The Perpetual Flute, control, and knowledge sharing


The Book of Knowledge of Ingenious Mechanical Devices contains four perpetual flutes. On the first one I wrote here, the current post is about the remaining three flutes. Each flute has a single page in the book, in comparison the Elephant Clock which takes twenty-two pages and the Castle Clock who is the champion with forty-one pages! The flutes are much simpler and are based on a single principle of compressing air in water containers to creates the sound. The name “flute” is somewhat misleading, and a whistle might be more appropriate as no fingering or an ability to change the pitch(sound frequency).  Some alteration is achieved through the use of two flutes (two whistles), each with a different sound. The uniqueness of each perpetual flute is the way al-Jazari control switching between the two flutes, and this is the main focus of this post.

Three perpetual flutes, left of the tilting buckets, center balance and on the right floats. Topkapi manuscript, 1206.

Fine technology and control theory

A considerable part of the work of al-Jazari falls in the category of fine technology. The term “fine technology” historically, embraces a whole range of machines for various purposes: water clocks, automata, astronomical instruments (not al-Jazari), and more. Some were intended to measure time or for other scientific needs, some for fun and amusement. What was common to all these devices, is a considerable engineering skill and subtle use of mechanisms and control systems. Control theory deals with dynamic systems (change over time) and how their behavior depends on feedback. This is a very wide field with applications from biology to robotics. The control theory contains heavy mathematics that scares students at the Technion and dates from the 19th century ~ seven hundred years after al-Jazari.

Despite mathematics, the control questions remain identical from the 12th century to the present day. It’s easy to think about air conditioning. When We define the desired temperature, the air conditioner will continue to cool as long as the room is above the set temperature and stop its operation when the room is at the right temperature. Although it sounds simple, the control of the air conditioner requires differential equations, and it is relatively complex. Al-Jazari had no electronics or detectors, but the same exact task. There is no difference between activating and stopping the air conditioner and activating and stopping the “perpetual flute.” The four perpetual flutes are a comprehensive class, with demonstrations, in the possible control methods for a 12th-century engineer.

How does it work?

The technical explanation, as always, will be colored in blue, so anyone who is not interested in tilting pipes and floats can skip those bits. The three flutes are identical in all their components except the control system. All three of the perpetual flutes have a permanent water supply. In all cases, there are two water tanks to which two flutes, or more precisely whistles, are attached. All the water tank are being emptied using a siphon. There’s an explanation of a siphon here. It almost seems like al-Jazari has prepared a lesson on control systems, so he made sure that all other elements are identical. In all three flutes, the water flows into a bowl welded to a pipe or a tilting apparatus. The pipe is slightly heavier on the right side, and the water flows towards tank B and fills it. The air that was in the tank is compressed out through flute B, which makes a whistling sound. When the tank is full, the control system will transfer the flow of water to tank A, and the siphon will empty tank B. This process repeats itself as long as the water flows.

  1. Perpetual Flute with tipping buckets. We have met the tipping buckets several times, for example, in “The fountain that changes its shape” or “The automaton of a standing slave holding a Fish and A Goblet”. The tipping bucket (in red) is balanced, as you see in the drawing. When it is full, according to the sketch it will happen at any minute, the weight of the water at the front-end is heavy enough to make the tipping bucket swing, and the rod (marked) will push the bowl upward so it would tilt to the left and water would fill the other tank
  2. Perpetual flute with balance controlThe tilting pipe has two openings. The main opening fills Tank, A as can be seen in the drawing below. The secondary opening is smaller, and the water flows diagonally to the balance pan. This is a classical scale, and the weight of water in a bowl will pull the tilting pipe in its direction. When Tank B would be full, the weight of the water would be enough to turn the tilting pipe to start filling tank A.  to fill the container in. Pay attention to the dish attached to the bowl and make it empty its waters.

