Fire-Place, a contrivance for communicating heat to rooms, and also for answering various pur-poses of art and manufacture. - With respect to the latter kind, we propose to treat under the articles of Furnace and Stove.
In the construction of fire-places for domestic purposes, the chief object is the saving of fuel: with this intention, several ingenious artists have invented different kind* of grates, more or less adapted to' that useful end.
The fire-places in general use are, 1. The large open ones, which were commonly adopted in former times, and are still retained in the country, and in kitchens : they require a wide funnel, consume a a great quantity of fuel, and generally smoke, unless the door, or a window, be left open.
2. The modern fire-places generally adopted in towns, are constructed with low breasts and hearths, narrowed by jambs. These being more contracted than the antiquated chimnies, easily keep the room free from smoke ; but the funnel necessarily occasions a considerable draught of air, which rushing in at every crevice, renders the situation of those who are exposed to it very uncomfortable, and even dangerous : for it is unquestionable, that most of the diseases that proceed from colds, may be justly attributed to the strong draught of chimnies, by which, in severe weather, persons are scorched before, while they are freezing behind. Such fire-places, therefore, are of little service in heating rooms, as the surrounding air, which is warmed by the direct rays of the Fire, does hot remain in the apartment, but is continually collected in the chimJ ney, by the current of cold air which surrounds it, and by which it is in a short time carried off. Nor is this the only inconvenience attendant on such improper contrivances, for the greatest part of the fire is lost, in consequence of its being absorbed by the back, jambs, and hearth, which are dark and obscure, and reflect very little, so that the heat flies directly up the chimney.
3. To remedy this inconvenience, an ingenious Frenchman, named GaugeR, . in the year 1709, proposed seven different constructions of a new kind of chimnies, in which there are hollow cavities, formed by means of iron plates inserted in the back, jambs, and hearth: through these the heat passes and warms the air in those cavities, which is thus continually communicated to the room. Although many advantages arise from this arrangement, yet the expence necessarily incurred, must ever be an insuperable obstacle to its general adoption.
4. Another kind of fire-place is the Holland iron-stove, which has a flue proceeding from < the top, and a small iron door that opens into the apartment. They serve to warm a room, lessen the consumption of fuel, and to produce a constant change of air; but, as the fire is too much confined, it is neither suffi-ciently chearful, nor calculated for culinary purposes, and is therefore employed chiefly to work-shops.
5. The German stove consists of five iron plates, which are screwed closely together in such a manner, that the fuel may be put into it from another room, and even from the outside of the house. This stove warms rooms with little fuel, and is not' attended with any danger from the irruption of cold air; but it admits of no change or draught of air in the room, and the fire is likewise concealed.
Such are the inconveniencies at-tending the fire-places in general use ; and, though we by no means, wish to depreciate the inventions of Count Rum ford, yet we are of opinion that the Pennsylvania fire-place, which was originally contrived by Dr. Franklin, is eminently adapted to domestic purposes, both for its economy in the consumption of fuel, and on account of its efficacious mode of imparting heat. From these considerations, we have,been induced to procure several cuts, by which the reader will be enabled to form a proper estimate of an invention which appears to be susceptible only of very few improvements. Dr. Franklin's machine consists :
1. Of a bottom plate or hearth-piece, as in the annexed figure, with a rising moulding in front, for a fender 3with two perforated ears, F, G, for the reception of two screw-rods ; - a long air-hole a, a, through which the external air passes into an air-box ; and also of three -moke-holes, represented by dark squares in B, C, through which the smoke descends and escapes; beside these, there are double ledges for receiv-ing the lower edges of the other plates.
2. A back plate without holes, that is furnished with a pair of ledges to receive
3. The two side plates, each of which has a similar pair of ledges, for the reception of the side ledges of the front plate, together with a shoulder on which it rests; there are likewise two pair of ledges for the purpose of admitting the lateral edges of the two middle plates that form the air-box ; and also an oblong air-hole through which the air warmed in the box is discharged into the room ; together with a wing or bracket,
as at H, and small hole, as at R, in which the axis of the register is to move.
