Chimney, in building, is that part of a house, where the fire is made, and which is provided with a tube, or funnel, to carry off the smoke.

Notwithstanding the magnificence of the Grecian and Roman architecture, it is very doubtful whether their common dwelling-houses had chimnies; for they made use both of stoves, and holes cut in the roofs of their houses, to admit the free egress of smoke. But as Virgil mentions chimnies, we may infer, that they were not wholly unknown to the ancients.

Method of Building Chimnies, , that it-ill not smoke : Mason have adopted different methods of drawing up the funnels of chinmies, generally regulated by their own fancy and judgment, which are often influenced by local customs : hence they are seldom directed by sound and rational principles. It frequently happens, that the smoking of chimnies is occasioned by their being carried up narrower at the top than below, or in a zig-zag form, or in angles ; indeed, in some instances, this is owing to accidental causes ; but, for the most part, it must be attributed to those above mentioned. When chimnies are constructed in a pyramidal or tapering form, especially if the house be of a considerable height, there is much reason to apprehend that they will smoke : the air of a room being rarefied, is forced into the fuunel of the chimney, and receives from the fire an additional impetus to carry up the smoke. Thus it is evident that, as the smoke ascends, the impelling force is lessened ; it moves slower, and consequently requires a greater proportion of space to circulate through ; whereas, in the usual way, it has less room, from the sides of the chimney being gradually contracted. Although this method of constructing chimnies may not meet with general approbation, because is supposed that the wider a chimney is at the top, the more liberty the wind has to blow down. yet, on the other hand, it is obvious that, from the structure of the chimney, and from other causes, the wind, having no resistance to overcome, must necessarily return, and thus facilitate the free egress of the smoke. In the usual manner of building pyramidal chimnies, when a current of air rushes down-wards, the wind and smoke are in a manner confined, and as the resistance is less from below, the smoke bursts out into the room. Hence the reverse method before suggested, has proved effectual, after every other expedient had failed, and even in a house, standing in the most disadvantageous situation, namely, under a lofty mountain to the southward, from whichblasts wereblown down upon it. A vent was carried up without angles, as perpendicular as possible, being made several inches wider at the top than at the bottom : the funnel was contracted in a throat directly above the fire-place, and widened gradually upwards. Since that time, the house has not only ceased to smoke, but, when the. doors stand open, the draught is so strong that it will carry a piece of paper up to the top of the chim-ney. The advantage of erecting chimnies after this mode, are so evident, that we venture strongly to recommend its adoption; for, independently of their being exempt from smoking, and contributing to purify the atmosphere, by the rapid current of air continually circulating through the apartment, it will prevent large quantities of soot from accumulating, and consequently remove every apprehension of their taking fire.

Various other experiments have been made, with a view to prevent or cure smoky chimnies : of these we shall enumerate only the two following, which deserve particular notice. The first is, not to suffer the height of the mantle to exceed one-third of that of the room, and to carry the jaumbs and breast upright, at least to the ceiling, when they should be turned or sloped as easily and gradually as possible. The jaumbs from the hearth to the mantle should describe the form of a curve ; and the lower part of the mantle, a broad horizontal plane : the distance from the inside of the breast to the back, on each side the throat, being from ten to fourteen or sixteen inches, according to the size of the chimney. This mole of reducing smoky chimnies, are informed, has repeatedly been found successful.

Another method, which is at-led with but little expence, consists in grate, of a bath stove, eleven or twelve inches distant from the fender; and in cutting away the back of the chimney, so as to leave a space of two inches between the back of the grate, and that of the chimney. If the grate be of the common form, the sides should be filled up with brick-work, and faced with Dutch-tiles. By this construction, the ait that passes behind the back of the grate will impel the smoke with an increased velocity, and thus prevent it from bursting into the room. Smoky chimnies are frequently occasioned by their being so very narrow as scarcely to admit the children, usually employed for the purpose of sweeping them, to reach properly to the top. This evil may be remedied, and that inhuman practice rendered unnecessary, by adopting the following mode, which has been used for time immemorial in Edinburgh, Glasgow, and other cities in the North; and which ef-fectually answers the end intended. Procure a rope for the purpose, twice the length of the height of the chimney, to the middle of which is to be tied a bush (of broom, furze, etc.) sufficiently large to fill the chimney. Put one end of the rope down the whole passage; and, if there be any windings in it, a bullet, or round stone, is to be tied to the extremity of the rope, and the wood-end of the bush introduced after the rope has descended into the chamber, where a person must pull it downward. By the elasticity of its twigs, the bush sweeps the sides of the chimney as it descends, and carries the soot with it. Should it be necessary for the man at the top, who has hold of the other end of the rope, to draw the bush up again, the person below must turn the latter, so as to send the wood-end uppermost, before he gives notice to the assistant at the top to pull it upwards. Chim-nies thus cleaned, never require one-tenth part of the repairs, rendered necessary where they are swept by children: for, as these are obliged to work themselves up, by pressing their knees and feet on one side, and their backs on the other, they not unfrequently force out the bricks that divide, the chim-nies. This is the chief cause why, in many houses of the metropolis, a fire in one apartment always fills the adjoining ones with smoke, and sometimes even the neighbouring house. Whole buildings have often been burnt down, from this concealed cause ; as a foul chimney, taking fire, communicates it by these apertures to empty apartments, or to such as were filled with lumber; and in which it was thought unnecessary to make any search, after the fire had been extinguished in the chimney where it first began. We, therefore, seriously recommend this practice to be universally adopted, as an object of interest, not less than on account of its humane tendency. It would, farther, be no detriment to those who procure their subsistence by the sweeping of chimnies : for, if this plan should be countenanced, they would be as necessary, then, for the convenience of the public as they are at present; and those very persons would be unavoidably induced to provide themselves with ropes for that purpose. Lastly, such a beneficial change might afford the only practicable means of rescuing many unfortunate children from their degraded situation; pre-vent many accidents by which they become deformed; and obviate the evils attendant on a premature old age.p>

Among the treatises published on this subject, besides those contained in Count Rumford's Experimental Essays, we shall mention only Mr. David Porter's Consi-* derations on the present State of Chimney-sweepers, published some years since; and Mr. Tho. Dan-forths pamphlet, entitled The Theory of' Chimnies and Fire-places investigated, etc. (8vo. 1s. 1796.) The latter is an ingenious, but the former is a practical and valuable essay, which, together with another on the same subject, Mr. Porter has printed at his own ex-pence, and distributed gratis for the benefit of the public ; a liberality not common to authors.