  1. Perpetual flute with buoys

Each of the tanks has a buoy chamber. When the water rises in the buoy rises with them, and the rod attached to it will cause the tilting pipe to reverse the direction of the flow of water, and the water flows toward the other tank.

Generosity of Knowledge

At the end of the book, al-Jazari writes:

“In this five chapters [a little strange, there are six categories in the book, I have not seen anyone who discussed this discrepancy?] I have described roots which have many branches and great usefulness. When the descriptions are mastered, from them many more [things] may be created. I have omitted to mention many devices which I invented, for fear of obscurity or ambiguity. In what I have mentioned there is information for him who seeks information and profit for him who has zeal.”

I think that al-Jazari wrote these lines personally to me. Al-Jazari’s address bore fruits. The book in general, and these chapters specifically are written for a future reader who would like to learn and build the machines.

  1. Al-Jazari was ahead of his time in his willingness to share knowledge. The Cathedral of Vasily the Blessed is one of the most famous monuments in Moscow. It was built in the sixteen century on orders from Ivan the Terrible. The architect was probably Postnik Yakovlev. According to the legend, Ivan the Terrible blinded Yakovlev so that he could never build anything so beautiful again. It is unclear whether the legend is true, or just a myth, but the desire to preserve knowledge, or ability, is familiar to all of us from the workplace or the university or at least from the literature and movies. Al-Jazari is the opposite. He really went out into the world with a passion to share his knowledge. In this way, he is a magician of engineering, who broke the oath of magicians and brought the hidden knowledge to all mankind.
  2. The world as a whole assumes that “knowledge is money.” It can be seen in the payment we charge for consulting, in the patents industry and more. There is a secondary alternative stream in which people and companies are willing to share free knowledge for their enjoyment and joy of sharing. The open-source movement, the makers, centers in the community or Wikipedia are just a few examples. How to maintain this, what is the model of existence is a complex question that did not bother al-Jazari, an engineer in Saleh Nasser al-Din’s Artuqid Court.
  3. I do not know about the attempts of building machines from the book in seven hundred years since his writing, but quite many attempts to realize al-Jazari’s vision in the 20th century and the 21st centuries. You can read about restorations here. In all cases, the mechanisms, the machines worked wonderfully. I am building the elephant clock from Legos [Hebrew] these days and hope that I will continue this tradition.


The fountain that changes its shape and the controversy with the Banu Musa

“Allah has promised the believing men and believing women gardens beneath which rivers flow, wherein they abide eternally.”

Qur’an 9:72

The fountain with two tipping buckets, Topkapi manuscript, 1206


The Muslim paradise is called Jannah ( جنّة), literally “garden.”  Every time heaven is mentioned in the holy book of Qur’an, there is a description of flowing water and fruit-bearing trees. This is not surprising because Islam came from the desert, hot and arid lands. I would like to ignore the other attributes of al-Jannah such as houris; splendid companions of equal age, lovely eyed and virgins, who will accompany the faithful. My only focus is on the scenery. Like Garden of Eden in the Bible, there are four rivers in Jannah, the Euphrates flows according to both books, but the other rivers are different, and they have a common source named Salsabil (سلسبيل).

Gardens were significant to Islam from its inception. The garden landscaping has a spiritual meaning which exceeds the human need for shade and water. They are perceived as a place of rest and contemplation, an earthly equivalent to life in heaven. This metaphor reached its peak in Chahar-bagh, (چهارباغ), in which the garden was divided into four parts by water channels; the four water channels being the four rivers of paradise with a fountain in the center of a pool, representing Salsabil. I think that al-Jazari’s deep interest in fountains is related to the importance of gardens in Islam. 

A miniature of paradise from the 16th century

How does the fountain work?

The fountain of al-Jazari is installed in a pool. For an hour the fountain shoots up from the main orifice and then for one hour it emits six curving jets from six nozzles, and the process repeats itself. Today it is a trivial task for any engineer, but in the 12th century, with no electronics or electric valves, it was almost a miracle. The technical explanation, as always, will be colored in blue, so anyone who is not interested in early control systems can skip those bits.

