CHAPTER III.

THE ORIGIN OF THE STEAM ENGINE. All works that treat of the history of the steam engine speak of the eolipile of Heron as the most ancient manifestation known of that power which to-day fills the world. But very few persons know that we also find in the “Pneumatics” of the Greek engineer the germs of the tubular boiler and of the Papin cock which has been replaced in modern engines by the long D-valve. Here, in the first place, is a literal translation of the two passages that have reference to the apparatus, so often cited, of Heron: “_Balls may be held in the air by the following method_: “Fire is lighted under a boiler that contains water and is closed at its upper part. From the cover starts a tube which rises vertically, and at the extremity of which a hollow hemisphere is in communication with it. On placing a light ball in this hemisphere it will happen that the steam, on rising through the tube, will raise the ball in such a way that it will remain suspended.[9] [9] Fig. 1 is borrowed from a MS. of the “Pneumatics” dating back to the Renaissance. The boiler should have been represented over a fireplace. “_To cause the revolution of a sphere on a pivot by means of a boiler placed over a fire._ “Let Α Β (Fig. 2[10]) be a boiler containing water and placed over a fire. It is closed by means of a cover, Γ Λ, which is traversed by a bent tube, Ε Ζ Η, whose extremity, Η, enters the hollow sphere, Θ Κ, in the direction of the latter’s diameter. At the other extremity is placed the pivot, Α Μ Ν, which is fixed upon the cover, Γ Λ. There are added to the sphere, at the two extremities of one of its diameters, two tubes bent at right angles and perpendicular to the line, Η Ν. When the boiler is heated, the steam will pass through the tube, Ε Ζ Η, into the small sphere, and, issuing through the bent tubes into the atmosphere, will cause it to revolve _in situ_.” [10] This figure, likewise borrowed from a MS. of the Renaissance, is sufficiently clear to allow letters to be dispensed with. The following apparatus, likewise described by Heron, but not so well known as those that preceded, shows that the ancients employed steam (mixed with hot air, it is true) for causing liquids to rise. According to Father Kircher, who reports it on the faith of an author named Bitho, there was at Saïs, Egypt, a temple dedicated to Minerva in which there was an altar upon which, when a fire was lighted, Dionysius and Artemis (Bacchus and Diana) poured, one of them wine, and the other milk. The miracle was performed as follows: “_On lighting a fire upon an altar, figures make libations and serpents hiss_ (Fig. 3).[11] [11] The letters on the engraving are again dispensed with. [Illustration: FIG. 1.--HERON’S EOLIPILE.] [Illustration: FIG. 2.--HERON’S WHIRLING EOLOPILE.] “Let Α Β be a hollow pedestal upon which there is an altar, Γ, in whose interior there is a large tube, Δ Ε, that descends from the fireplace into the pedestal and divides into three small tubes. One of the latter, Ε Ζ, runs to the serpent’s mouth; another, Ε Ζ Η, to a vessel, Κ Δ, suitable for containing wine, and the bottom of which should be above the figure, Μ, as this tube has to be connected with the cover of the vessel, Κ Λ, by a grating; and the third tube, Ε Ν Ξ, rises likewise to a vessel, Ο, suitable for receiving wine, and is connected in the same way with its cover. The two latter tubes are soldered to the bottoms of the vessels, and in each of these vessels there is a siphon, Ρ Σ and Τ Υ. One extremity of each of these tubes dips into the wine, while the other, which ends in the hand of the figure that is to make the libation, traverses the side of the wine vessel. When you wish to light the fire, you will first put a little water into the tubes so that they shall not be burst by the dryness of the fire, and you will stop up all the apertures so that the air shall not escape. Then the blast from the fire, mixed with the water, will rise through the tubes up to the gratings, and, passing through these, will press upon the wine and cause it to flow through the siphons, Ρ Σ and Τ Υ. The wine issuing thus from the hands of the figures, the latter will appear to make libations as long as the altar is burning. As for the other tube, which leads the blast to the serpent’s mouth, it causes the latter to hiss.” [Illustration: FIG. 3.--HERON’S MARVELOUS ALTAR.] As regards the cock and the tubular boiler, we find these in a hot-water stove which Heron calls by the Græco-Latin name _miliarion_, because of its resemblance to a milestone. Fig. 4 shows us, in the center, the fireplace in the shape of a vertical cylinder, which should have beneath it an air vent that is not shown in the cut. All around this there is a boiler, likewise cylindrical, filled with water. A certain number of tubes, such as Ο Κ and Μ Ν, put its different parts in communication by passing through the fireplace, and thus increase the heating surface. [Illustration: 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.