Magic, Stage Illusions and Scientific Diversions, Including Trick Photography

by Albert A. Hopkins

If, now, the transverse rod, γ Φ, be lowered at Φ the piston, Ρ Σ, will rise and compress the air in the box, Ν Σ Ο Π, and such air will close the aperture of the small box through the intermedium of the platysmatim described above. It will then pass into Ε Ζ Η by means of the tube, Κ Η, then into the transverse tube Α Α′, through the tube Ζ Ζ′, and finally from the transverse tube into the pipes, if the orifices correspond to those of the covers, and this will occur when all the covers (or only a few of them) have been pushed toward the interior.

FIGS. 2 AND 3.—DETAILS OF THE HYDRAULIC ORGAN
SHOWN IN FIG. 1.

In order that their orifices may be open when it is desired to make certain pipes resound, and that they may be closed when it is desired to cause the sound to cease, the following arrangement is employed: Let us consider isolately one of the mouths placed at the extremity ([Fig. 3]). Let γ δ be this mouth, δ its orifice, Α Α′ the transverse tube, and σ the cover that is adapted and the aperture of which does not coincide with the apertures of the pipes at this moment. Let us now suppose a jointed arrangement composed of three rods, δ, μ, and ν, the rod, ε δ, being attached to the cover, σ, and the system as a whole moving around a pin, μ. It will be seen that if we lower with the hand the extremity, ν, of the system toward the orifice of the glossocomiums, we shall cause the cover to move toward the interior, and that, when it arrives there, its orifice will coincide with the orifices of the pipes. In order that, upon removing the hand, the cover may be carried back toward the exterior and close all communication, an arrangement such as the following may be employed. Beneath a number of glossocomiums, there is established a bar equal in length to and parallel with the tube, Α Α′, and to which are fixed strong curved plates of horn, such as γ, placed opposite γ δ. A cord is fixed to the end of this plate and winds around the extremity, δ, in such a way that when the cover is moved toward the exterior the cord shall be taut. If the extremity, ν, then be lowered, and the register be thus pushed into the interior, the cord will draw upon the horn plate, and by its force, right it. But as soon as the pressure ceases, the plate will resume its former position and draw the cover back in such a way as to prevent its orifice from establishing a communication. This arrangement being adopted for all the glossocomiums, it will be seen that in order to cause any one of the pipes to resound, it will suffice to depress the corresponding key with the finger. When, on the contrary, it is desired to cause the sound to cease, we shall merely have to lift the finger, and the effect will be produced by the motion of the cover.

Water is poured into the small altar in order that the compressed air that is driven from the box, Ν Π, may, owing to the pressure of the liquid, be retained in the damper, Ε Ζ Η, and thus supply the pipes. When the piston, Ρ Σ, is raised, it therefore expels the air from the box into the damper, as has been explained. Then, when it is lowered, it opens the platysmatim of the small box. By this means, the box, Ν Π, becomes filled with air from the exterior, which the piston, raised anew, drives again into the damper.

It would be better to render the rod, Τ γ, immovable at Τ, around a pin, and fix at the bottom, Ρ, of the piston a ring through which this pin would pass, so that the piston would have no lateral motion, but would rise and descend with exact perpendicularity.

Porta, at the beginning of the seventeenth century, constructed at Naples a hydraulic organ according to the arrangement just described. A few years afterward, in 1645, Father Kircher constructed another at Rome for Pope Innocent X. These organs had the defect of not preserving the note, but of giving a series of harmonies. On the other hand, they produced an exceedingly agreeable tremolo. It was probably these unusual variations in sound that charmed the ears of the Greeks and Romans.

Heron afterwards describes a bellows organ, motion to which is communicated not by manual power, but by a windmill. [Fig. 4] shows the arrangement with sufficient clearness to permit us to dispense with a description. It is interesting to reproduce, in that it carries the origin of windmills (which it is claimed were unknown to antiquity, because Vitruvius and Varro do not speak of them) back at least to the second century before our era.