At some distance from the pool, al-Jazari built a high house into which the water flowed. This section does not appear in the drawing. The water from the high house flew into the copper bowl welded to a pipe with four openings. This is the same drawing as above, but with my captions.

At the bottom of the titling pipe, al-Jazari welded a ring which is seated on an axle so that the pipe is like a kids seesaw. The right side is slightly heavier, and therefore it tilts to the right, and the water comes from both openings on the right. The main opening fills the tank and the narrow pipe which shoots the water up in the air. The secondary opening is much smaller, and it slowly fills the tipping bucket (in red). In the drawing, the tipping bucket is almost full. After one hour, the weight of the water at the front-end is heavy enough to make the tipping bucket swing, and the black rod will push the tilting pipe upward so the seesaw would tilt to the left and water fill the other tank, the wide pipe around the narrow pipe and comes out in six jets. The process repeats itself.

Banū Mūsā

Al-Jazari opens the fourth Category “On fountains which change their shapes at known intervals and on perpetual flutes” with a brief statement:

“I did not follow the system of the Banū Mūsā, may God have mercy upon them, who in earlier times distinguished themselves in the matters covered by these subjects.”

The Banū Mūsā brothers are the predecessors of al-Jazari and are important to understanding his work. Banū Mūsā, the sons of Moses, is the name shared by three scholars, brothers from the ninth-century, sons of Mūsā ibn Shākir, a Persian astronomer. At a young age, they join the famous House of Wisdom, a library and a translation center in Baghdad. It is known that the brothers wrote together more than 20 books, but most have been lost over the years. Their most famous book and only two copies survived is The Book of Ingenious Devices (كتاب الحيل Kitab al-Hiyal( which al-Jazari is referring. The book was commissioned by the Abbasid Caliph of Baghdad, Abu Jafar al-Ma’mun ibn Harun (786–833), who instructed the Banu Musa to acquire all of the Hellenistic texts that had been preserved during the decline and fall of Roman civilization. This rescue operation has cultural importance, which exceeds by far the current post. Some of the devices described in their Book were inspired by the works of Hero of Alexandria and Philo of Byzantium, as well as ancient Persian, Chinese, and Indian engineering. However, many of the other devices described in the book were original inventions by the Banu Musa brothers. Donald Hill, who translated this book, as well as al-Jazari’s book, wrote:

“The Banu Musa went “well beyond anything achieved by Hero or Philo.” Their preoccupation with automatic controls distinguishes them from their Greek predecessors, including the “use of self-operating valves, timing devices, delay systems, and other concepts of great ingenuity.”

The book describes the construction of 100 devices, including seven automatic fountains.

What is the Controversy?

Al-Jazari did not specify which fountain he is referring to, but he did write:

“They made the alternation [fountain water shapes] with vanes turned by wind or by water so that the fountains were changed at every rotation, but this is too short an interval for the change to appear [to the full effect]. Then in two designs they used a pipe like an almost horizontal balance arm. The water flowed through it …”

It is clear that this is the fountain he is referring to:

A fountain that alternates water shapes by use of a balance from
The Self Changing Fountain of Banu Musa bin Shakir by Prof. Salim T S Al-Hassani

He concludes: ” I do not know whence this confusion [came], from the original or from the copy.”

For those who really want to dive into the details, you can see here the fountains the Banu Musa. There could be no argument that al-Jazari borrowed key concepts from the Banu Musa, including the placement of a narrow pipe within a wide pipe, the concept of two water tanks and variable feeding with time. His main disagreement is over the control method. In his opinion, the intervals were too short, and the result could be erratic. He’s probably right. Al-Jazari explains what’s wrong with the design, but the details are of little importance. The technology changed so dramatically that the historical techniques to control the timing are only an odd puzzle of how we can control timing before we had, electronics and electric valves. However, curiosity and skepticism are the best guides for every engineer today, just like eight centuries ago.

