THE WATER ORGAN
1. With regard to water organs, however, I shall not fail with all
possible brevity and precision to touch upon their principles, and to
give a sufficient description of them. A wooden base is constructed, and
on it is set an altar-shaped box made of bronze. Uprights, fastened
together like ladders, are set up on the base, to the right and to the
left (of the altar). They hold the bronze pump-cylinders, the moveable
bottoms of which, carefully turned on a lathe, have iron elbows fastened
to their centres and jointed to levers, and are wrapped in fleeces of
wool. In the tops of the cylinders are openings, each about three digits
in diameter. Close to these openings are bronze dolphins, mounted on
joints and holding chains in their mouths, from which hang cymbal-shaped
valves, let down under the openings in the cylinders.
2. Inside the altar, which holds the water, is a regulator shaped like
an inverted funnel, under which there are cubes, each about three digits
high, keeping a free space below between the lips of the regulator and
the bottom of the altar. Tightly fixed on the neck of the regulator is
the windchest, which supports the principal part of the contrivance,
called in Greek the [Greek: kanôn mousikos]. Running longitudinally,
there are four channels in it if it is a tetrachord; six, if it is a
hexachord; eight, if it is an octachord.
3. Each of the channels has a cock in it, furnished with an iron handle.
These handles, when turned, open ventholes from the windchest into the
channels. From the channels to the canon there are vertical openings
corresponding to ventholes in a board above, which board is termed
[Greek: pinax] in Greek. Between this board and the canon are inserted
sliders, pierced with holes to correspond, and rubbed with oil so that
they can be easily moved and slid back into place again. They close the
above-mentioned openings, and are called the plinths. Their going and
coming now closes and now opens the holes.
4. These sliders have iron jacks fixed to them, and connected with the
keys, and the keys, when touched, make the sliders move regularly. To
the upper surface of the openings in the board, where the wind finds
egress from the channels, rings are soldered, and into them the reeds of
all the organ pipes are inserted. From the cylinders there are
connecting pipes attached to the neck of the regulator, and directed
towards the ventholes in the windchest. In the pipes are valves, turned
on a lathe, and set (where the pipes are connected with the cylinders).
When the windchest has received the air, these valves will stop up the
openings, and prevent the wind from coming back again.
5. So, when the levers are raised, the elbows draw down the bottoms of
the cylinders as far as they can go; and the dolphins, which are mounted
on joints, let the cymbals fall into the cylinders, thus filling the
interiors with air. Then the elbows, raising the bottoms within the
cylinders by repeated and violent blows, and stopping the openings above
by means of the cymbals, compress the air which is enclosed in the
cylinders, and force it into the pipes, through which it runs into the
regulator, and through its neck into the windchest. With a stronger
motion of the levers, the air is still more compressed, streams through
the apertures of the cocks, and fills the channels with wind.
6. So, when the keys, touched by the hand, drive the sliders forward and
draw them back regularly, alternately stopping and opening the holes,
they produce resonant sounds in a great variety of melodies conforming
to the laws of music.
With my best efforts I have striven to set forth an obscure subject
clearly in writing, but the theory of it is not easy, nor readily
understood by all, save only those who have had some practice in things
of this kind. If anybody has failed to understand it, he will certainly
find, when he comes to know the thing itself, that it is carefully and
exquisitely contrived in all respects.