4. An air-box, which is composed of the two middle plates D, E, and F, G.
The first of these two cuts has five thin ledges or partitions, cast on it, the edges of which are received into as many pair of ledges, cast in the other; the tops of all the cavities formed by these ledges are covered by another ledge of the same form and depth, which is cast with them ; so that when the plates are put together, and the joints luted, there can be no communication between the air-box and the smoke. In the winding passages of this box, fresh air is warmed, as it passes into the room.
5. A front plate, which is arched on the under side, and ornamented with foliage, etc. ' 6. A top plate,
with a pair of ears, M, N, which correspond to those in the bottom plate, and are perforated for the same purpose. It has likewise a pair of ledges that run round the under side, in order to receive the top edges of the front, back, and side-plates. The air-box is two and a half inches shorter than the top plate. All these plates are of cast iron ; and, when properly arranged, they are bound with a pair of slender rods of wrought iron, with screws; and the machine appears as in the preceding figure. There are also two thin plates of wrought iron, forming
7. The shutter ; the length and breadth of which are so proportioned, as completely to close the opening of the fire-place; it also serves to draw the fire, or to secure it during the night. This shutter is raised or depressed by means of two brass knobs ; and it slides in a groove left between the foremost ledge of the side-plates and the face of the front plate.
6. The register, which is placed between the back plate and air-box, and is furnished with a key; so that it may be turned on its axis, and raised or lowered at pleasure in an oblique position. The operation of this machine, and the method of fixing it, may be understood by attentively observing the profile of the chimney and fire-places in the following figure.
M is the mantle-piece, or breast of the chimney; C the funnel ; B the false back, made of brickwork within the chimney, at the distance of four inches from the true back, or upwards, from the top of which a closing is to be made over to the breast of the chimney ; in order that no air may enter except that which passes un-der the false back, and ascends behind it. E is the true back of the chimney} T. the top of the fire-place ; F the front of it; A the place where the fire is made ; D the air-box ; K the hole in the side plate, through which the warmed air is discharged from the air-box into the room, H is the hollow formed by removing some bricks from the hearth under the bottom plate, filled with fresh air, which enters at the passage. I, and ascends into the box through the air-hole in the bottom plate near G, the partition of the hollow, and which is designed to separate the air and smoke. - P, is the passage under the false back, and part of the hearth for the smoke, the course of which is pointed out by the arrows delineated in the last figure. The fire is to be made at A, when, the flame and smoke will ascend ; strike the top T, and communicate to it a considerable degree of heat; the smoke will turn over the air-box. descend between it and the back-plate to the holes near G in the bottom plate ; and heating in its passage all the plates of the machine, it will then proceed un-der and behind the false back, whence it will rise into the chimney. The air of the apartment contiguous to the several plates and warmed by them, become spe-cifically lighter than the other air in the room, and is compelled to rise ; but, being prevented by the closure over the fire-place, it is forced out into the room; and ascending by the mantle-piece to the ceiling, is again gradually driven down by the stream of newly warmed air which follows; so that the whole room in a short time acquires an equal temperature. The air also that is warmed beneath the bottom plate, and in the air-box, rises wit of the holes in the side plates, and thus warms, and continually changes that of the room.
In closing the chimney, it will be necessary to leave a square opening for a trap-door, by which a chimney-sweeper may ascend ; and which may be made of slate or tin, and be placed in such a di-rection, that, by being turned up against the back of the chimney when open, it may close the vacancy behind the false back, and discharge the soot which falls in sweeping upon the hearth. It will also be convenient to have a small hole, about five or six inches square, cut through near the ceiling into the funnel, and provided with a shutter which, being occasionally opened, may carry off the heated air of the room, as well as the smoke of tobacco, etc.
For a farther account of the manner of using this fire-place, the advantages attending it, answers to cavils and objections, together with instructions for bricklayers in fixing it, we refer the reader to Dr. Franklin's "Experiments and Observations on Electricity " etc. 4 to. 10s. (5d. 1769.