Through the use solely of oil or water, it produces illuminating gas or pure hydrogen for all the applications that may be required of them. It consists of three parts, viz., of a vaporizer, A, which converts the liquids into gas; of a distributer, B, which contains and distributes the liquids to be converted into gas, and of a regulator, C, which automatically regulates the flow of the liquids in proportion as they are used. [Illustration: FIG. 1.--FOUCAULT'S GAS APPARATUS.] In the vaporizer Mr. Foucault, the inventor of the apparatus, obtains a perfectly regular combustion through the use of a central column, 15, charged with fuel, closed at the upper part, open beneath, and entering a furnace that is fed by it with regularity, the zone of combustion not being able to extend beyond the level of the draught. The grate, 16, is capable of revolving upon its axis in order to separate the cinders. It also oscillates, and is provided with jaws for crushing the fuel; and it may likewise be lowered so as to let the fire drop into the ash-pan when it is desired to stop operations. The vaporizer, properly so called, is not placed directly over the fire, and for this reason the production of a spheroidal state of the liquid is avoided. It consists of a vessel, 44, into which the liquid is led by a pipe, 43. The cast-iron evaporating vessel, 14, is provided with appendages, 14 _bis_, which dip into the liquid and bring about its evaporation. A refractory clay sleeve, 41, protects the lower part of the cylinder, 15, from the fire, and diminishes the smoke passages at 42. The vapor produced makes its way vertically through a layer of charcoal placed between the evaporating vessel, 14, and the receiver, 17, and serving to decompose the aqueous vapor formed. All clay and red and white lead joints are done away with in this part of the apparatus, as are also packing bolts. Thus, at the upper part the cover, 19, is provided with a rim that enters a cavity filled with lead, so, too, the lower part of the evaporating vessel, 14, rests in a channel containing lead. There is also at 30, a joint of the same character for the rim of the external cylindrical vessel, 18. Both this latter and the receiver, 17, dip beneath into a tank of water, 66.