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forming your Society. If it meets with obstruction from the want of proper encouragement or otherwise, I would have you attempt some other method of proceeding in your design; for I shall be very sorry to have it entirely dropped. May you not, as printer, propose to print at certain times a collection of such pieces on the subject of your former proposals, which any shall think proper to send you, and, by way of specimen, to print such papers as your friends may have communicated to you in consequence of your proposals ? For this purpose you may desire a subscription by all persons indifferently for your encouragement. I do not propose, that every thing be printed that shall be sent. You may communicate them to the best judges with you of the several subjects on which these papers shall happen to be written, where you are not willing entirely to trust to your own judgment; and, if they be found not fit for the press, you may return them with remarks, or make some excuse for not publishing them. This I expect will in time produce a Society as proposed, by giving men of learning or genius some knowledge of one another, and will avoid some difficulties that always attend the forming of societies in their beginning. Three hundred copies may be sufficient at first, till it be discovered what encouragement the undertaking meets with; and such a number, I cannot doubt, will sell. I am, &c.
EXPLAINED; THEIR ADVANTAGES ABOVE EVERY OTHER METHOD
IIAVE BEEN RAISED AGAINST THE USE OF THEM ANSWERED AND
03VIATED. WITH DIRECTIONS FOR PUTTING THEM UP, AND FOR
PRINTED AND SOLD BY B. FRANKLIN, 1744.
Several editions of this tract have been published, in Europe and America, and sometimes with a wrong date. The above title is a transcript from that of the first edition. In his autobiography he thus speaks of this performance. “Having, in 1742, invented an open stove for the better warming of rooms, and at the same time saving fuel, as the fresh air admitted was warmed in cntering, I made a present of the model to Mr. Robert Grace, one of my early friends, who, having an iron furnace, found the caşting of the plates for these stoves a profitable thing, as they were growing in demand. To promote that demand, I wrote and published a pamphlet, intitled 'An Account of the new-invented Pennsylvanian Fireplaces,' &c. This pamphlet had a good effect. Governor Thomas was so pleased with the construction of this stove, as described in it, that he offered to give me a patent for the sole vending of them for a term of years; but I declined it from a principle, which has crer weighed with me on such occasions, viz. That, as we enjoy
grcat advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously.
“ An ironmonger in London, however, assuming a good deal of my pamphlet, and working it up into his own, and 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. 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.”
In an edition of the author's writings on electrical and philosophical subjects, published in London in the year 1769, the following note is appended to this tract.
“Soon after the foregoing piece was published, some persons in England, in imitation of Mr. Franklin's invention, made what they call • Pennsylvanian Fire-places, with Improvements’; the principal of which pretended improvements is, a contraction of the passages in the air-box, originally designed for admitting a quantity of fresh air, and warming it as it entered the room.
The contracting these passages gains indeed more room for the grate, but in a great measure defeats their intention. For, if the passages in the air-box do not greatly exceed in dimensions the amount of all the crevices by which cold air can enter the room, they will not considerably prevent, as they were intended to do, the entry of cold air through these crevices.”. -Editor.
In these northern colonies the inhabitants keep fires to sit by generally seven months in the year ; that is, from the beginning of October to the end of April ; and, in some winters, near eight months, by taking in part of September and May.
Wood, our common fuel, which within these hundred years might be had at every man's door, must now be fetched near one hundred miles to some towns, and makes a very considerable article in the expense of families.
As therefore so much of the comfort and conveniency of our lives, for so great a part of the year, depends on the article of fire ; since fuel is become so expensive, and, as the country is more cleared and settled, will of course grow scarcer and dearer, any new proposal for saving the wood, and for lessening the charge and augmenting the benefit of fire, by some particular method of making and managing it, may at least be thought worth consideration.
The new fire-places are a late invention to that purpose, of which this paper is intended to give a particular account.
That the reader may the better judge, whether this method of managing fire has any advantage over those heretofore in use, it
proper to consider both the old and new methods, separately and particularly, and afterwards make the comparison.
In order to this it is necessary to understand well, some few of the properties of air and fire, viz.
1. Air is rarefied by heat, and condensed by cold, that is, the same quantity of air takes up more space when warm than when cold. This may be shown by several very easy experiments. Take any clear glass
. bottle (a Florence flask stript of the straw is best), place it before the fire, and, as the air within is warmed and rarefied, part of it will be driven out of the bottle; turn it up, place its mouth in a vessel of water, and remove it from the fire; then, as the air within cools and contracts, you will see the water rise in the neck of the bottle, supplying the place of just so much air as was driven out. Hold a large hot coal near the side of the bottle, and, as the air within feels the heat, it will again distend and force out the water. Or, fill a bladder not quite full of air, tie the neck tight, and lay it before a fire as near as may be without scorching the
bladder; as the air within heats, you will perceive it to swell and fill the bladder, till it becomes tight, as if full blown; remove it to a cool place, and you will see it fall gradually, till it becomes as lank as at first.
2. Air rarefied and distended by heat is specifically * lighter than it was before, and will rise in other air of greater density. As wood, oil, or any other matter specifically lighter than water, if placed at the bottom of a vessel of water will rise till it comes to the top; so rarefied air will rise in common air, till it either comes to air of equal weight, or is by cold reduced to its former density
A fire, then, being made in 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. 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.
1. Fire (that is, common fire) throws out light, heat, and smoke (or fume.) The two first move in right lines, and with great swiftness; the latter is but jus* 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
• Body or matter of any sort is said to be specifically heavier or lighter than other matter, when it has more or less substance or weight in the same dimensions. VOL. VI.