HIS Manner of Performance is by Plates of Iron, Copper, and Brass, placed in the Chimney, after its being prepared to receive them, at four Inches from the Back, Jambs, and Hearth, with a Communication to the external Air; which first entered under the Hearth-Plate, and made several Turnings and Windings, through Partitions between the inside of the Chimney, and those Plates representing, as it were, a re-curved Canal; one End whereof joins the outward Air, and the other comes out of the Top of one of the Jambs of the Chimney. The Use and Intent of these Chimnies is only for burning of Wood, the Heat whereof is more diffused than that of Turf or Peat. THE Invention was extremely ingenious, the Room was warmed, in all its Parts, with great Equality; cold Air was prevented rushing through Crevices; the Funnel was supplied by a Trap-Door, or Bellows, upon the Hearth-Plate; and much less Wood served to make a Fire: but the Expence was found to be so great, especially in old Chimnies, that they never came into much use, and are now entirely laid aside: The upright Heat was likewise all lost in all those Chimnies. SECONDLY, the ingenious Dr. _Desaguliers_ gives the Construction of two kinds of Chimnies; one for burning Turf and Peat upon the Hearth, and the other for Sea-Coal in a Stove-Grate, made in a particular Manner. IN the Description of the First, he says, That in Chimnies where Wood is burnt the Cavities behind the Back and Sides, after the Manner that the _French_ Author directs, are very useful; but where you have the Heat very strong, it will be proper to make the Cavities as near the Fire as possible; and tho’ the Course of the Air will be shorter, yet the great Heat it acquires in that Case will make Amends for the Shortness of the Passage. THE Shape and Manner of the Chimney is the same as directed by Mons. _Gauger_, with this difference, that the Doctor’s has no Cavity under the Hearth; only a divided Box made of Plate-Iron, upon which the Fire is placed, and an horizontal Cavity behind the Back, faced with Plate-Iron; so low, that the Fire lies against it: Through this Preparation comes a Stream of external Air, in several Turnings and Windings, and from thence is carried up a Passage within the Brick-Work in one of the Corners, as high as the Mantle-Piece; from the Corner it is brought forward to the under side of the Mantle-Piece, where it makes several Turnings in a Tin Canal, from which it is at last convey’d into the Room. HE likewise recommends the Trap-Bellows in this Construction of Stoves.