Curiosity and Doubts

Anybody who taught high school or Bachelor’s degree in science or technology knows that academic success is no guarantee for curiosity, healthy doubts, or critical thinking in general. Excellent students can answer the questions in the exam but find it difficult to ask questions about a scientific paper or engineering presentation, to test if the assumptions are robust and can stand rigorous evaluation, if there is an alternative explanation or if there can be another model. Many excellent and feel uncomfortable with the new requirements so different from their previous experience in school. In parenthesis, as an educator, I have to say that this is not a decree of fate and schools can do a lot, but that’s another discussion. My encounter with al–Jazari is limited to his book, but beyond is high of engineering capabilities, it is clear he was curious and had a healthy measure of inquisitiveness and skepticism. He checked the water regulator attributed to Archimedes and found it insufficient, he read the Banu Musa and had his doubts regarding the control method. Beyond the benefit of the healthy engineering skepticism, as he adds question marks, I like him more.


Al-Jazari and Versailles Fountains


There are six different fountains in The Book of Knowledge of Ingenious Mechanical Devices. This seems somewhat excessive. I suggested in a previous post that this can be explained by the importance of gardens in Islam. However there is another option; Throughout history, rulers asked their engineers and artists to create tangible displays of their power and wealth to impressed their allies and intimidate enemies. The Versailles fountains is an extraordinary example of ignoring cost and engineering complexity to demonstrate power and control. I will elaborate below.

Versailles Fountains, unknown photographer, Wikipedia Commons

The six Fountains of al-Jazari- How do they work?

Combined Drawing, Six Fountains, Topkapi manuscript, 1206

The technical explanation, as always, will be colored in blue, so anyone who is not interested in tilting pipes and floats can skip those bits. I wrote about the first fountain here (in Hebrew). The second fountain has an identical mechanism. The only addition is an extra delivery pipe, so when one fountain is producing a single jet the other fountain is throwing six arcs, and after an hour they switch, and the fountain that was producing a single jet is throwing six arcs and vice versa. The other fountains have a different mechanism, producing different water jets and have different timings. However, there is a lot in common:

  1. All fountains operate by the force of gravity. A house was built at some distance from the fountain and water were raised to a sufficient height to provide the jets. One of al-Jazari pumps, from category V, was probably used for this purpose. Raising the water and their transport are not included in the drawings.
  2. All fountains include a change in the water flow direction. In five out of six this is accomplished using a pipe that could tilt. This is a drawing from the book, and I added labels for clarity.

    Tilting pipe, First Fountain, Topkapi manuscript, 1206

    The water flows into the bowl welded to the transverse pipe that can be tilted (tilting pipe). The pipe is slightly more heavy on the side of tank A, and the water respectively flows into water tank A and water flows from the two right openings. Most of the water ran from the main opening to the right tank. The smaller opening has an onyx mouthpiece and will fill the tipping bucket slowly. At the right time, the tipping bucket would tip and push the tilting pipe upward, shifting the flow to tank B.

  3. All the fountains of al-Jazari had a time-based control system. Today It’s trivial to control the fountain with a microcontroller and computational power, or timing requirements are simple engineering task in comparison to any mobile phone. In the twelve century, it was a significant engineering challenge, and al-Jazari offers a variety of solutions. I have explained already the tipping buckets in the first two fountains. Fountain three and four utilize floats for the control mechanism:When the pipe is tilted to the right, the water will flow into tank A. The plug is closed so the flow to the fountain head is blocked and the tank will fill. The float is limited to the corner but it free to move up and down and will rise with the rising water. After fifteen minutes the float will lift the pipe extension, and the pipe will tilt to the left. The swing of the pipe will pull plug A’ opening the water path to the fountain head. At the same time, water will begin to flow to tank B, and the plug will seal the water flow from tank B.
  4. All six fountains of al-Jazari end with two concentric pipes and different end units. In the post about the first fountain I showed how al-Jazari generated a single jet upward, followed by six jets in a shape of arcs but there are many more options:

    Drawing of an alternative end unit. The fourth fountain, Topkapi manuscript, 1206 with my labels

The water flows in the inner pipe that is connected to tank A. The water shoots out from the inner pipe with force into the shield and descends from its perimeter like a “tent”. When the water switch to tank B, it will flow in the outer pipe generating six (in the drawing you see only two) arcs.

