In stoves gas should always be burned with the Bunsen burner, which is generally employed by chemists when they make use of gas for heating purposes. It consists of a small brass cylinder, or chimney, set over the gas-jet, like the glass of an argand lamp, with openings near the bottom to allow air to enter. The gas being admitted into this before lighting, mixes with the air, and when lighted at the top, which is usually cov ered with wire-gauze or perforated metal, burns with a pale-blue flame. The most complete combustion and the greatest heat are obtained in this way. Smoke, properly so called, there is none. Still, it must not be forgot that there is burned air—a cubic foot of carbonic acid, besides a quantity of watery vapor, foi every cubic foot of gas used; and, therefore, even with the Bunsen burner, these gaseous products should, wherever it is possible, be conducted away.
A pleasant and very serviceable gas-stove might be constructed by making the casing double, to contain water. It has been ascertained that a gallon of water may be brought to the boiling point in 20 minutes by burning 4 cubic ft. of gas, which, at 4s. 6d. per 1000 ft., costs less than a farthing. The cost of doing the same by a newly-lighted coal fire is more than threefold.
Steam and Rot —The immediate warming agent in these two methods is the same as in Arnott's and other low-temperature stoves—viz., an extensive metallic sur face moderately heated; but instead of heating these surfaces by direct contact with the fire, the heat is first communicated to water or steam, and thence to the metal of a sys tem of pipes. This affords great facility in distributing the heat at will over all parts of a building; and these methods are peculiarly adapted to factories, workshops, and other large establishments. Other advantages are—freedom from dust, and from all risk of overheating and ignition.
generally adopted in establishments where steam-power is used, as the same boiler and furnace serve both purposes. When steam enters a cold vessel it is condensed into water, and at the same time gives out its latent heat till the vessel is raised to 212°, when the condensation ceases. The condensing vessel is usually a cast-iron pipe placed round the wall of the apartment near the floor. In admitting fresh air into the room it may be made to pass over this pipe, and thus be warmed. The steam is conducted from the boiler by a smaller tube, which may be covered with list or other material, to prevent all condensation by the way; and the admission of the steam is regulated by a cock within the apartment, means being provided for allowing the air to escape. Where a pipe cannot be laid round the rocni, a coil of pipe may be formed, or the steam may be admitted into a large vessel or into a hollow statue, forming a steam-stove. Allowance must be made for the expansion of the tubes by heat; and they are so arranged that the condensed water is conveyed back to the boiler.
There can be no proper comparison between this plan of heating and that of common fire-places. Coal-fires cannot warm the air in large workshops; the heat is confined to
their own immediate neighborhood; hence the workmen are often obliged to draw near the grate to warm themselves. According to the plan adopted every part of the house is equally heated, and the whole of the workmen are as comfortable during the hardest frosts as if they were working in a pleasant summer day. It is difficult to esti mate the expense of supplying tub heat, seeing that the steam happens to be drawn from a boiler which is always in operation for other purposes. Excellent, however, as the process is, it is for many reasons unsuited to private dwelling-houses.
In calculating how much surface of steam-pipe will be sufficient to warm a room, it is customary to allow about 1 foot square for every 6 ft. of single glass window, of usual thickness; as much for every 120 ft. of wall, roof, and ceiling, of ordinary material and thickness; and as much for every 6 cubic ft. of hot air escaping per minute as ventila tion, and replaced by cold air.
Hot Water.—Hot-water apparatus was applied as early as 1777 by M. Bonnemain, in Paris, to warm the hot-houses at the Jardin des Plantes, as well as for the artificial hatching of chickens. It was first introduced into England by the Marquis de Cha bannes in 1816, and is now used in many large buildings. It is more economical than steam, except where a steam-boiler is required for machinery; and from this and other advantages it is generally preferred to steam-apparatus. One of these advantages is that the heat begins to be distributed, in some degree, as soon as the fire is lighted, while with steam-apparatus the whole of the water must be at boiling-heat before any steam enters the pipes.
There are two kinds of hot-water apparatus—high-pressure and low pressure. In the first the water is confined, and can be heated to any degree; in the other it is open to the air, and cannot be heated above 212°. Fig. 3 will explain the way in which water is made to carry the heat of a furnace to any part of a building by the low-pressure method. a is a boiler, from the top of which a tube issues, and after circulating through the building, re-enters near the bottom. At the top of the circuit there is a funnel, or a small cistern, c, by which the tubes and boiler may be kept full. When the fire is lighted at the bottom of the boiler, the heated portion of water, being lighter than the rest, rises toward the top through the tube bb, while the colder water from dd flows in to take its place. The tube is made to traverse the apartments to be warmed, where it gives out its heat to the air; the returning portion of the pipe is' thus always colder and there fore heavier than the other, so that the circulation is constantly kept up. The warming surface is increased, wherever it is neces sary, by coiling the pipe, or by making expansions upon it of various forms, so as to constitut3 water-stoves.