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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 same stack with others, some of them shorter, that drew very well, and I saw nothing to prevent its doing the same. In fine, after every other examination I could think of, I was obliged to own the insufficiency of my skill. But my friend, who made no pretensions to such kind of knowledge, afterwards discovered the cause himself. He got to the top of the funnel by a ladder, and looking down, found it filled with twigs and straw cemented by earth, and lined with feathers. It seems the house, after being built, had stood empty some years before he occupied it; and he concluded that some large birds had taken advantage of its retired situation to make their nest there. The rubbish, considerable in quantity, being removed, and the funnel cleared, the chimney drew well and gave satisfaction.

In general, smoke is a very tractable thing, easily governed and directed when one knows the principles, and is well informed of the circumstances. You know I made it descend in my Pennsylvania stove. I formerly had a more simple construction, in which the same effect was produced, but visible to the eye (Plate, figure 7.) It was composed of two plates A B and C D, placed as in the figure. The lower plate A B rested with its edge in the angle made by the hearth with the back of the chimney. The upper plate was fixed to the breast, and lapped over the lower about six inches wide and the length of the plates (near two feet) between them. Every other passage of air into the funnel was well stopped. When therefore a fire was made at E, for the first time with charcoal, till the air in the funnel was a little heated through the plates, and then wood laid on, the smoke would rise to A, turn over the edge of that plate, descend to D, then turn under the edge of the upper plate, and go up the chimney. It was pretty to see, but of no great use. Placing therefore the under plate in a higher situation, I removed the upper plate C D, and placed it perpendicularly (Plate, figure 8) so that the upper edge of the lower plate A B came within about three inches of it, and might be pushed farther from it, or suffered to come nearer to it, by a moveable wedge between them. The flame then ascending from the fire at E, was carried to strike the upper plate, made it very hot, and its heat rose and spread with the rarefied air into the room.

I believe you have seen in use with me, the contrivance of a sliding-plate over the fire, seemingly placed to oppose the rising of the smoke, leaving but a small passage for it, between the edge of the plate and the back of the chimney. It is particularly described, and its uses explained, in my former printed

instance of the tractability of smoke.*

What is called the Staffordshire chimney (See the Plate, facing page 396) affords an example of the same kind. The opening of the chimney is bricked up, even with the foreedge of its jambs, leaving open only a passage over the grate of the same width, and perhaps eight inches high. The grate consists of semicircular bars, their upper bar of the greatest diameter, the others under it smaller and smaller, so that it has the appearance of half a round basket. It is, with the coals it contains, wholly without the wall that shuts up the chimney, yet the smoke bends and enters the passage above it, the draft being strong, because no air can enter that is not obliged to pass near or through the fire, so that all that the funnel is filled with is much heated, and of course much rarefied.

Much more of the prosperity of a winter country depends on the plenty and cheapness of fuel, than is generally imagined. In travelling I have observed, that in those parts where the inhabitants can have neither wood, nor coal, nor turf, but at excessive prices, the working people live in miserable hovels, are ragged, and have nothing comfortable about them. But when fuel is cheap (or where they have the art of managing it to advantage) they are well furnished with necessaries, and have decent habitations. The obvious reason is, that the working hours of such people are the profitable hours, and they who cannot afford sufficient fuel have fewer such hours in the twenty-four, than those who have it cheap and plenty: for much of the domestic work of poor women, such as spinning, sewing, knitting; and of the men in those manufactures that require little bodily exercise, cannot well be performed where the fingers are numbed with cold; those people therefore, in cold weather, are induced to go to bed sooner, and lie longer in a morning than they would do if they could have good fires or warm stoves to sit by; and their hours of work are not sufficient to produce the means of comfortable subsistence. works, therefore, such as roads, canals, &c. by which fuel may be brought cheap into such countries from distant places, are of great utility; and those who promote them may be reckoned among the benefactors of mankind.

Those public

I have great pleasure in having thus complied with your request, and in the reflection, that the friendship you honour me with, and in which I have ever been so happy, has continued so many years without the smallest interruption. Our distance from each other is now augmented, and nature must soon put an end to the possibility of my continuing our

* See Notes at the end of this paper, No. II.

correspondence: but if consciousness and
memory remain in a future state, my esteem
and respect for you, my dear friend, will be
everlasting.
B. FRANKLIN.

