The following passages, taken from Books IX and X of Vitruvius, describe several inventions attributed to Ctesibius of Alexandria, including hydraulic pumps, pneumatic devices, and the water organ. The text illustrates the operating principles based on air compression and hydraulic flow regulation, dwelling in particular on the mechanical structure of the hydraulis: cylinders, valves, air ducts, keys, and sounding pipes. The technical terminology reflects the ancient mechanical tradition and modern translations of the treatise.
BOOK IX – CHAPTER IX
On certain kinds of clocks and their inventors
(…)The methods for making water-clocks were also discovered by the same writers; and the first was Ctesibius of Alexandria, who also made discoveries regarding natural spirits and pneumatic things: and it is worth knowing for students how these things were invented. Ctesibius was born in Alexandria to a barber father: he, distinguishing himself from others by his talent and great industry, gained fame as an enthusiast for ingenious contrivances; having wished to hang in his father’s shop a mirror in such a way that, by lowering or raising it, he could draw it with a hidden cord with a counterweight, he constructed the machine in this way. He fixed a wooden channel under a beam and placed pulleys in it: he stretched a cord through the channel to the end, and there placed tubes, through which he lowered a lead ball with the cord: it happened that the hair running through the narrow part of the tubes pressed the enclosed air, and swiftly pushing out into the open the quantity of compressed air from the tubes, produced with the encounter and contact a clear sound: thus, Ctesibius having observed that from the contact of the air and the expulsion, winds and voices were formed, working on these principles was the first to make hydraulic machines, automata, water games, engines of levers and of peritrachea, and many kinds of amusements, and among these he even composed clocks with water.
BOOK X – CHAPTER XII
On the machine of Ctesibius
We must now demonstrate the machine of Ctesibius, which raises water to a great height. This is made of copper, and at the bottom two similar small cylinders are made at a short distance apart, with two pipes, fork-shaped, equally attached, and corresponding to a basin in the middle: in this basin are made flap valves attached lightly over the upper mouths of the pipes, which, by closing their holes, do not allow what has been driven into the basin by the force of air to escape. Over the basin there is a cover, like an inverted funnel, which must be bound and joined to the basin with a pin held with a wedge, so that the force of the flood of water may not lift it: finally, the pipe called the trumpet is tied on top, and raised as high as one wishes. The cylinders have below the lower mouths of the pipes the flap valves placed over those holes that are in the bottom: from above, the pistons well worked on the lathe, and oiled, tied with rods to the cranks, are moved within the cylinders in such a way that, alternately, continually pressing the air that is found there with the water, with the holes closed by the flap valves, they strike and push with the force of air the water into the basin through the mouths of the pipes, from which the cover, receiving it, pushes it up through the trumpet to a great height. Thus from a lower reservoir, water is raised for fountains. Not that this is the only invention of Ctesibius, but there are many others, of various kinds, which by forcing this confined liquid teach how to produce with air effects similar to natural ones: such is that of the blackbirds, which moving make songs: thus the oengibaloi, which move little statues that drink, and other similar things, which attract with pleasure both sight and hearing: but I have selected among these those things that I have considered most useful and necessary, so that in the previous book I thought of treating of clocks, and in this of the method of raising water: all the others, which are not necessary but for pleasure, he who is curious of them will be able to find them in the books of Ctesibius himself.
BOOK X – CHAPTER XIII
On water organs
I shall not omit therefore to touch very briefly, and as best I can, upon the structure of hydraulic organs. On a wooden base a copper case is placed: over the same base there rise, to the right and left, rails bound like ladders, and between them are enclosed the copper cylinders with movable pistons, perfectly worked on the lathe, with iron rods attached by hinges to the levers and covered with skins; moreover there are in the upper plane holes of about three fingers each, near which, near the hinges, there are bronze dolphins which hold with chains hanging from their mouths cymbals lowered under the holes of the cylinders. Inside the case, where the water is kept, there is then a kind of funnel placed upside down, under which two small blocks of about three fingers serve to level the distance between the lower lips of the funnel and the bottom of the case: above its neck a well-fitted box supports the head of the machine, which in Greek is called canon musicos; over this along its length are made channels — that is, if it is tetrachord, four; if hexachord, six; if octachord, eight — within each channel are then placed as many keys with iron handles, so that by turning these the communication between the case and the channels may be opened. The canon then has the holes registered across the channels, corresponding to the openings in the upper board, which in Greek is called pinax: between the board and the canon are interposed small rails, perforated in the same way, but oiled with oil, so that they may be easily pushed and drawn back and forth, and serve to close those holes, and are called pleuritides, so that the going and returning of these closes some and opens others. These small rails have iron springs attached and joined to the keys, so that touching these, the rails also move: above the board are holes through which the wind passes beyond into the pipes; and in the rails are set rings to which correspond the mouths of all the pipes: from the cylinders depart conduits attached to wooden shoulders, and reach the openings in the box: there are attached flap valves turned on a lathe, which after the wind has entered the box, by closing the holes, do not allow it to escape. Thus when the levers are raised, the handles lower the stanchions attached at the hinges, and lowering toward the mouth the cymbals fill the vacuum of the cylinders with air; but when the handles raise the pistons inside the cylinders, with the frequent blows, because the upper holes are closed by the cymbals, the air that is found enclosed there, forced by the pressures, is obliged to pass into the pipes, and from there to the wooden ones, through whose necks it passes into the box: so with the frequent motion of the levers, the air often pressed penetrates through the openings of the keys, and fills the channels with wind. So when the keys touched by the hands come to push or draw them consecutively, alternately closing and opening holes, they make the tones sound in many and different modulations according to musical rules. I have done everything possible to explain clearly an obscure thing, to demonstrate it in writing; and nonetheless this mechanism is difficult, nor to be understood by all, but only by those who are trained in these things: and if anyone has understood it little from the writings, seeing it in operation, he will certainly find everything curiously and subtly arranged.
