smoke or smell. The ma unnel, (Plate, figure in diameter at the chine in which it was made, if I remember top about twelve inches, at the bottom near the right, was of this form (see Plate, figure 1.) grate about five inches; its height twelve made of plate iron. Some clear burning inches. This is set on the barrel Č, which is charcoals were put into the opening of the ten inches diameter and two feet long, closed short tube A, and supported there by the grate at each end E E. From one end rises a pipe B. The air, as soon as the tubes grew warm, or flue about four inches diameter, on which would ascend in the longer leg Čand go out other pieces of pipe are set, which are graat D, consequently air must enter at A de- dually contracted to D, where the opening is scending to B. In this course it must be heat- but about two inches. Those pipes must to ed by the burning coals through which it gether be at least four feet high. B is an passed, and rise more forcibly in the longer iron grate. F F are iron handles guarded tube, in proportion to its degree of heat or ra- with wood, by which the stove is to be lifted refaction, and length of that tube. For such and moved. It stands on three legs. Care a machine is a kind of inverted syphon ; and must be taken to stop well all the joints, that as the greater weight of water in the longer no smoke may leak through. leg of a common syphon in descending is ac “When this stove is to be used, it must companied by an ascent of the same fluid in first be carried into the kitchen and placed in the shorter; so, in this inverted syphon, the the chimney near the fire. There burning greater quantity of levity of air in the longer wood must be laid and left upon its grate till leg, in rising, is accompanied by the descent the barrel C is warm, and the smoke no longer of air in the shorter. The things to be burn- rises at A, but descends towards C. Then it ed being laid on the hot coals at A, the smoke is to be carried into the room which it is to must descend through those coals, be convert- warm.
When once the barrel C is warm, ed into flame, which, after destroying the of fresh wood may be thrown into the vessel A fensive smell, came out at the end of the longer as often as one pleases, the flame descends tube as mere heated air.
and without smoke, which is so consumed that Whoever would repeat this experimentwith only a vapour passes out at D. success must take care that the part A, B, of "As this vapour is unwholesome, and afthe short tube, be quite full of burning coals, fects the head, one may be freed from it, by 80 that no part of the smoke may descend and fixing in the wall of the room an inverted funpass by them without going through them, nel, such as people use to hang over lamps, and being converted into flame; and that the through which their smoke goes out as longer tube be so heated as that the current through a chimney. This funnel carries out of ascending hot air is established in it before all the vapour cleverly, so that one finds no the things to be burnt are laid on the coals; inconvenience from it, even though the openotherwise there will be a disappointment. ing D be placed a span below the mouth of
It does not appear either in the Memoirs the said funnel G. The neck of the funnel is of the Academy of Sciences, or Philosophical better when made gradually bending, than if Transactions of the English Royal Society, turned in a right angle. that any improvement was ever made of this “The cause of the draft downwards in the ingenious experiment, by applying it to useful stove is the pressure of the outward air, purposes. But there is a German book, en- which, falling into the vessel A in a column titled Vulcanus Famulans, by John George of twelve inches diameter, finds only a resistLeutmann, P. D. printed at Wirtemberg in ing passage at the grate B, of five inches, and 1723, which describes, among a great variety one at D, of two inches, which are much 100 of other stoves for warming rooms, one, which weak to drive it back again'; besides, A stands