To remedy the evils resulting from burnt air, close stoves are made with a double case, so that there shall be a body of air between the fire and the air of the room. It is on this principle, modified in various ways, that a large number of stoves have been constructed; of which one, by Mr. Sylvester, may be briefly described. There is a hollow cast-iron box, on the outside of which are cast several ribs. Those ribs are about three-quarters of an inch thick, and project three or four inches beyond the surface of the box; and their object is to increase the heating surface; for the fire being lighted in the hollow of the box, the conducting power of the iron causes the whole exterior case of the box, together with the projecting ribs, to become heated. The box is placed within an ornamental case, the sides and top of which are fretted with lattice-work, to allow free access to the air, which enters through the lattices at the sides and escapes from the top of the stove, passing in its passage over the ribbed surface of the heated box. The grating on which the fuel lies is formed of a number of loose bars fitted together into a frame, and prolonged so as to emit heat into the room as well as to support the fuel. Everything is so arranged as to give as much iron surface as possible, so as to communicate heat to the surrounding air; while at the same time the extent of the heated surface prevents any one part from being excessively and injuriously heated. Dr. Arnott’s Stove. To describe all the “chunk” stoves, “Vesta” stoves, “Olmsted” stoves, and other similar contrivances of modern times, would fill a volume instead of a few pages. We may, however, speak briefly of Dr. Arnott’s stoves as a means of showing some of the inconveniences to which close stoves are liable, if not constructed with care. This stove consists of an external case of iron, of any ornamental shape. Within this case is placed a box made of fire-clay, to contain the fuel, having a grating at the bottom; and there is a space left between the fire-box and the exterior case, to prevent the communication of too much heat to the latter. Thee pedestal of the stove forms the ash-pit; and there is no communication between the stove and the ash-pit, except through the grating at the bottom of the fire-box. A small external hole in the ash-pit, covered by a valve, admits the air to the fire; and according as this valve is more or less open, the vividness of the combustion is increased or diminished, and thence the greater or less heat produced by the stove. The quantity of air admitted by this valve is governed by a self-regulating apparatus, either by the expansion and contraction of air confined by mercury in a tube, or by the unequal expansion of different metals. The smoke escapes through a pipe at the back of the stove; but the fuel employed is such as to yield very little smoke. By adjusting the regulator so as to admit only a small quantity or