OBSERVATIONS CONCERNING OPEN CHIMNEY
An Account of various Faults that have been committed by Workmen, in England, who have been employed in altering Chimney Fireplaces, and fitting them up according to the Method recommended by the Author, in his Fourth Essay. Consequences which have resulted from these Mistakes. Necessity of adhering strictly, and without Deviation, to the Directions which have been given. Those Particulars are pointed out in which Workmen are most liable to fail.
I WAS much flattered on my return to England, in September, I798, after an absence of two years, to find that the improvements in the construction of chimney fireplaces, which I had recommended in my Fourth Essay, published in London in the beginning of the year I796, were coming into use in various parts of the country; and I have since taken a good deal of pains to find out how they have answered, and what faults and imperfections have been discovered in them. And as the information I have obtained by these inquiries has enabled me to make several remarks and observa-
Of Chimney Fireplaces.
It has been objected to these fireplaces, that they sometimes occasion dust and ashes to come into the room when the fire is stirred. I have examined several fireplaces said to have been fitted up on my principles, that have certainly had that fault; but I have commonly, I might say invariably, found, that their imperfections have arisen from faults in their construction. Either the grate has been brought out too far into the room, or the opening of the fireplace in front has been left too wide or too high, or the workman has neglected to lower and to round off the breast of the chimney, or, what I have often found to he the case, several of these faults have existed together, in the same fireplace.
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 chimneys, setting about the work with their minds strongly prepossessed with what they consider as the leading principle in the construction of these fireplaces, namely, 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, and that has the same tendency, in neglecting
This I have not only recommended in my Essay on Chimney Fireplaces, but have given the most particular directions how it is to be done (see page 531), and, to mark the importance of the object still more strongly, have accompanied those directions by an engraving.
It is indeed a very important point, that the throat of the chimney should be near the fire, and it should always be carefully attended to. It is likewise very important to "round off the breast of the chimney," though this, I find, is very often entirely neglected, even by workmen who have had much practice in the construction of the fireplaces I have recommended.
The breast of a chimney should always be rounded off in the neatest manner possible, beginning from the very front of the lower part of the mantle, and ending at the narrowest part of the throat of the chimney, where the breast ends in the front part of the perpendicular canal of the chimney. If the under surface of the mantle is flat and wide, it will be impossible to round off the breast properly; and that circumstance alone renders it indispensably necessary, in those cases, to alter the mantle, or to run under it a thinner piece of stone, or a thin wall of bricks, supported on an iron bar, in order that the breast of the chimney may be brought to be of the proper form, and the throat of the chimney may be brought into its proper situation.
If the under side of the mantle be left broad and flat, it is easy to perceive that the cloud of dust or light ashes that rises from a coal fire nearly burned out when it is violently stirred about with a poker, striking perpendicularly against this flat part of it, must unavoid-
Another very common fault that I have observed in chimney fireplaces, that have been altered on what have been called my principles, and which has a direct tendency to bring dust, and even smoke, into the room, is the sloping of the covings too much, and leaving the opening of the fireplace in front too wide. I have said, in my Essay on Chimney Fireplaces, that where chimneys are well constructed and well situated, and have never been apt to smoke, in altering them the covings may be placed at an angle of 135 degrees with the back; but I have expressly said that they should never exceed that angle, and have stated at large the bad consequences that must follow from making the opening of a fireplace very wide, when its depth is very shallow (see page 510). I have also expressly said (page 530), that, for chimneys that are apt to smoke, the covings should be placed less obliquely, in respect to the back, than in others that have not that fault. But most of the workmen who have altered chimneys seem to have paid little attention to these distinctions, and I have frequently found, and sometimes in fireplaces that have been remarkably shallow, that the covings have been placed at an angle even more oblique than that above mentioned.
Another cause that sometimes has considerable effect in bringing dust and smoke into rooms, from the fires that are made in them, is the great nicety with which the doors and windows are fitted in their frames, which pre-
How many fireplaces in close rooms have been cured completely of throwing puffs of smoke and dust into the room, merely by placing a register stove in them! But there is surely nothing peculiar to a register-stove that could enable It to perform such a cure, but merely as it serves to diminish the width and height of the opening of the fireplace; and how much easier could this be done with marble, or other stone, or with bricks and mortar, plastered over and incrusted in front with proper ornaments in stucco, or in artificial stone!
I am the more anxious that something of this sort should be Introduced, as the openings of chimney fireplaces are In general certainly too wide and too high, and as I am convinced that there is no way of reducing them to a proper size, that would be so cheap, or more effectual, or that could be made more ornamental.
Those who are fond of the glitter of polished steel, and have no objection to the expense of it, or to the labour that is required to keep it bright, may surround their fireplaces in front with a border of it, for there it will do no harm, and may use grates and fenders of the most exquisite workmanship; but if they wish to have a pleasant; cheerful, and economical fire, the covings of their fireplaces must be placed obliquely, and they must not be constructed of metal; and if the sides and back
I have abundant reason to think, that if, in constructing or altering chimney fireplaces, the rules laid down in my essay on that subject are strictly adhered to, chimneys so fitted up will very seldom be found either to smoke, or to throw out dust into the room; and should they be found to have either of these faults, there is a remedy for the evil, as effectual as it is simple and obvious: Bring down the mantle and the throat of the chimney lower; and if it should be found necessary, reduce the width of the opening of the fireplace in front, and diminish obliquity of the covings.
