mon length of cord-wood, may be burnt conveniently; and for the smaller such wood may be sawed into thirds. Where coals are the fuel, the grates will be proportioned to the openings. The same depth is nearly necessary to all, the funnels being all made of a size proper to admit a chimney-sweeper. If, in large and elegant rooms, custom or fancy should require the appearance of a large chimney, it may be formed of extensive marginal decorations, in marble, &c. In time, perhaps, that which is fittest in the nature of things may come to be thought handsomest. But at present, when men and women in different countries show themselves dissatisfied with the forms God has given to their heads, waists and feet, and pretend to shape them more perfectly, it is hardly to be expected that they will be content always with the best form of a chimney. And there are some, I know, so bigoted to the fancy of a large noble opening, that rather than change it they would submit to have damaged furniture, sore eyes, and skins almost smoked to bacon.

3. Another cause of smoky chimneys is too short a funnel. This happens necessarily in some cases, as where a chimney is required in a low building; for, if the funnel be raised high above the roof, in order to strengthen its draft, it is then in danger of being blown down, and crushing the roof in its fall.

Remedies.- Contract the opening of the chimney, so as to oblige all the entering air to pass through or very near the fire; whereby it will be more heated and rarefied, the funnel itself be more warmed, and its contents have more of what may be called the force of levity, so as to rise strongly and maintain a good draft at the opening.

Or you may in some cases, to advantage, build additional stories over the low building, which will support a high funnel.

4. Another very common cause of the smoking of chimneys is their overpowering one another. For instance, if there be two chimneys in one large room, and you make fires in both of them, the doors and windows close shut, you will find that the greater and stronger fire shall overpower the weaker, and draw air down its funnel to supply its own demand; which air, descending in the weaker funnel, will drive down its smoke, and force it into the room. If, instead of being in one room, the two chimneys are in two different rooms communicating by a door, the case is the same whenever that door is open. In a very tight house, I have known a kitchen chimney on the lowest floor, when it had a great fire in it, overpower any other chimney in the house, and draw air and smoke into its room as often as the door was opened communicating with the staircase.

Remedy. Take care that every room has the means of supplying itself from without with the air its chimney may require, so that no one of them may be obliged to borrow from another, nor under the necessity of lending. A variety of these means have been already described.

5. Another cause of smoking is when the tops of chimneys are commanded by higher buildings, or by a hill, so that the wind blowing over such eminences falls like water over a dam, sometimes almost perpendicularly on the tops of the chimneys that lie in its way, and beats down the smoke contained in them.

Remedy. That commonly applied to this case is a turn-cap made of tin or plate iron, covering the chimney above and on three sides, open on one side, turning on a spindle, and which, being guided or governed by a vane, always presents its back to the current. This, I believe, may be generally effectual, though not certain, as there may be cases in which it will not succeed. Raising your funnels, if practicable, so as their tops may be higher, or at least equal with the commanding eminence, is more to be depended on. But the turning-cap, being easier and cheaper, should first be tried.

6. There is another case of command, the reverse of that last mentioned. It is where the commanding eminence is further from the wind than the chimney commanded.

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Remedy. I know of but one, which is to raise such funnel higher than the roof, supporting it, if necessary, by iron bars. For a turn-cap in this case has no effect, the dammed up air pressing down through it, in whatever position the wind may have placed its opening.

7. Chimneys, otherwise drawing well, are sometimes made to smoke by the improper and inconvenient situation of a door. The remedies are obvious and easy. Either put an intervening screen from the wall round great part of the fireplace; or, which is perhaps preferable, shift the hinges of your door, so as it may open the other way, and when open throw the air along the other wall.

8. A room that has no fire in its chimney is sometimes filled with smoke, which is received at the top of its funnel, and descends into the room.

The remedy is to have a sliding plate that will shut perfectly the offending funnel.

9. Chimneys which generally draw well do nevertheless sometimes give smoke into the rooms, it being driven down by strong winds passing over the tops of their funnels, though not

descending from any commanding eminence. This case is most frequent where the funnel is short, and the opening turned from the wind. It is the more grievous when it happens to be a cold wind that produces the effect, because, when you most want your fire, you are sometimes obliged to extinguish it.

Remedies.In some places, particularly in Venice, where they have not stacks of chimneys, but single flues, the custom is, to open or widen the top of the flue rounding in the true form of a funnel; which some think may prevent the effect just mentioned, for that the wind blowing over one of the edges into the funnel may be slanted out again on the other side by its form. I have had no experience of this; but I have lived in a windy country, where the contrary is practised, the tops of the flues being narrowed inwards, so as to form a slit for the issue of the smoke, long as the breadth of the funnel, and only four inches wide. This seems to have been contrived on a supposition that the entry of the wind would thereby be obstructed, and, perhaps, it might have been imagined that the whole force of the rising warm air being condensed, as it were, in the narrow opening, would thereby be strengthened, so as to overcome the resistance of the wind. This, however, did not always succeed; for when the wind was at north-east and blew fresh the smoke was forced down by fits into the room I commonly sat in, so as to oblige me to shift the fire into another. The position of the slit in this funnel was, indeed, north-east and south-west. Perhaps, if it had lain across the wind, the effect might have been different. But on this I can give no certainty. It seems a matter proper to be referred to experiment. Possibly a turncap might have been serviceable, but it was not tried.

