A very effective kind of close stove, particularly adapted to large rooms, halls, and churches, and possessing considerable novelty of appearance, has lately been introduced into this country by Mr. J. B. Nott, from the United States. In the upper part of a low pedestal is a large capacious chamber, capable of holding a sufficient supply of coals for the day's consumption; from this receptacle the coals gradually sink down, as they are consumed, in front of the grate, and are deposited upon an arched grating, supported upon a pivot, upon which it is made to oscillate, (by using the poker as a lever for that purpose,) and thereby clear the bars of ashes; and when it may be necessary to clear or put out the fire entirely, the said vibrating grating is moved through a greater angle, by which all the ignited fuel thereon is thrown out at either end of the arch. To give the lively appearance of an open fire, and the security of a close stove, the front of the stove is enclosed by windows of talc, through which the glowing fuel is seen.

The air is admitted for lighting the fire by leaving the ash-pit drawer a little way open, and when ignition is complete, the drawer may be entirely shut, as sufficient air finds its way through the imperfect junctions or fittings of the metal, to preserve a vivid combustion of the fuel. The fire chamber is encased in fire brick, or some other suitable slow conductor, which prevents the surrounding cast iron from obtaining that high temperature which is found to deteriorate the air of the apartment, and the heat is in consequence more uniformly diffused over the other parts of the structure, which presents altogether a very extensive surface of metal for the radiation of heat, principally derived from a tall ornamented chimney, of a flat pyramidal or pilaster-like form. In this chimney there is a turn valve, to regulate the egress of air, the action of which, together with the management of the ingress crevice at the ash-pit drawer, determines the quantity of heat or the rate of combustion of the fuel. In fitting a stove of this kind to a room having the ordinary cavity for the fire-place, Mr. Nott converts the latter into a hot air chamber, and places his close stove upon the hearth in front.

A stove of this kind is employed for warming the extensive range of rooms at the Museum of National Manufactures and the Mechanic Arts, in Leicester-square, which it does most efficiently, with very great economy of fuel. Anthracite, or stone coal, which is almost wholly free from bituminous matter, and emits, in consequence, scarcely any smoke, may be very advantageously burned in stoves of this kind.

German, Pyramidal, Pedestal, Sarcophagus, etc. Stoves. - All grates of this class are, strictly speaking, close stoves, the fire being entirely shut up within them, the flue or chimney usually consisting of a metallic pipe, which is conducted through the walls of the room to the external atmosphere. The German stove is a vertical cylinder of sheet iron, mounted upon legs, having internally, and about midway, a short cylinder of cast iron, with a grating at bottom, which constitutes the fire room, and underneath is the ash pit. The tops, which are variously formed to suit particular purposes, are made to take on and off, so as to allow of baths, boilers, or retorts, to fill up the aperture, and thus become the cover to the upper part of the furnace; the application of heat is thus very convenient and effective, and is much used for chemical processes, and manufacturing operations on the small scale. The pyramidal, pedestal, and sarcophagus stoves are of similar internal construction to the German or cylinder stoves, but they are usually of cast iron, and designed with a view to ornament as well as utility: their external forms are explained by their names.

Having now described the principal varieties of stove grates or fire-places in their most improved forms, (including air stoves, which will be found under the article Air), we shall close this part of the subject by a few observations on the proper construction of fire-places in general, in order that the reader may understand the defects that may exist in his own, and know how to apply the remedy. In open fires the bars should not be larger than is necessary for strength, as they obstruct the radiation of heat, and prevent the egress of air, which is requisite for making the fire burn clear. To attain a clear fire, Mr. Tredgold justly says, that the sides of the burning fuel should be at least half surrounded with slow conductors of heat, otherwise the heat developed will pass off so quickly by conduction, that the fuel will burn dead, and that heat which ought to be radiated will be expended in warming the walls, etc. behind the fire. Iron is a very rapid conductor of heat, and therefore it should be used as sparingly as possible.

Fire brick, a slow conductor, is employed with much advantage for the backs and ends of grates by a few manufacturers, but ironmongers in general seem to think it more desirable to use iron than to economize fuel, or to work on sound principles.

But when a fire-place, made of slow conducting materials, is large and filled with fuel, as soon as the fire becomes bright the heat is extremely intense and scorching; when the fire is in this state it is often too powerful for the room, though perhaps barely sufficient when the combustion is less perfect. This may be remedied by any method which enables us to expose a greater surface of hot matter with the same bulk of fuel, and at a lower degree of heat. Some time ago " fire balls," (spheres made of baked clay,) were used with this object; but their inconvenience, when not judiciously attended to, brought them into disrepute. An improved substitute for them has been suggested by Mr. Tredgold, when the fire is of greater length than 18 inches; that of building a projection from the back of the grate (and of the same depth) to within three inches of the front bars. This projection should be of good fire brick, and built firmly in with the other part of the back. Thus is left a space for a sufficient body of fire on each side, and the surface is increased without adding to the mass of burning fuel. The combustion of the fuel in an open grate should not be faster than is necessary to produce a clear fire.

To guard against the loss of heat by the warm air of the room ascending the chimney, two partial remedies have been adopted - that of lowering the mantel, and contracting the throat of the chimney; but the first of these remedies impairs the ventilation of the room, and the second, causing a rapid draught, increases the consumption of fuel. For some rules in duly proportioning the flues, see the article Chimney. A grate should offer as little obstruction as possible to the radiation of heat, and therefore the usual mass of metal below the front bars, called a fret, is objectionable; and the sectional form of bars should be that of a wedge, with the sharp extremity rounded off, which part should be inside, or next to the fuel, as it is advantageous to have as little metal as possible in contact with the fuel. There is, however, no objection to the employment of metallic covings, as reflectors of heat, when separated by a slow conductor from the metal of the grate; and instead of these being blackened, as they are usually in the common Rumford stoves, they should be bright or polished surfaces, and preferably of brass to the other common metals. The angle best suited for the covings is 45° with the front line of the grate.

The height of the grate from the floor is an object of some importance; if it be placed too low, the heat is expended almost wholly on the hearth, and the fire-place seems buried within the fender; if it be placed too high, a person's face is scorched, while too small a portion of heat is given to the floor to render a room comfortable; but a high mantel has the advantage of producing a more effectual ventilation. Mr. Tredgold considered that the top bar of stoves ought not to be less than 20 inches from the floor, and never exceed 2 feet; and when the lower part of the fire is not buried in a mass of metal work, there will be an abundant supply of heat thrown upon the floor from the greater height. The space between the top bar and the mantel will require to be proportioned to the size of the room and the height of the chimney, and in ordinary cases may be about 15 or 16 inches. With respect to the proportion of grates to different sized rooms, Mr. Tredgold has, from observation, deduced the following rule: - Let the length of the front of the grate be made one inch for each foot in length of the room, and the depth of the front be half an inch for each foot in breadth of the room.

If the length of the room be such as requires the grate to be longer than 21/2 feet, two fire-places will be necessary; and in that case the same proportions may be adopted, divided into two grates, unless the room be very wide, when a greater length should be given, and less depth, so as to preserve an equivalent area. For various information connected with this subject, see the articles Ventilation, Combustion, Air, Furnaces, etc.