Notes for the Letter upon Chimneys.
No. I.

appears

nifest three ways. First, when the fire burns briskly in cold weather, the howling or whistling noise made by the wind, as it enters the 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, opening the door of the room about half an 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 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 monochord.* He does not indeed lay much stress on this; but it shows that we like the appearance of principles; and where we have not true ones, we have some satisfaction in producing such as are imaginary.

No. II.

just sufficient, when the plate is in, to keep the door nearly shut, by resisting the pressure of the air that would force it open; then, when the plate is drawn out, the door will be outward cold air endeavouring to get in to forced open by the increased pressure of the supply the place of the warm air, that now passes out of the room to go up the chimney. In our common open chimneys, half the fuel is wasted, and its effect lost; the air it has warmed being immediately drawn off. Selet-veral of my acquaintance, having seen this simple machine in my room, have imitated it at their own houses, and it seems likely to become pretty common. I describe it thus particularly to you, because I think it would be useful in Boston, where firing is often dear,

The description of the sliding plates here promised, and which hath been since brought into use under various names, with some immaterial changes, is contained in a former ter to James Bowdoin, Esq. as follows:

To James Bowdoin, Boston. LONDON, December 2, 1758. I HAVE executed here an easy simple contrivance, that I have long since had in speculation, for keeping rooms warmer in cold weather than they generally are, and with less fire. It is this: the opening of the chimney is contracted, by brick-work faced with marble slabs, to about two feet between the jambs, and the breast brought down to within about three feet of the hearth. An iron frame is placed just under the breasts, and extending quite to the back of the chimney, so that a plate of the same metal may slide horizontally backwards and forwards in the grooves on each side of the frame. This plate is just so large as to fill the whole space,and shut the chimney entirely when thrust quite in, which is convenient when there is no fire. Drawing it out, so as to leave a space between its further edge and the back, of about two inches; this space is sufficient for the smoke to pass; and so large a part of the funnel being stopt by the rest of the plate, the passage of warm air out of the room, up the chimney, is obstructed and retarded, and by that means much cold air is prevented from coming in through crevices, to supply its place. This effect is made ma

*Upon comparing these proportions with those arising from the common divisions of the monochord, it happens that the first answers to unisons, and although the second is a discord, the third answers to the third minor, the fourth to the third major, the fifth to the

fourth, the sixth to the fifth, and the seventh to the octave."-NUTSHELLS, page 85.

Mentioning chimneys puts me in mind of a property I formerly had occasion to observe in them, which I have not found taken notice of by others; it is, that in the summer time, when no fire is made in the chimneys, there is, nevertheless, a regular draft of air through them, continually passing upwards, from about five or six o'clock in the afternoon, till eight or nine o'clock the next morning, when the current begins to slacken and hesitate a little, for about half an hour, and then sets as strongly down again, which it continues to do till towards five in the afternoon, then slackens and hesitates as before, going sometimes a little up, then a little down, till, in about half an hour, it gets into a steady upward current for the night, which continues till eight or nine the next day; the hours varying a little as the days lengthen and shorten, and sometimes varying from sudden changes in the weather; as if, after being long warm, it should begin to grow cool about noon, while the air was coming down the chimney, the current will then change earlier than the usual hour, &c.

This property in chimneys I imagine we might turn to some account, and render improper, for the future, the old saying, as useless as a chimney in summer. If the opening of the chimney, from the breast down to the hearth, be closed by a slight moveable frame

or two, in the manner of doors, covered with canvass, that will let the air through, but keep out the flies; and another little frame set within upon the hearth, with hooks on which to hang joints of meat, fowls, &c. wrapt well in wet linen cloths, three or four fold, I am confident, that if the linen is kept wet, by sprinkling it once a day, the meat would be so cooled by the evaporation, carried on continually by means of the passing air, that it would keep a week or more in the hottest weather. Butter and milk might likewise be kept cool, in vessels or bottles covered with wet cloths. A shallow tray, or keeler, should be under the frame to receive any water that might drip from the wetted cloths. I think, too, that this property of chimneys might, by means of smoke-jack vanes, be applied to some mechanical purposes, where a small but pretty constant power only is wanted.

ing through the house, as they should choose; and the same, though reversed in its current, during the stillest night.