The Power of the ruler and the amazing story of the fountains of Versailles

I hope that my summary of the fountains shows how much thought and effort went into fountains’ engineering by al-Jazari like the Banu Musa before him. In a post (in Hebrew) about the controversy with the Banu Musa, I assumed that al-Jazari deep interest in fountains is related to the importance of gardens in Islam. However, there is another option, after all, grandiose fountains are not limited to medieval Muslim engineers.

Louis XIV built Versailles (Château de Versailles), one of the greatest achievements in French 17th century art and the emergence of the Rococo style, not only as a place of residence for the Royal family but as a part of an elaborate plan to centralize the French government and form absolute monarchy. To accomplish this, he placed the palace outside Paris, forcing the nobles to spend time at Versailles, becoming his captive guests. He has spent ridiculous sums of money in design, with gold trim and built the gardens of Versailles with many fountains. Some claim that the central political structure in France today is the result of his actions. Either way, Versailles became a source of envy and admiration from other Royal houses, and Louis XIV was the most powerful King in Europe. The story of Versailles fountains is less known.

The water challenge appeared began as more and more fountains were added. Originally water was pumped into the gardens from ponds near the château. However, there was never enough water to keep all the fountains running at the same time. Jean-Baptiste Colbert, the French Minister of Finances and notable politician, put aside the kingdom business and came up with a system by which the people who maintained the fountains would signal each other with whistles upon the approach of the king so the fountains on the route of the king will be functioning… The most ambitious project was to bring water from the river Seine. The pump was called  “Marly Machine” (machine de Marly)

Nicolas de Fer, 1720, Marly Machine

Pump power was provided by 14 water wheels, each 12 meters in diameter, driving a total of 257 pumps. The most remarkable aspect of this array was that the wheels not only drove directly connected piston pumps but also transmitted power 650 meters up a hill from there, the water was distributed by an aqueduct and pipes.

.Overstating the size of this project is impossible. It could happen only in a courtyard entirely isolated from the realities of life of the people.  A staggering workforce of 1800 employees for seven years was needed to construct the machine, more than 100,000 tons of wood, 17,000 tons of iron and 800 tons of lead.

This text, like other texts on fountains, tends to use numbers to praise and glorify the fountain. The little Prince thought it was a problem of Grown-ups :

“Grown-ups like numbers. When you tell them about a new friend, they never ask questions about what really matters. They never ask: ‘What does his voice sound like?’ ‘What games does he like best?’ ‘Does he collect butterflies?’ They ask: ‘How old is he?’ ‘How many brothers does he have?’ ‘How much does he weigh?’ ‘How much money does he have?’ Only then do they think they know him. If you tell grown-ups, ‘I saw a beautiful red brick house, with geraniums at the windows and doves at the roof…,’ they won’t be able to imagine such a house. You have to tell them, ‘I saw a house worth a thousand francs.’ Then they exclaim, ‘What a pretty house! “

I think fountains draw out of us more “numbers” than most things. If you are like the Little Prince and numbers are not your cup of tea, you might still like to know that the amount of water delivered to Versailles was larger than the water consumption of Paris as a whole!  The machine suffered (of course) from frequent breakdowns, required a large permanent team of technicians and engineers to maintain her, but still survived the French Revolution and worked 133 (!)  years until 1817, the year of the invention of the bicycle. I haven’t found any evidence that Louis XIV, the Sun King ever saw all this as excessive or a waste. On the contrary, he showed it proudly to his guests, including the Tsar Peter the great, who was so excited, that he built the Peterhof Palace and gardens, near the Gulf of Finland, with Versailles as a model with the largest fountain complex in the world and called one of the building after Marly

This is not the end of extravagant fountains. The following is a quote from the website of the Dubai fountains and is also excelling in using numbers. Before anything else, this is a tourist site, but behind the words, you can still hear the fountain as  a symbol of power and control:

“The Dubai Fountain is the world’s tallest performing fountain.

