FIG. 4.—HERON’S TUBULAR BOILER.
The cock, Τ, serves to let off hot water, and the funnel, Σ, to introduce cold water into the boiler through a tube which runs to the bottom of the latter. The object of the bent tube is to allow of the escape of air when water is poured in, and to give exit to the steam that may be formed, and thus avoid the ejection of water through the funnel, Σ. Heron, in his text, says that this tube debouches in the interior of the funnel so that it shall not be perceived, and not as we have shown it for the sake of greater clearness. In the figure there may be seen a compartment formed by two vertical plates that make an angle into which water cannot enter. This is designed for actuating different figures through the play of the steam and of the several way cocks that I have mentioned. This latter consists of two concentric tubes capable of revolving with slight friction one within the other. The external tube, Γ Δ, is fixed to the upper side of the stove, and traverses it. It contains three apertures, φ, ψ, and χ, placed at different levels, and communicating, through small tubes, with the figures that are to be presently mentioned. The internal tube, Α Β, is open at its lower part, and thus communicates with the interior of the compartment, but is closed at its upper part, which latter debouches above the stove and may be manœuvered by the handle, Α. It contains three apertures at the same levels as apertures φ, ψ, and χ, but differently placed, so that when, through a rotary motion of the tube, Α Β, one of them is brought opposite an aperture of the same level in the tube, Γ Δ, the two others do not correspond. The positions that it is necessary to give them in order that such correspondences shall occur are denoted by marks engraved on the visible portions of the tubes. The tube, φ, terminates in a serpent’s head which bends toward the fireplace, and tube, ψ, terminates in a triton who holds a trumpet to his mouth. Finally the tube, χ, carries at its extremity a whistle that debouches in the body of a bird filled with water.
It will now be seen what will occur. The tube, Α Β, is removed and a little water is put into the compartment. This water flows into the tube, Λ Ξ (which passes under the fireplace and is closed at the side opposite its aperture, Ξ), and is converted into steam. When the tube, Α Β, has been replaced, the steam may at will be passed into the body of the bird, which will warble, or into that of the triton, who will blow his trumpet, or, finally, into that of the serpent, which will blow into the fire and quicken the flames.
CHAPTER IV.
GREEK LAMPS, TOYS, ETC.
PERPETUAL LAMPS.
The ancients utilized, in their prestiges, combustible gases, which, in many places, were disengaged naturally from the earth.
The Arab Schiangia, in a passage quoted by Father Kircher, expresses himself in this wise: