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instead of being carried up the chimney, and thus lost,may be detained in these passages, and thence communi-cated to the air of the room to which they lie exposed jand (3) applying to the fire a quantity of solid matter,which, being once heated, preserves its heat long. Someingenious furnaces, on these principles, are described inthe Transactions of the Swedish Academy, and in thesecond edition of Reaumur’s Art of hatching Birds. AUthese contrivances are united in the following combinationof the two pots and the hoop.

The undermost pot has the small grate introduced intoits lower part, the fire-place door closed, and the ash-pitdoor or the bottom hole open for admitting air. Beingthen charged with small pieces of charcoal, and somelighted coals thrown above them, its top is covered bythe largest of the grates, and on this is placed the hoopand dome, filled with balls of baked earth, or with piecesof bricks, so disposed as to leave small vacuities betweenthem. If the stove is placed in the middle of a room, itsinjurious burnt air may be carried oft, by a pipe insertedlaterally into the larger door of the dome, and communi-cating at the other end, which should be raised eight orten inches, with the chimney of the room ; all the otherapertures of the dome being closed.

The furnace, thus charged, will keep up a moderate andnearly equal warmth for many hours, without injury oroffence ; the charcoal burning down exceeding slowly ;and the heated balls or bricks continuing the warmth for aconsiderable time aster the fuel is consumed. Fresh char-coal may be occasionally supplied through the door abovethe grate : the check, which the balls give to the motionof the air through the furnace, renders the consumptionof this also flow, and it may still be made more so,at pleasure, by stopping a part of the aperture winch

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