At over 900 ft in length – equivalent to over two football pitches – The Dubai Fountain is situated on the 30-acre Burj Lake and performs to a selection of international melodies.

The fountain has a unique design comprising five circles of varying sizes and two arcs and features powerful water nozzles that shoot water up to impressive heights equivalent to that of a 50-story building…..The fountain performs to a range of different songs from classical to contemporary Arabic and world music. When operational, the fountain has over 22,000 gallons of water in the air at any given moment.


The Perpetual Flute and al-Jazari’s Library


The Book of Knowledge of Ingenious Mechanical Devices contains quite a few musical automatons. Some of them such as the musical boat we have already met in previous posts, others such as the world’s first drum machine, we will meet in a future post. The fourth category deals mainly with fountains, but there are also four perpetual flutes, which use the flow of water to compress the air through a flute thus replacing the flautist. Al-Jazari specified three sources for his works, Apollonius the Indian carpenter, a drawing from an unknown source, and a work by the eminent inventor, Hibat Alla Husayn al Astrurlabi. It made me wonder about his library.

Figure 1 The perpetual flute, scattered pages (copy from 1315) (Metropolitan Museum, New York)

How does the flute work?

The technical explanation, as always, will be colored in blue, so anyone who is not interested in the tilting pipes and floats can skip those bits. This is a drawing from the book, and I added labels for clarity.

Figure 2 The perpetual flute (1206). Topkapi manuscript (with added labels)

There is a constant water supply to the perpetual flute. The water flows into the bowl welded to a transverse pipe that can be tilted (tilting pipe). The pipe is slightly heavier on the side of tank A, and the water thus flows into that tank. The air is pushed out, and the only way is through flute A, so a sound is heard. Although it is called a ‘flute’, it is more like a whistle as the pitch cannot be changed, and there is no parallel for different fingering producing different notes. At the same time, plug B is pulled out, thus emptying tank B. The water will continue to flow into tank A and float A will rise with it. At some point, float  A will push the tilting pipe upward, and shift the water flow to tank B. The water will rise in tank B  and the only route for the air will be through flute B. This process repeats itself as long as the waters supply continues.


The literature survey and al-Jazari’s Library

Any research or technology development project starts with a literature survey. Students, especially in the early stages of their training in science or technology, feel that the survey is tedious, and perhaps a formality and not helpful. But in time they will learn that the survey is needed to map the current information available and is essential from the very early stages of understanding the theory and developing the methodology until the final stage of writing the paper, the patent request or the research report. Modern scientific disciplines emerged centuries after al-Jazari. I do not know if literature surveys were the norm in early scientific papers. Was al-Jazari a precursor in using them or is he following a known path? In previous posts, we saw references, and a critique of the work of Archimedes and the Banu Musa. But in this chapter three resources are mentioned:

  • “I came across a well-known paper by Apollonius, the Indian carpenter: he made a wheel which turns slowly and opens water outlets…”
  • “I also examined another old instrument, about which I found no written report, but a drawing. In this, the flute is like a nay having eight holes”.
  • “I [also] examined a paper written in Baghdad in year 517 A.H. by the eminent inventor Hibat Allah al-Husayn al-Asturlibl, in which he makes a real innovation….”