I think, too, this property might be made of use to miners; as, where several shafts or pits are sunk perpendicularly into the earth, communicating at bottom by horizontal passages, which is a common case, if a chimney of thirty or forty feet high were built over one of the shafts, or so near the shaft, that the chimney might communicate with the top of the shaft, all air being excluded but what should pass up or down by the shaft, a constant change of air would, by this means, be produced in the passages below, tending to secure the workmen from those damps which so frequently incommode them. For the fresh air would be almost always going down the open shaft, to go up the chimney, or down the chimney, to 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 roof of 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 succeswarmth 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 middle temperature between the heat of the day and the coldness of the night. This middle temperature it communicates to the air contained in it. If the state of the outward air be cooler than that in the funnel of the chimney, it will, by being heavier, force it to rise, and go out at the top. What supplies its place from below, being warmed, in its turn, by the warmer funnel, is likewise forced up by the colder and weightier air below, and so the current is continued till the next day, when the sun gradually changes the state of the outward air, makes it first as warm as the funnel of the chimney can make it (when the current begins to hesitate) and afterwards warmer. The funnel, being cooler than the air that comes into it, cools that air, makes it heavier than the outward air, of course it descends; and what succeeds it from above being cooled in its turn, the descending current continues till towards evening, when it again hesitates and changes its course, from the change of warmth in the outward air, and the nearly remaining same middle temperature in the funnel.

Upon this principle, if a house were built behind Beacon-hill, an adit carried from one of the doors into the hill horizontally, till it meet with a perpendicular shaft sunk from its top, it seems probable to me, that those who lived in the house would constantly, in the heat even of the calmest day, have as much cool air pass

together. If the outside of such a chimney be painted black, the effect will be still greater and the current stronger.

No. III.

It is said the northern Chinese have a method of warming their ground floors, which is ingenious. Those floors are made of tiles, a foot square and two inches thick, their corners being supported by bricks set on end, that are a foot long and four inches square; the tiles, too, join into each other, by ridges and hollows along their sides. This forms a hollow under the whole floor, which on one side of the house has an opening into the air, where a fire is made, and it has a funnel rising from the other side to carry off the smoke. The fuel is a sulphurous pitcoal, the smell of which in the room is thus avoided, while the floor, and of course the room, is well warmed. But as the underside of the floor must grow foul with soot, and a thick coat of soot prevents much of the direct application of the hot air to the tiles, I conceive that burning the smoke, by obliging it to descend through red coals, would in this construction be very advantageous, as more heat would be given by the flame than by the smoke, and the floor being thereby kept free from soot would be more heated with less fire. For this purpose I would propose erecting the funnel close to the grate, so as to have only an iron plate between 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 grate 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 may be visited by it before it enters the funnel F, by the two passages E E, very little of the heat will be lost, and a winter roomn thus rendered very comfortable.

No. IV.

PAGE 404. Few can imagine, &c. It is said the Icelanders have very little fuel, chiefly drift wood that comes upon their coast. To receive more advantage from its heat, they make their doors low, and have a stage round the room above the door, like a gallery, wherein the women can sit and work, the men read or write, &c. The roof being tight, the warm air is confined by it and kept from rising higher and escaping; and the cold air, which enters the house when the door is opened, cannot rise above the level of the top of the door, because it is heavier than the warm air above the door, and so those in the gallery are not incommoded by it. Some of our too lofty rooms might have a stage so constructed as to make a temporay gallery above, for the winter, to be taken away in summer. Sedentary people would find much comfort

there in cold weather.

No. V.

PAGE 410. Where they have the art of managing it, &c. In some houses of the lower people, among the northern nations of Europe, and among the poorer sort of Germans in Pennsylvania, I have observed this construction, which appears very advantageous. (Plate, figure 11.) A is the kitchen with its chimney; B an iron stove in the stove-room. In a corner of the chimney is a hole through the back into the stove, to put in fuel, and another hole above it to let the smoke of the stove come back into the chimney. As soon as the cooking is over, the brands in the kitchen chimney are put through the hole to supply the stove, so that there is seldom more than one fire burning at a time. In the floor over the stove-room, is a small trap-door, to let the warm air rise occasionally into the chamber. Thus the whole house is warmed at little ex

Miscellaneous Observations.