These alterations will certainly be effectual to prevent either smoke or dust from coming into the room when there is a fire burning in the grate; but it sometimes happens, and indeed not unfrequently, that dust and soot are drawn down a chimney in which there is no fire, to the great annoyance of those who are in the room, and to the great damage of the furniture. When this happens, it is commonly occasioned by a very strong draught up another chimney, in which there is a fire, in an adjoining room; and when that is the case, the most simple remedy is to alter that other chimney, and, constructing its fireplace on good principles, to reduce its throat to reasonable dimensions. But if the passage of the air down a chimney in which there is no fire is occasioned by strong eddies of wind, there is no remedy for that evil but placing a chimney-pot, of a peculiar construction, on the top of the chimney, which shall counteract the effect of those eddies; or by closing up the throat of the chimney occasionally, by a door made for that purpose of sheet-iron.
As this plate, situated at the back part of the chimney, could not produce any of those bad effects that have with reason been attributed to the registers of common register-stoves (which are placed on the breast of the chimney), it appears to me to be very probable, that it would be found useful as a register for occasionally altering the size of the throat of the chimney, and regulating its draught, as well as for occasionally closing up that passage entirely. It would certainly be worth while to try the experiment.*
Before I quit this subject, I must mention another fault, which workmen employed in altering chimney fireplaces that are furnished with grates or stoves with sloping backs are very apt to make. They leave the back of the grate in its place, and instead of carrying up the back of the fireplace perpendicularly from the bottom of the grate, they first begin to carry it up perpendicularly from the top of the iron plate that forms the back of the grate; and as this plate not only slopes backwards considerably, but rises several inches above the
* Since the introduction of the cottage and gridiron grates, this contrivance has come into very general use, and experience has shown it to be extremely useful. I would strongly recommend it to those who fit up chimney fireplaces on these principles, never to omit this register; it costs a mere trifle, and is very useful on many accounts.
As I am giving an account of the mistakes that have been made by some of those who have been employed in fitting up chimney fireplaces on the principles I have publicly recommended, it will naturally be expected that I should take some notice of those numerous improvements that have been announced to the public, said to have been made in stoves, grates, etc., to which advertisers in the newspapers have thought proper to affix my name. As I am extremely anxious not to injure any man, either in his reputation for ingenuity, or in his trade, or in any other way, I shall not say one word more on this subject than what I feel it to be my duty to the public to declare, namely, that I am not the inventor of any of those stoves or grates that have been offered to the public for sale under my name.
Having mentioned the inconveniences that sometimes
In building a house, an air-canal, about twelve or fifteen inches square, in the clear, and open at both ends, may be constructed in or near the centre of each stack of chimneys; and two branches from this aircanal, both furnished with registers, may open into each of the adjoining rooms, one of these branches opening into the fireplace, just under the grate, and the other over the fireplace, and near the top of the room, or just under the ceiling. Each of these branches should be about four inches square, in the clear; and to prevent the uncouth appearance of the open mouth of that which opens into the room over the fireplace, it may be masked by a medallion, a picture, or any other piece of ornamental furniture proper for that use, placed before it at the distance of one or two inches from the side or wall of the room.
The bottom of this air-tube should reach to the ground, where it should communicate freely with the open air of the atmosphere; but it should not rise quite so high as the chimneys (or canals for carrying off the smoke) are carried up, but should end (by lateral open-
If this air-tube be situated in the middle of a building, it is evident that a horizontal canal or tube of communication must be carried from its lower orifice to some open place without the building, in order to establish a free circulation of fresh air, both upwards and downwards, in the air-tube. I say both upwards and downwards, for sometimes the current of air in the tube will be found to set upwards, and sometimes downwards. Its direction will depend on the winds that happen to prevail, or rather on the eddies they occasion in the air out of doors in the neighbourhood of the buildings; and it is no small advantage that will arise from leaving both ends of the air-tube open, that the tube will always be supplied with a sufficiency of air, whatever eddies the winds may occasion. It is easy to perceive how powerfully this must operate to prevent those puffs of smoke which, in high winds, are frequently thrown into some rooms by the eddies, and the partial rarefactions of the air that they occasion; but this is far from being the only or the most important of the advantages that will be derived from this air-tube. Those who consider what an immense quantity of air is required to supply the current that sets up the chimney of an open fireplace, where there is a fire burning, must perceive what an enormous loss of heat there must be, when all this expense of air is supplied by the warmed air of the room, and that all this warmed air is necessarily and constantly replaced by the cold air from without, which finds its way into the room by the crevices of the doors and windows. But all this waste of heat, or any part of it, at pleasure, may be prevented by the
But there are, I am told, persons in this country, who are so fond of seeing what is called a great roaring fire, that even with its attendant inconveniences, of roasting and freezing opposite sides of the body at the same time, they prefer it to the genial and equable warmth which a smaller fire, properly managed, may be made to produce, even in an open chimney fireplace. To recommend the air-tubes to persons of that description, I would tell them, that, by closing up, by means of its register, the lower branch of communication (that which ends just under the grate) and setting that situated near the top of the room wide open, they may indulge themselves with having a very large fire in the room with little heat, and this with much less inconvenience from currents of cold air from the doors and windows than they now experience.
It is easy to perceive that by a proper use of the two registers, together with a judicious management of the fire, the air in the room may either be made hotter or colder, or may be kept at any given temperature, or the room may be most effectually ventilated; and that this change of air may be effected either gradually or more suddenly. And here it may perhaps he the proper place to observe, that in all our reasonings and speculations relative to the heating of rooms by means of open chim-
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.
It is really astonishing how little attention is paid to events which happen frequently, however interesting they may be as objects of curious investigation, or however they may be connected with the comforts and enjoyments of life. Things near us, and which are familiar to us, are seldom objects of our meditations. How few persons are there who ever took the trouble to bestow a thought on the subject in question, though it is, in the highest degree, curious and interesting!
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