The German principle, which might advantageously be adopted to a greater extent in England, is to build a fire-brick structure with the furnace at the base and the flue winding from side to side 3 or 4 times, and terminating at the top into an ordinary brick chimney; this structure projects into the apartment and is covered with porcelain ware, and the appearance often exhibits great taste and skill, as it will be understood that the structure is not rigidly square, but is often very beautiful from an architectural point of view. The good effect experienced is that after 3 or 4 hours’ firing, the mass of brickwork becomes thoroughly heated and the fire is permitted to go out; communication with the chimney is stopped by means of a damper, and every confidence can then be placed in the stove giving out abundance of warmth for the remainder of the day, as the brickwork takes hours to become moderately cool, and the whole of the heat it contains must be diffused into the apartment. It will be noticed that a minimum of heat is lost by this arrangement, and the result is very satisfactory from an economical standing; but it has not the cheerful appearance of our open fires, and efficient ventilation is required. This plan can, however, be satisfactorily adopted for halls or cold situations; in the former it has the further advantage in most instances of warming the stairways and landings in the upper part of the house by the ascension of the heated air. Fire-brick stoves are made by Doulton & Co., Lambeth, London, and are finished in their majolica and Doulton ware; it is needless to add, these wares give the stoves a very handsome appearance. _Hot-air Furnace._--The close stove is really a hot-air furnace, but it is restricted to heating the air in the room. Other hot-air furnaces are designed to obtain a supply of fresh air and heat it before passing it into the room. The heated air from a fireplace is available to the apartment for only about 12 per cent. of the total amount of heat produced; all the rest passes up the chimney. The close stove, on the contrary, utilises 85-90 per cent. of the heat produced, and loses through the smoke-pipe only about as much as the open fireplace saves--10-15 per cent. And herein lies the striking difference between the relative healthiness of the atmosphere heated by a close stove and an open fireplace. The amount of air which hourly passes through a close stove, heated with a brisk fire, is, on an average, equal to only about 1/10 the capacity of the room warmed, and consequently such stove requires, if unaided, 10 hours to effect a change of the atmosphere in every such apartment. Thus stagnant and heated, the air becomes filled with the impurities of respiration and cutaneous transpiration.