Figure 3 Treatise on the Design and Construction of a Hydraulic Flute Playing Machine. Attributed to ‘Apollonius the Carpenter and Geometer’ (sixteenth century) (British Library: Oriental Manuscripts)

In the next post about the perpetual flute with two tipping buckets, I hope to elaborate on these early works and what survived the hundreds of years that passed. However, the fact that al-Jazari had three different sources for the perpetual flute made me think that he had quite an impressive library. Was this the Diyarbakir Palace Library? In the library, were there shelves dedicated to engineering and technology? Who else was reading these books? Maybe these books were in his workshop? Manuscripts were done by hand and required a lot of careful writing and drawing. The price of a manuscript must have been very high, so how would it have been possible? I wish we had answers to all these questions, but we do not. However, some more general information is available.


Manuscripts and libraries in the golden age of Islam

Paper was invented in ancient China. Legend says that two Chinese prisoners captured by the Abbasid Empire after the victory in the Battle of Talas (Kyrgyzstan) in 751, revealed the secrets of paper making. I do not know if this true or not, but there is enough historical evidence for a dramatic paper revolution in the Muslim world in the ninth and the tenth century. In Baghdad, the Chinese art of paper making was improved and mechanized. Linen and rags replaced the traditional mulberry tree bark as raw material. The use of water-powered or animal-powered mills for preparing the pulp helped in transforming paper-making into an industry. The Muslims also introduced the use of trip hammers. The producers in Baghdad and Syria became the main suppliers of paper to Europe. Paper became cheaper and of better quality. The Islamic culture in the Middle Ages, which originally had higher literacy rates, certainly in comparison to Europe, was becoming a leader in sophisticated book production processes, flourishing book markets and rich libraries. All this resulted in a dramatic increase in the availability of books and their accessibility to various segments of the population.

The adoption and industrialization of paper-making is the opposite of the Ottoman Empire’s refusal to embrace Gutenberg’s printing press revolution. It requires another post, but until the eighteenth century, the Turks allowed only non-Muslims, especially Jews, to print. Two revolutions: paper was adopted and the printing press was rejected, both extreme examples of how technology affects culture and society and how seemingly technological decisions can change society.

We know quite a lot about libraries in the Muslim world. The first of which is the House of Wisdom ((بيت الحكمة‎;) founded by Harun al-Rashid, the fifth Abbasid Caliph in Baghdad and the House of Knowledge ((دار العلم) established by Al-Hakim bi-Amr Allah, sixth Fatimid Caliph in Cairo. The two libraries were centers of Islamic learning of the Qur’an and Hadith, philosophy and astronomy. The Fatimid historian Al-Musabbihi wrote:

into this house, they brought all the books that [the Caliph] ordered to be brought there, that is, all the manuscripts in all the domains of science and culture, to an extent to which they had never been brought together for a prince. He allowed access to all this to people from all walks of life, whether they wanted to read books or dip into them… He granted substantial salaries to all those who were appointed by him there to do service, jurists and others… He also donated what people need: ink, writing reeds, paper, and inkstands”.

Figure 4 Scholars in the Library in Baghdad, illustration by Al-Wasiti (1237)

There are fantastic stories about the size and richness of these libraries. For example, it is said that during the Mongol siege of Baghdad in 1258 AD, the House of Wisdom was destroyed. The books were thrown into the Tigris River in such quantities that the river was black with the ink. Nasir al-Din al-Tusi rescued about 400,000 manuscripts which he took to Maragheh before the siege. The closest I came to Al-Jazari’s library was a short remark in the diaries of Carl Süssheim. He was an Islamic historian and orientalist. In his diaries, he tells a story about Emiri Efendi who sold him precious manuscripts. According to Emiri Efendi, Saladin, founder of the Ayyubid dynasty who defeated the Crusaders at the decisive Battle of Karney Hattin, “scattered the library in Diyarbakir which contained millions of volumes”. I could not find any other reference to support this. All this information makes manuscripts more accessible than I originally thought, but I still wonder what al-Jazari’s library looked like.