In nearly all gas fires and stoves the gas is burnt with an admixture of air (atmospheric gas, 1 of gas and 2 of air), by means of an atmospheric burner; this is not only a source of economy, but atmospheric gas has the very great advantage of being smokeless; but for this, a gas fire would be an impossibility; it must, however, be borne in mind that although smokeless this gas gives off products of combustion (carbonic acid, watery vapour, &c.), which must be carried away by a flue or other means. The portable stoves are always provided with a nozzle for attaching a smoke-pipe. There is still a doubt as to which is most economical, coal or gas: we cannot do better than quote the words of a well-known gas-stove maker, Chas. Wilson, of Leeds. He says, speaking of heating by gas: “It is not cheaper than coal, taking fuel for fuel and continually used, unless, as in the case of offices where labour has to be employed to light fires, clean grates, &c.; but it is cheaper than coal if occasionally used, as in the case of bedrooms, or sitting-rooms used by visitors, or rooms used by children for music, &c.; for bedrooms it is especially adapted for use for an hour or two at night or in the morning or for giving an unvarying heat all night. It is preferable in the matter of cleanliness, and a true solution of the smoke-abatement problem” (probably a coal-stove manufacturer would speak as much in favour of fire-grates). It should be seen when purchasing gas fires that they have silent burners, as some make an objectionable hissing noise when in use. [Illustration: 45. Calorigen Stove.] “The Calorigen” Gas Hot-air Stove, Fig. 45 (Farwig & Co., 36 Queen Street, Cheapside, London), consists of an outer sheet-iron casing with a burner at the base inside, and proper accommodation for exit of products of combustion. A coil of good-sized sheet-iron pipe is affixed within the stove; the lower end of the coil is connected with the outer air and the upper end opens into the apartment, thus producing a free inflow of fresh air at any temperature desired, from 60° to 200° F. or higher at will. The chief advantage of a gas stove is the immediate lighting and extinguishing, and needing no attention.