The Russian stove is intended as a sort of magazine, in which a great quantity of heat maybe quickly accumulated, to be afterwards slowly communicated to the apartment. The stove is therefore made of a massive size. It is formed of brick-work, clay, glazed tiles, which together form a great mass of matter to be heated by the fuel; and there is in every part a considerable thickness of slow-conducting material between the fuel and the air of the room. The fire is kindled early in the morning, after which the stove door is shut, and the air aperture below left open for some time as a means of admitting draught to the fire; but in the course of a short time the fire-door is opened to check the draught, so as to prevent the too rapid combustion of the fuel. In this way the combustion is allowed to go on, and the substance of the stove becomes warmed, after which the air passages are shut, so as to prevent any abstraction of heat by the current that would otherwise be occasioned. The stove thus becomes a great mass of heated matter, which is gradually pouring warmth into the apartment during the whole of the day; and as the temperature of the surface never becomes very high, the impurities in the atmosphere are not decomposed, and it is consequently free from those offensive effluvia, unavoidable when metal stoves are used. The fuel is allowed to be nearly burnt out before the apertures of the stove are closed; and therein the stove differs greatly from those hitherto considered; the heated air within the stove being so completely shut in that it can find no outlet, except through the substance of the brickwork. The modifications of the arrangements whereby warmed air is conveyed from one room to another, may next be noticed. In such cases the air either escapes from a heated receptacle outside the fire-case, or else it merely passes over a heated metallic surface. The following description relates to one variety of the first of these two methods. In the lower part of a house or building is a cast-metal double stove; the inner part forming the stove, and the outer one the case or envelope. The fuel is burned in the inner stove, and the smoke produced during the process of combustion is carried off by a chimney, which passes through both stoves or cases, and is conveyed to the outside of the building. The outer case includes not only the furnace or inner stove, but also a considerable space occupied by the air of the atmosphere, which is freely admitted through a number of holes placed around it; and when any current of warmed air is produced, it passes off from the space between the outer case and the inner stove, and is conveyed by tubes to any apartment in the building; so that the rooms are warmed by the air which has passed between the outer case and the inner stove.