CHIMNEYS, whose funnels go up in the north wall of a house, and are exposed to the north winds, are not so apt to draw well as those in a south wall; because, when rendered cold by those winds, they draw downwards,

Chimneys, enclosed in the body of a house, are better than those whose funnels are exposed in cold walls.

Chimneys in stacks are apt to draw better than separate funnels, because the funnels, that have constant fires in them warm the

others, in some degree, that have none.

One of the funnels, in a house I once occupied, had a particular funnel joined to the south side of the stack, so that three of its sides were exposed to the sun in the course side E during the morning, the south side S of the day, viz. (Plate, figure 12.) the east in the middle part of the day, and the west side W during the afternoon, while its north side was sheltered by the stack from the cold winds. This funnel which came from the ground-floor, and had a considerable height above the roof, was constantly in a strong drawing state day and night, winter and

summer.

Blacking of funnels, exposed to the sun, would probably make them draw still stronger.

In Paris I saw a fire-place so ingeniously contrived as to serve conveniently two rooms, a bedchamber and a study. The funnel over the fire was round. The fire-place was of cast iron (Plate, figure 13.) having an upright back A, and two horizontal semicircular plates B C, the whole so ordered as to turn on the pivots D E. The plate B always stopped that part of the round funnel that was next to the room without fire, while the other half of the funnel over the fire was always open. By this means a servant in the morning could make a fire on the hearth C, then in the study, without disturbing the master by going into his chamber; and the master, when he rose, could, with a touch of his foot, turn the chimney on its pivots, and bring the fire into 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 prin

to his study. The room which had no fire in
it was also warmed by the heat coming
through the back plate, and spreading in the
room, as it could not go up the chimney.

Description of a new Stove for burning of
Pitcoal, and consuming all its Smoke.-
Read in the American Philosophical So-
ciety, January 28, 1786.

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ciple, and probably from the hint thereby
given, though the French experiment is not
mentioned. This book being scarce, I have
translated the chapter describing the stove, viz.
"Vulcanus Famulans, by John George
Leutmann, P. D. Wirtemberg, 1723.
"CHAP. VII.

down under itself, and gives no smoke, but however a very unwholesome vapour.

"In the figure, A is an iron vessel like a funnel, (Plate, figure 20.) in diameter at the top about twelve inches, at the bottom near the grate about five inches; its height twelve inches. This is set on the barrel C, which is ten inches diameter and two feet long, closed at each end E E. From one end rises a pipe or flue about four inches diameter, on which other pieces of pipe are set, which are gradually contracted to D, where the opening is but about two inches. Those pipes must together be at least four feet high. B is an iron grate. F F are iron handles guarded with wood, by which the stove is to be lifted and moved. It stands on three legs. Care must be taken to stop well all the joints, that no smoke may leak through.

"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 might be burnt in the middle of a chamber such as woollen rags, feathers, &c. without creating the least smoke or smell. The machine in which it was made, if I remember right, was of this form (see Plate, figure 1.) made of plate iron. Some clear burning charcoals were put into the opening of the short tube A, and supported there by the grate B. The air, as soon as the tubes grew warm, would ascend in the longer leg C and go out at D, consequently air must enter at A descending to B. In this course it must be heated by the burning coals through which it passed, and rise more forcibly in the longer tube, in proportion to its degree of heat or rarefaction, and length of that tube. For such a machine is a kind of inverted syphon; and as the greater weight of water in the longer 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 only a vapour passes out at D.

Whoever would repeat this experimentwith success must take care that the part A, B, of the short tube, be quite full of burning coals, so that no part of the smoke may descend and pass by them without going through them, and being converted into flame; and that the longer tube be so heated as that the current of ascending hot air is established in it before the things to be burnt are laid on the coals; otherwise there will be a disappointment.

"As this vapour is unwholesome, and affects the head, one may be freed from it, by fixing in the wall of the room an inverted funnel, such as people use to hang over lamps, through which their smoke goes out as through a chimney. This funnel carries out all the vapour cleverly, so that one finds no inconvenience from it, even though the opening D be placed a span below the mouth of the said funnel G. The neck of the funnel is better when made gradually bending, than if turned in a right angle.

It does not appear either in the Memoirs of the Academy of Sciences, or Philosophical Transactions of the English Royal Society, 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 too of other stoves for warming rooms, one, which | weak to drive it back again; besides, A stands

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