FITTINGS-UP OF VILLA DWELLING-ROOMS. 1031 this part (the three fourths) will not become ignited ; but will remain as a supply to the fire ; gradually becoming heated, and gradually sinking down to supply the place of the lower portion which has been consumed. By elongating this chamber at its upper extremity, it is apparent that this principle may be carried to any extent ; and that a reservoir of coal may be formed, which will supply a continuous fire, for ten, twelve, or any number of hours, or even days, if necessary. Upon the top of this pile of heating coal there is placed a movable ceiling ; consisting of an iron or brick slab, which descends as the pile of coal sinks. The effect of this movable ceiling is, to keep the air that enters through the crevices of the stove from acting upon the coal lying above the outlet; either by cooling it, or by supplying it with the means of combustion. The foregoing arrangement insures the continued supply of heated coal, after an hour or two lias elapsed ; and the next thing to be pointed out is the contrivance by which a constant supply of heated air is obtained for supporting combustion. This last is a condition of the greatest importance ; for a much greater amount of heat is produced by burning hot coals with hot air, than by an opposite arrangement. The grating before mentioned, as sup- porting the coals, is of peculiar construction. It consists of thin bars which are segments of cii-cles bolted together ; and the whole, when bolted, is sustained by an axle protruding through one side of the heat producer, or fuel-chamber. To this protruding end of the axle, a winch is applied ; so that the grating may be either rocked from side to side, and thus sift the ashes into the ash-drawer beneath ; or else it may be turned round, and thus empty the fuel-chamber of its contents. The meshes of the grating, being thin and numerous, present a great extent of heated surface ; by passing over which the air is heated as it enters the stove. In one word, this rotatory grate approaches as nearly ns possible to the wire gauze of Davj-'s safety lamp, and its operation is precisely the con- verse of that of the wire^auze. In the lamp, the flame is cooled as it issues through the meshes of the gauze ; in my stove, the air is heated as it issues through the numerous insterstices of the grating. In the front of the fuel-chamber is placed a fine vertical grating, covered ■with a sash glazed with talc, of several inches square, by means of which