Chimneys have not been long in use in England. I formerly saw a book printed in the time of Queen Elizabeth, which remarked the then modern improvements of living, and mentioned among others the convenience of chimneys. "Our forefathers," said the author, "had no chimneys. There was in each dwelling-house only one place for a fire, and the smoke went out through a hole in the roof; but now there is scarce a gentleman's house in England that has not at least one chimney in it." When there was but one chimney, its top might then be opened as a funnel; and, perhaps, borrowing the form from the Venetians, it was then the flue of a chimney got that name.

Such is now the growth of luxury, that in both England and France we must have a chimney for every room; and in some houses every possessor of a chamber, and almost every servant, will have a fire; so that, the flues being necessarily built in

stacks, the opening of each as a funnel is impracticable. This change of manners soon consumed the fire-wood of England, and will soon render fuel extremely scarce and dear in France, if the use of coals be not introduced in the latter kingdom, as it has been in the former, where it at first met with opposition; for there is extant in the records of one of Queen Elizabeth's Parliaments a motion made by a member, reciting, "That many dyers, brewers, smiths, and other artificers of London, had, of late, taken to the use of pit-coal for their fires, instead of wood, which filled the air with noxious vapors and smoke, very prejudicial to the health, particularly of persons coming out of the country; and therefore moving that a law might pass to prohibit the use of such fuel (at least during the session of Parliament) by those artificers."

It seems it was not then commonly used in private houses. Its supposed unwholesomeness was an objection. Luckily, the inhabitants of London have got over that objection, and now think it rather contributes to render their air salubrious, as they have had no general pestilential disorder since the general use of coals, when, before it, such were frequent. Paris still burns wood at an enormous expense, continually augmenting; the inhabitants having still that prejudice to overcome. In Germany you are happy in the use of stoves, which save fuel wonderfully your people are very ingenious in the management of fire, but they may still learn something in that art from the Chinese, whose country, being greatly populous and fully cultivated, has little room left for the growth of wood, and, having not much other fuel that is good, have been forced upon many inventions, during a course of ages, for making a little fire go as far as possible.

I have thus gone through all the common causes of the smoking of chimneys that I can at present recollect as having fallen under my observation; communicating the remedies that I have known successfully used for the different cases, together with the principles on which both the disease and the remedy depend, and confessing my ignorance wherever I have been sensible of it. You will do well, if you publish, as you propose, this letter, to add in notes, or, as you please, such observations as may have occurred to your attentive mind; and, if other philosophers will do the same, this part of science, though humble, yet of great utility, may in time be perfected. For many years past, I have rarely met with a case of a smoky chimney which has not been solvable on these principles, and cured by these remedies, where people have been willing to apply them;

which is indeed not always the case, for many have prejudices in favor of the nostrums of pretending chimney doctors and fumists, and some have conceits and fancies of their own, which they rather choose to try than to lengthen a funnel, alter the size of an opening, or admit air into a room, however necessary; for some are as much afraid of fresh air as persons in the hydrophobia are of fresh water.

I myself had formerly this prejudice, this aërophobia, as I now account it; and, dreading the supposed dangerous effects of cool air, I considered it as an enemy, and closed with extreme care every crevice in the rooms I inhabited. Experience has convinced me of my error. I now look upon fresh air as a friend; I even sleep with an open window. I am persuaded that no common air from without is so unwholesome as the air within a close room that has been often breathed and not changed. Moist air, too, which formerly I thought pernicious, gives me now no apprehensions; for, considering that no dampness of air applied to the outside of my skin can be equal to what is applied to and touches it within, my whole body being full of moisture, and finding that I can lie two hours in a bath twice a week, covered with water, which certainly is much damper than any air can be, and this for years together, without catching cold, or being in any other manner disordered by it, I no longer dread mere moisture, either in air or in sheets or shirts; and I find it of importance to the happiness of life, the being freed from vain terrors, especially of objects that we are every day exposed inevitably to meet with.

You physicians have of late happily discovered, after a contrary opinion had prevailed some ages, that fresh and cool air does good to persons in the small-pox and other fevers. It is to be hoped that in another century or two we may all find out that it is not bad even for people in health. And, as to moist air, here I am at this present writing in a ship with above forty persons, who have had no other but moist air to breathe for six weeks past; everything we touch is damp, and nothing dries, yet we are all as healthy as we should be on the mountains of Switzerland, whose inhabitants are not more so than those of Bermuda or St. Helena, islands on whose rocks the waves are dashed into millions of particles, which fill the air with damp, but produce no diseases, the moisture being pure, unmixed with the poisonous vapors arising from putrid marshes and stagnant pools, in which many insects die and corrupt the water. These places only, in my opinion, which, however, I submit to yours, afford unwholesome air; and, that it is not the mere water contained