Dr. Arnott, in 1855, published a volume " On the Smokeless Fire place, Chimney-valves, and other means, old and new, of obtaining healthful Warmth and Ventilation." Hia chief object was to describe a kind of open stove which ho had invented, as the result of combining many principles long known, but only in part acted on. In this, as in other cases, he generously threw all patent privileges aside, and sought how best he might serve the public generally. The chief fault. of open fire-places being the production of smoke, waste of fuel, unequal heating, and troublesome management, he devised a plan for lessening, if not preventing, all these evils. One day's charge of fuel is supplied at once, in a box beneath the grate. The coal is borne upwards, when by a moveable false bottom in the box, which is raised easily by the poker as a lever, with notches and ratchets to retain the false bottom at any height. The box is from 8 to 18 inches deep, and con tains from 20Ibs. to 3011m. of fuel. In warm weather, the fire is kept dull by not raising the bottom so high or so often as in cold weather. To light the fire, paper and wood are laid on the coal ; and on this three or four inches of cinder or partially coked coal. The wood soon kindles tho cinder, and the pitchy vapour from the coal rises through the wood-flame and cinder-flame, ignites, and adds to the heat, without producing smoke. It is important that no air should peas up through the coal-box ; to insure this, the false bottom moves up tightly. The coal only burns at the top, but it keeps alight with great tenacity. Even if no fuel were left in the grate, the coal in the box would burn gently downwards, and endure through a whole night. The grate is accompanied by an improved form of chimney-valve, &c. Any kind of coal, culm, or coke will do. A room may be kept warm all night, by leaving the valve and throat of the chimney only a little open, and thereby drawing away only a little of the warmed air. Dr. Arnott, having .tried his new open smokeless fire-place in many ways, has found that it saves one-third of the fuel, cures a smoky or ill-drawing chimney, ventilates the room through the valve, diffuses the heat about the room, requires no tending for twelve hours together, renders chimney-sweeping unnecessary, and calls for very little personal attend ance. We may add that Dr. Arnott combats an opinion, now very prevalent, that a modern low grate warms the floor of a room better than one of greater height. In the usual position of a hearth-rug, more beat comes down upon it if the grate be moderately high. If the grate be low, hardly any hest striA es it ; it merely passes horizon tally over it, while cold air rushes along the floor in the opposite direction, on its way to feed the fire.
Close Stoves.—The common Dutch stove is one of the simplest examples of a close stove. It generally consists of a cylindrical case of sheet iron, within and near the bottom of which is a grating for con taining the fueL There is an ash-pit beneath the grating, and three openings to the interior—one to the ash-pit, one for introducing the fuel above, and one leading to'a flue or chimney. When the fuel-door is closed and the ash-door open, there is then one aperture by which cold air can enter to feed the combustion, and another by which the smoke can escape. In this form of stove the heated iron case warms the sir of the room by conduction rather than radiation, and all this air becomes much more nearly equalised In temperature than by a common fire. There is also great economy of fuel, and an absence of smoke and dust On the other hand, inconvenience arises from the highly heated iron, the temperature of which is so great as to decompose many of the heterogeneous particles always floating in the air. The air acquires a burnt and eulphureons odour ; it exercises a dry and shrivelling effect on objects in the room ; and it often gives headache and giddiness to those who are exposed to it. In Germany the stoves are made on this
principle, but are often more ornamental in their character.
The Russians contrive their close stoves on a different principle.
Earthenware and brickwork are largely used, instead of metal, as a means of making the heat less intense near the stove, and of keeping up a reservoir of beat after the fire is extinguished. The stove is built in a massive style, and consists of a series of chambers, of which the lowest serves as the fireplace, and the upper ones as flues ; and being composed almost entirely of brick and porcelain, the outer surface remains at a moderate temperature for a very long period.
Within the last thirty years many forms of stove have been devised, with the view of obviating some of the objections urged against those used on the Continent. Where, as in a common German or Dutch stove, the burning fuel conies in contact with the metal of which the stove is formed, this metal becomes so highly heated as to produce upon the surrounding air the deleterious effects before alluded to. Dr. Arnott has the merit of having drawn attention in a particular manner to this subject. The problem which Dr. Arnett sought to solve was, to obtain a considerable extent of surface heated not much above 200°, as a means of warming apartments. lie first caused a kind of water stove or tank to be constructed, having a fire-box in its centre ; and by certain arratfgements for the admission of air and the emission of smoke, he kept the water always nearly at the boiling temperature. This apparatus being however both expensive and difficult to manage, he dispensed with the water, and surrounded the fire merely with a body of air. In the new form of stove, the fuel is put into a small fire-box, enclosed within a larger case of sheet-iron ; the only openings in the outer case being a door at which the fuel is introduced, an air hole beneath the grate, and a chimney for the exit of smoke, which chimney, being merely a metallic tube three or four inches in diameter, can be easily arranged in position. The interior of the outer case is nearly divided into two parts by a partition so adjusted as to cause a continued circulation of the heated air within, and hence an equable heating of the outer case. The air-vent leading to the fire is provided with a valve, by which the admission of air is rendered more or less abundant according as the fire within is less or more intense. It was one point in Dr. Arnott's system to make the stove a " self-regulating " one, by providing apparatus whereby the valve would open and shut at the proper times to maintain any required temperature ; and he suggests six or eight different modes of arrangement, from which the maker of the stove may select one. Dr. Arnett states :—" During the winter, 1836-7, which was very long and severe, my library was warmed by the thermometer-stove alone. The fire was never extinguished, except for experiment, or to allow the removal of pieces of stone which had been in the coal; and this might have been prevented by making the grate with a moveable or shifting bar. The temperature was uniformly from 60° to 63°. I might have made it as much lower or higher as I liked. The quantity of coal used (Welsh stone-coal) was, for several of the colder months, six pounds a day ; less than a pennyworth, or at the rate of half a ton in the six winter months." This kind of stove possesses many advantages ; but it is not free from defects. It is liable to the objection already stated with regard to the unpleasant feeling consequent on the use of all stoves of the kind, and indeed with it more than others ; for owing to the very slight expenditure of fuel, there is little or no change in the atmosphere.